UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Occupational health and fitness : a treatise on the relationship between physical fitness and health… Bardsley, John Edward 1982

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Notice for Google Chrome users:
If you are having trouble viewing or searching the PDF with Google Chrome, please download it here instead.

Item Metadata

Download

Media
831-UBC_1982_A6_7 B36_5.pdf [ 21.63MB ]
Metadata
JSON: 831-1.0095177.json
JSON-LD: 831-1.0095177-ld.json
RDF/XML (Pretty): 831-1.0095177-rdf.xml
RDF/JSON: 831-1.0095177-rdf.json
Turtle: 831-1.0095177-turtle.txt
N-Triples: 831-1.0095177-rdf-ntriples.txt
Original Record: 831-1.0095177-source.json
Full Text
831-1.0095177-fulltext.txt
Citation
831-1.0095177.ris

Full Text

OCCUPATIONAL HEALTH AND FITNESS A t r e a t i s e on the r e l a t i o n s h i p between p h y s i c a l f i t n e s s and h e a l t h status as they apply to the occ u p a t i o n a l s e t t i n g , w i t h p a r t i c u l a r emphasis on aerobic f i t n e s s , coronary heart disease and the Canadian m i l i t a r y . by JOHN EDWARD BARDSLEY CD., 3.A., M.Sc, Ph.D., M.D. (Queen's U n i v e r s i t y , Kingston) A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (Health Services Planning) We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA May 19 82 ©John Edward Bardsley, 1982 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree t h a t permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the head of my department or by h i s or her r e p r e s e n t a t i v e s . I t i s understood that copying o r p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission. John Edward Bardsley Department of Health Care and Epidemiology The U n i v e r s i t y of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date May, 19fl? (3/81) ABSTRACT Bardsley, John Edward, M.Sc, U n i v e r s i t y of 3 r i t i s h Columbia May, 19 82. Occupational Health and F i t n e s s . A t r e a t i s e on the r e l a t i o n s h i p between p h y s i c a l f i t n e s s and h e a l t h s t a t u s as they apply to the occupational s e t t i n g , w i t h p a r t i c u l a r emphasis on aerobic f i t n e s s , coronary heart disease and the Canadian m i l i t a r y Supervisor: John Milsum. Coronary heart disease takes a large t o l l of middle-aged males thereby reducing the o v e r a l l occupational f i t n e s s and poten t i a l of the workforce. Most of the r i s k f a c t o r s f o r CHD (and other diseases) are self-determined and/or the r e s u l t of preven-table behaviour or a l t e r a b l e environment. The M u l t i p l e Risk Factor Hypothesis and the CHD r i s k f a c t o r s are reviewed i n d e t a i l i n Chapter 2. I t i s more the i n t e r a c t i o n among r i s k f a c t o r s w i t h i n supposedly "normal" l i m i t s , r a t h e r than abnor-mally high l e v e l s of one or a few f a c t o r s which r e s u l t s i n the development of CHD, a phenomenon which obscures the issue of causation. I t i s hypothesized that the imbalance between the c o l l e c t i v e pathogenic e f f e c t s of r i s k f a c t o r s and the a b i l i t y of the body to r e s i s t and/or r e p a i r such e f f e c t s cause CHD. States such as sedentariness and obesity i n which most of the r i s k f a c -tors tend to be c l u s t e r e d are important r i s k i n d i c a t o r s . More-over, since the o v e r a l l r i s k p r o f i l e i s improved w i t h r e v e r s a l of these two s t a t e s through r e g u l a r aerobic a c t i v i t y and weight l o s s , the l a t t e r two are key i n t e r v e n t i o n s i n CHD prevention. Risk f a c t o r screening t o i d e n t i f y those at r i s k and subsequent m o d i f i c a t i o n of the r i s k s t a t u s are u s e f u l manoeuvers f o r the prevention of CHD. As w e l l as being secondary to the ravages of such diseases as CHD, occupational p r o d u c t i v i t y i s a l s o reduced by poor l e v e l s of employee p h y s i c a l f i t n e s s . The r e c o g n i t i o n by employers of the p o t e n t i a l success of CHD prevention programs and the i n c r e a -sed p r o d u c t i v i t y of the f i t employee has l e d to the emergence of employer-sponsored oc c u p a t i o n a l f i t n e s s programs. Such programs are based on a w h o l i s t i c health-enhancement approach wi t h r e g u l a r aerobic p h y s i c a l a c t i v i t y as the core. The opera-t i v e p r i n c i p l e s , contents ( i n c l u d i n g the what and how of the a l l important assessment component) and b e n e f i t s of such programs are reviewed i n Chapter 3. A review of the s t a t e of h e a l t h and f i t n e s s i n the Canadian Forces and the experimental p o r t i o n of the t h e s i s make up Chapte 4. In s p i t e of p o l i c i e s , orders and programs to ensure the h e a l t h and f i t n e s s of Canadian Forces' personnel, the CF remains a f a i r l y h i g h - r i s k p o p u l a t i o n . The c r o s s - s e c t i o n a l study on the h e a l t h and f i t n e s s of 2 83 CF personnel at N a t i o n a l Defence Head-quarters shows that Other Ranks c o n s t i t u t e a h i g h e r - r i s k rank grouping than O f f i c e r s , as do lower ranks i n both of these two major rank groupings. Volunteers appear to be a s e l f - s e l e c t e d sub-population which i s h e a l t h i e r and f i t t e r than average. Aerobic f i t n e s s (VO^ max) , o besity and r e s t i n g heart r a t e emerge - i v -as the three key i n d i c a t o r s of h e a l t h and CHD r i s k s t a t u s . Chapter 5 summarizes the t h e s i s and contains conclusions and recommendations to the CF f o r future a c t i o n s which are a l s o a p p l i c a b l e t o most occupational s e t t i n g s . - v -TABLE OF CONTENTS Page Abst r a c t i i L i s t of Tables x i i L i s t of Figures xv Acknowledgements ' x v i Chapter 1 I n t r o d u c t i o n 2 Chapter 2 Risk F a c t o r s , Health and Coronary Heart Disease 8 A Self-Determination of Health 9 1. The Almeda County Study 10 B Coronary Heart Disease 11 1. Pathology 12 2. C l i n i c a l Aspects 14 3. I n i t i a t i n g Event '15 4. M u l t i p l e Risk Factor Hypothesis 17 C Risk Factors 21 1. Fundamental B i o l o g i c a l Factors 21 1.1 Age 21 1.2 Sex and Oral Contraceptives 23 1.3 Race 2 5 1.4 Family H i s t o r y 2 6 2. P s y c h o s o c i a l Factors 27 2.1 Socioeconomic Status 2 7 2.2 S t r e s s 30 2.3 Coronary-Prone Behaviour 32 3. Environmental Factors 35 3.1 Hard Water 35 3.2 A l t i t u d e 35 4. L i f e s t y l e Factors 36 4.1 Diet 36 4.2 Smoking 43 4.3 P h y s i c a l A c t i v i t y and E x e r c i s e 49 a. Aerobic A c t i v i t y 50 b. E f f e c t s of Aerobic P h y s i c a l A c t i v i t y on the Body 51 (i) P h y s i o l o g i c a l E f f e c t s 53 ( i i ) P s y c h o l o g i c a l E f f e c t s 65 ( i i i ) Summary 65 c. P h y s i c a l A c t i v i t y and Health 66 d. P h y s i c a l A c t i v i t y as a P r o t e c t i v e F a c t o r f o r CHD 69 (i) An Independent Factor? 70 ( i i ) A R e s t r i c t e d Factor? 72 ( i i i ) Occupational versus Leisure-Time P h y s i c a l A c t i v i t y 73 - v i -Page 4. L i f e s t y l e Factors (cont'd) (iv) A Threshold E f f e c t 76 (v) Modes of A c t i o n of Aerobic E x e r c i s e on CHD 78 (vi) E x e r c i s e as a P r e c i p i -t a t o r of Acute Events 81 ( v i i ) Summary 81 e. The A s s o c i a t i o n of A c t i v i t y w i t h Other Risk Factors 82 (i) Obesity/Overweight 85 ( i i ) Serum T r i g l y c e r i d e s 87 ( i i i ) Serum C h o l e s t e r o l s 88 (iv) Blood Pressure 91 (v) Smoking 92 (vi) Serum U r i c A c i d 93 ( v i i ) Blood Sugar 93 ( v i i i ) F i b r i n o l y s i s 94 (ix) Mental Stress 94 (x) Fundamental B i o l o g i c a l Factors 9 5 (xi) Summary 96 f. Conclusions 96 5. Body Composition Factors 101 5.1 Height 101 5.2 Somatotype 101 5.3 Overweight and Obesity 102 a. The E f f e c t s of Obesity on the Body 104 b. Obesity, Overweight and Health 106 (i) M o r t a l i t y 109 ( i i ) M o r b i d i t y 110 ( i i i ) A Reversible Risk F a c t o r 111 (iv) Obesity as a Risk Factor f o r CHD 112 (v) A s s o c i a t i o n s Between Overweight/Obesity and Other Risk Factors 115 (vi) Summary 119 6. P h y s i o l o g i c a l Factors 121 6.1 Lung Function 121 6.2 Resting Heart Rate 12 3 6.3 High Blood Pressure 126 6.4 Aerobic F i t n e s s 129 a. Determinants 130 b. Aerobic F i t n e s s and General Health 132 c. Aerobic F i t n e s s as a Risk Factor f o r CHD 133 d. Aerobic F i t n e s s and Other Risk Factors 134 e. Summary 138 - v i i -Page 7. Hematological Factors 141 7.1 C l o t t i n g Factors 141 7.2 Blood Sugar 142 7.3 Serum U r i c A c i d and Gout 143 7.4 Serum L i p i d s 147 a. L i p i d Metabolism 14 8 b. Serum T r i g l y c e r i d e s 151 c. The C h o l e s t e r o l s 153 (i) T o t a l Serum C h o l e s t e r o l 153 ( i i ) Low Density L i p o p r o t e i n -C h o l e s t e r o l 156 ( i i i ) High Density L i p o p r o t e i n -C h o l e s t e r o l 157 (iv) Summary 162 8. Medical Disorders as Risk Factors 164 8.1 EKG Abnormalities 164 8.2 Diabetes M e l l i t u s 165 D General Discussion 168 1. General Aspects 168 2. "Safe" Levels 171 2.1 Smoking 172 2.2 Body Composition 172 2.3 Height 17 3 2.4 Resting Heart Rate 173 2.5 Blood Pressure 174 2.6 Aerobic A c t i v i t y and F i t n e s s 174 2.7 V i t a l Capacity 175 2.8 Serum T r i g l y c e r i d e s 175 2.9 T o t a l Serum C h o l e s t e r o l 175 2.10HDL-C 176 3. Reference Population Levels of Risk Factors 178 4. Risk Factor I n t e r a c t i o n s 183 5. Risk P r o f i l e s 185 6. Causative or A s s o c i a t i v e ? 187 7. Prevention 19 0 8. Section Summary 198 E Chapter Summary 199 Chapter 3 Health and F i t n e s s i n the Workplace 201 A I n t r o d u c t i o n 2 02 B The B e n e f i t of Occupational F i t n e s s Programs 20 3 1. Occupational F i t n e s s Programs -Cost E f f e c t i v e ? 204 2. The F i t Employee 20 6 3. Section Summary 20 8 C Occupational F i t n e s s Programs 20 8 1. What Makes For a Su c c e s s f u l Program? 20 8 2. Factors I n f l u e n c i n g Attendance 211 - v i i i -Page 3. Program Operation 213 4. Health Assessment 218 4.1 Medical Screening 218 4.2 Assessment of Health Status 219 a. What to Include? 22 0 b. How to Measure: 221 c. Assessment of Obesity 225 (i) Weight/Height Indices 226 ( i i ) S k i n f o l d Thicknesses 227 ( i i i ) R e l a t i v e Weights 2 30 (iv) Combined Approaches 2 32 (v) Summary 2 33 d. Assessment of P h y s i c a l A c t i v i t y 234 e. Assessment of P h y s i c a l F i t n e s s 235 (i) The B i c y c l e Ergometer 236 ( i i ) The Canadian Home Fi t n e s s Test 237 ( i i i ) Time/Distance Tests 238 (iv) Other Tests 239 (v) Summary 240 5. Constituents of the Program I t s e l f 2 41 5.1 The Ex e r c i s e Component 242 a. Components 2 42 b. Stages 243 c. F l e x i b i l i t y and Strength 243 d. Aerobic E x e r c i s e 244 (i) Types of Aerobic E x e r c i s e . 247 ( i i ) Standards of V0 2 max 2 48 e. Summary 2 49 5.2 Other Components 2 50 a. E d u c a t i o n a l M a t e r i a l 251 b. Behaviour Change Elements 2 51 c. Program E v a l u a t i o n 252 6. Section Summary 252 Chapter 4 Health and F i t n e s s i n the Canadian Forces 2 54 A I n t r o d u c t i o n 255 1. High Risk Populations 257 2. Health and F i t n e s s i n the Canadian Forces 260 3. N a t i o n a l Defence Headquarters 264 B M a t e r i a l s and Methods 266 1. Study Design 2 66 2. Reference Population 2 66 3. Experimental Populations 266 4. Study Sequence 2 67 5. Study V a r i a b l e s 269 5.1 Rank 2 69 5.2 Age 2 70 - i x -Page 5. Study V a r i a b l e s (cont'd) 5.3 Height 270 5.4 Weight 270 5.5 Frame Size 271 5.6 " I d e a l " , "Maximum" and R e l a t i v e Body Weight 271 5.7 Weight/Height Indices 271 5.8 S k i n f o l d Thicknesses 271 5.9 Resting Heart Rate 272 5.10 Blood Pressure 272 5.11 Blood Work 273 5.12 Smoking 273 5.13 Pulmonary Function 274 5.14 Aerobic (Cardiopulmonary) F i t n e s s 274 5.15 Risk Factors 276 6. S t a t i s t i c a l Analyses 277 Results 278 1. Representativeness of the Study Populations 278 2 . Comparison of the Study Popula-t i o n s 280 3. Prevalence of High Risk Levels of Study V a r i a b l e s 2 82 4. Age 285 5. Rank 287 5.1 General 287 5.2 O f f i c e r s and Other Ranks 290 5.3 O f f i c e r s 292 5.4 Other Ranks 295 6. F i t n e s s 297 6.1 Step-Wise M u l t i p l e Regression 297 6.2 Simple and P a r t i a l C o r r e l a -t i o n s 300 6.3 C a t e g o r i c a l A n a l y s i s by t - t e s t 300 6.4 C a t e g o r i c a l A n a l y s i s by C h i -square 307 a. Good + E x c e l l e n t versus Poor + F a i r 307 b. V0„ max <40 versus >40. 312 7. Overweight/Obesity 317 7.1 I n d i c a t o r s of Obesity 317 7.2 Simple and P a r t i a l C o r r e l a -t i o n s 321 7.3 C a t e g o r i c a l A n a l y s i s by t - t e s t 321 7.4 C a t e g o r i c a l A n a l y s i s by C h i -square 324 8. Resting Heart Rate 328 8.1 Step-wise M u l t i p l e Regression 328 8.2 Simple and P a r t i a l C o r r e l a -t i o n s 329 8.3 C a t e g o r i c a l A n a l y s i s by t - t e s t 331 - x -Page 8. Resting Heart Rate (cont'd) 8.4 C a t e g o r i c a l A n a l y s i s by C h i -square 3 33 9. Smoking 335 9.1 Simple and P a r t i a l Corre-l a t i o n s 337 9.2 C a t e g o r i c a l A n a l y s i s by C h i -square 3 35 10. Miscellaneous A s s o c i a t i o n s 337 10.1 Simple and P a r t i a l C o r r e l a -t i o n s 337 10.2 C a t e g o r i c a l A n a l y s i s by C h i -square 339 D Discussion 346 1. Representativeness of the Study Populations 346 2. Volunteers 3 46 3. Prevalence of High Risk Levels of Study V a r i a b l e s 347 3.1 Aerobic F i t n e s s 347 a. B a s i c Levels 3 47 b. Comparison to Other Populations 3 49 c. Summary 3 49 3.2 Obesity/Overweight 350 3.3 Serum L i p i d s 351 3.4 Blood Pressure 352 3.5 Smoking 352 3.6 Summary 353 4. Age 3 55 5. Rank 356 5.1 General 356 5.2 O f f i c e r s 358 5.3 Other Ranks 35 8 5.4 O f f i c e r s versus Other Ranks 359 5.5 Summary 360 6. Aerobic F i t n e s s 3 61 6.1 As a Health and Risk Status I n d i c a t o r 361 6.2 Regression Equations 363 7. Resting Heart Rate 363 7.1 As a Health and Risk Status I n d i c a t o r 363 8. Obesity/Overweight 364 8.1 A Best Measurement? 364 8.2 As a Health and Risk Status I n d i c a t o r 365 9. Smoking 365 10. Miscellaneous A s s o c i a t i o n s Among Study V a r i a b l e s 366 E Chapter Summary - x i -Chapter 5 O v e r a l l Summary, Conclusions and Recommendations A O v e r a l l Summary B Conclusions C Recommendations Appendix 1 A Model of the Causation of Coron Heart Disease References - x i i -LIST OF TABLES Table T i t l e Page 2.1 Risk Factors f o r Coronary Heart Disease 19 2.2 Aerobic E x e r c i s e and B o d i l y Functions 54 2.3 A s s o c i a t i o n s Between Regular Aerobic A c t i v i t y and Other Risk Factors 86 2.4 The E f f e c t s of Obesity on the Body 107 2.5 A s s o c i a t i o n s Between Overweight/Obesity and Other Risk Factors 116 2.6 A s s o c i a t i o n s Between Aerobic F i t n e s s and Other Risk Factors 13 9 2.7 A s s o c i a t i o n s Between Serum U r i c A c i d and Other Risk Factors 145 2.8 A s s o c i a t i o n s Between HDL and Other Risk Factors 1 161 2.9 "Safe" Levels of Risk Factors 177 2.10 Reference Population Levels of Health-Related V a r i a b l e s 179 2.11 Reference V0 2 max Levels 181 2.12 The A s s o c i a t i o n Among the Commonly Referred To CHD Risk Factors 186 3.1 The B e n e f i t s of Aerobic E x e r c i s e and F i t n e s s to the Workplace 209 3.2 Program Q u a l i t i e s f o r Success and Regular Attendance 210 3.3 The Stages i n a Health Promotion Program 214 3.4 Components of Health Assessment 222 4.1 B a s i c S t a t i s t i c s f o r the Reference and Study Populations 2 79 4.2 Study Population Means 281 4.3 Prevalence of High Risk Levels of Study V a r i a b l e s 283 4.4 C o r r e l a t i o n C o e f f i c i e n t s f o r Age 2 86 - x i i i -Table T i t l e Page 4.5 Cross Tabulation of Age and Risk Factors 28 8 4.6 C o r r e l a t i o n C o e f f i c i e n t s f o r Rank 289 4.7 Comparison of O f f i c e r s and Other Ranks 2 91 4.8 Prevalence of High Risk Levels of Study V a r i a b l e s i n O f f i c e r s and Other Ranks 29 3 4.9 Means f o r O f f i c e r s 294 4.10 Means f o r Other Ranks 2 96 4.11 C o r r e l a t i o n C o e f f i c i e n t s f o r V0 2 max 299 4.1Z Means Under F i t n e s s Categories 301 4.13 Results of t - t e s t A n a l y s i s of F i t n e s s Categories . 302 4.14 Comparison of Two F i t n e s s Groups 305 4.15 Comparison of Two V0 2 max Groups 30 6 4.16 F i t n e s s versus Serum C h o l e s t e r o l and S y s t o l i c Blood Pressure 308 4.17 F i t n e s s versus Blood Sugar and Lung Function 310 4.18 F i t n e s s versus Smoking 311 4.19 F i t n e s s versus Risk Factors 313 4.20 V0 2 max versus Risk Factors 315 4.21 C o r r e l a t i o n C o e f f i c i e n t s f o r Weight I n d i c a t o r s 319 4.22 C o r r e l a t i o n C o e f f i c i e n t s Among Weight I n d i c a t o r s 320 4.23 C o r r e l a t i o n of Obesity Indices and Other. Study V a r i a b l e s 322 4.2 4 Comparison of Two Obesity Groups 32 3 4.25 Obesity versus Serum U r i c A c i d and S y s t o l i c Blood Pressure 325 4.2 6 Cross Tabulation of BMI and Risk Factors 32 7 4.2 7 C o r r e l a t i o n C o e f f i c i e n t s f o r Resting Heart Rate 3 30 ~ x i v ~ Table T i t l e Page 4.2 8 Comparison of Two Resting Heart Rate Groups 3 32 4.29 Cross Tabulation of Resting Heart Rate w i t h Serum U r i c A c i d and BMI 334 4.30 Cross Tabulation of Smoking w i t h Lung Function 336 4.31 Cross Tabulation of Smoking with Serum U r i c A c i d and D i a s t o l i c Blood Pressure 338 4.32 C o r r e l a t i o n C o e f f i c i e n t s Between Blood Pressures and Serum L i p i d s 340 4.33 Cross Tabulations of T r i g l y c e r i d e s w i t h U r i c A c i d and Blood Sugar 341 4.34 Cross Tabulations of U r i c A c i d w i t h Blood Pressures 342 4.35 Cross Tabulations of T r i g l y c e r i d e s w i t h Blood Pressure, and Blood Sugar w i t h Lung Function 344 - XV -LIST OF FIGURES Figure T i t l e Page A . l The Pathogenesis of CHD as an Imbalance 388 - x v i -ACKNOWLEDGEMENTS Thanks t o : The Canadian Forces, f o r sponsoring me. Corinna Lusk, f o r t a k i n g on the onerous task of t y p i n g t h i s tome and doing such a good job. Ronnie S i t z o , f o r h i s patience and s k i l l i n h e l p i n g me with the s t a t i s t i c a l analyses. L y a l l Howlett and the NDHQ MIR f o r doing the medical a p p r a i s a l s . Curt A l l e n and the E x e r c i s e Physiology Section of DCIEM f o r doing the f i t n e s s a p p r a i s a l s . Terry Anderson and Ted Rhodes, f o r agreeing t o be on my committee. John Milsum, f o r agreeing t o be my s u p e r v i s o r , h i s respect f o r my i n d i v i d u a l i t y and the many hours spent i n our mutual quest f o r s p i r i t u a l development. Gena and Roy, my parents, f o r passing on to me the values of hard work, thoroughness and high standards. J e f f r e y and P a u l , my sons, f o r t h e i r l o v e , support and uncomplaining s a c r i f i c e of my time. Penny, my w i f e , f o r her s a c r i f i c e s , support, devotion and love. This t h e s i s i s dedicated to her. God, f o r the people mentioned above and f o r g r a n t i n g me the time, a b i l i t y and wherewithal to complete t h i s work. - 1 -CHAPTER 1 INTRODUCTION - 2 -CHAPTER 1  INTRODUCTION The o v e r a l l l e v e l of f i t n e s s of employees i s very important to any work f o r c e , determining the type and amount of work each i n d i v i d u a l can perform. C e r t a i n types of employment, f o r example f i r e - f i g h t i n g and p o l i c e work, where unexpected demands may be placed on the i n d i v i d u a l , render the l e v e l of o v e r a l l f i t n e s s of paramount importance. M i l i t a r y work c o n s t i t u t e s an extreme example of such employment since m i l i t a r y forces may w e l l be c a l l e d away from home base during times of n a t i o n a l or i n t e r n a t i o n a l c r i s i s , o f t e n t o areas of c l i m a t i c and geographical extremes, and to work of unaccustomed r i g o r and s t r e s s . Within the m i l i t a r y context, the exi g e n c i e s of war place the greatest demands on human f i t n e s s , and i t i s f o r t h i s u l t i m a t e , o f t e n unpredictable t h r e a t that m i l i t a r y forces must c o n s t a n t l y be prepared. M i l i t a r y forces have long recognized the values of high l e v e l s of h e a l t h and f i t n e s s i n t h e i r members i n ensuring optimal o p e r a t i o n a l preparedness. Pre-enrollment, and p e r i o d i c medical examinations, with e x a c t i n g standards to be met i n the areas of medical c o n d i t i o n i n c l u d i n g body composition, are b u i l t i n t o m i l i t a r y r o u t i n e . Most m i l i t a r y forces a l s o have standards of p h y s i c a l f i t n e s s f o r enrollment, r e t e n t i o n and c e r t a i n employ-ment. Thus programs t o promote and t e s t f o r the s t a t e of p h y s i -c a l f i t n e s s , p a r t i c u l a r l y c a r d i o r e s p i r a t o r y (= aerobic) f i t n e s s , - 3 -are a l s o a c h a r a c t e r i s t i c of m i l i t a r y r o u t i n e . Unfortunately, the two areas of o v e r a l l f i t n e s s , namely medical and p h y s i c a l f i t n e s s , have been disconnected, both conceptually and p r a c t i -c a l l y . However, the r e c o g n i t i o n of the importance of coronary heart disease to the work force may w e l l have a f f o r d e d a u n i -f y i n g bond. The l a s t h a l f - c e n t r y has seen a boom i n research concerning ischemic or coronary heart disease, the p r i n c i p a l k i l l e r i n wes-ter n s o c i e t y , p a r t i c u l a r l y of middle-aged men, and thus of personnel i n the work f o r c e . With t h i s research has emerged the concept of r i s k f a c t o r s , and the r e a l i z a t i o n t h a t many of these r i s k f a c t o r s are the r e s u l t s of environment and l i f e s t y l e . Such a r e a l i z a t i o n reached prominence i n Canada w i t h the p u b l i -2 6 8 c a t i o n of A New Perspe c t i v e on the Health of Canadians Risk f a c t o r s have been recognized as good i n d i c a t o r s of l i f e t i m e h e a l t h s t a t u s , and screening f o r them has become an accepted p r a c t i c e to i d e n t i f y high r i s k i n d i v i d u a l s and popul a t i o n s . Of l a t e , great emphasis has been placed on t h e i r m o d i f i c a t i o n f o r 4-u 4.- *. 10,220,298,389 , the prevention of coronary heart disease and other d i s o r d e r s . The unique o p p o r t u n i t i e s f o r such i n the m i l i t a r y 155 s e t t i n g have been pointed out One r i s k f a c t o r which has commanded a l o t of a t t e n t i o n i s p h y s i c a l i n a c t i v i t y or sedentariness. The i d e n t i f i c a t i o n of sedentariness as a p o s s i b l e r i s k f a c t o r f o r coronary heart disease, i n conjunction w i t h the acceptance of r e g u l a r e x e r c i s e - 4 -as an e f f e c t i v e t h e r a p e u t i c modality i n the r e h a b i l i t a t i o n of heart attack v i c t i m s has l e d to the e x p l o r a t i o n of r e g u l a r aerobic e x e r c i s e as a preventive s t r a t e g y against CHD. Such a t t e n t i o n has r e s u l t e d i n an examination, or indeed a re-exami-n a t i o n , of the connection between r e g u l a r p h y s i c a l a c t i v i t y and h e a l t h i n general, epitomized by the 19 74 Canadian N a t i o n a l 195 Conference on F i t n e s s and Health . Such an examination has i n d i c a t e d that r e g u l a r p h y s i c a l a c t i v i t y as an element of l i f e -s t y l e , and concomitant c a r d i o r e s p i r a t o r y f i t n e s s as a personal a t t r i b u t e , may w e l l be a s s o c i a t e d w i t h , or indeed determinative of, enhanced h e a l t h and reduced r i s k f a c t o r s f o r i l l h e a l t h g e n e r a l l y , and coronary heart disease s p e c i f i c a l l y . Industry and business have responded to t h i s s i t u a t i o n by embarking enthu-s i a s t i c a l l y on employer-sponsored p h y s i c a l f i t n e s s programs as p a r t of o v e r a l l h e a l t h promotion endeavours. These programs seem to have met w i t h considerable success, i n terms of both i n d i v i d u a l h e a l t h enhancement and i n d u s t r i a l p r o d u c t i v i t y . However, i n s p i t e of such enthusiasm on the p a r t of c i v i l i a n employers, concern has been expressed over the e f f i c a c y of m i l i -t a r y h e a l t h and f i t n e s s programs i n maintaining p h y s i c a l and o v e r a l l f i t n e s s . Moreover, concerning j u s t p h y s i c a l f i t n e s s , the d e s i r a b i l i t y of i t s l e v e l s beyond t h a t r e q u i r e d f o r the p h y s i c a l performance of the peace-time job have been questioned. Both of these concerns were h i g h l i g h t e d at the 19 78 NATO P h y s i c a l F i t n e s s 340 Symposium . I t seems i r o n i c indeed that at a time when the c i v i l i a n s e c t o r i s r e c o g n i z i n g the values of p h y s i c a l f i t n e s s to - 5 -the o v e r a l l h e a l t h and p r o d u c t i v i t y of i t s employees, the m i l i t a r y sector should be q u e s t i o n i n g the v a l i d i t y of i t s h i s t o r i c a l requirements f o r p h y s i c a l f i t n e s s . The d i s p a r i t y could w e l l l i e i n the disconnectedness of h e a l t h and f i t n e s s i n the m i l i t a r y s e t t i n g . However, research has i n d i c a t e d t h a t a c l o s e a s s o c i a t i o n e x i s t s between p h y s i c a l f i t n e s s , p a r t i c u l a r l y c a r d i o r e s p i r a t o r y f i t n e s s , and general h e a l t h . Thus, q u i t e apart from the short term p h y s i c a l requirements f o r job performance, p h y s i c a l f i t n e s s appears to have i m p l i c a t i o n s f o r h e a l t h s t a t u s , and thereby long term job performance. This t h e s i s w i l l examine the r e l a t i o n s h i p between p h y s i c a l a c t i v i t y and f i t n e s s on the one hand and -. h e a l t h and job performance on the other. Aerobic a c t i v i t y and f i t n e s s w i l l be emphasized on the f i t n e s s s i d e , and coronary heart disease on the h e a l t h s i d e . The t h e s i s c o n s i s t s of three major p a r t s . The f i r s t major pa r t (Chapter 2) deals predominantly w i t h coronary heart disease and the concept of r i s k f a c t o r s . In reviewing CHD and i t s r i s k f a c t o r s , I want t o f o s t e r an understanding of how the presence of r i s k f a c t o r s may c o n t r i b u t e to the occurrence of CHD, and conversely how t h e i r m o d i f i c a t i o n may prevent i t s occurrence, or reduce i t s s e v e r i t y . Thus, the primary purposes of Chapter 2 are to define what c o n s t i t u t e s r i s k of l o s s of h e a l t h , p a r t i c u l a r l y through the development of CHD, and thereby to r e v e a l how such - 6 -r i s k can be improved or reversed. P a r t i c u l a r emphasis w i l l be placed on c a r d i o r e s p i r a t o r y f i t n e s s and o b e s i t y . Chapter 3 w i l l examine h e a l t h and f i t n e s s i n the context of the work s e t t i n g . I n d u s t r i a l f i t n e s s programs w i l l be examined as to type, contents, standards, assessment (what i t assessed and the techniques f o r i t ) and e f f i c a c y . The primary purposes of Chapter 3 are to study the r e l a t i o n s h i p between f i t n e s s and i n d u s t r i a l p r o d u c t i v i t y and what c o n s t i t u t e s an e f f e c t i v e program to promote such a s t a t e of f i t n e s s . Chapter 4 i s the experimental s e c t i o n r e l a t e d t o the Canadian Armed Forces (CF). This s e c t i o n w i l l s t a r t w i t h an examination of m i l i t a r y f orces as high r i s k populations and pro-gress to a review of what i s known of the s t a t e of h e a l t h and f i t n e s s of CF personnel. Subsequently, the c r o s s - s e c t i o n a l study done on the h e a l t h and f i t n e s s s t a t u s of 2 83 male personnel at N a t i o n a l Defence Headquarters i n Ottawa w i l l be presented. Once again, p a r t i c u l a r a t t e n t i o n w i l l be placed on c a r d i o r e s p i r a t o r y f i t n e s s and o b e s i t y , as w e l l as on r e s t i n g heart r a t e . Chapter 5 i s an o v e r a l l summary l e a d i n g to conclusions and recommendations. The o v e r a l l flow of the t h e s i s , then, i s meant to be as f o l l o w s . Chapter 2 i s meant to examine the connection between st a t e of f i t n e s s , p a r t i c u l a r l y c a r d i o r e s p i r a t o r y f i t n e s s , and - 7 -h e a l t h , s p e c i f i c a l l y coronary heart disease. With t h i s i n mind, Chapter 3 i s designed to examine the connection between f i t n e s s and h e a l t h on one hand, and i n d u s t r i a l p r o d u c t i v i t y on the other, as w e l l as t o review the present s t a t e of i n d u s t r i a l f i t n e s s programs. A l l of the foregoing leads t o Chapter 4 which e n t a i l s an examination of m i l i t a r y forces as p o s s i b l y high r i s k popu-l a t i o n s as a lead o f f to the study of h e a l t h and f i t n e s s of NDHQ male personnel. Chapter 5 then summarizes a l l of the foregoing chapters f o r the purposes of a r r i v i n g at conclusions and subse-quent recommendations concerning o c c u p a t i o n a l h e a l t h - r e l a t e d p o l i c i e s and programs, p a r t i c u l a r l y f o r the CF. - 8 -CHAPTER 2 RISK FACTORS, HEALTH AND CORONARY HEART DISEASE - 9 -CHAPTER 2 RISK FACTORS'/ HEALTH AND CORONARY HEART DISEASE A. SELF-DETERMINATION OF HEALTH Notwithstanding the advances i n medical technology, the greatest r e a l i z a t i o n i n the h e a l t h f i e l d over the past t h i r t y or so years has been that the way i n which we l i v e - our l i f e s t y l e -i s a, i f not the major determinant of our h e a l t h . Unquestionably our genetic makeup a l s o plays a p i v o t a l r o l e , as do chance and s o c i a l s e t t i n g . However, s k i n cancer i s rare indeed i n those who p r o t e c t themselves from the sun; obe s i t y i n those who gear t h e i r food intake t o energy needs; c i r r h o s i s of the l i v e r i n those who do not drink e x c e s s i v e l y ; e t ce t e r a . Such h a b i t s , which are l a r g e l y v o l u n t a r y , have become known as "self-imposed" r i s k s . Health and Welfare Canada f o r m a l l y recognized t h i s phenome-non when i t s t a t e d that future improvements i n the h e a l t h of Canadians l i e mainly i n improving the environment and moderating 2 68 "self-imposed" r i s k s through l i f e s t y l e change. And so, i t seems, do future improvements i n the cost of i l l h e a l t h t o Canadians g e n e r a l l y , and employers s p e c i f i c a l l y . In the Canadian Forces alone, i n 1973, f i n a n c i a l l osses through premature death and retirement, l o s t man-years and h e a l t h care costs secondary t o 29 such "self-imposed" r i s k s exceeded $25 m i l l i o n . These f i g u r e s are considered c o n s e r v a t i v e , and do not i n c l u d e other f a c t o r s , such as time l o s t and not recorded, reduced p r o d u c t i v i t y and the inestimable t o l l i n human s u f f e r i n g and l o s s of e x p e r t i s e . I l l - 10 -h e a l t h r e l a t e d to l i f e s t y l e , then, i s an important area f o r occupational h e a l t h . 1. The Almeda County Study L i f e s t y l e and self-imposed r i s k s i n r e l a t i o n to h e a l t h 35 57 477-g e n e r a l l y i s seen i n the work of Breslow and colleagues ' ' Using general m o r t a l i t y as t h e i r prime i n d i c a t o r of h e a l t h s t a t u s , they s t u d i e d a population of about 4,000 C a l i f o r n i a n s w i t h r e s -pect to seven v a r i a b l e s : a l c o h o l consumption, c i g a r e t t e smoking, p h y s i c a l a c t i v i t y , s l e e p , r e l a t i v e weight and two aspects of e a t i n g h a b i t s , r e g u l a r i t y of b r e a k f a s t i n g and indulgence i n between-meal snacking. A f t e r nine years of o b s e r v a t i o n , they found t h a t those people who d i d not smoke, were of d e s i r a b l e weight (average weight -10%), consumed a l c o h o l moderately, were r e g u l a r l y p h y s i c a l l y a c t i v e (the more the better) and got 7-8 hours s l e e p , had the lowest m o r t a l i t y . Although there was some controversy surrounding the s i g n i f i c a n c e of r e g u l a r b r e a k f a s t i n g 35 and abstinence from between-meal snacking , i t was g e n e r a l l y concluded t h a t the greater number of p o s i t i v e t r a i t s i n the l i f e -s t y l e the lower the m o r t a l i t y . For example, those w i t h a l l seven t r a i t s had a lower m o r t a l i t y - by 2 8% f o r males, 43% f o r females -than those w i t h three or fewer. People w i t h intermediate numbers of t r a i t s had intermediate m o r t a l i t y r a t e s . The general p i c t u r e t h a t emerges from t h e i r study i s t h a t a l i f e s t y l e w i t h the seven p o s i t i v e components described i s asso-- 11 -c i a t e d w i t h enhanced h e a l t h as i n d i c a t e d by l o n g e v i t y . Although a cause and e f f e c t r e l a t i o n s h i p cannot be proven by such a study, simply because we may be l o o k i n g a t the r e s u l t s of s e l e c t i o n , c e r t a i n of the v a r i a b l e s s t u d i e d are, i n t h e i r negative form, known to cause l o s s of he a l t h and l i f e , f o r example smoking, o b e s i t y , lack of p h y s i c a l a c t i v i t y and overindulgence i n a l c o h o l . Thus, i t would be p l a u s i b l e t h a t , from a negative p e r s p e c t i v e , these l i f e s t y l e components are " r i s k f a c t o r s " f o r l o s s of h e a l t h and premature m o r t a l i t y , w i t h an increased number of negative f a c t o r s l e a d i n g to e a r l i e r m o r t a l i t y . I t i s worthy of s t r e s s i n g here th a t most of these f a c t o r s are habits;• however, o b e s i t y i s a personal t r a i t , a l b e i t , l o g i c a l l y , the end r e s u l t of one or more h a b i t s . The concept o f r i s k f a c t o r s has gained prominence i n the f i e l d of coronary heart disease, which w i l l now be reviewed i n considerable d e t a i l due to i t s s i n g u l a r importance to s o c i e t y g e n e r a l l y , and the work force i n p a r t i c u l a r . B. CORONARY HEART DISEASE In Canada, as i n most i n d u s t r i a l i z e d c o u n t r i e s , coronary heart disease i s the p r i n c i p a l cause of morbidity and mo r t a l i t y . ' 74 Canada ranked seventh i n the world f o r death from CHD i n 196 7. The disease predominantly a f f e c t s males, e s p e c i a l l y middle-aged males, f o r which i t i s the p r i n c i p a l k i l l e r . I t has been asc e r t a i n e d t h a t 1 i n 5 North American men w i l l develop c l i n i c a l CHD by age 6 0 . 7 4 , 4 3 7 In Canada there are 40,000 new heart 540 attacks each year i n the 30 to 60 age group. Thus, CHD i s of p a r t i c u l a r i n t e r e s t to business and i n d u s t r y , and other 12 employers, where such an age group c o n s t i t u t e s the workforce I t i s obviously a disease of utmost importance to any m i l i t a r y f o r c e . Indeed, c a r d i o v a s c u l a r disease i n the U.S. A i r Force was estimated to have cost i n excess of $40 m i l l i o n per year between 52 3 19 74 and 19 77 , the costs being l a r g e l y secondary to premature retirement, death, l o s t man-days and h e a l t h care c o s t s . 1. Pathology CHD i s almost wholly caused by a t h e r o s c l e r o s i s of the coronary a r t e r i e s , and a c c o r d i n g l y can be considered e s s e n t i a l l y synonymous wi t h coronary a r t e r y disease (CAD), w i t h a t h e r o s c l e r o -t i c heart disease and w i t h a r t e r i o s c l e r o t i c heart disease (ASHD) since a t h e r o s c l e r o s i s i s the commonest form of a r t e r i o s c l e r o s i s (hardening of the a r t e r i e s ) . L i k e a l l a t h e r o s c l e r o s i s , CHD s t a r t s i n the l i n i n g of the a r t e r y , the i n t i m a , and progresses by a p r o l i f e r a t i o n of smooth muscle and build-up of c h o l e s t e r o l and other substances l e a d i n g to the s o - c a l l e d a t h e r o s c l e r o t i c plaque. The plaque then grows u n t i l the lumen (bore) of the a r t e r y i s so r e s t r i c t e d that an adequate blood supply can no longer be s u p p l i e d to the organ, i n t h i s case the heart. Such a lack of blood, or ischemia, (thus CHD i s a l s o synonymous w i t h ischemic heart disease, IHD) r e s u l t s i n a lack of oxygen, u s u a l l y on e x e r t i o n , l e a d i n g t o angina p e c t o r i s (heart p a i n ) . I f the ischemia i s severe enough, myocardial i n f a r c t i o n (heart attack) can occur. Although most heart attacks are accompanied by severe chest p a i n , 25% are completely asymptomatic"^. Heart attack may a l s o be p r e c i p i t a t e d by a blood c l o t b l o c k i n g the - 13 -flow at the s i t e of the a t h e r o s c l e r o t i c narrowing, and, indeed, may occur secondary to 44 d i f f e r e n t diseases^^^. The end r e s u l t of a heart attack i s death of a segment of heart muscle and, subsequently, impaired heart f u n c t i o n . I f the a t t a c k i s severe enough, the v i c t i m may d i e ; 25% of a l l heart attack v i c t i m s die 437 w i t h i n three hours, 70% of which do not make i t to h o s p i t a l ; and 35% die w i t h i n the week. Death i s u s u a l l y due e i t h e r to f a i l u r e of the heart as a pump (congestive heart f a i l u r e ) or to f a i l u r e of the normal e l e c t r i c a l conduction system of the heart l e a d i n g t o abnormal beats ( a r r y t h m i a s ) , the most s e r i o u s of which i s v e n t r i c u l a r f i b r i l l a t i o n . I f the e l e c t r i c a l conduc-t i o n system i s i n i t i a l l y and s e r i o u s l y a f f e c t e d by the ischemia, an arrythmia, followed by sudden death, may be the r e s u l t . Sudden death accounts f o r 50 to 60% of the m o r t a l i t y due to 49 CHD . The prognosis f o r people w i t h c l i n i c a l CHD i s guarded since they are f i v e times more l i k e l y to die w i t h i n f i v e years than 437 the average c i t i z e n of the same age . The e f f e c t s of bypass surgery on l o n g e v i t y are i n c o n s i s t e n t , although the q u a l i t y of l i f e seems improved. Conservative management o f f e r s hope, but the chance of the p a t i e n t reaching h i s pre-disease p o t e n t i a l i s scant indeed. 104 458 The disease seems t o s t a r t i n childhood ' . Evidence f o r t h i s i s derived predominantly from post-mortem stud i e s of young men k i l l e d by acts of v i o l e n c e . For example, young American - 14 -s o l d i e r s (average age 22) k i l l e d i n the Korean and Vietnam wars had some degree of coronary a t h e r o s c l e r o s i s : over 77% i n the Korean and 45% i n the Vietnam study. Even at t h i s young age the disease can be severe. The Korean f i n d i n g s showed th a t over 15% of s o l d i e r s had greater than 50% o c c l u s i o n of at l e a s t one coro-nary a r t e r y ; the Vietnam study showed "severe" disease i n 5% of s o l d i e r s . Studies of m i l i t a r y p i l o t s k i l l e d i n a i r c r a f t a c c i -379 dents show s i m i l a r f i n d i n g s . R i g a l and colleagues s t u d i e d 222 p i l o t s and found that 6 8% of those aged 20 - 29 years had some CHD, w i t h 17% e i t h e r moderate or marked. They found s i m i l a r 302 r e s u l t s i n n o n - f l y e r s who died t r a u m a t i c a l l y . Mason st u d i e d 2 75 a i r c r a f t accident v i c t i m s w i t h a mean age of 2 7 years (mostly RAF and RN aircrew) and found s i g n i f i c a n t lumenal r e s t r i c t i o n i n 22% of cases and disease obvious to the eye i n 35%. Although no s t a t i s t i c a l l y s i g n i f i c a n t d i f f e r e n c e was found between aircrew and c o n t r o l s i n e i t h e r study, both authors agreed t h a t there was a high incidence of asymptomatic moderate or marked CHD i n 2 34 young men g e n e r a l l y and a l s o i n young p i l o t s . Jung found i n d i r e c t evidence of CHD i n 14% of 1000 German A i r Force p i l o t s using the abnormal electrocardiogram (EKG) as an i n d i c a t o r . 2. C l i n i c a l Aspects CHD i s an i n s i d i o u s disease. The t y p i c a l case i s a man who i s completely symptom-free u n t i l h i s f i r s t major event, which can be angina p e c t o r i s (heart p a i n ) , myocardial i n f a r c t i o n (heart a t t a c k ) , e i t h e r n o n - f a t a l or f a t a l , or even sudden death. For example, Cumming and c o l l e a g u e s 1 0 0 found an incidence of ischemic - 15 -EKGs ( i n d i c a t i v e of CHD) i n about 10% of m e d i c a l l y screened, asymptomatic, otherwise h e a l t h y , volunteer, male Winnipeggers. At the stage of symptoms or abnormal EKGs, the disease i s u s u a l l y severe and supposedly e s s e n t i a l l y i r r e v e r s i b l e . As already mentioned, about 2 5% of cases of heart attack are unknown t o the v i c t i m at the time of the attack and these people are at f i v e times the average r i s k of a f u r t h e r event. Moreover, f o r a s i z e -able p o r t i o n of people, the f i r s t event i s f a t a l . 3. I n i t i a t i n g Event Like most diseases, the pathogenesis of CHD i n v o l v e s an i n i t i a t i n g event followed by a developmental p e r i o d during which the disease worsens to the p o i n t of c l i n i c a l symptoms or s i g n s . Although CHD has been e x t e n s i v e l y s t u d i e d , i t s cause remains contested. I t i s g e n e r a l l y agreed t h a t the disease has a m u l t i -f a c t o r i a l pathogenesis. However, what a c t u a l l y causes the i n i t i a l i n j u r y to the a r t e r i a l l i n i n g remains moot. One theory i n keeping w i t h the c e n t r a l r o l e of serum choles-513 t e r o l , i s the "Fat C e l l Syndrome". This theory i s based on an overabundance of c h o l e s t e r o l i n the a r t e r i a l c e l l s , l e a d i n g to the c e l l s i n a b i l i t y to cope w i t h i t , and subsequent b l o a t i n g , b u r s t i n g and death. The abnormally high i n t r a c e l l u l a r c h o l e s t e r o l r e s u l t s from an imbalance between low density l i p o p r o t e i n choles-t e r o l (LDL-C) and high density l i p o p r o t e i n c h o l e s t e r o l (HDL-C). The l a t t e r not only blocks the uptake of the former by c e l l s , - 16 -but a l s o removes c h o l e s t e r o l from the blood and body. I f the LDL/HDL r a t i o i s such that a net i n f l u x of c h o l e s t e r o l i n t o c e l l s r e s u l t s , then a r t e r i a l i n j u r y ensues and a t h e r o s c l e r o s i s begins. 3 87 Another p r i n c i p a l theory i s "Response-to-injury" wherein a t h e r o s c l e r o s i s s t a r t s at the s i t e of i n t i m a l i n j u r y and develops at that s i t e by p l a t e l e t aggregation, c l o t t i n g and subsequent c l o t o r g a n i z a t i o n , i n c l u d i n g the i n c o r p o r a t i o n of c h o l e s t e r o l . 445 In keeping w i t h t h i s theory, Stebheas f e l t t h a t such i n t i m a l i n j u r y was caused by dynamic s t r e s s . His theory i s supported by 164 the review of Glagov , who a l s o noted the non-uniform d i s t r i -b u t i o n of a t h e r o s c l e r o s i s i n human a r t e r i e s . Glagov f e l t t h a t s t r e s s e s such as increased blood pressure, h e a r t . r a t e and/or abnormal heart f u n c t i o n were probably the e t i o l o g i c f a c t o r s i n the i n i t i a l v e s s e l i n j u r y . The coronary a r t e r i e s were f e l t to be p a r t i c u l a r l y s u s c e p t i b l e to such s t r e s s e s due to t h e i r unique s t r u c t u r e and blood supply. Another t h e o r e t i c a l i n j u r i o u s f a c t o r , adding yet again to the ubiquitous nature of v i r u s e s i n medicine, i s a v i r u s . G.C. Burch 65 ' po s t u l a t e d that v i r a l i n f e c t i o n s , e s p e c i a l l y w i t h Coxsackie v i r u s , by damaging the l i n i n g of the a r t e r i e s during childhood could lead to a t h e r o s c l e r o s i s i n l a t e r l i f e . P.R. B u r c h ^ , however, f e e l s t h a t there i s evidence which shows tha t the i n i t i a l l e s i o n i s caused by the emergence of a "forbidden clone" of the body's defence c e l l s l e a d i n g t o an autoimmune response (where the body attacks i t s e l f , i n t h i s case the intima) i n g e n e t i c a l l y - 17 -predisposed people. The genes f o r the autoaggressive i n i t i a t i o n and subsequent development of CHD are f e l t t o be independent. 4. The M u l t i p l e Risk Factor Hypothesis A primary i n j u r y to the a r t e r i a l i n t i m a appears to be the 30 8 sine qua non f o r the development of CHD, whatever the i n i t i a t o r 3 87 The "response to i n j u r y hypothesis" , j u s t discussed, whereby the a t h e r o s c l e r o t i c plaque i s deposited at the s i t e of i n j u r y seems the most popular model f o r the development of CHD. As w i t h the i n i t i a t i n g event, i t seems l o g i c a l t h a t f u r t h e r develop-ment should i n v o l v e s u s c e p t i b i l i t y based on genetic p r e d i s p o s i -2 38 t i o n . In studying the epidemiology of CHD, i n v e s t i g a t o r s have reported numerous a s s o c i a t i o n s between i n d i v i d u a l h a b i t s and personal t r a i t s , and the existence or development of the disease, i n a fashion s i m i l a r to t h a t already discussed i n Breslow and cohorts' work on general m o r t a l i t y and l i f e s t y l e (p.10). The v a r i a b l e s so a s s o c i a t e d became known as r i s k f a c t o r s and, thus, 49 the " m u l t i p l e r i s k f a c t o r hypothesis" of the pathogenesis of CHD was born. E p i d e m i o l o g i c a l s t u d i e s have shown th a t CHD i s by and large 443 443 a disease of economically developed c o u n t r i e s . Stamler noted that as n a t i o n a l income r i s e s so does the incidence of smoking, sedentariness and d i e t s high i n c a l o r i e s , s a turated f a t s and c h o l e s t e r o l , l e a d i n g t o "diseases of l i f e s t y l e " , of which CHD i s the major one. S i m i l a r l y , Dock"*""^  s t a t e s a l l i t e -- 18 -r a t i v e l y t h a t CHD i s a disease caused by " s t u f f i n g , , s i t t i n g , smoking and s i p p i n g " . These r i s k f a c t o r s are personal h a b i t s . E p i d e m i o l o g i c a l s t u d i e s have a l s o i d e n t i f i e d other r i s k f a c t o r s which are e s s e n t i a l l y i n d i v i d u a l t r a i t s , although many of them are the end products of r e l a t e d h a b i t s . Such r i s k f a c t o r s can be morphological (e.g. body composition), hematological (blood c o n s t i t u e n t s ) , p h y s i o l o g i c a l (e.g. c a r d i o r e s p i r a t o r y f i t n e s s ) , p a t h o l o g i c a l (e.g. high blood pressure, o b e s i t y , diabetes m e l l i t u s ) , b e h a v i o r a l (e.g. coronary-prone or Type A b e h a v i o r ) , p s y c h o l o g i c a l (e.g. s t r e s s ) , s o c i a l (e.g. socio-economic s t a t u s ) , genetic (e.g. sex, race) or temporal (age) i n nature. 43 7 Stamler has defined r i s k f a c t o r s as "those h a b i t s , t r a i t s , and abnormalities a s s o c i a t e d with a s i z e a b l e (e.g. 100% or more) increase i n s u s c e p t i b i l i t y to coronary heart disease". Based on t h i s d e f i n i t i o n , he concluded that a l l of the e n t r i e s i n Table 2.1 marked w i t h the s u p e r s c r i p t 1 q u a l i f i e d as r i s k f a c t o r s . Super-s c r i p t s have a l s o been used here t o i d e n t i f y e n t r i e s considered bona f i d e r i s k f a c t o r s i n major reviews done by prominent authors (Borhani, 2; C a s t e l l i , 3) and o r g a n i z a t i o n s (the American Heart A s s o c i a t i o n , 4; and the J o i n t Working Party of the Royal College of P h y s i c i a n s of London and the B r i t i s h Cardiac S o c i e t y , 5). Other, unmarked e n t r i e s have been proposed as r i s k f a c t o r s by other researchers w i t h references as i n d i c a t e d . The annotation, "M" r e f e r s t o whether the f a c t o r i s considered a major r i s k f a c t o r , and the numeral to the number of references so r e f e r r i n g . Table 2.1 Risk Factors f o r Coronary Heart Disease The r i s k f a c t o r s f o r coronary heart disease reported i n the l i t e r a t u r e . The s u p e r s c r i p t s f o r each f a c t o r denote t h e i r acceptance as a r i s k f a c t o r i n the f i v e major reviews as f o l l o w s : 1, S t a m l e r ^ 7 ; 2, B o r h a n i ^ ; 3, C a s t e l l i ^ ; 4, The American Heart A s s o c i a t i o n 1 0 ; and 5, The J o i n t Working Party of the Royal College of Physicians of London and the B r i t i s h Cardiac S o c i e t y ^ ^ ^ . The second column l i s t s other supporting references f o r each f a c t o r . The t h i r d column i n d i c a t e s whether the f a c t o r i s considered major (M) w i t h the numeral i n d i c a t i n g the number of references considering i t major. Category 1. Fundamental Biology 2. Psycho-S o c i a l 3. Environmen-t a l 4. L i f e s t y l e Factor 5. P h y s i o l o -g i c a l a) b) c) d) a) b) c) a) b) c) d) e) 1-5 Age1" 5 Male Sex Race Family H i s t o r y 1-5 Socioeconomic Status Mental S t r e s s l - 5 Type A P e r s o n a l i t y ' a) Hard Water b) A l t i t u d e 4,5 Smoking A l c o h o l D i e t : i ) 1-5 Saturated Fat 1,3,4,5 i i ) F i b r e 1-5 P h y s i c a l A c t i v i t y B i r t h C o n t r o l P i l l s a) High Blood Pressure i ) S y s t o l i c i i ) D i a s t o l i c , b) Resting Heart Rate c) V i t a l C a p a c i t y l / 2 4,5 1-5 Other References 55,96,311,364 73,96,285 73,2 85,333,3 6 4,3 85,431,436 385 311,364,436 73,285,385 14,15,96 336 55,73,96,220,2 36,2 85,2 86,298,311 73,246,436 332 73,9 6,2 85,2 86,333,36 4,436,478 49,73,96,220,2 36,2 85,298,333,431, 436 ,458 55,100,286,311,355,364 100 ,311,3 6 4,365,385 ,3 86 311,478 100,436 Annotation 1 M 1 M 1 M 6 M 1 M 5 M 1 M 2 M Table 2.1 Risk Factors f o r Coronary Heart Category Factor 1-5 6. Hematologi- a) Serum L i p i d s : c a l i ) T o t a l Serum C h o l e s t e r o l (TSC) i i ) LDL-C i i i ) HDL-C iv ) T r i g l y c e r i d e s v) HDL/TSC Ratio-j^ 2 b) Serum U r i c A c i d ' ^ c) F a s t i n g Blood Sugar d) Abnormal Glucose ^ 2 Tolerance ' e) Hemoglobin/^ Hematocrit f) F i b r i n o l y s i s 7. Body Compo- a) Height^_^ s i t i o n b) Weight 2 c) Somatotype d) O b e s i t y l - 5 8. Medical a) Diabetes m e l l i t u s Disorders b) Hypothyroidisml>2 c) Renal D i s e a s e l d) Goutl 3 e) EKG Abnormalities ' 1-5 Disease (cont'd) Other References Annotation 55,73,96,100,220,236,246,298, 7 M 311,36 4,365,3 85,431,436,45 8,478 321,385,431 285, 321,431 96,364,385,431,478 236,436 364,431,436 236,311 55,311 114,458 286,333 55,73,2 36,2 86,311,33 3,365,431 236,364,436,437 73,96,285,311,333,385 1 M 437 55,100,365 - 21 -C. RISK FACTORS This s e c t i o n w i l l d i s c u s s the r i s k f a c t o r s i n d e t a i l . Concentration w i l l be given to the a s s o c i a t i o n with CHD, but reference w i l l be made to other d i s o r d e r s , and h e a l t h and m o r t a l i t y g e n e r a l l y , where appr o p r i a t e . The s e c t i o n w i l l deal with r i s k f a c t o r s under the f o l l o w i n g groupings: 1. Fundamental B i o l o g i c a l F a c t o r s , 2. P s y c h o s o c i a l , 3. Environmental, 4. L i f e -s t y l e , 5. Body Composition, 6. P h y s i o l o g i c a l , 7. Hematological and 8. Medical Disorders. 1. Fundamental B i o l o g i c a l Factors 1.1 Age 2 38 365 Age i s a powerful r i s k f a c t o r f o r CHD ' and, indeed, f o r l o s s of he a l t h g e n e r a l l y . Ageing in c l u d e s a gradual process 307 342 of degeneration i n a v a r i e t y of b o d i l y f u n c t i o n s ' , the extreme forms of which can be seen as disease. Thus, many diseases a s s o c i a t e d with ageing have come to be known as "dege-n e r a t i v e d i s o r d e r s " . However, much of the e f f e c t of age i s undoubtedly due to the amount of time over which c e r t a i n agents have a chance to ac t . Between the i n i t i a t i o n of a d i s o r d e r and i t s c l i n i c a l m a n i f e s t a t i o n i s the s o - c a l l e d l a t e n t p e r i o d . The longer one l i v e s the more l i k e l y w i l l i t be', f o r example, that atheroma w i l l develop to such a degree t h a t adequate blood supply to s p e c i f i c organs w i l l be compromised (assuming i n i t i a -t i o n and s u s c e p t i b i l i t y ) . - 22 -Moreover, the longer one l i v e s the greater the chance of exposure to a wider v a r i e t y of i n i t i a t i n g and p r e c i p i t a t i n g agents. For example, c e r t a i n CHD r i s k f a c t o r s are known t o increase w i t h age: serum c h o l e s t e r o l 7 ' 3 4 ' 7 0 ' 1 6 0 ' 2 1 0 ' 3 6 5 ' 4 1 7 ' 437,471 , , ., . . 70 . . , ., 7,210,417,471 , low d e n s i t y l i p o p r o t e i n s , t r i g l y c e r i d e s , , . . 160,288,437 , 165,179 . , . 327, 365 o b e s i t y , blood pressure ' (both s y s t o l i c 7 32 7 and d i a s t o l i c ' , although the P o o l i n g P r o j e c t d i d not observe 444 such an e f f e c t on the l a t t e r ) and f a s t i n g blood sugar . Other r i s k f a c t o r s are a l s o adversely modified w i t h age, f o r example 83437 179 decreasing p h y s i c a l a c t i v i t y ' , c a r d i o r e s p i r a t o r y f i t n e s s ' 288,307,485 , , _ 288 „. . , , - . and lung f u n c t i o n . S t i l l other f a c t o r s are 12 8 improved w i t h age: increased high density l i p o p r o t e i n s (HDL) ' 417 ' , , , . . . 307 , , n 296 and reduced heart rate . Mann and colleagues even pos-t u l a t e that the coronary ve s s e l s enlarge to compensate f o r i n c r e a s i n g a t h e r o s c l e r o s i s w i t h age. Moreover, the potency of 312 r i s k f a c t o r s v a r i e s w i t h age. As Medalie and coworkers p o i n t out, the CHD p r e d i c t i v e c a p a c i t y of c h o l e s t e r o l , blood pressure, smoking and diabetes m e l l i t u s decrease w i t h age while that of HDL-C increases w i t h age. Although the b a s i c e f f e c t s of ageing on CHD and other d i s o r d e r s are assumed to be u n a l t e r a b l e , there i s no question that some of the e f f e c t s of ageing taken as normal sequelae i n our s o c i e t y can be staved o f f by appropriate h e a l t h measures. For example, w i t h continued r e g u l a r p h y s i c a l a c t i v i t y the l o s s of c a r d i o r e s p i r a t o r y f i t n e s s w i t h age normally seen i n western 485 c u l t u r e s i s markedly reduced . The same could be s a i d - 2 3 -concerning o b e s i t y . Other r i s k f a c t o r s and di s o r d e r s can a l s o be staved o f f when appropriate h e a l t h p r a c t i c e s are followed throughout l i f e . 1 . 2 Sex and o r a l Contraceptives 2 38 Another very powerful r i s k f a c t o r f o r CHD i s sex Men are much more s u s c e p t i b l e to CHD and almost a l l non-gender-r e l a t e d d i s o r d e r s and, as a r e s u l t , s u f f e r from a higher 2 68 o v e r a l l death r a t e a t a l l ages than women . As a r e s u l t , Canadian men, e s p e c i a l l y the young and l e s s e r educated ones., 5 0 5 are considered a h i g h - r i s k group . P a r t of the higher rates f o r diseases, e s p e c i a l l y CHD, could be accounted f o r by the higher l e v e l s of r i s k f a c t o r s i n men; r e l a t i v e to women, men v. o - j ^ • ^ • v . w - i J 1 6 5 , 3 4 9 , 3 5 0 , have been reported as having higher blood pressures ' 5 0 5 . . , • T i , 7 0 , 3 4 9 , 3 5 0 , , , , c , serum t r i g l y c e r i d e l e v e l s and lower l e v e l s of 70 4 1 7 HDL-C ' . Men a l s o tend to have a greater aggregation of 349 350 r i s k f a c t o r s , w i t h higher l e v e l s at a younger age ' . , the 365 l a t t e r c h a r a c t e r i s t i c being c r i t i c a l f o r r i s k f a c t o r potency In a d d i t i o n , c e r t a i n r i s k f a c t o r s seem to be much more potent i n males than i n females. For example, B r a y ^ has observed t h a t obesity i n males i s a s s o c i a t e d w i t h a much higher m o r t a l i t y than comparable l e v e l s i n females. O v e r a l l , the CHD p r e d i c t a b i l i t y 2 3 5 4 3 1 of r i s k f a c t o r s v a r i e s between males and females ' The female advantage i s l a r g e l y l o s t w i t h menopause. In a d d i t i o n , whatever p r o t e c t s the premenopausal female from CHD (and other disorders) can be o f f s e t by co n d i t i o n s such as - 24 -diabetes m e l l i t u s ' L , J . On the other hand, men seem to lose t h e i r 73 sex disadvantage w i t h advancing years; according to C a s t e l l maleness i s a potent r i s k f a c t o r only i n men l e s s than 50. The above c h a r a c t e r i s t i c s of gender as a r i s k f a c t o r could help to 2 35 e x p l a i n the r a t h e r unexpected r e s u l t s of J u u s t i l a . In h i s f i e l d survey of r u r a l F inns, 40 to 59 years of age, J u u s t i l a found t h a t women had a greater incidence of IHD than men, but the disease was a l s o much l e s s severe. The p r o t e c t i v e f a c t o r (or f a c t o r s ) i n women remains a mystery. Female metabolism, predominantly a f f e c t e d by t h e i r hormonal c h a r a c t e r i s t i c s , seems of primary importance. The f a c t that the female advantage i s l o s t w i t h the presence of a severe metabolic abnormality such as diabetes mellitus"'"^ would support such a statement. In a d d i t i o n , when hormonal balance i s di s r u p t e d by e x t e r n a l l y administered hormones i n the form of b i r t h c o n t r o l p i l l s , the r i s k of CHD i n c r e a s e s ^ , e s p e c i a l l y 389 10 a f t e r age 40 , and i n the presence of c i g a r e t t e smoking . I t i s noteworthy that o r a l c o n t r a c e p t i v e s are ass o c i a t e d with abnor-m a l i t i e s of l i p i d and carbohydrate metabolism l e a d i n g to elevated 10 417 417 t r i g l y c e r i d e s ' , c h o l e s t e r o l ( e s p e c i a l l y LDL-C) and reduced HDL-C4"''7, as w e l l as increased r i s k of diabetes m e l l i t u s " ^ Oral contraceptives are as s o c i a t e d with other abnormalities such as increased blood pressure and enhanced blood c l o t t i n g " ^ . A l l of the attendant abnormalities could w e l l play a r o l e i n deter-mining the a s s o c i a t i o n of o r a l c o n t r a c e p t i v e s w i t h blood v e s s e l pathology"^. The most important e f f e c t of the metabolic a l t e r a -- 25 -t i o n s may w e l l be the dramatic decrease i n the HDL/LDL r a t i o , which i s one of the most e x c i t i n g and promising f a c t o r s i n CHD at present (see p.163). 1.3 Race D i f f e r e n t races s u f f e r from diseases at d i f f e r e n t r a t e s , 43 7 CHD being no exception . Some evidence suggests that t h i s 437 411 e f f e c t i s p r i m a r i l y due to environment and l i f e s t y l e . For example, blacks are known t o have a decreased incidence of CHD. 72 Cassel found t h a t blacks had one-half the incidence of CHD seen i n whites i n the Evans County, Georgia Study. However, when he compared black and white sharecroppers, groups having b a s i c a l l y the same socioeconomic status and a c t i v i t y l e v e l s , he found no d i f f e r e n c e i n the in c i d e n c e . On the other hand, some studies have suggested a r a c i a l s u s c e p t i b i l i t y or r e s i s t a n c e . 2 36 Kagan and ass o c i a t e s , i n the Honolulu Heart Study, found t h a t Japanese Americans had one-half the incidence o f , and much decreased m o r t a l i t y from CHD when compared t o the Framingham 49 4 pop u l a t i o n . Wyndham reported t h a t South A f r i c a n s had around twice as many CHD deaths as Americans. None of these stud i e s 2 46 i s c o n c l u s i v e . However, Keys' Seven Country Study showed t h a t , with the p o s s i b l e exception of c h o l e s t e r o l , r i s k f a c t o r s were i n c o n s i s t e n t i n p r e d i c t i v e power from n a t i o n to n a t i o n . The most l o g i c a l conclusion from a l l of the above i s t h a t race as a f a c t o r i s a combination of genetic s u s c e p t i b i l i t y and the e f f e c t s of environment and c u l t u r e . - 26 -1.4 Family H i s t o r y 49 191 There i s evidence f o r a polygenic i n h e r i t a n c e of CHD ' , but i t i s exceedingly d i f f i c u l t to separate the e f f e c t s of h e r e d i t y and f a m i l i a l environment. In t h e i r study c o r r e l a t i n g r i s k f a c t o r s w i t h angiographically-demonstrated CHD, Sodhi and 431 coworkers found t h a t f a m i l y h i s t o r y was o v e r a l l the second most potent f a c t o r , and i n men the most potent. The r e s u l t s of 74 the Framingham Study , however, showed that f a m i l y h i s t o r y was a weak r i s k f a c t o r , even when i n i t s most potent form where the male's f a t h e r died of CHD a t l e s s than 60 years of age. More-478 over, Wilhelmsen and T i b b l i n found t h a t i t was not a s i g n i -f i c a n t f a c t o r i n t h e i r Scandinavian "Men Born i n 1913 Study". 191 Harvald i n h i s review of the genetic f a c t o r s i n CHD f e l t t h a t the evidence showed t h a t genetic i n f l u e n c e was r a t h e r l i m i t e d but was more important i n women than men because the former have a heavier genetic p r e d i s p o s i t i o n . He concluded, however, that CHD was the end r e s u l t of an a d d i t i v e e f f e c t of s e v e r a l genetic and environmental f a c t o r s , a conclusion supported by the American Heart A s s o c i a t i o n i n i t s r e v i e w 1 ^ . These genetic f a c t o r s may operate on CHD through r i s k f a c t o r s such as h y p e r l i p i d e m i a s , 96 hypertension and diabetes m e l l i t u s as w e l l as d i r e c t l y . 5 30 Hamby has r e c e n t l y reviewed the h e r e d i t a r y aspects of CHD. - 27 -2 . Psycho'social Factors 2.1 Socioeconomic Status I t i s an i n t e r n a t i o n a l phenomenon that those of low s o c i o -452 economic status s u f f e r from increased morbidity and m o r t a l i t y S e l t z e r and J a b l o n 4 0 0 reviewed the l i t e r a t u r e on socioeconomic status and general m o r t a l i t y and found evidence that lower edu-c a t i o n a l l e v e l and socioeconomic status were a s s o c i a t e d w i t h high-er m o r t a l i t y . They concluded t h a t the s o - c a l l e d " s o c i a l l y favoured" and the "economically advantaged" have decreased 477 general m o r t a l i t y . Wiley and Comacho i n t h e i r Almeda County Study found that low socioeconomic st a t u s (defined by education, income and occupational status) was as s o c i a t e d w i t h increased m o r b i d i t y , m o r t a l i t y and d i s a b i l i t y . The r e s u l t s of the 19 81 505 Canada Health Survey underscore these a s s o c i a t i o n s . 2 X6 Socioeconomic st a t u s i s al s o a r i s k f a c t o r f o r CHD 407 Shekelle and colleagues found that lower e d u c a t i o n a l groups had a higher incidence of CHD, f i n d i n g s s i m i l a r to those of 3 85 Rosenman and coworkers i n the Western C o l l a b o r a t i v e Group Study. N e i t h e r group found any a s s o c i a t i o n w i t h income. However, 2 99 Marmot and cohorts , i n a study of B r i t i s h c i v i l s ervants, found that lower grades had 3.6 times the CHD m o r t a l i t y of the highest grades (administrators) when c o n t r o l l e d f o r other r i s k f a c t o r s , although t h e i r study d i d not separate e d u c a t i o n a l from 203 occupational s t a t u s . S i m i l a r l y , Hmckle , i n the P a c i f i c Northwest B e l l Telephone Company Health Survey, found a 30% reduction i n CHD among white c o l l a r workers compared to blue - 28 -c o l l a r workers. Socioeconomic status has an e f f e c t on CHD independent of 29 9 other r i s k f a c t o r s . However, i t a l s o acts through other r i s k f a c t o r s which could w e l l r e f l e c t the more hazardous environment 452 of the poor and t h e i r l e s s adequate means of coping . Skinner 42 8 and colleagues found that the higher s o c i a l c l a s s e s were heav i e r , f a t t e r and t a l l e r , smoked l e s s and had lower blood pressures and r e s t i n g heart rates than the lower c l a s s e s . Holme and coworkers , i n t h e i r Oslo Study, reported that those w i t h higher socioeconomic status (represented by a combination of educ a t i o n a l and income l e v e l ) were heavier and t a l l e r , had lower weight f o r he i g h t , smoked l e s s , had lower c h o l e s t e r o l and t r i g l y -c e r i d e l e v e l s and blood pressures, had more p h y s i c a l a c t i v i t y at l e i s u r e and lower o v e r a l l r i s k scores than those w i t h lower 20 3 s t a t u s . Hmckle a l s o found t h a t white c o l l a r workers were t a l l e r and slimmer, had lower c h o l e s t e r o l l e v e l s and blood pressures, smoked l e s s and were under l e s s perceived home -,and job - r e l a t e d s t r e s s than blue c o l l a r workers. S i m i l a r l y , Marmot 29 9 and colleagues found that higher grade c i v i l servants were t a l l e r and l i g h t e r f o r h e i g h t , had lower blood pressures and blood sugar, smoked l e s s and were more a c t i v e i n l e i s u r e time than lower grade employees. 29 9 The Marmot group's r e s u l t s a l s o showed that the lower grades had lower c h o l e s t e r o l values. This f i n d i n g i s at odds 203 210 wit h the f i n d i n g s of Hi n c k l e , Hoover and colleagues and - 29 -2 06 Holme and associates , where higher values of c h o l e s t e r o l (and t r i g l y c e r i d e s ) were found i n those w i t h lower e d u c a t i o n a l l e v e l s and occupational s t a t u s . A l s o i n c o n f l i c t w i t h the l a t t e r groups 15 7 of authors i s the report by Garrt and a s s o c i a t e s t h a t as s o c i o -economic status r i s e s , so does the' l e v e l of o b e s i t y i n men, w i t h 157 the opposite r e l a t i o n s h i p i n women . This f i n d i n g i s i n keeping 42 8 with the report of Skinner and associates however. The above r e s u l t s g e n e r a l l y support the observations of 477 Wiley and Comacho t h a t those w i t h higher incomes and educa-t i o n a l l e v e l s have more h e a l t h f u l l i f e s t y l e s on the whole. More-over, t h e i r observations may w e l l r e f l e c t the f a c t that the h e a l t h f u l l i f e s t y l e changes over the l a s t ten years have l a r g e l y occurred i n the higher educated segment of the p o p u l a t i o n 1 0 and serve to e x p l a i n the apparent turnaround t h a t has occurred i n the 20 6 a s s o c i a t i o n of socioeconomic st a t u s and CHD . Such a turnaround 224 225 i s i n keeping w i t h Jenkins' ' theory t h a t during u r b a n i -z a t i o n the upper c l a s s e s are at increased r i s k e a r l i e r on, the lower c l a s s e s toward the end. This theory a l s o helps e x p l a i n 72 the apparently incongruous r e s u l t s reported by Cassel i n the Evans County Study where higher c l a s s whites had twice the CHD incidence of lower c l a s s whites. I t deserves s t r e s s i n g that socioeconomic s t a t u s i s a poorly s t u d i e d r i s k f a c t o r , since the lowest socioeconomic groups are not i n c l u d e d i n most st u d i e s and do not u s u a l l y volunteer i n any 472 case . These lowest socioeconomic groups a l s o u s u a l l y l i v e i n - 30 -very hazardous environment, use medical care f a c i l i t i e s inade-452 • quately and are subjected to a wide v a r i e t y of s o c i a l s t r e s s e s , the e f f e c t s of which are j u s t now being appreciated. 2.2 Stress Stress i s a d i f f i c u l t concept to d e f i n e , and thus very 29 8 d i f f i c u l t to study i n r e l a t i o n to disease. Marmot i n h i s review of the epidemiology of CHD f e l t t h a t the only s t r e s s -r e l a t e d phenomena c o r r e l a t e d w i t h CHD were s o c i a l m o b i l i t y , s t r e s s f u l l i f e events and l e v e l of emotional support. Shekelle 40 7 and colleagues took a broader perspe c t i v e and f e l t t hat many s o c i a l i n c o n g r u i t i e s were l i n k e d to the incidence of CHD, w i t h the incidence being i n p r o p o r t i o n to the number of such inco n -g r u i t i e s . Other f a c t o r s r e l a t e d to s t r e s s that have been connec-49 4 37 ted w i t h CHD are: s o c i a l and geographical m o b i l i t y ' , 4 37 u r b a n i z a t i o n , r e l a t i o n s h i p s w i t h superiors at work,and wife 311 at home , suppressed h o s t i l i t y , work overload and frequent job ' 19 4 ^ . . . .... changes , time consciousness, excessive competitiveness, preoccupation w i t h deadlines, chronic impatience, t a k i n g one's 74 work home and polyphasia (doing more than one t h i n g at a time) In an i n t e r e s t i n g study i n 40 to 59 year o l d Danish men, Gyntel-18 3 berg showed a c o r r e l a t i o n between the use of s l e e p i n g p i l l s and t r a n q u i l i z e r s and CHD. Several reviews on t h i s t o p i c have been done. Wi l l i a m s and 481 Gentry concluded from t h e i r review that a n x i e t y and depression were the two p r i n c i p a l p s y c h o l o g i c a l f a c t o r s which not only were - 31 -asso c i a t e d w i t h an increased r i s k of CHD but were al s o common t r i g g e r s of acute events, such as angina and heart attack. 222—225 Jenkins , i n a s e r i e s of reviews, f e l t t hat c o n s i s t e n t evidence was a v a i l a b l e r e l a t i n g a n x i e t y , depression, sleep d i s -turbance and s o m a t i c i z i n g (manifesting p s y c h o l o g i c a l problems as p h y s i c a l complaints) to CHD, s p e c i f i c a l l y angina p e c t o r i s . He a l s o f e l t t hat the evidence was good r e l a t i n g obsessiveness and o v e r c o n t r o l to heart attack. Evidence was deemed f a i r l y good fo r l i f e problems and d i s s a t i s f a c t i o n , but i n c o n c l u s i v e f o r the 225 r e s t of the f a c t o r s l x s t e d above. Jenkins f e l t t h a t the common pathway f o r the e f f e c t s of a l l p s y c h o l o g i c a l f a c t o r s -i n c l u d i n g Type A behavior which w i l l be reviewed next - was the neuroendocrine svstem. Mental s t r e s s , a c t i n g through the neuroendocrine system, can cause a wide v a r i e t y of nervous and hormonal responses i n the c a r d i o v a s c u l a r system, as w e l l as many other b o d i l y systems, r e s u l t i n g i n an even wider v a r i e t y of biochemical, p h y s i o l o g i c a l , metabolic and be h a v i o r a l responses. Stress can thus p r e c i p i -144 t a t e acute events such as angina, arrythmias and heart attack ' 458 However, chronic s t r e s s could well- c o n t r i b u t e to the pathogenesis of CHD independently'., or through i t s m o d i f i c a t i o n of known r i s k f a c t o r s . For example, s t r e s s can r e s u l t i n i n c r e a -ses i n blood pressure, serum c h o l e s t e r o l and t r i g l y c e r i d e s and the tendency of the blood to c l o t , (through enhanced c o a g u l a b i l i t y 144 and p l a t e l e t a g g r e g a b i l i t y ) . Stress may a l s o c o n t r i b u t e to CHD and other d i s o r d e r s i n ways not yet appreciated. - 32 -2.3 Coronary-Prone Behavior Coronary-prone, or Type A, behavior i s c h a r a c t e r i z e d by extreme competitiveness, d r i v e and time urgency"^ as w e l l as 150 451 repressed h o s t i l i t y ' . This behavior i s a form of constant s t r e s s but w i l l be considered separately due to i t s r e c o g n i t i o n as a d i s c r e t e and r e a d i l y i d e n t i f i a b l e r i s k f a c t o r " ^ ' ^ ' 4 3 7 . Type A behavior can be e a s i l y assessed through the Jenkins A c t i v i t y Survey, a s e l f - a d m i n i s t e r e d , m u l t i p l e choice t e s t deve-22 6 loped by Jenkins and colleagues . This method produces a JAS score, which has"been widely used i n studying Type A beha-v i o r i n r e l a t i o n to CHD. People w i t h Type A p e r s o n a l i t i e s do show a v a r i e t y of unique bi o c h e m i c a l , metabolic and p h y s i o l o g i c a l t r a i t s i n a d d i t i o n to the p e r s o n a l i t y t r a i t s . Type As excrete more a d r e n a l i n (epine-phrine)"'"^"'" and ACTH ( a d r e n o - c o r t i c o t r o p i c hormone) '''^  than avera-ge, but have a decreased response to the l a t t e r ; thus t h e i r C o r t i s o l l e v e l s are normal. They are a l s o characterized by a 151 hyperinsulinemic response to a glucose load , but no abnorma-l i t i e s i n blood glucose have been noticed"'"^"''' ^  ^ . They do have decreased blood l e v e l s of growth hormone but normal t h y r o i d 150 f u n c t i o n . Friedman found the abnormalities of serum l i p i d s q u i t e s t r i k i n g . His s t u d i e s have shown that almost a l l people with t r i g l y c e r i d e s i n excess of 100 (mg per 100 ml) and those w i t h t o t a l c h o l e s t e r o l s greater than 250,. but l e s s than 400 , had Type A p e r s o n a l i t i e s . As was a l l u d e d to wi t h respect to s t r e s s , most of these e f f e c t s are probably the r e s u l t s of - 33 -a c t i v i t y of the neuroendocrine system which has been i m p l i c a t e d 22 5 481 i n the connection between Type A and CHD ' Type A behavior, l i k e s t r e s s , has been c r e d i t e d w i t h both 194 408 481 p r e c i p i t a t i n g acute CHD events ' ' and c o n t r i b u t i n g t o 194 225 255 458 the pathogenesis of CHD ' ' ' . Type A people have been 144 226 estimated to be at double to quadruple the r i s k of deve-222—225 l o p i n g CHD compared to Type B. Jenkins , i n h i s review s e r i e s on the psychosomatic aspects of CHD, f e l t t h a t the e v i -dence was convincing i n connecting Type A not only to the prevalence of CHD and r i s k of recurrence of heart a t t a c k , but a l s o to the degree of a t h e r o s c l e r o s i s . A key element i n the e f f e c t s of Type A (and s t r e s s ) may be the production of nonadre-150 n a l i n (norepinephrine) which Friedman says i s p o t e n t i a l l y artery-damaging and thrombogenic. Type A behavior has been shown to be a r i s k f a c t o r inde-pendent of other CHD r i s k f a c t o r s 1 9 4 ' 2 5 5 , 3 8 5 , 4 5 8 . However, i t 385 i s a l s o a s s o c i a t e d i n t e r a c t i v e l y w i t h other r i s k f a c t o r s , . Type A i s a s s o c i a t e d w i t h e l e v a t e d serum l i p i d s , both choles--.150,151,385,408 , . . , . , 151,385 , • , t e r o l and t r i g l y c e r i d e s ' and with increased , . 385,40 8,481 7V,,, , . ,. , , • >_ ^ smoking ' . Although some studi e s have shown i t t o be r e l a t e d to el e v a t e d blood pressure, both s y s t o l i c and d i a s t o l i c 385,481 . _ _ . . .. 408 ., , others have found no such a s s o c i a t i o n . S i m i l a r l y , 481 a s s o c i a t i o n w i t h heart r a t e has been reported as both p o s i t i v e and negative ( i n m a l e s ) 4 ^ 8 . I t has been a s s o c i a t e d w i t h enhanced 150 blood c l o t t i n g but no a s s o c i a t i o n has been found with serum - 34 -u r i c a c i d or blood sugar a b n o r m a l i t i e s 1 " ^ 1 ' 4 0 ^  or with body w e i g h t 4 0 ^ . Shekelle and c o l l e a g u e s 4 0 ^ found a p o s i t i v e c o r r e l a -t i o n w i t h socioeconomic s t a t u s and, indeed, Type A was found t o 194 be an independent r i s k f a c t o r i n the Framingham Study only i n white c o l l a r workers. I t seems to be an i n t e r n a t i o n a l r i s k 194 408 f a c t o r which a f f e c t s both sexes ' but i s age-dependent. Shekelle and c o l l e a g u e s 4 0 ^ found a negative a s s o c i a t i o n with 194 age. Haynes and coworkers i n the Framingham Study found t h a t , i n the 55 to 64 age group, Type A was twice more potent a r i s k f a c t o r than i n the 45 to 5 4 group. The r e s u l t s of therapy f o r Type A p e r s o n a l i t i e s have been 481 encouraging . Along with marked s u b j e c t i v e improvement, there have been reductions i n blood pressure, and serum choles-t e r o l and t r i g l y c e r i d e l e v e l s . These r e s u l t s would support the 55 p r e d i c t i o n made from the Western C o l l a b o r a t i v e Group Study t h a t , had the r i s k of Type A been removed, the r i s k of CHD would have been reduced by 31%. L i t t l e wonder, then, t h a t Jenkins ~ f e e l s t h a t Type A behavior i s a major r i s k f a c t o r . - 35 -3. Environmental Factors 3.1 Hard Water Hard water seems to be a p r o t e c t i v e f a c t o r against the development of CHD 1 0' 1 4. T h i n d 4 " ^ f e l t t hat the mechanism of a c t i o n was through tr a c e metals i n the water a c t i n g t o lower serum l i p i d s . One such metal i s chromium. Chromium i s i n v o l v e d i n c e l l u l a r receptor's f o r i n s u l i n and, when d e f i c i e n t , c a u s e s an 221 i n s u l i n - r e s i s t a n t s t a t e and elevated i n s u l i n l e v e l s . Anderson 15 and colleagues f e l t t h a t magnesium may w e l l be the f a c t o r i n the water, p o s s i b l y l e a d i n g to reduced s u s c e p t i b i l i t y of the heart to arrythmias or general heart muscle pathology. Comstock 8 5 and coworkers , i n a recent a r t i c l e , hedged t h e i r hypothesis by d e c l a r i n g t h a t the odds on a water f a c t o r accounting f o r the d i f f e r e n c e i n CHD deaths from one area to another were not great. The e l u s i v e water f a c t o r remains to be found. 3.2 A l t i t u d e 336 Mortimer and a s s o c i a t e s reported that men r e s i d i n g at high a l t i t u d e s had reduced m o r t a l i t y from CHD. They a l s o noted that such people had r e l a t i v e l y lower blood pressures and increased coronary v a s c u l a r i t y . T h e i r main hypothesis f o r the reduction i n CHD m o r t a l i t y was the p r o t e c t i v e e f f e c t of p h y s i c a l a c t i v i t y . They f e l t t hat the e f f e c t of r o u t i n e p h y s i c a l a c t i -v i t y at a l t i t u d e was l i k e that of strenuous e x e r c i s e at sea l e v e l , thus endowing the men w i t h the p r o t e c t i v e e f f e c t of r e g u l a r strenuous e x e r c i s e (see p. 78). -. 36 -4. L i f e s t y l e Factors 4.1 Diet D i e t i s an exceedingly important f a c t o r i n h e a l t h and, as f o r most other l i f e s t y l e f a c t o r s , balance i s the key. The e f f e c t s of undernourishment on h e a l t h are not j u s t problems of underdeveloped count r i e s i n a t e c h n o l o g i c a l age, f o r they can be seen i n the lower socioeconomic groups of most western n a t i o n s . Indeed, they can be seen i n almost any c l a s s given our penchant f o r fad d i e t s and f a s t foods. Undernourished people are more prone to a wide v a r i e t y of i l l n e s s e s , most notably i n f e c t i o u s diseases, due to impairment of t h e i r body's defence mechanisms. However, i n western s o c i e t i e s , o v e r n u t r i t i o n i s a t l e a s t as great a problem. The d i e t s of i n d u s t r i a l i z e d c o u n t r i e s are i n o r d i n a t e l y high i n c a l o r i e s g e n e r a l l y , and i n f a t , p r o t e i n , a l c o h o l , sugar and s a l t s p e c i f i c a l l y , as w e l l as too low i n f i b r e . These d i e t a r y i n d i s c r e t i o n s are "self-imposed r i s k s " f o r many 29 prominent "diseases of choice or l i f e s t y l e " . Obesity w i l l be discussed l a t e r (p.102). In t h i s s e c t i o n I w i l l s t i c k t o d i e t as i t a f f e c t s other d i s o r d e r s , p a r t i c u l a r l y CHD. a. Saturated Fat The average western d i e t contains a l o t of animal products, and thus contains a l o t of p r o t e i n , s a t u r a t e d f a t and c h o l e s t e r o l , and too l i t t l e f i b r e and complex carbohydrates. Other than p r o t e i n , these d i e t a r y components have a l l been i m p l i -cated as r i s k f a c t o r s of CHD. Dietary saturated f a t (and 2 46 attendant serum c h o l e s t e r o l ) was the only r i s k f a c t o r i n Keys' - 37 -Seven Country Study that was c o n s i s t e n t across a l l n a t i o n s . Since the percentage of the d i e t a r y c a l o r i e s d e r i v e d from s a t u -2 46 rated f a t i s d i r e c t l y r e l a t e d to serum c h o l e s t e r o l l e v e l s , ;>. and s i n c e c h o l e s t e r o l , one of the main i n g r e d i e n t s of atheromata, i s derived from serum c h o l e s t e r o l , many authors have dogmatically h e l d t h a t saturated f a t i n the d i e t i s the key r i s k f a c t o r f o r a t h e r o s c l e r o s i s , p a r t i c u l a r l y C H D 1 0 < 9 5 > 1 1 5 ' 2 4 6 ' 4 3 7 ' 4 3 8 . Stamler 43 7 i n p a r t i c u l a r f e e l s t h a t i t i s the "key, primary, i n d i s p e n -sable e t i o l o g i c f a c t o r " , the other r i s k f a c t o r s being simply . . ,,438 ... 66,92,293, 308,445 , , co n t r i b u t o r y . Other authors ' ' e q u a l l y adamantly disagree. The stu d i e s on d i e t a r y s a t u r a t e d f a t r e s t r i c t i o n have been d i s a p p o i n t i n g and e q u i v o c a l i n a l t e r i n g CHD (p.194). Thus, the debate w i l l undoubtedly go on. I t seems, however, t h a t a reduction i n d i e t a r y s a t u r a t e d f a t , and animal products g e n e r a l l y , i s prudent - and may soon become an economic n e c e s s i t y i n any event - i f f o r no other reason that i t i s very high i n c a l o r i e s and thus c o n t r i b u t e s t o obes i t y and gout. b. Refined Carbohydrate Table sugar, or sucrose, i s consumed i n enormous amounts by western s o c i e t i e s ' ^ 5 . I t has been i n c r i m i n a t e d i n the patho-genesis of de n t a l c a r i e s and obes i t y and p o s s i b l y plays a r o l e 105 i n the development of diabetes m e l l i t u s . Although i t was 10 9 suspected as a d i r e c t r i s k f a c t o r f o r CHD , such a hypothesis 389 96 has l a r g e l y been r e f u t e d . However, Crawford maintains t h a t i t c o n t r i b u t e s t o the development of CHD through o b e s i t y . High Q 3 89'' sucrose intake i s a l s o a s s o c i a t e d w i t h high serum c h o l e s t e r o l - 38 -and t r i g l y c e r i d e " ^ 3 l e v e l s . Since i t i s a source of t r u l y "empty" c a l o r i e s (that i s , i t i s not e s s e n t i a l to the body's needs) i t could be e l i m i n a t e d from the d i e t not only without untoward p h y s i c a l repercussions, but a l s o w i t h a l o t of b e n e f i t . c. Unrefined Carbohydrates Unrefined, or complex, carbohydrates, a l s o r e f e r r e d to as st a r c h e s , are a h e a l t h f u l source of n u t r i t i o n i f taken i n moderation. S u b s t i t u t i o n of starches f o r f a t i n the d i e t has 12 l e d to lower CHD death rates and xt has been hypothesized that i t may be p r o t e c t i v e against CHD10'10~*. More starches and l e s s f a t i n the t y p i c a l North American d i e t would be h e a l t h f u l , 105 e a s i e r on the budget, and promote a greater intake of f i b r e d. F i b r e F i b r e , obtained from such foods as whole g r a i n c e r e a l s and other such sources of complex carbohydrates, i s markedly d e f i c i e n t i n the d i e t of most i n d u s t r i a l i z e d c o u n t r i e s . F i b r e not only adds bulk t o the s t o o l , thereby f a c i l i t a t i n g bowel f u n c t i o n , i t a l s o aids i n the metabolism and e x c r e t i o n of l i p i d s , b i l e and drugs. Through i t s e f f e c t on the larg e bowel, i t has a preventive e f f e c t on c o n s t i p a t i o n , hemorrhoids, d i v e r t i c u l a r disease and p o s s i b l e c o l o n i c cancer. I t has a l s o been r e c e n t l y 10 332 389 r e l a t e d to CHD ' , although t h i s e f f e c t has not been proven e. P r o t e i n Diets very high i n p r o t e i n , such as high meat d i e t s , - 39 -have a high purine content which c o n t r i b u t e s to the develop-105 ment of gout . P r o t e i n g e n e r a l l y i s not a r i s k f a c t o r f o r CHD, although there i s some evidence l i n k i n g milk p r o t e i n to 105 a t h e r o s c l e r o s i s and CHD . As w i t h a l l d i e t a r y p r a c t i c e s , d i s c r e t i o n and moderation b e f i t the consumption of p r o t e i n . The a s s o c i a t i o n s w i t h a lack of p r o t e i n are d e a l t w i t h by Davidson and associates Coffee Coffee was at one time suspected as a r i s k f a c t o r f o r 495 CHD, but t h i s hypothesis has l a r g e l y been r e f u t e d , the e f f e c t s being due t o the a s s o c i a t i o n between coffee consumption and 389 c i g a r e t t e smoking . However, c o f f e e , and other beverages high i n c a f f e i n e , can give r i s e to c a f f e i n i s m , a syndrone charac-t e r i z e d by i r r i t a b i l i t y , insomnia and other nervous symptoms. 105 I t can a l s o cause c a r d i a c arrhythmias and d i g e s t i v e problems g. Table S a l t The average North American d i e t contains 15 grams of t a b l e s a l t , or sodium c h l o r i d e , per day, although a l l that i s needed i s a mere 100 to 200 m i l l i g r a m s 1 ^ 5 . Meneely and 313 Battarbee have concluded that such a high sodium, and/or low potassium d i e t i s the c a r d i n a l cause of high blood pressure. Goldberg 1** 5, i n h i s review of hypertension, agrees but would add that the i n d i v i d u a l must be s u s c e p t i b l e , the l a t t e r presu-mably g e n e t i c a l l y determined. - 40 -148 From the per s p e c t i v e of prevention of hypertension, F r e i s has s t a t e d that a reduction i n d i e t a r y s a l t to below two grams per day would prevent the m a j o r i t y of hypertension and r e s u l t i n i t s disappearance as a major p u b l i c h e a l t h problem. Meneely 313 and Battarbee agree but add t h a t potassium, an element they f e e l i s p r o t e c t i v e against high blood pressure, should be added to the d i e t . Given that supplementary s a l t i s not needed, even 14 8 i n p h y s i c a l l y a c t i v e people i n severely hot climates , the 313 recommendations f o r a low sodium/high potassium d i e t are prudent as w e l l as l o g i c a l . h. A l c o h o l The consumption of a l c o h o l i c beverages i n i n d u s t r i a -l i z e d c o u n t r i e s i s very h i g h , w i t h a l c o h o l c o n s t i t u t i n g a s i g n i -f i c a n t p o r t i o n of the average a d u l t d a i l y c a l o r i c i n t a k e 1 0 " ' . Excessive use of a l c o h o l has been i m p l i c a t e d i n Canada as the main cause of c i r r h o s i s of the l i v e r , as w e l l as c o n t r i b u t i n g to encephalopathy, m a l n u t r i t i o n , obesity and accidents of a l l 2 6 8 kinds, p a r t i c u l a r l y motor v e h i c l e accidents . A l c o h o l excess-es have a l s o been a s s o c i a t e d w i t h p a n c r e a t i t i s , g a s t r i t i s , hepa-t i t i s , cardiomyopathy, neuropathy and many p s y c h o s o c i a l problems 10"^ and c e r t a i n c a n c e r s 1 0 . I t i s the p r i n c i p a l substance of abuse i n i n d u s t r i a l i z e d s o c i e t i e s . In s p i t e of the i l l e f f e c t s mentioned above, a l c o h o l does, have a good side i f taken i n moderation. Davidson and 105 colleagues f e e l t h a t a l c o h o l i s a u s e f u l s o c i a l adjunct i n - 41 -promoting f e l l o w s h i p and s o c i a l i n t e r c o u r s e as w e l l as i n d i v i -dual r e l a x a t i o n . As noted e a r l i e r , moderate d r i n k e r s - defined 35 as someone who consumes 1 to 2 d r i n k s at a time , or 17 to 45 477 drinks per month - had the best m o r t a l i t y r a t e r e l a t i v e to both abstainers and excessive d r i n k e r s 3 5 ' 4 7 7 . Laporte and 2 71 a s s o c i a t e s p o i n t out t h a t a U-shaped curve of a l c o h o l consump-t i o n r e l a t i v e to CHD i s an i n t e r n a t i o n a l phenomenon and i s pronounced f o r beer with the U-shape l e s s e n i n g f o r wine, and a l l but disappearing f o r s p i r i t s . The curve a p p l i e s to both the 2 71 incidence of CHD and m o r t a l i t y therefrom . Other authors have a l s o reported a r e c i p r o c a l r e l a t i o n s h i p between moderate a l c o h o l consumption and C HD 1^ 7 7 4 / 2 5^, i n c l u d i n g Hennekens and coworkers 19 8 183 i n t h e i r review. Gyntelberg , however, found no such a s s o c i a t i o n i n h i s study of Danish men aged 40 to 59 years, and 42 4 Rose and Cohen report t h a t t e e t o t a l e r s l i v e longer than d r i n k e r s . 256 K l a t s k y and a s s o c i a t e s found that moderate a l c o h o l consumption r e t a i n e d the inverse r e l a t i o n s h i p when c o n t r o l l e d f o r the f o l l o w i n g r i s k f a c t o r s : c i g a r e t t e smoking, s y s t o l i c and d i a s t o l i c blood pressures, blood sugar, ^ s k i n f o l d thickness ( o b e s i t y ) , c h o l e s t e r o l and age. Such r e s u l t s , however, do not r u l e out the p o s s i b i l i t y t h a t a l c o h o l i s a c t i n g through the p o s i t i v e m o d i f i c a t i o n of other r i s k f a c t o r s . For example, Yano 495 and associates reported a negative a s s o c i a t i o n w i t h r e l a t i v e weight and s k i n f o l d t h i c k n e s s . Moderate use i s a l s o known to be a s s o c i a t e d w i t h elevated H D L 1 0 ' 7 4 ' 7 6 ' 4 9 5 , a f a c t o r thought to be - 42 -p r o t e c t i v e a g a i n s t CHD (see p.157). The e f f e c t of HDL was 417 e s p e c i a l l y pronounced i n males . I t i s a l s o a s s o c i a t e d w i t h 76 495 495 a decrease i n LDL ' and t o t a l c h o l e s t e r o l , although 417 Shephard and coworkers reported a p o s i t i v e a s s o c i a t i o n w i t h both t o t a l serum c h o l e s t e r o l and LDL. These opposite e f f e c t s on LDL and t o t a l c h o l e s t e r o l may w e l l be dose-related, since Yano and associates were working only w i t h moderate consumption, whereas Shephard and a s s o c i a t e s were not so r e s t r i c t e d , and indeed d i d f i n d a d o s e - r e l a t e d e f f e c t of a l c o h o l on LDL, t o t a l c h o l e s t e r o l and t r i g l y c e r i d e s . The e f f e c t s on HDL and LDL are 495 f e l t by Yano and colleagues to e x p l a i n p a r t l y the ameliora-t i n g e f f e c t s of a l c o h o l on CHD. Consumption of a l c o h o l , however, i s a s s o c i a t e d adversely w i t h other r i s k f a c t o r s : i t has been reported t o be p o s i t i v e l y a s s o c i a t e d w i t h c i g a r e t t e smoking ( f o r which i t 529 increases the carcinogenic e f f e c t s ), serum u r i c a c i d l e v e l s , 495 76 417 and s y s t o l i c blood pressure and serum t r i g l y c e r i d e s ' ' 495 The e f f e c t of q u a n t i t y i s underscored by the r e s u l t s of 257 s e v e r a l s t u d i e s . Although K l a t s k y and colleagues found no r i s k with two or fewer a l c o h o l i c d r i n k s per day, they found th a t greater than two d r i n k s was a s s o c i a t e d w i t h increased s y s t o l i c and d i a s t o l i c blood pressures, even when c o n t r o l l e d f o r age, race, sex, smoking, c o f f e e , o b e s i t y and education. They concluded that immoderate a l c o h o l use was a r i s k f a c t o r f o r hypertension, a conclusion supported by the American Heart A s s o c i a t i o n 1 0 . S i m i l a r f i n d i n g s were reported by Gyntelberg - 43 -186 and Mayer i n t h e i r study of Danish middle-aged men. Once again, i t would appear t h a t moderation i s the key! 4.2 Smoking Smoking i s a common r i s k f a c t o r , even at high l e v e l s . Approximately 40% of Canadians smoke, o n e - t h i r d of which smoke 505 at l e v e l s greater than 22 c i g a r e t t e s per day . However, about 25% of Canadian adu l t s are professed ex-smokers, and 31% have 505 never smoked . Smoking i n Canada i s more common i n the young, the l e s s educated, the unemployed, the blue c o l l a r worker and the d r i n k e r , such groups thus being at high r i s k of the nume-rous complications a s s o c i a t e d w i t h the h a b i t . Smoking, e s p e c i a l l y c i g a r e t t e smoking, i s as s o c i a t e d w i t h a wide v a r i e t y of diseases and d i s o r d e r s , i n c l u d i n g cancers (lung, l a r y n x , pharynx, mouth, esophagus, pancreas and b l a d d e r ) , chronic o b s t r u c t i v e lung diseases (emphysema and chronic bron-c h i t i s ) , p e p t i c u l c e r , p e r i p h e r a l v a s c u l a r diseases, b i r t h d i s -529 orders and CHD . Smoking i s a l s o known to decrease the oxygen-c a r r y i n g c a p a c i t y of the blood, a f f e c t blood c l o t t i n g and cause a r r y t h m i a s 1 ^ . Not s u r p r i s i n g l y / t h e n , compared to non-smokers 477 smokers are i n poorer general h e a l t h and have increased 35 477 general m o r t a l i t y ' , e s p e c i a l l y those who smoke two or more 353 packages of c i g a r e t t e s per day. Paffenbarger and as s o c i a t e s reported from t h e i r study t h a t smokers had increased r i s k of death from chronic o b s t r u c t i v e lung disease, pneumonia, cancer 49 and heart a t t a c k . Borhani c a l c u l a t e d that 33% of the excess - 44 -531 m o r t a l i t y seen i n smokers was due to CHD. Kannel f e e l s t h a t smoking c o n s t i t u t e s 20% of the r i s k f o r CHD i n men under 65. C i g a r e t t e smoking i s considered one of the main r i s k f a c t o r s f o r CHD - one of the s o - c a l l e d " b i g three", along w i t h i -i * , , . . . , , , 10,49,220,298,365,437,458 c h o l e s t e r o l and high blood pressure t I f indeed smoking i s causative of CHD, the mechanism i s not 533 simple . C e r t a i n l y smoking does have a v a r i e t y of p o t e n t i a l l y i n j u r i o u s e f f e c t s such as i n c r e a s i n g the catecholamine l e v e l s i n the blood, decreasing p l a t e l e t s u r v i v a l time, i n c r e a s i n g p l a t e l e t cohesiveness, decreasing the oxygen-carrying capacity of the blood and i n c r e a s i n g the tendency to v e n t r i c u l a r a r r h y t h -10 5 32 mias ' . These mechanisms, as w e l l as the t o x i n s i n the 10 532 smoke, may w e l l l e a d to damage of the endothelium ' and acc e l e r a t e a t h e r o s c l e r o s i s 1 0 . However, smoking may a l s o act p a r t i a l l y through a s s o c i a t e d changes i n other r i s k f a c t o r s such as increased heart r a t e and blood pressure or decreased HDL-C 1 0, although i t has been reported to be a r i s k f a c t o r independent 10 9 7 of the others ' . Thus, d i r e c t l y and i n d i r e c t l y , smoking could be associated w i t h CHD at any of the three phases, i n i t i a l i n j u r y , atherogenesis or p r e c i p i t a t i o n of an acute event. However, other reports of i t s a s s o c i a t i o n w i t h CHD have 246 been i n c o n s i s t e n t and v a r i a b l e . Keys i n h i s Seven Country Study found that smoking was c o n s i s t e n t l y r e l a t e d to CHD only i n the United States. Such i n t e r n a t i o n a l d i s p a r i t y i s supported 183 by other research. Gyntelberg , i n h i s study of Danish men - 45 -aged 40 to 59 years, found that smoking was not a s s o c i a t e d w i t h heart attack or angina. S i m i l a r r e s u l t s were reported by M i l l e r 321 235 and associates i n t h e i r Tromso Heart Study. J u u s t i l a i n h i s F i n n i s h Study found that smoking was not a r i s k f a c t o r i n women, and i n men only f o r the age groups 40 t o 44 years and beyond 65. Other discrepancies have a l s o been reported. Whereas 20 3 • Hinkle and associates reported t h a t the importance of smoking 312 as a r i s k f a c t o r increased w i t h age, Medalieand as s o c i a t e s , i n t h e i r American B e l l Telephone Study, reported j u s t the 49 opp o s i t e . In a d d i t i o n , whereas Borhani reported that i t takes ten years f o r the CHD r i s k of smokers to r e t u r n to t h a t of non-177 smokers, Gordon and her Framingham coworkers reported the 177 r e t u r n as abrupt. Gordon and colleagues f e l t t h a t t h e i r data supported a non-cumulative, t r a n s i e n t , r e v e r s i b l e t r i g g e r i n g e f f e c t of smoking as a r i s k f a c t o r , r a t h e r than an atherogenic 10 5 32 one. However, the American Heart A s s o c i a t i o n and Mustard f e e l t h a t smoking ac c e l e r a t e s atherogenesis and damages the 2 V 6 a r t e r i a l w a l l . The r e s u l t s of the Honolulu Heart Study show, as i n Framingham, th a t smoking i s r e l a t e d t o heart attack and CHD-related death, but not angina. In those stud i e s where smoking has been shown t o be a potent r i s k f a c t o r f o r CHD - and these f a r outweigh the s t u d i e s where i t i s not (see Table 1) - s e v e r a l p r o p e r t i e s have emerged. m, . r . . . , - I * . .74,238,298,365,533 TT... The e f f e c t of smoking i s dose-related . With - 46 -regard to type, c i g a r e t t e smoking i s unquestionably the most 437 potent r i s k f a c t o r : Stamler s t a t e s t h a t the r i s k of those who smoke c i g a r s or pipes and those who have q u i t c i g a r e t t e s i s 2 38 b a s i c a l l y the same as non-smokers. Kannel i n h i s review of the Framingham Study a l s o concluded that c i g a r and pipe smokers were at no increased r i s k f o r CHD. However, Morris and c o l l e a -333 gues , i n t h e i r B r i t i s h C i v i l Servant Study, d i d f i n d a graded e f f e c t going from non-smokers to ex-smokers to c i g a r and pipe to various l e v e l s of c i g a r e t t e smoking. At the other 524 extreme, Rose and Cohen r e p o r t t h a t c i g a r and pipe smokers l i v e longer than non-smokers. Smoking as a r i s k f a c t o r i s not as prone to being c l u s t e r e d 9 7 as are many of the other r i s k f a c t o r s . However, i t i s asso-c i a t e d w i t h other r i s k f a c t o r s both p o s i t i v e l y and n e g a t i v e l y and i s purported to be most d e l e t e r i o u s i n combination w i t h 533 other r i s k f a c t o r s , e s p e c i a l l y i n high r i s k groups . G y n t e l -186 berg and Mayer found a negative a s s o c i a t i o n between smoking and blood pressure when c o n t r o l l e d for age, r e l a t i v e weight and a l c o h o l use. S i m i l a r f i n d i n g s were reported by Goldbourt and 167 Medalie i n t h e i r I s r a e l i Study. The l a t t e r authors a l s o found d o s e - r e l a t e d a s s o c i a t i o n s as f o l l o w s : p o s i t i v e w i t h h e i g h t , heart r a t e , hemoglobin, hematocrit, t o t a l c h o l e s t e r o l and LDL; negative w i t h weight, s k i n f o l d t h i c k n e s s , u r i c a c i d , e d u c a t i o n a l l e v e l , a c t i v i t y i n l e i s u r e time, work s t a t u s , and 417 HDL. Shephard and colleagues i n t h e i r Toronto Employee Study, a l s o found a negative a s s o c i a t i o n w i t h HDL and, i n women, - 47 -a p o s i t i v e a s s o c i a t i o n w i t h LDL, and i n a d d i t i o n reported a p o s i t i v e , dose-related a s s o c i a t i o n w i t h t r i g l y c e r i d e s . Results 159 . • • from the Framingham Study a l s o showed a negative a s s o c i a t i o n between smoking and HDL when c o n t r o l l e d f o r o b e s i t y and a l c o h o l 12 8 use. Enger and associates a l s o found smokers to have lower HDL l e v e l s than t h e i r non-smoking Scandinavian counterparts. Smoking and obesity are commonly known to be i n v e r s e l y r e l a t e d ' . Furthermore, no c o r r e l a t i o n has been shown between 135 215 smoking and blood sugar ' Smoking emerges as a v a r i a b l e r i s k f a c t o r , r a t h e r s e t apart 39 9 from the r e s t . S e l t z e r , i n h i s e d i t o r i a l on smoking and c a r d i o v a s c u l a r diseases, f e l t t h a t the evidence, at best, only showed smoking to be a r i s k f a c t o r f o r a l i m i t e d segment of the p o p u l a t i o n . He a l s o s t r e s s e d that smokers were " d i f f e r e n t people" i n morphology, physiology, biochemistry, p e r s o n a l i t y and l i f e s t y l e . Such a s t a t e , he suggested, would support the theory that smoking i s g e n e t i c a l l y i n h e r i t e d . Moreover, the genes f o r smoking could w e l l be a s s o c i a t e d w i t h those determining CHD i n the same person. This hypothesis i s i d e n t i c a l to the c o n s t i t u -6 6 t i o n a l a s s o c i a t i o n theory of Burch . However, Goldbourt and 16 7 Medalie s t u d i e d the c h a r a c t e r i s t i c s of smokers i n I s r a e l and, because the d i f f e r e n c e s were so s m a l l , although s t a t i s t i c a l l y s i g n i f i c a n t , they f e l t t hat c o n s t i t u t i o n a l d i f f e r e n c e s could not account f o r the increased morbidity and m o r t a l i t y s u f f e r e d by 533 smokers. Tweed supports such a stance as w e l l . - 48 -Smoking as a r i s k f a c t o r remains an enigma. E f f o r t s at g e t t i n g people to stop smoking have been f r u s t r a t i n g and disap-p o i n t i n g ^ 0 ^ . Moreover, even i n st u d i e s where people have 462 stopped smoking, the r e s u l t s have been oftimes d i s a p p o i n t i n g 3 83 Rose and Hamilton , i n a randomized, c o n t r o l l e d t r i a l on middle-aged men, d i d achieve a reduction of the symptoms of chronic b r o n c h i t i s and a h a l t i n g of worsening lung f u n c t i o n , but, a f t e r e i g h t years, saw no e f f e c t on m o r t a l i t y . Rose and Hamilton's c o n t r o l group a l s o had a high r a t e of smoking cessa-533 t i o n , so t h e i r r e s u l t s may not be r e l i a b l e . In a d d i t i o n , the p e r i o d of observation may not be long enough, since Gordon and 177 coworkers found a 50% reduction i n CHD, independent of other r i s k f a c t o r s , i n those who q u i t smoking but the o v e r a l l morta-49 l i t y r e d uction f e l l s l o w l y . Such f i n d i n g s support Borhani's contention that i t takes ten years f o r the o v e r a l l r i s k of the person who gives up smoking to r e t u r n to t h a t of the "never-533 smoker". Length of time notwithstanding, Tweed maintains that smoking c e s s a t i o n does reduce the r i s k . Moreover, Kannel 531 , i n h i s recent update on the r o l e of c i g a r e t t e smoking on CHD, maintains t h a t smokingcessation i n the U.S. accounts f o r 50% of the decrease i n CHD noted since 1968. In s p i t e of the confusion and c o n t r a d i c t i o n s , there i s l i t t l e doubt th a t smoking c e s s a t i o n i s a h e a l t h f u l b e h a v i o u r a l change. 49 -4.3 P h y s i c a l A c t i v i t y and' E x e r c i s e I n t e r e s t i n the area of e x e r c i s e , p h y s i c a l a c t i v i t y and f i t n e s s has boomed over the l a s t ten to f i t e e n years. Numerous books and s p e c i a l e d i t i o n s of j o u r n a l s on f i t n e s s have been publ i s h e d , the f o l l o w i n g of which I would recommend to the reader: references 23, 131, 179, 231, 362, 409, 410, 412. The i n t e r e s t , however, has not been purely academic. The r i s i n g 2 6 8 costs of modern h e a l t h care and the t o l l taken by CHD were both l a r g e l y responsible f o r a resurgence of i n t e r e s t i n p h y s i -c a l a c t i v i t y and f i t n e s s i n r e l a t i o n to h e a l t h g e n e r a l l y , and CHD s p e c i f i c a l l y . Such i n t e r e s t i s t y p i f i e d by r e l a t e d n a t i o n a l events. Canada hosted the I n t e r n a t i o n a l Symposium on P h y s i c a l 3 6 8 A c t i v i t y and Cardiovascular Health i n 1966 , i n 1974 h e l d the 19 5 N a t i o n a l Conference on F i t n e s s and Health , and was the s i t e 340 of the NATO Symposium t o n P h y s i c a l F i t n e s s i n 19 78 I n t e r e s t i n t h i s area i s a l s o a t t e s t e d t o by the p l e t h o r a of books on p h y s i c a l a c t i v i t y and general h e a l t h (the f o l l o w i n g are h i g h l y recommended: references 13, 17, 62, 83, 265, 273, 364, 463) and CHD (the f o l l o w i n g are recommended: references 12, 141, 142, 272, 297, 335, 363, 487). Numerous reviews of e x e r c i s e and i t s a s s o c i a t i o n w i t h CHD have also been published. The f o l l o w i n g references are considered e x c e l l e n t , both f o r t h e i r content and t h e i r i n n o v a t i v e t h i n k i n g : references 145, 146, 152, 154, 156, 189, 192, 204, 248, 272, 278, 286, 366, 427, 453, 459, 49 4. Business and i n d u s t r y have a l s o c o n t r i b u t e d to the renewed i n t e r e s t i n t h i s area due t o the a s s o c i a t i o n between - 50 -f i t n e s s and h e a l t h , and p r o d u c t i v i t y . Once again, Canada sponso-19 6 red a 19 74 N a t i o n a l Conference on Employee F i t n e s s and subse-82 queritly p u b l i s h e d a book on the t o p i c . Western m i l i t a r y forces have shown i n t e r e s t f o r the same r e a s o n s ^ " . In t h i s s e c t i o n I w i l l deal w i t h p h y s i c a l a c t i v i t y and e x e r c i s e . The s e c t i o n w i l l s t a r t w i t h a d e f i n i t i o n of aerobic a c t i v i t y . Subsequently, I w i l l deal w i t h the b a s i c physiology of aerobics as a basis f o r the next s e c t i o n which deals w i t h the e f f e c t s of aerobic a c t i v i t y on the body. The l a t t e r s e c t i o n i n turn sets the stage f o r the l a s t two se c t i o n s on re g u l a r aerobic p h y s i c a l a c t i v i t y as a p o s i t i v e r i s k f a c t o r f o r h e a l t h , e s p e c i a l l y CHD, and i t s r e l a t i o n s h i p t o other r i s k f a c t o r s . a. Aerobic A c t i v i t y P h y s i c a l a c t i v i t y can take on many forms. In t h i s t h e s i s I w i l l r e s t r i c t myself to that a c t i v i t y which predomi-nant l y s t i m u l a t e s the c a r d i o v a s c u l a r and r e s p i r a t o r y systems, the s o - c a l l e d aerobic a c t i v i t y . E s s e n t i a l l y , aerobic e x e r c i s e i n v o l v e s r e p e t i t i v e a c t i o n of the large muscle groups, such as the l e g s , u s u a l l y f o r locomotion.. Furthermore, f o r most of the e f f e c t s r e f e r r e d t o , e x e r c i s e needs t o be of a c e r t a i n i n t e n s i t y , frequency and du r a t i o n . The i n t e n s i t y has to be such as to r e s u l t i n a heart r a t e reaching 60 to 80% of the maximum heart rate f o r age, the l a t t e r being approximately 220 beats/min. 2 86 minus age i n years . The e x e r c i s e must a l s o be of adequate duration ( i n periods of at l e a s t 15 t o 20 minutes) and r e g u l a r - 51 -(two to three times per week) since a l l of the e f f e c t s tend to s t a r t r e v e r s i n g a f t e r s e v e r a l days of r e s t 1 and may disappear 2 79 e n t i r e l y w i t h i n 10 weeks . Therefore, to maintain the e f f e c t s , the e x e r c i s e must be l i f e l o n g as w e l l . E x e r c i s e w i t h such q u a l i t i e s leads t o an increase i n c a r d i o r e s p i r a t o r y or aerobic f i t n e s s and i s thus deemed as a t r a i n i n g l e v e l . As w i l l be discussed l a t e r , such t r a i n i n g l e v e l e x e r c i s e seems to be optimal f o r the r e a l i z a t i o n of both the body performance and h e a l t h b e n e f i t s . Depending on the s t a t e of f i t n e s s of the i n d i v i d u a l , a t r a i n i n g l e v e l of exer-c i s e can be achieved through even m i l d forms of e x e r c i s e such as walking. The more f i t the person, the more strenuous the exer-c i s e needs to be to have a t r a i n i n g e f f e c t . b. E f f e c t s of Aerobic P h y s i c a l A c t i v i t y on the Body P h y s i c a l - a c t i v i t y r e q uires muscular a c t i o n , and the l a t t e r r e q u i r e s three e s s e n t i a l " s e r v i c e s " to the muscles: a supply of oxygen, a supply of f u e l , and a means of g e t t i n g r i d of waste products. A l l three are s u p p l i e d by the blood through the actions of the c a r d i o v a s c u l a r and r e s p i r a t o r y systems. Muscles do have a supply of f u e l - muscle glycogen - that w i l l keep them l a r g e l y s u p p l i e d f o r up t o 10 minutes; however, f o r more lengthy e x e r c i s e , muscles r e l y p r o g r e s s i v e l y more on blood glucose and f a t t y acids f o r f u e l . These f u e l s , derived r e s p e c t i v e l y from l i v e r glycogen and f a t depots, need to be t r a n s p o r t e d to the muscles. This f u e l t r a n s p o r t and the sub-- 52 -sequent waste d i s p o s a l are u s u a l l y handled e a s i l y by the body. However, the t h i r d s e r v i c e , supplying oxygen, i s r a t e - l i m i t i n g . Oxygen t r a n s f e r from the a i r to the muscles c o n s i s t s of 412 four components : 1) v e n t i l a t i o n ( b r e a t h i n g ) , 2) pulmonary gas exchange ( t r a n s f e r of oxygen from the lungs to the blood sys-tem) , 3) blood t r a n s p o r t (most of the oxygen i s transported by hemoglobin which i s contained i n s i d e the red blood c e l l s ) and, 4) t i s s u e gas exchange ( t r a n s f e r of oxygen from the blood t o the muscles). In the muscle c e l l s , the oxygen i s then combined with the f u e l to produce energy f o r muscle c o n t r a c t i o n , thus c o n s t i t u t i n g a f i f t h step i n oxygen uptake and use. Since oxygen uptake and use i s the l i m i t i n g f a c t o r (excluding p h y s i -c a l d e f o r m i t i e s and disease s t a t e s ) , the maximum r a t e a t which oxygen i s taken up by the body (V0 2 max) i s considered a r e l i a b l e estimate of a person's c a r d i o r e s p i r a t o r y or aerobic 485 c o n d i t i o n . Moreover, since i t i s r e l a t i v e l y easy to measure, both d i r e c t l y i n the l a b o r a t o r y , and i n d i r e c t l y using heart rate as an i n d i c a t o r , i t i s widely accepted as the i n t e r n a t i o n a l 416 standard measurement of aerobic f i t n e s s . I t i s u s u a l l y expressed i n m i l l i l i t r e s of oxygen taken up per kilogram of body weight per minute (ml/kg.min), although body weight can be l e f t out. Regular e x e r c i s e at the t r a i n i n g l e v e l does lead , • A v.- * - 4 . 21,83,102,179,234,378,412,432 ,485 to improved aerobic f i t n e s s 479 but, as Wilhelmsen p o i n t s out, c o n s t i t u t i o n a l f a c t o r s are a l s o of great importance. V0 2 max w i l l be discussed more thoroughly l a t e r (p.129). - 53 -Because of i t s need f o r the three b a s i c " s e r v i c e s " , e s p e c i a l l y oxygen and f u e l d e l i v e r y , p h y s i c a l a c t i v i t y places demands on the systems responsible f o r them. In a d d i t i o n , because a c t i v i t y i s a form of p h y s i c a l s t r e s s , i t places demands on the b o d i l y systems i n v o l v e d i n s t r e s s response. Thus, phy-s i c a l a c t i v i t y places p a r t i c u l a r demands on the f o l l o w i n g systems: c a r d i o v a s c u l a r (heart and blood v e s s e l s ) , r e s p i r a t o r y (lungs and muscles of r e s p i r a t i o n ) , nervous ( e s p e c i a l l y the sympathetic component responsible f o r s t r e s s response), endo-c r i n e (hormone-producing organs, such as the adrenal glands which are s t r e s s responders, and the glands which regulate f u e l needs - the pancreas) and f u e l storage ( f a t c e l l s and l i v e r ) . With reguar p h y s i c a l a c t i v i t y , and thus r e g u l a r demands placed on the body, p a r t i c u l a r l y on the above organ systems, the body's metabolism adapts t o t h i s form of chronic s t r e s s r e s u l t i n g i n a new metabolic steady s t a t e , or homeostasis. Such an adaptive process i s i l l u s t r a t e d by the e f f e c t s on the body occasioned by s u b j e c t i n g a sedentary i n d i v i d u a l to r e g u l a r aerobic p h y s i c a l a c t i v i t y a t , or near, the t r a i n i n g l e v e l , as w i l l now be discussed. (i) P h y s i o l o g i c a l E f f e c t s The e f f e c t s of aerobic p h y s i c a l a c t i v i t y on the organ systems of the body are summarized i n Table 2.2. This s e c t i o n w i l l be devoted to d i s c u s s i n g some of the more important phy-s i o l o g i c a l e f f e c t s , p a r t i c u l a r l y where such a d i s c u s s i o n w i l l a llow a b e t t e r understanding of the r o l e of p h y s i c a l a c t i v i t y Table 2.2 Aerobic E x e r c i s e and B o d i l y Functions The e f f e c t s of t r a i n i n g l e v e l aerobic e x e r c i s e on b o d i l y functions i n man, seen over the long run. BODY PART/PROCESS INCREASE DECREASE Heart Blood Vessels Blood Function S i z e and weight C o n t r a c t i l i t y F i l l i n g of chambers Stroke volume Cardiac output Oxygen e x t r a c -t i o n from blood E f f i c i e n c y of oxygen use O v e r a l l e f f i -ciency S i z e of coro-nary a r t e r i e s Number of coro-nary c o l l a t e r a l s Number of coro-nary c a p i l l a r i e s E f f i c i e n c y Splanchnic flow Volume Red Blood C e l l Mass Hemoglobin con-c e n t r a t i o n F i b r i n o l y s i s References 1,179 ,397,485 179 154 1,83,179,412 424,485 1,412,424,485 1,412,486 179,286 171,461 179,424,461 154,179 ,424,461 1,154,397,424, 485 13,171,461 181 1,412,461,485 461 1,485 24,114,127,336, 424 ,461,482 Function Resting Heart Rate Exercise Heart Rate Maximum Heart Rate Arrythmias Double Product (Heart work) Recovery time P e r i p h e r a l r e s i s t a n c e Blood Pressure P l a t e l e t aggre-gation References 83,162,171,179,234 286,397,424,440, 461,485 171,179,234,286,378, 485 179,286 336,461 9,179,286,336,359 83,171,286,485 1,13,162,179,440,461 485 336,461 Table 2.2 Aerobic E x e r c i s e and B o d i l y Functions BODY INCREASE  PART/PROCESS Function References Blood Arterio-venous 1,21,179 (cont'd) oxygen d i f f e -rence Lungs V e n t i l a t i o n 1,378,485 V i t a l c a p acity 378,412,497 Muscles Number of c a p i l - 1,154,397,424 l a r i e s 485 E f f i c i e n c y 171,286 Oxygen e x t r a c - 1,412,486 t i o n Metabolism Glucose t o l e - 158,461,486 rance I n s u l i n b i n d i n g 432 s i t e s LCAT A c t i v i t y 287 L i p o p r o t e i n l i - 341 pase a c t i v i t y E f f i c i e n c y of carbohydrate 336 metabolism HDL 138,341,431 E f f i c i e n c y of 424 l i p i d s metabolism Hormones Thyroxin 461 Growth Hormone 4,138,461 Glucagon 4,178,424,494 C o r t i s o l 138 (cont'd) DECREASE Function References. Absorption of d i e t a r y f a t Production of l i p i d s by l i v e r Serum l i p i d s : g e n e r a l l y t r i g l y c e r i d e s t o t a l choles-t e r o l VLDL LDL 424 424 486 41,138,181,434,4 162,181,440,461 181,424 181 I n s u l i n 4,41,138,181,42 4 432,494 Adrenalin 4,181,234 Noradrenalin 4,181,234 Testosterone 4 C o r t i s o l 4,234 Table 2.2 Aerobic E x e r c i s e and B o d i l y Functions (cont'd) BODY PART/PROCESS INCREASE Function Body Lean body mass Composition References 138 DECREASE Function Weight Body Fat References 162,378,412,440,48 1,41,440,461,485, 486 Nervous System Psychologi-c a l General Parasympathetic tone Autonomic adap-t a t i o n s A p p e t i t e regu-l a t i o n A l e r t n e s s and r e f l e x e s Sleep Stress t o l e -rance Prudent l i v i n g h a b i t s V0 2 max F u n c t i o n a l c a p a c i t y Heat t o l e r a n c e 179 154,217 41,305,425 234,372,378 144,336,378 234,372 461 21,83,102,179, 234,378,412,432, 485 486 Sympathetic tone Neurohumoral overreaction Smoking Mental Stress Tension Appetite Degeneration wi t h age S u s c e p t i b i l i t y to i l l n e s s 179 461 77,162,286,497 45,82,83,144,162, 336,378,461,486 83,372,378 56,336 367 82,83,265,463 197,358 - 57 -i n CHD and other diseases, both as a p o s i t i v e f a c t o r i n i t s e l f , and i n r e l a t i o n to other r i s k f a c t o r s . The d r i v i n g force behind the supply of oxygen and f u e l to the muscles (and other b o d i l y t i s s u e s ) i s the heart. The heart i s a pump. The r i g h t s i d e of the heart r e c e i v e s de-oxygenated and waste-laden blood from the body through the venous side of the va s c u l a r system, and pumps i t t o the lungs where oxygen i s picked up and carbon d i o x i d e i s given o f f ; t h i s oxygenated blood then 'returns to the l e f t s i de of the heart whence i t i s pumped out to the t i s s u e s of the r e s t of the body through the a r t e r i a l s i de of the va s c u l a r system. The heart, being a muscle, needs oxygen and f u e l , which i t receives through the coronary a r t e r i e s . During e x e r c i s e , the body's needs f o r oxygen and f u e l r i s e s , n e c e s s i t a t i n g the heart to beat f a s t e r . As w i t h a l l muscles, such an increased work load leads to increase i n the s i z e of the heart muscle (myocardial hypertrophy) e s p e c i a l l y of 1 179 39 7 485 the l e f t v e n t r i c l e ' ' ' l e a d i n g to increased strength of 179 each heart beat (myocardial c o n t r a c t i l i t y ) . With the demand 378 412 49 7 fo r more oxygen, the v i t a l c a p acity of the lungs ' ' and 1 378 4 85 pulmonary v e n t i l a t i o n ' ' both increase l e a d i n g to enhanced oxygenation of the blood. The demand f o r more oxygen a l s o re->\ 461 497 s u i t s i n increases i n the red blood c e l l mass ' , and hemo--i 4- 4 . - 1,485 , . . , , 1, 412,461,485 _ . globm concentration ' and blood volume ' ' ' Such increases r e s u l t i n greater oxygen-carrying c a p a c i t y of the - 58 -blood. These increases a l s o n e c e s s i t a t e the heart handling more blood, r e s u l t i n g i n heart chamber enlargement. Moreover, the conditioned heart relaxes more q u i c k l y thus a l l o w i n g 154 greater f i l l i n g of those enlarged chambers . Combined w i t h increased myocardial c o n t r a c t i l i t y , the o v e r a l l r e s u l t i s t h a t the amount of blood pumped by each heart beat (stroke volume) ,1,83,179 ,412,424,485 m. . ^ . i s i ncreased This e f f e c t i s so pronounced that the heart does not have to beat as f a s t to supply the same 83 162 171 179 amount of oxygen, r e s u l t i n g i n decreased r e s t i n g ' ' ' ' 234,286,424,440,461,485 . 171,179,234,286,378,485 ' ' ' ' and e x e r c i s e ' ' ' ' ' heart r a t e s . Such decreases r e s u l t i n decreased blood v e l o c i t y , 45 7 which i n turn reduces damage to the intima of the a r t e r i e s On balance, the e f f e c t s of enhanced stroke volume are r e l a t i -v ely greater than the e f f e c t s of reduced working and r e s t i n g heart r a t e s , so t h a t c a r d i a c output at a given work load remains -.1,412,424,485 ' 179 ,286 , increased ' ' ' Thus maximum heart rate ' and the . . . u 83,171,286,485 , time to recover r e s t i n g heart rate ' ' are both decreased. The increase i n c a r d i a c output i s r e s p o n s i b l e f o r » approximately 50% of the improvement i n VO2 max seen w i t h . 1,21,179 ex e r c i s e Concomitantly, the s y s t o l i c blood pressure i s decrea-,1.13,162,179,440,461,485 m U , . .. . , , sed ' ' ' ' ' ' The combination of a lowered s y s t o l i c blood pressure and heart rate leads to a lower pres-. . . , .9,179,286,336,359 • . v n n sure-rate product ' ' ' ' at a l l work l e v e l s , - 59 -i n d i c a t i v e of decreased heart work, and thus oxygen needs. However, the increased demands on the heart muscle have a l s o caused an increase i n coronary c i r c u l a t i o n through an increase • K * n 4- i 1 5 4 , 1 7 9 , 4 2 4 , 4 6 1 , . , , i n the number of c o l l a t e r a l s / muscle c a p i l l a r i e s 1 , 1 5 4 , 3 9 7 , 4 2 4 , 4 8 5 , . . . 1 7 9 , 2 9 6 , ' ' ' and the s i z e of the coronary a r t e r i e s ' 4 2 4 4 6 1 ' . Through use, the he a r t muscle has a l s o become much 1 7 9 2 86 more e f f i c i e n t at using oxygen ' . The o v e r a l l r e s u l t i s a heart which r e q u i r e s l e s s oxygen, but which i s capable of 1 7 1 supplying i t s e l f w i t h more, and thus i s much more e f f i c i e n t ' 4 6 1 Such a heart i s capable of coping with both unexpected demands, f o r example that created by sudden s t r e s s , and wi t h chronic problems, such as a compromised blood supply created by a t h e r o s c l e r o s i s of the coronary a r t e r i e s . In the conditioned r a t heart, blood flow i s maintained even i n the presence of 1 5 4 hypoxia; thus i f heart attack does occur, i t i s l e s s extensive In a d d i t i o n to the above, e x e r c i s e leads to adaptations 1 5 4 2 1 7 i n the endocrine and autonomic nervous sytems ' . The r e s u l t i s a decrease i n sympathetic, and an increase i n parasympathetic 1 7 9 tone . Along w i t h the hormonal changes, the r e s u l t i s enhanced 154 autonomic and hormonal c o n t r o l of c a r d i o v a s c u l a r f u n c t i o n , ab e t t i n g the lowered heart r a t e and s y s t o l i c blood pressure, , . . . , • 1 3 , 1 7 1 , 4 6 1 m , and causing improvement i n v a s c u l a r e f f i c i e n c y . The e f f e c t s on the heart are sometimes seen on the EKG as sinus bradycardia and primary and secondary a t r i o - v e n t r i c u l a r heart 1 7 9 blocks , once misconstrued as p a t h o l o g i c a l changes. The general improvement i n heart f u n c t i o n i n g , along w i t h a p o s s i b l y - 60 -154 increased a v a i l a b i l i t y of calcium , r e s u l t s i n a heart much 336 461 more r e s i s t a n t to arrythmias ' . Thus, i f ischemia or heart attack does occur, the heart i s much l e s s l i k e l y to be a f f l i c t e d w i t h f a t a l arrythmias. These p o s i t i v e e f f e c t s on the he a r t , lungs and blood vessels are unquestionably p a r t l y r e s p o n s i b l e f o r the widespread use of aer o b i c e x e r c i s e as a t h e r a p e u t i c and 154 459 540 r e h a b i l i t a t i v e modality f o r CHD ' ' and lung and vascu-427 459 l a r d i s o r d e r s ' , as w e l l as f o r i t s p r o p h y l a c t i c use. Along w i t h the above-mentioned changes i n heart, blood v e s s e l s , lungs and blood, the muscles (and other t i s s u e s ) a l s o change. They increase i n s i z e and strength and become more 171 2 86 e f f i c i e n t , both i n t h e i r metabolism ' and i n t h e i r a b i l i t y to e x t r a c t oxygen from the b l o o d 1 ' 4 1 2 ' 4 8 (^. The l a t t e r r e s u l t s i n a lar g e increase i n the d i f f e r e n c e i n blood oxygen concentra-t i o n s between the a r t e r i a l and venous sides of the va s c u l a r system. Such a d i f f e r e n c e accounts f o r approximately the other 50% of the increase i n VG^ max seen w i t h e x e r c i s e . The i n c r e a -sed VC>2 max means that the same work load r e q u i r e s l e s s e x e r t i o n and l e s s s t r a i n on the heart and other systems, than i t would have before r e g u l a r e x e r c i s e . Moreover, the person can work longer, that i s , has greater stamina or endurance. O v e r a l l , a f t e r improving h i s VC^ max a person can do more work f o r longer periods and has a much greater reserve f o r the unexpected 486 than he d i d before. As Wiimore puts i t , he has a gre a t e r " f u n c t i o n a l c a p a c i t y " . - 6 1 -Aerobic e x e r c i s e a l s o leads to reduced p l a t e l e t aggre-g a t i o n 3 3 ^ ' 4 ^ , and thus a decreased tendency of the blood to c l o t . The e f f e c t has obvious i m p l i c a t i o n s f o r heart attack and str o k e . In a d d i t i o n , e x e r c i s e leads to enhanced f i b r i n o l y s i s , '. , . , . . 2 4 , 1 1 4 , 1 2 7 , 3 3 6 , 4 2 4 , 4 6 1 , 4 8 2 . . . , , , , or c l o t d i s s o l u t i o n f which could w e l l l i m i t , or undo, the i l l e f f e c t s of c l o t t i n g . This e f f e c t , 2 4 which i s temporary, r e p o r t e d l y l a s t i n g only 30 minutes t o two 12 7 hours , may w e l l be r e l a t e d to the t r i g l y c e r i d e - l o w e r i n g 4 2 4 e f f e c t of e x e r c i s e . The e f f e c t on f i b r i n o l y s i s does not n -i 24 occur i n a l l people Aerobic e x e r c i s e has some very i n t e r e s t i n g metabolic e f f e c t s , unquestionably i n f l u e n c e d by the e f f e c t s of e x e r c i s e on 424 the neuro-endocrine systems . As can be seen from Table 2 . 2 many hormones are a l t e r e d by aerobic e x e r c i s e . The b a s i s f o r many of these e f f e c t s l i e s i n the increased demand f o r f u e l s . Aerobic e x e r c i s e , u n l i k e anaerobic e x e r c i s e (that i s , short burts of intense a c t i v i t y where oxygen p r o v i s i o n can not keep pace wi t h use) r e l i e s l a r g e l y on the metabolism of f a t s as w e l l as carbohydrates. The fuel-demanding e f f e c t s of e x e r c i s e are seen both during and a f t e r the e x e r c i s e p e r i o d . During e x e r c i s e , the e f f e c t s depend on both the i n t e n s i t y of the e x e r c i s e and i t s d u r a t i o n . As noted, such adequate aerobic e x e r c i s e done on a regu l a r b a s i s a l s o r e s u l t s i n long-term b o d i l y adaptations. The e f f e c t s discussed here w i l l be r e s t r i c t e d to m i l d to - 62 -moderate i n t e n s i t i e s , s ince severe e x e r c i s e i s n e i t h e r what i s encountered i n normal l i v i n g , nor recommended. The reader should bear i n mind th a t when " e x e r c i s e " i s r e f e r r e d to from here on i n the t h e s i s , i t i s of the aerobic type. When ex e r c i s e begins the muscles immediately need oxygen and f u e l . Thus, blood flow to the muscle i n need i s enhanced by d i l a t i o n of the blood vessels supplying i t , and the ca r d i o v a s c u l a r system i s primed to supply more blood v i a the adaptations mentioned p r e v i o u s l y . Before such adaptations take p l a c e , the muscle r e l i e s on i t s own i n t e r n a l f u e l s t o r e , muscle glycogen, which i s thus the p r i n c i p a l f u e l during the f i r s t ten 13 8 minutes of e x e r c i s e . With the enhanced blood supply the muscle switches t o r e l i a n c e on blood-borne f u e l s . Over the next t h i r t y minutes the amount of blood glucose (produced by break-down of l i v e r glycogen through a process c a l l e d glycogenolysis) used by the muscle increases d r a m a t i c a l l y . A s i m i l a r increase i s seen i n the amount of free f a t t y a c i d s , derived from the breakdown of t r i g l y c e r i d e s i n f a t t i s s u e s through a process c a l l e d l i p o l y s i s . A f t e r about 40 minutes, the blood glucose i s sup p l i e d l e s s by gly c o g e n o l y s i s and more by i t s s y n t h e s i s i n the l i v e r - gluconeogenesis - from such precursors as l a c t a t e , pyruvate, g l y c e r o l and al a n i n e . These precursors are derived e s s e n t i a l l y as f o l l o w s : the f i r s t two from carbohydrate metabolism, g l y c e r o l from t r i g l y c e r i d e breakdown and alanine from p r o t e i n metabolism. When e x e r c i s e i s done r e g u l a r l y , the repeated demand f o r short-term adaptations r e s u l t s i n long-- 63 -term changes p a r t i c u l a r l y i n hormonal balance. At present, i t would appear t h a t the p r i n c i p a l r e g u l a -t o r s of f u e l metabolism w i t h e x e r c i s e are i n s u l i n and i t s opposites, the s o - c a l l e d counterregulatory hormones: glucagon, C o r t i s o l , catecholamines (adrenalin and noradrenaline and growth hormone. Over the long term r e g u l a r e x e r c i s e r e s u l t s i n a decrease i n serum i n s u l i n l e v e l s and an increase i n the others. The decrease i n i n s u l i n and increase i n glucagon are probably secondary to the e f f e c t s on the adrenergic nervous system and 13 8 catacholamine s e c r e t i o n r e s p e c t i v e l y . The a l t e r e d balance between i n s u l i n and the counterregulatory hormones promotes both the breakdown of glycogen i n the l i v e r and muscle and the synthesis of glucose from the b a s i c breakdown products of f u e l s (gluconeogenesis). E x e r c i s e a l s o increases c e l l u l a r sen-41 818 s i t i v i t y to i n s u l i n ' , p o s s i b l y by i n c r e a s i n g the number 432 . . of c e l l u l a r b i n d i n g s i t e s . Such increased s e n s i t i v i t y enhan-ces the passage of glucose i n t o the c e l l s even i n the presence 424 of the lowered i n s u l i n l e v e l s E x e r c i s e leads to an increase i n the a c t i v i t y of the 341 enzyme, l i p o p r o t e i n l i p a s e . , which breaks down plasma t r i g l y -c e r ides i n t o free f a t t y acids and g l y c e r o l . The g l y c e r o l i s then used f o r gluconeogenesis i n the l i v e r , and the free f a t t y acids as f u e l f o r the muscles. The a c t i v i t y of the enzyme l e c i t h i n : c h o l e s t e r o l a c y l t r a n s f e r a s e (LCAT) i s a l s o increased 2 87 The combination of these two enzymic e f f e c t s i s a reduc-- 64 -491 431 t i o n i n t r i g l y c e r i d e s and e l e v a t i o n i n HDL-C . These enzymes may w e l l be a c t i v a t e d by the a l t e r e d balance between i n s u l i n and the counterregulatory hormones, which does r e s u l t i n the m o b i l i z i n g of f u e l s . These e f f e c t s , plus the e x e r c i s e -mediated decrease i n both absorption of d i e t a r y f a t by the gut 424 and production of l i p i d s by the l i v e r , r e s u l t i n a decrease ,. ., 486 - m a . - - , - A 41,138,181, • i n most serum l i p i d s , e s p e c i a l l y t r i g l y c e r i d e s ' ' 434,494 , ^ , a. n o. 4 . -.162,181,440,461,, W T T V r 1 8 1 , ' , but a l s o t o t a l c h o l e s t e r o l ' ' ' (both VLDL and LDL . ,138,341. l s e d ' ) 424 181 and LDL are decreased, although the HDL p o r t i o n i s ra The long-term metabolic e f f e c t s of r e g u l a r aerobic 336 e x e r c i s e are: more e f f i c i e n t carbohydrate metabolism , w i t h , , , . , 158,461,486 , . ,, . ,. , ^ . enhanced glucose t o l e r a n c e , ( e s p e c i a l l y i n d i a b e t i c s 138 who can accordingly reduce t h e i r i n s u l i n needs ) and; more 424 e f f i c i e n t l i p i d metabolism w i t h greater turnover of the body's l i p i d s and a t i p i n the body's energy balance toward the nega-424 t i v e ( c a t a b o l i c ) side r e s u l t i n g i n a reduction i n the amount 4T u A * 4.1,41,440,461,485,486 « . , , . . of body f a t 7 These e f f e c t s on body f a t , coupled w i t h the e f f e c t s of e x e r c i s e i n enhancing musculature, 485 r e s u l t i n an increase i n lean body mass , and u s u a l l y a A 4 . - 4- 4 . T u A • U 4 - 162,378,412,440 ,485 „ reduction i n t o t a l body weight ' . The e f f e c t s on weight and obes i t y are a l s o i n f l u e n c e d by a p p e t i t e becoming geared to a c t u a l c a l o r i e need w i t h r e g u l a r e x e r c i s e 4 1 , ' 4^~*. Contrary to popular b e l i e f , the net r e s u l t of e x e r c i s e i s a r e -56 336 duction of appeti t e ' , not an inc r e a s e . Some of t h i s reducing e f f e c t may w e l l be p s y c h o l o g i c a l i n o r i g i n . - 65 -( i i ) P s y c h o l o g i c a l E f f e c t s As w e l l as a f f e c t i n g e a t i n g behaviour, e x e r c i s e does have other e f f e c t s on the psyche. Regular aerobic e x e r c i s e , . . .. . . , 45,82,83,144,162,336,378, reduces s u b j e c t i v e f e e l i n g s of s t r e s s 461,486 , . , . . , 234,372 , and promotes an increased s t r e s s tolerance 12 7 E l i o t and colleagues concluded from t h e i r s t u d i e s t h a t aerobic c o n d i t i o n i n g r e s u l t e d i n p h y s i o l o g i c consequences that counter-balanced those induced by p s y c h o l o g i c a l s t r e s s . E x e r c i s e has i i , n , . , 144,336,378 , - ,. a l s o been reported to enhance sleep ' , reduce f e e l i n g s . . . 83,372,378 , . . 144 . ' . , of tension and anxiety , increase a l e r t n e s s and , .. 372,378 ,,. 128 .. .. 234 concentration , f l u i d i n t e l l i g e n c e , r e a c t i o n times , 3 72 378 v i s u a l speed , j o i e de v i v r e , s e l f - c o n f i d e n c e and morale , 425 144 and enhanced self-esteem and w e l l - b e i n g . I t has a l s o been reported to be as s o c i a t e d with prudent l i v i n g h a b i t s gene-,, 461 , , , ... . 77,162,286,497 , , ,.117, r a l l y , and decreased smoking , enhanced d i e t ' 3 7 8 and increased l e i s u r e - t i m e p h y s i c a l a c t i v i t y 3 7 8 s p e c i f i -c a l l y . A l l of these e f f e c t s could w e l l be i n t e r - r e l a t e d , and p o s s i b l y r e l a t e d as w e l l to the p h y s i o l o g i c and metabolic e f f e c t s p r e v i o u s l y discussed, p a r t i c u l a r l y the changes i n the autonomic nervous system which determines the s t r e s s response. ( i i i ) Summary Regular, aerobic p h y s i c a l a c t i v i t y e x e r t s many p o s i t i v e C Of* e f f e c t s on the body . In t h e i r WHO book, H a b i t u a l P h y s i c a l 13 A c t i v i t y and Health, Andersen and colleagues s t r e s s the bene-f i c i a l e f f e c t s on the locomotor, d i g e s t i v e , r e s p i r a t o r y and car-d i o v a s c u l a r systems, and on general organ f u n c t i o n and c e l l - 66 -13 2 3 metabolism. They conclude , as do Astrand and Rodahl , t h a t re g u l a r aerobic a c t i v i t y i s e s s e n t i a l f o r optimal human func-23 . . t i o n i n g . The human body was made for a c t i v i t y , such a c t i v i t y keeping i t tuned, that i s , keeping a l l of the metabolic proces-ses running o p t i m a l l y , enabling the bio c h e m i c a l , p h y s i o l o g i c a l and anatomical components to f o l l o w s u i t . And i t must be r e g u l a r and l i f e l o n g , s ince the e f f e c t s s t a r t to reverse a f t e r s e v e r a l days of r e s t 1 . The r e s u l t i s a new l e v e l of homeostasis where the extremes u s u a l l y a s s o c i a t e d w i t h sedentariness, f o r example high blood pressure and heart r a t e on the one s i d e , and high serum l i p i d s and obesity on the other, are normalized. In other words, the body reaches an optimal s t a t e of balance. The b o d i l y e f f e c t s p r e v i o u s l y discussed have profund 36 7 i m p l i c a t i o n s f o r h e a l t h . Polednak i n h i s book "The Longevity of A t h l e t e s " concluded t h a t p h y s i c a l t r a i n i n g l e d t o changes i n body f u n c t i o n i n g which run counter to degenerations normally seen w i t h aging. This phenomenon has a l s o been reported by o t h e r s ^ 1 1 ' ^ . L i t t l e wonder, then, t h a t Andersen and c o l l e a -13 2 3 486 gues , Astrand and Rodahl and others maintain that r e g u l a r aerobic a c t i v i t y , and i t s attendant optimal human f u n c t i o n i n g , are e s s e n t i a l f o r optimal human h e a l t h . I w i l l now look at some of the evidence. c. P h y s i c a l ; A c t i v i t y and Health R e c a l l t h a t one of the seven l i f e s t y l e f a c t o r s asso-c i a t e d w i t h enhanced h e a l t h and l o n g e v i t y i n the Almeda County - 67 -35 57 477 study of Breslow and colleagues ' ' was r e g u l a r p h y s i c a l 477 a c t i v i t y . From th a t study Wiley and Camacho concluded that h e a l t h status increased w i t h the amount of p h y s i c a l a c t i v i t y . 35 B e l l o c concluded f u r t h e r that r e g u l a r p h y s i c a l a c t i v i t y was 52 4 p o s i t i v e l y a s s o c i a t e d w i t h l o n g e v i t y . Rose and Cohen found that those w i t h heavy o f f - j o b p h y s i c a l a c t i v i t y l i v e d i n excess of f i v e years longer than those w i t h l i g h t a c t i v i t y . Zeiner-49 8 Henricksen , i n h i s study of Norwegian middle-aged men, found that p h y s i c a l l y a c t i v e men had lower m o r t a l i t y , e s p e c i a l l y from 243 CHD, than those l e s s active.. Karvonen reported that F i n n i s h cross-country s k i e r s l i v e d 4.3 years longer than the average and a l s o seldom smoked and had lower blood pressures. Kraus 2 65 and Raab i n t h e i r book e n t i t l e d "Hypokinetic Disease" f e l t that c o n d i t i o n s due to chronic lack of e x e r c i s e accounted f o r about 40% of a l l i l l n e s s , i n c l u d i n g such d i s o r d e r s as o b e s i t y , high blood pressure and CHD. The United States P u b l i c Health 46 3 Service published r e s u l t s of the N a t i o n a l Health Survey w i t h respect to h e a l t h c h a r a c t e r i s t i c s of persons w i t h chronic a c t i v i t y l i m i t a t i o n , the r e s u l t s r e v e a l i n g that such people used p h y s i c i a n s e r v i c e s and s h o r t - s t a y h o s p i t a l s more, and were much more prone to acute i l l n e s s e s and i n j u r i e s r e s u l t i n g i n short-term d i s a b i l i t y . However, these r e s u l t s do not d i s c r i m i -nate between acute episodes r e l a t e d to the chronic c o n d i t i o n and those not s o - r e l a t e d . '.!.' The Ontario Health Insurance Plan Study done by Quasar 82 Systems showed th a t people who had higher l e v e l s of c a r d i o -- 68 -— r e s p i r a t o r y f i t n e s s had s i g n i f i c a n t l y fewer medical insurance 8 3 claims. In a d d i t i o n , Collishaw and Salmon , i n reviewing phy-s i c a l a c t i v i t y i n Canada, noted t h a t those employees who were p h y s i c a l l y a c t i v e were s i c k l e s s f r e q u e n t l y , had s h o r t e r d u r a t i o n of i l l n e s s and s u f f e r e d from fewer a c c i d e n t s . These st u d i e s are 5 05 supported by the recent Canada Health Survey , which showed that p h y s i c a l a c t i v i t y and f i t n e s s were r e l a t e d p o s i t i v e l y to good h e a l t h s t a t u s . P h y s i c a l l y a c t i v e people have both fewer v i s i t s t o the doctor and d i s a b i l i t y days, l e s s long-term a c t i v i t y l i m i t a t i o n s , take fewer drugs and have lower blood pressures and enhanced emotional w e l l - b e i n g . Moreover, f i t people smoked l e s s . None of these studies can be considered d e f i n i t i v e i n proving r e g u l a r p h y s i c a l a c t i v i t y r e s u l t s i n , or preserves, b e t t e r h e a l t h . We may be seeing simply the e f f e c t s of c o n s t i t u -t i o n a l a s s o c i a t i o n . However, e x e r c i s e has been shown to have a b e n e f i c i a l e f f e c t on the r e h a b i l i t a t i o n of people w i t h a v a r i e t y 2 36 2 44 of i l l n e s s e s , i n c l u d i n g mental and p h y s i c a l types, most notably CHD, diabetes m e l l i t u s , o b e s i t y , hypertension, hyper-l i p i d e m i a s , a r t h r i t i s and pulmonary and va s c u l a r d i s o r d e r s . Indeed, post-heart a t t a c k p a t i e n t s who e n r o l l i n an e x e r c i s e program have a 50% reduced r i s k of recurrence compared to more 540 t r a d i t i o n a l therapy . Regular aerobic a c t i v i t y a l s o r e s u l t s i n a reduction of many h e a l t h r i s k f a c t o r s and an e l e v a t i o n i n many p r o t e c t i v e f a c t o r s (p. 82). In a d d i t i o n , as we have seen, re g u l a r aerobic e x e r c i s e r e s u l t s i n many sa l u b r i o u s e f f e c t s on the body (some d i r e c t l y and i n d i r e c t l y r e l a t e d to r i s k f a c t o r - 69 -m o d i f i c a t i o n ) , many of which, such as lowered blood pressure, weight and serum l i p i d s , are disorde r s i n t h e i r own r i g h t . The foregoing information s t r o n g l y suggests that r e g u l a r aerobic p h y s i c a l a c t i v i t y not only promotes h e a l t h but a l s o prevents and ameliorates i l l n e s s . I t s r e l a t i o n s h i p to CHD w i l l now be discussed i n d e t a i l , both due to the s i n g u l a r importance of t h i s d i s o r d e r and due to the i n t e r e s t i n g concepts the r e l a t i o n -ship r a i s e s . d. Physical' A c t i v i t y as a Pr o t e c t i v e ; Factor f o r CHD P h y s i c a l a c t i v i t y as a f a c t o r i n r e l a t i o n to h e a l t h demonstrates a U-shaped curve. At the one extreme i s seden-t a r i n e s s which gives r i s e to the c o l l e c t i o n of d i s o r d e r s 2 65 r e f e r r e d to by Kraus and Raab as "hypokinetic diseases", i n c l u d i n g CHD. At t h i s end of the curve, p h y s i c a l i n a c t i v i t y i s p o s i t i v e l y a s s o c i a t e d w i t h CHD and can thus be construed as a true r i s k f a c t o r . At the other end of the curve i s the overuse syndrome, and, f o r CHD, p r e c i p i t a t i o n of acute events. In the middle of the curve, aerobic a c t i v i t y , e s p e c i a l l y at the t r a i n i n g l e v e l , i s n e g a t i v e l y a s s o c i a t e d w i t h CHD and other d i s o r d e r s and could thus be considered a p r o t e c t i v e f a c t o r , o r , as some would have i t , a negative r i s k f a c t o r . Is i n a c t i v i t y as a r i s k f a c t o r prevalent? Apparently, yes. As of 19 76, 41% of Canadians had no form of adequate 83 e x e r c i s e , and 5 3% had mainly sedentary jobs . The recent Canada 5 05 Health Survey revealed t h a t only 36% of Canadians e x e r c i s e - 70 -at the minimal recommended l e v e l , sedentariness as a r i s k f a c t o r i s does not seem to be alone i n t h i s to be most pr e v a l e n t i n the lower which have higher l e v e l s of other These data would suggest t h a t prev a l e n t indeed. And Canada respect. Moreover, i t seems 8 3 , 3 6 5 , 5 0 5 socxoeconomic groups ' r i s k f a c t o r s as w e l l . The o r i g i n a l s t u d i e s done on the r e l a t i o n s h i p of p h y s i c a l a c t i v i t y to CHD were occupational s t u d i e s on such groups as 3 3 1 3 3 4 4 2 7 busmen and farmers . Skinner , i n h i s comprehensive review of the t o p i c as of 1 9 6 6 , concluded that the evidence was merely "inference" due to the e f f e c t s of s e l e c t i o n , confounding v a r i a b l e s , environmental f a c t o r s (e.g. job t r a n s f e r s ) and the d i f f i c u l t y i n assessing what was " a c t i v e " and what was not. 3 3 1 o r i g i n a l study , these problems have been h i g h l i g h t e d by the Although study designs have improved since Morris and colleagues i l i g h t e d by the J-V. a. u u A 4.1. 4. • 1 4 5 , 1 4 6 , 1 5 2 , 1 5 4 , s e v e r a l reviews that have been done on the t o p i c 1 9 2 , 2 4 7 , 3 6 3 , 4 5 3 T • 3 J - J . - . • 1 9 9 , 3 2 9 , 4 9 4 ' ' ' . I n a d d i t i o n , more recent reviews ' ' have pointed to c o n s t i t u t i o n a l a s s o c i a t i o n as e x p l a i n i n g the r e l a t i o n s h i p . The problems i n study design and i n t e r p r e t a t i o n o 1 4 . i- 4 . 1 4 3 0 , 5 0 2 , 5 1 4 - 5 1 7 r e s u l t s have been reviewed r e c e n t l y ' . I n conse-4 3 0 quence, Sobolsky and colleagues have proposed a c o n t r o l l e d , p r o s p ective t r i a l . In s p i t e of these problems, however, much v a l i d i nformation has been c o l l e c t e d . (i) An'Independent Factor? Numerous studi e s have shown p h y s i c a l a c t i v i t y to be neg a t i v e l y a s s o c i a t e d with CHD independent of other f a c t o r s . - 71 -Kannel and h i s Framingham a s s o c i a t e s ' 1 1 " reported that sedentary-people had twice the CHD ( e s p e c i a l l y m o r t a l i t y ) of t h e i r a c t i v e counterparts, independent of r e l a t i v e weight, c h o l e s t e r o l and 329 blood pressure. Morris and colleagues , i n t h e i r study of B r i t i s h c i v i l servants, found that those who partook r e g u l a r l y of vigorous aerobic a c t i v i t y i n l e i s u r e time had h a l f the rate of f i r s t events of CHD t h a t sedentary employees had, indepen-dent of family h i s t o r y of CHD, shortness, body weight, smoking, high blood pressure and diabetes m e l l i t u s . Brunner and coworkers 63,64^ ^ n t h e i r study of over 10,000 people aged 40 to 64 years i n an I s r a e l i k i b b u t z , found t h a t the more sedentary people had s i g n i f i c a n t l y higher incidence of CHD than t h e i r more a c t i v e contemporaries, independent of age, sex, d i e t , c h o l e s t e r o l , t r i -g l y c e r i d e s , o b e s i t y , and l e i s u r e time a c t i v i t i e s . However, the authors of both of these s t u d i e s could not r u l e out the e f f e c t s of s e l e c t i o n on t h e i r r e s u l t s . The e f f e c t s of s e l e c t i o n were also queried by Hennekens 199 and a s s o c i a t e s i n t h e i r r e s u l t s from a r e t r o s p e c t i v e , matched c o n t r o l l e d study of 30 to 70 year o l d s . T h e i r r e s u l t s showed that people who were more p h y s i c a l l y a c t i v e during l e i s u r e time had lower CHD m o r t a l i t y than the sedentary c o n t r o l s even when adjusted f o r r e l a t i v e weight, race, coffee consumption, smoking, high blood pressure and job s t a t u s . Thus they f e l t t hat e x e r c i s e had a p r o t e c t i v e , r a t h e r than a s e l e c t i v e or c o n s t i t u t i o n a l 351 e f f e c t . A s i m i l a r c onclusion was reached by Paffenbarger based on a review of the l i t e r a t u r e and on h i s s t u d i e s of long-- 72 -351 355 352 357 shoremen 7 and c o l l e g e alumni 7 i n which the data were c o n t r o l l e d f o r other r e l a t e d CHD r i s k f a c t o r s . In a;recent e d i -t o r i a l , Paffenbarger and Hyde conclude that adequate p h y s i c a l a c t i v i t y does p r o t e c t against CHD independent of, as w e l l as through the m o d i f i c a t i o n of other r i s k f a c t o r s . I t s independent strength i s greater than body weight, but l e s s than high blood 352 pressure and smoking ( i i ) A R e s t r i c t e d Factor? P h y s i c a l a c t i v i t y i s one f a c t o r which has been repor-ted t o be as s o c i a t e d w i t h only c e r t a i n of the presentations of 351 353 355 CHD. Paffenbarger and colleagues ' 7 have shown that low work-related p h y s i c a l a c t i v i t y i n longshoremen was a s s o c i a t e d 353 wit h CHD (and stroke ) m o r t a l i t y , e s p e c i a l l y sudden death. 357 Their College Alumni Study , which concerned l e i s u r e - t i m e p h y s i c a l a c t i v i t y , showed a r e l a t i o n s h i p w i t h CHD i n general. The s t u d i e s of Morris and colleagues on l e i s u r e - t i m e p h y s i c a l a c t i v i t y i n male c i v i l servants showed an a s s o c i a t i o n w i t h both 77330 328 CHD m o r t a l i t y 7 and f i r s t events of any type , but more * JT J_ i 329 m. „ . . , 237,238,240 . . . so f o r f a t a l ones . The Framingham Study 7 , which d i d not d i s c r i m i n a t e as to type of a c t i v i t y , showed th a t increased p h y s i c a l a c t i v i t y was n e g a t i v e l y a s s o c i a t e d w i t h heart a t t a c k s , e s p e c i a l l y f a t a l ones, as w e l l as p o s i t i v e l y 74 w i t h angina p e c t o r i s . T h e i r recent review , however, reported a general decrease i n CHD morbidity and m o r t a l i t y w i t h increased l e i s u r e - t i m e p h y s i c a l a c t i v i t y . - 73 -145 192 The reviews by Fox and H a s k e l l ' concluded t h a t increased p h y s i c a l a c t i v i t y was c o r r e l a t e d n e g a t i v e l y w i t h heart a t t a c k , p a r t i c u l a r l y f a t a l ones, but th a t i t may w e l l be a r i s k f a c t o r f o r angina, e s p e c i a l l y i f the a c t i v i t y i s work-related. Further e l a b o r a t i o n concerning the importance of type of a c t i -183 v i t y i s obtained from the study by Gyntelberg . His study revealed t h a t p h y s i c a l a c t i v i t y a t work showed no s i g n i f i c a n t r e l a t i o n s h i p to heart a t t a c k but was p o s i t i v e l y a s s o c i a t e d w i t h angina, whereas p h y s i c a l a c t i v i t y during l e i s u r e time was nega-t i v e l y a s s o c i a t e d w i t h both. Indeed, of h i s middle-aged (40 to 59 years old) Danish men, those who were p h y s i c a l l y a c t i v e i n l e i s u r e time had v i r t u a l l y no CHD symptoms at a l l . Other studies which have d e a l t s o l e l y w i t h l e i s u r e - t i m e a c t i v i t y ' ' 381 have a l s o reported a negative c o r r e l a t i o n between vigorous a c t i v i t y and CHD g e n e r a l l y . ( i i i ) Occupational Versus Leisure-Time P h y s i c a l A c t i v i t y 183 As w e l l as Gyntelberg , numerous authors from seve-r a l c o u n t r i e s have reported a discrepancy between the r e l a t i o n -ship of occupational and l e i s u r e - t i m e p h y s i c a l a c t i v i t y and _„r.511/524 „ , . 64,199, 385,479 . _ CHD ' . Several such authors ' ' ' have found t h a t l e i s u r e - t i m e , but not occupational p h y s i c a l a c t i v i t y , had a op c p r o t e c t i v e e f f e c t f o r CHD, although Rosenman and colleagues 52 5 d i d observe a trend f o r occupational a c t i v i t y , but l a t e r , i n t h e i r male Federal Employees Study, found no a s s o c i a t i o n with 329 occupational a c t i v i t y . Morris and a s s o c i a t e s d i d f i n d both types of a c t i v i t y s i g n i f i c a n t l y a s s o c i a t e d w i t h CHD. However, - 74 -occupational vigorous a c t i v i t y was only s i g n i f i c a n t a f t e r age 50 and even then to a l e s s e r degree than l e i s u r e - t i m e e x e r c i s e . Bearing i n mind the numerous st u d i e s t h a t have shown an a s s o c i a -t i o n between occupational p h y s i c a l a c t i v i t y and CHD, i t would 10 494 appear that both types can probably be so r e l a t e d ' P a r t of the explanation f o r the discrepancy may r e s i d e i n s e l e c t i o n . Those people who are p h y s i c a l l y a c t i v e at l e i s u r e could w e l l be d i f f e r e n t c o n s t i t u t i o n a l l y from those a c t i v e on the job, w i t h the l a t t e r being more prone g e n e t i c a l l y (or the former more r e s i s t a n t ) to CHD. Those w i t h increased occupational a c t i v i t y do seem to have reduced l e i s u r e a c t i v i t y and v i c e versa 517 The s e l e c t i o n e f f e c t may a l s o apply to assocxated rxsk 3 86 f a c t o r s and l i f e s t y l e . For example, Wilhelmsen and coworkers found t h a t l e i s u r e - t i m e a c t i v i t y was n e g a t i v e l y a s s o c i a t e d with smoking and a l c o h o l intemperance, wh i l e occupational a c t i v i t y was p o s i t i v e l y a s s o c i a t e d . In a d d i t i o n , most (80%) of those who had stopped smoking were i n the a c t i v e - i n - l e i s u r e - t i m e group. 277 Hennekens and colleagues found a negative assocxatxon between l e i s u r e - t i m e a c t i v i t y and body weight, coffee consumption, smoking and high blood pressure, and a p o s i t i v e a s s o c i a t i o n 524 . . wxth job s t a t u s . Rose and Cohen found a posxtxve assocxatxon between l e i s u r e - t i m e a c t i v i t y and socioeconomic s t a t u s , i n t e l l i -gence, y o u t h f u l appearance and r u r a l l i v i n g , and a negative one with i l l n e s s e s , smoking, d r i n k i n g and worry. The opposite asso-c i a t i o n s were reported f o r o c c u p a t i o n a l a c t i v i t y . Rosenraan and 525 coworkers a l s o noted higher r i s k p r o f i l e s i n t h e i r male - 75 -f e d e r a l employees (aged 35 - 59) who had heavy work p h y s i c a l a c t i -v i t y , a f i n d i n g they f e l t was due to the lower socioeconomic sta t u s of t h i s group. These r e s u l t s would i n d i c a t e t h a t the l i f e s t y l e s and a s s o c i a t e d r i s k f a c t o r s are q u i t e d i f f e r e n t i n the two a c t i v i t y c a t e g o r i e s . Indeed, the discrepancy i n s o c i o -economic s t a t u s and c e r t a i n l i f e s t y l e h a b i t s was used by resear-277 370 chers ' to e x p l a i n why F i n n i s h lumberjacks, who had the most p h y s i c a l l y demanding jobs, a l s o had the highest CHD morta-l i t y . K a r v o n e n 5 1 1 concludes: "Endurance sports appear to be a s s o c i a t e d w i t h long l i f e , w hile p h y s i c a l l y heavy occupations may show the opposite". However, the l i f e s t y l e e x planation cannot e x p l a i n a l l 314 aspects. Menotti and a s s o c i a t e s found that I t a l i a n r a i l w a y employees who had the h e a v i e s t work d i d indeed have the lowest m o r t a l i t y from CHD, i n s p i t e of a higher m o r t a l i t y from a l l other causes, most notably lung d i s o r d e r s , v i o l e n c e and cancers. These r e s u l t s do i n d i c a t e that an adverse l i f e s t y l e i s asso-c i a t e d w i t h heavy work a c t i v i t y , but why the apparent p r o t e c t i v e e f f e c t f o r CHD i n t h i s case? The answer may w e l l l i e i n the nature of the job and thus the nature of the p h y s i c a l a c t i v i t y 4 78 so a s s o c i a t e d . For example, Wilhelmsen and T i b b l i n found that l e i s u r e - t i m e , but not occupational a c t i v i t y was a s s o c i a t e d n e g a t i v e l y w i t h r e s t i n g heart r a t e , suggesting t h a t l e i s u r e -time a c t i v i t y was having a t r a i n i n g e f f e c t but o c c u p a t i o n a l not. Such an explanation i s supported by p o s i t i v e c o r r e l a t i o n s between V0 o max and l e i s u r e - t i m e a c t i v i t y , but not w i t h occu-- 76 -p a t i o n a l J " 0 ' i ' z D U . I t could w e l l be that heavy occupational a c t i -184 v i t y i s o f t e n muscular and/or anaerobic, and not aerobic ; or i f a e r o b i c , of too low an i n t e n s i t y to have a t r a i n i n g e f f e c t . The s o c i a l and p h y s i c a l environments r e l a t e d to various occupa-t i o n s may a l s o play a r o l e . (iv) A Threshold E f f e c t B a s s l e r ^ 0 0 was one of the f i r s t to equate amount of e x e r c i s e w i t h p r o t e c t i o n against CHD. He f e l t that marathon runners are immune to CHD, and although the stance has a l s o 5X6522 been r e f u t e d ' i t s t i l l r a i s e d the p o s s i b i l i t y of a t h r e s h o l d 72 e f f e c t . Cassel , i n summarizing the Evans County Epidemiologic Study, concluded that "sustained p h y s i c a l a c t i v i t y above a c e r t a i n t h r e s h o l d value was p r o t e c t i v e against CHD". This study was probably the f i r s t to i n d i c a t e that there was a t h r e s h o l d 146 fo r e f f e c t . Fox and Naughton i n t h e i r review discussed the p o s s i b i l i t y t h a t the i n t e n s i t y , d u r a t i o n , frequency and type of e x e r c i s e were important. In a l a t e r review, Fox, Naughton and 5 36 Gorman found t h a t t h r e s h o l d values reported i n the l i t e r a t u r e ranged from 400 to 1200 K C a l per day i n excess of normal' r e q u i -rements. Energy expenditure over such thresholds halved the new incidence of CHD. The concept of t h r e s h o l d i s now widely 29 8 accepted , as i s the f a c t t h a t the e x e r c i s e needs to be aerobic. 351 Paffenbarger i n h i s longshoremen study concluded that to be e f f e c t i v e , work a c t i v i t y had to be greater than f i v e - 77 -k i l o c a l o r i e s (kcal) per minute, or 1,500 k c a l per week, over b a s a l metabolism. S i m i l a r f i n d i n g s were reported from h i s 352 College Alumni Study , where the t h r e s h o l d f o r l e i s u r e a c t i -v i t y was a s c e r t a i n e d to be greater than 2,000 k c a l , but reaching a p l a t e a u at 3,000 k c a l per week. Morris and c o l l e a -gues, i n t h e i r B r i t i s h c i v i l servant study, reported a higher 77 329 th r e s h o l d f o r l e i s u r e a c t i v i t y . Their e a r l i e r s t u d i e s ' estimated the t h r e s h o l d at 7.5 k c a l per minute, t h i s f i g u r e being r e v i s e d upward w i t h l a t e r reports to e x e r t i o n a t l e v e l s • 328 greater than 50% of VG^ max f o r a t l e a s t 15 minutes per time , and f i n a l l y to aerobic e x e r c i s e of such an i n t e n s i t y needed to 333 produce a t r a i n i n g e f f e c t . The l a t t e r t h r e s h o l d range i s 4 78 al s o reported by Wilhelmsen and T i b b l i n and recommended by 18 8 2 86 Hansen . Long i n h i s review of the t o p i c concluded that the t h r e s h o l d was i n the range of 6 t o 8 k c a l per minute (com-parable to a b r i s k 4 m.p.h. walk) for.15 to 30 minutes per day. Long a l s o added th a t the evidence i n d i c a t e d that greater l e v e l s conferred even more p r o t e c t i o n . Moreover, i t seems g e n e r a l l y agreed that such a p a t t e r n of e x e r c i s e has t o be l i f e l o n g t o 4 . 4 . - 4 ^ 4.145,192,325, 357,363 maintain the p r o t e c t i v e e f f e c t ' . 172 P a r a d o x i c a l l y , Goldsmith s t a t e s t h a t man i s a c t u a l l y more p h y s i c a l l y a c t i v e now than he was i n more p r i m i t i v e days, but that h i s p a t t e r n of e x e r c i s e i s d i f f e r e n t i n a c r i t i c a l way, i n t h a t he p r e s e n t l y lacks the s i n g l e short burst of intense a a c t i v i t y each day which may give p r o t e c t i o n against CHD. Gold-smith l i k e n s the present a c t i v i t y p a t t e r n to a " r e s t l e s s herbivore" - 78 -as opposed to the more p r i m i t i v e " f i g h t i n g c a r n i v o r e " . Gold-173 smith and Hale f e l t that such short bursts of intense a c t i -v i t y (wherein i n t e n s i t y and duration were c r i t i c a l ) during hunting and food gathering were " a l l - i m p o r t a n t " f o r a t r a i n i n g e f f e c t t o ensure p h y s i c a l f i t n e s s . The apparent n e c e s s i t y f o r p h y s i c a l a c t i v i t y to be aerobic and at a t r a i n i n g l e v e l to have a p r o t e c t i v e e f f e c t f o r CHD may w e l l be e x p l a i n e d , at l e a s t i n p a r t , by the p h y s i o l o g i c a l , biochemical and metabolic e f f e c t s of e x e r c i s e of such i n t e n s i t y discussed p r e v i o u s l y (p. 51) . (v) Modes of A c t i o n of Aerobic E x e r c i s e on CHD P h y s i c a l a c t i v i t y , l i k e any of the other p r o t e c t i v e f a c t o r s , could a c t a t any one or a l l of three stages i n the development of CHD: i n i t i a t i o n , progression of a t h e r o s c l e r o s i s 164 and p r e c i p i t a t i o n of an acute event. Glagov f e e l s that r e g u l a r aerobic e x e r c i s e a f f o r d s r e s i s t a n c e to the i n i t i a t i o n of CHD by i t s e f f e c t s of reducing abnormal mechanical s t r e s s e s on the coronary a r t e r i e s through the f o l l o w i n g four p o s s i b l e means: decreased heart rate ( r e s t i n g and work), p o s i t i v e vascu-l a r adaptations r e s u l t i n g from r e g u l a r s t i m u l a t i o n , increased 457 a r t e r i a l diameter and reduction of blood pressure. Texon reported that aerobic t r a i n i n g l e d to a decreased heart r a t e which, through reducing the v e l o c i t y of blood, reduced the damage to the a r t e r i e s ( i n t i m a l p r o l i f e r a t i o n ) . Thus, the absence of such abnormal mechanical s t r e s s e s could e i t h e r pre-vent or delay the i n i t i a l i n t i m a l i n j u r y and could thus a f f e c t - 79 -the whole subsequent development of CHD. As pointed out e a r l i e r , p h y s i c a l a c t i v i t y has been most s t r o n g l y c o r r e l a t e d i n v e r s e l y with f a t a l heart attack and sudden death. Any p r o t e c t i v e e f f e c t of r e g u l a r aerobic a c t i v i t y a gainst acute events i s unquestionably e x p l a i n e d by the e f f e c t s of such e x e r c i s e on the body as discussed p r e v i o u s l y . 329 The increased blood flow to the heart , p a r t i c u l a r l y as f a c i -T+. 4- A K u A 1 4- 145,237,240 ,323,354 l i t a t e d by enhanced coronary v a s c u l a t u r e , has been c r e d i t e d w i t h reducing the incidence of acute events, as has the increased e f f i c i e n c y of the heart l e a d i n g to decrea-A A A ±. -> * • -u 145,154,164, sed oxygen needs and b e t t e r t o l e r a n c e of ischemia 323 329 ' . In a d d i t i o n , the e f f e c t of aerobic a c t i v i t y i n redu-154 329 354 ci n g the v u l n e r a b i l i t y of the heart t o arrythmias ' ' has been put forward to e x p l a i n p a r t i c u l a r l y the a s s o c i a t i o n w i t h sudden death. F i n a l l y , the e f f e c t of a reduction i n the c l o t t i n g tendency, and enhanced c l o t d i s s o l u t i o n ( f i b r i n o l y s i s ) 145 323 329 ' ' ' have a l s o been considered as p a r t i a l e x p l a n a t i o n s . The p o s s i b l e e f f e c t of aerobic a c t i v i t y on atheroge-nesis has given r i s e to considerable debate. Some authors, such 2 40 as Kannel and colleagues , maintain that e x e r c i s e has no e f f e c t on the a t h e r o s c l e r o t i c process, and others , such as 192 H a s k e l l and Fox , contend that i t has l i t t l e e f f e c t . The evidence, both i n d i r e c t and d i r e c t , i s c o n f l i c t i n g . Some researchers working w i t h s t r e s s e l e c t r o c a r d i o g r a p h y have repor-ted a negative a s s o c i a t i o n between reg u l a r aerobic a c t i v i t y and - 80 -K T*.- 1 3 0 u - i 4-u 100 ,443 , . , , EKG abnormalities , wh i l e others ' have reported no such a s s o c i a t i o n . D i r e c t evidence from autopsy s t u d i e s i s more h e l p f u l . 96 Crawford , based on autopsies of motor v e h i c l e accident v i c t i m s , concluded that p h y s i c a l a c t i v i t y was a s s o c i a t e d nega-380 t i v e l y w i t h a t h e r o s c l e r o s i s of the coronary a r t e r i e s . Rissanen found t h a t men i n occupations demanding r e g u l a r p h y s i c a l a c t i -v i t y had l e s s extensive a t h e r o s c l e r o s i s than t h e i r sedentary 32 3 contemporaries. M i t r a m and coworkers found that sedentary workers over 40 had more severe narrowing of t h e i r coronary a r t e r i e s than t h e i r more a c t i v e peers, but not enough t o account f o r the excess of CHD i n the former. They thus concluded t h a t p h y s i c a l a c t i v i t y does indeed a f f e c t atherogenesis, but a l s o has important e f f e c t s on CHD through i t s a c t i o n s on heart f u n c t i o n and c i r c u l a t i o n and the n a t u r a l h i s t o r y of c l o t f o r -mation and d i s s o l u t i o n . 154 F r o e l i c h e r and as s o c i a t e s f e e l that p h y s i c a l a c t i v i -t y i s not d i r e c t l y r e l a t e d t o atherogenesis, but may be i n d i -r e c t l y r e l a t e d through i t s e f f e c t s on other CHD r i s k f a c t o r s . Moreover, such m o d i f i c a t i o n of r i s k f a c t o r s by e x e r c i s e may a l s o e x p l a i n p a r t of the e f f e c t s on the i n i t i a t i o n of CHD and the 45 145 202 p r e c i p i t a t i o n of acute events. Numerous authors ' ' ' 286 ,354,437 , , . , . , _ . ,.^. . . ' ' have hypothesized r i s k f a c t o r m o d i f i c a t i o n as an explanation f o r the e f f e c t s of aerobic a c t i v i t y , p a r t i c u l a r l y 4.1, v, 14. 4.- r u m „316 ,329 , , 145,286,437 through a l t e r a t i o n s of HDL-C ' and ob e s i t y ' ' - 81 -Indeed, i n a c t i v i t y and obe s i t y are as impressive i n t h e i r asso-c i a t i o n s w i t h d e l e t e r i o u s l e v e l s of many other r i s k f a c t o r s ( i n c l u d i n g one another) as t h e i r opposites, aerobic a c t i v i t y and leanness, are w i t h s a l u b r i o u s l e v e l s . (vi) E x e r c i s e as a P r e c i p i t a t o r of Acute Events Quite apart from the p r o t e c t i v e e f f e c t s of e x e r c i s e , which operate over the long term, are the short-term e f f e c t s of ina p p r o p r i a t e p h y s i c a l e x e r t i o n on a person already a f f l i c t e d with CHD. As was noted p r e v i o u s l y , a t h e r o s c l e r o s i s of the coronary a r t e r i e s r e s u l t s i n a reduced c a p a b i l i t y of supplying oxygen to the he a r t , a s i t u a t i o n aggravated by e x e r t i o n , which n e c e s s i t a t e s increased heart work and oxygen needs. Thus, 2 89 unaccustomed p h y s i c a l a c t i v i t y can lead t o c a r d i a c ischemia 204 289 347 which may cause angina or heart a t t a c k ' ' , e s p e c i a l l y i n those over f o r t y who smoke and have a fami l y h i s t o r y of 347 CHD . Such ischemia may a l s o lead to e l e c t r i c a l i n s t a b i l i t y 2 89 and thereby sudden death. However, i f a s e n s i b l e warmup i s used, the ischemia and dramatic increase i n s y s t o l i c blood 32 pressure are both abolished . Thus, i t i s the sudden and unac-customed e x e r t i o n i n people who are u n f i t and who possess other 34 7 CHD r i s k f a c t o r s that pose high r i s k . P h y s i c a l a c t i v i t y i s 251 safe i f adequate judgment i s used ( v i i ) Summary In summary, the evidence, i n d i c a t e s t h a t aerobic p h y s i -c a l a c t i v i t y a f f o r d s a p r o t e c t i v e e f f e c t against CHD, indepen-- 82 -dently of other r i s k f a c t o r s . However, i t seems to have a more pronounced e f f e c t on f a t a l events. Leisure-time a c t i v i t y , p o s s i b l y due to i t s more aerobic nature, o f f e r s a b e t t e r p r o t e c -t i v e e f f e c t than occupational a c t i v i t y . A t h r e s h o l d l e v e l of 6-8 kcal/min must be exceeded to b r i n g about the e f f e c t , and the e x e r c i s e must be i n continuous periods of 15-30 minutes, two to three times per week over the i n d i v i d u a l ' s l i f e . E x e r c i s e o f f e r s other h e a l t h b e n e f i t s as w e l l , and i s a s s o c i a t e d with reduced general m o r t a l i t y and morbidity. I t s mode of a c t i o n could be at any of the three stages of CHD development: i n i t i a t i o n , p rogression of a t h e r o s c l e r o s i s , or p r e c i p i t a t i o n of an acute event. For the l a t t e r i t can be both p r o t e c t i v e over the long term, and a p o t e n t i a l cause over the short term. P a r t of the e f f e c t a t a l l stages may be through the a s s o c i a t i o n w i t h other r i s k f a c t o r s . e. The A s s o c i a t i o n of A c t i v i t y w i t h Other Risk Factors E s t a b l i s h i n g an a s s o c i a t i o n between p h y s i c a l a c t i v i t y and other r i s k f a c t o r s i n v o l v e s problems s i m i l a r to the ones encountered i n e s t a b l i s h i n g i t s a s s o c i a t i o n w i t h CHD i t s e l f . 396 For example, Sedgwick and a s s o c i a t e s i n t h e i r study of men on an e x e r c i s e program concluded that the c l a s s i c a l r i s k f a c t o r s do not improve w i t h increased p h y s i c a l a c t i v i t y and f i t n e s s . However, t h e i r e x e r c i s e regimen was only one hour twice weekly and t h i s may w e l l not be frequent enough, and, since they d i d not monitor the e x e r c i s e pulse r a t e , there i s no d i r e c t way of t e l l i n g whether the i n t e n s i t y was adequate. The amount of - 83 -15 8 e x e r c i s e and i t s i n t e n s i t y are important c o n s i d e r a t i o n s Indeed, there i s a d e f i n i t e t h r e s h o l d e f f e c t f o r c e r t a i n f a c t o r s , 114 479 such as f i b r i n o l y s i s ' . There are a l s o problems w i t h the s t a r t i n g l e v e l of p h y s i c a l f i t n e s s (which i s not often measured) and the u l t i m a t e improvement i n the l e v e l s . Cooper and c o l l e a -89 * gues showed that only those i n the upper q u i n t i l e of VO^ max had c o n s i s t e n t l y lower values i n other r i s k f a c t o r s . 348 The type of e x e r c i s e seems important as w e l l 341 N i k k a l a and coworkers found that aerobic t r a i n i n g e x e r c i s e (long distance running) was e f f e c t i v e i n changing HDL-C; however, even very demanding anaerobic t r a i n i n g e x e r c i s e ') ( s p r i n t i n g ) was not. This phenomenon i s a l s o e x e m p l i f i e d by the f i n d i n g t h a t l e i s u r e - t i m e p h y s i c a l a c t i v i t y i s c o n s i s t e n t l y c o r r e l a t e d w i t h reduced r i s k f a c t o r s , whereas oc c u p a t i o n a l . ^ , 202,300,336,479 . , , , , a c t i v i t y may not be ' ' ' ; indeed, the l a t t e r may show • i • 262 ^ 4 . - * • 190 , the opposite c o r r e l a t i o n . Duration of e x e r c i s e and regu-49 7 l a r i t y of attendance (frequency) are a l s o determinants. Another problem i n e x e r c i s e study design i s c o n t r o l 2 86 f o r concomitant changes i n other behaviour , f o r example i n 2 62 d i e t , and t h i s a p p l i e s t o c o n t r o l s as w e l l . For example, 454 Taylor and colleagues reported no change i n c h o l e s t e r o l , blood pressure or smoking between t h e i r experimental group placed on an e x e r c i s e program and the c o n t r o l group; however, the c o n t r o l group a l s o showed s i g n i f i c a n t increases i n p h y s i c a l f i t n e s s l e v e l s i n d i c a t i n g that the members were indeed more - 84 -p h y s i c a l l y a c t i v e during the study than they had been before. The e f f e c t s of concomitant changes i n d i e t and a c t i v i t y i n c o n t r o l s a l s o obscured the r e s u l t s of Ilmarinen and c o l l e a -219 462 gues . T r i s t a n i has described the tendency f o r c o n t r o l groups i n c l i n i c a l t r i a l s to adopt p o s i t i v e behavioural changes i n response to being i n v o l v e d i n a study. The same reasoning a p p l i e s t o concomitant changes i n some other r i s k f a c t o r s which a f f e c t changes i n yet other r i s k f a c t o r s ; that i s , so that A i s as s o c i a t e d w i t h changes i n C only through B. For example, r e g u l a r aerobic e x e r c i s e i s asso-c i a t e d w i t h a reduction i n o b e s i t y , and obe s i t y i s known to be one r i s k f a c t o r w i t h which numerous other r i s k f a c t o r s are asso-218 32 6 c i a t e d . Some authors ' found that the e f f e c t s of e x e r c i s e on serum l i p i d s were i n s i g n i f i c a n t when account was taken of the attendant reduction i n o b e s i t y . In a d d i t i o n , i t i s known t h a t p h y s i c a l a c t i v i t y i s h i g h e r , the higher the socio-economic 83 336 statu s ' . One of these f a c t o r s could be a confounding v a r i a b l e . Not s u r p r i s i n g l y , the t o p i c of c o n s t i t u t i o n a l asso-c i a t i o n 'also comes up, e s p e c i a l l y w i t h respect t o cross-sec-190 t i o n a l s t u d i e s . Thus, when an a s s o c i a t i o n between p h y s i c a l a c t i v i t y and reduced r i s k f a c t o r s , or indeed between improvement i n p h y s i c a l f i t n e s s and reduced r i s k f a c t o r s , i s shown, i t could be simply the r e s u l t of selection... Indeed, Morris and asso-329 c i a t e s d i d f i n d that vigorous e x e r c i s e r s were t a l l e r and - 85 -l e s s obese, smoked l e s s and had longer f a m i l y l o n g e v i t y than 396 l e s s a c t i v e people. Sedgwick and as s o c i a t e s f e e l t h a t s e l e c -t i o n accounts f o r a l l such a s s o c i a t i o n s between p h y s i c a l a c t i -336 v i t y and both r i s k f a c t o r s and CHD. Mulcahy , however, f e e l s that the a s s o c i a t i o n " i s probably based on a combination of some 49 4 s e l e c t i o n and some degree of p r o t e c t i o n " . Wyndham i n h i s recent review of the t o p i c could not r u l e out c o n s t i t u t i o n a l e f f e c t s i n the a s s o c i a t i o n between p h y s i c a l a c t i v i t y and r i s k f a c t o r s . The r e s t r i c t i o n s of c o n s t i t u t i o n a l a s s o c i a t i o n s u r e l y apply when l o o k i n g at c r o s s - s e c t i o n a l s t u d i e s comparing runners 19 0 to non-runners . They a l s o apply when l o o k i n g at people of various f i t n e s s l e v e l s . However, i t i s p a r t i c u l a r l y d i f f i c u l t to invoke c o n s t i t u t i o n a l a s s o c i a t i o n i n e x p l a i n i n g the a s s o c i a -t i o n over time between improvement i n aerobic f i t n e s s , or properly-monitored aerobic a c t i v i t y , and improvement i n r i s k f a c t o r s t a t u s . There i s a l o t of evidence showing'j various a s s o c i a t i o n s between aerobic p h y s i c a l a c t i v i t y and CHD r i s k f a c t o r s , and l i t t l e evidence to the contrary. Table 2.3 summarizes the a s s o c i a t i o n s between r e g u l a r aerobic e x e r c i s e and other CHD r i s k f a c t o r s . (i) Ob e s i ty / 0 ve rwe i gh t t. 46 ... ,.. 233,270,287,291,294,329, With one exception , s t u d i e s 4 1 9 show ob e s i t y to be uniformly reduced by re g u l a r aerobic a c t i v i t y . The same does not apply to body weight, since - 86 -Table 2.3 A s s o c i a t i o n s Between Regular Aerobic A c t i v i t y and  Other Risk F a c t o r s . Each r i s k f a c t o r i s entered under the p o s i t i v e or negative columns depending on the type of a s s o c i a t i o n . P o s i t i v e Negative Socioeconomic st a t u s Occupational status E d u c a t i o n a l status Male sex F i b r i n o l y s i s V i t a l c a p acity Serum : HDL : HDL/TC Ratio Age Body weight Obesity Diet (high s a t u r a t e d f a t , c h o l e s t e r o l ) Serum : t o t a l c h o l e s t e r o l (TC) LDL-C VLDL-C T r i g l y c e r i d e s u r i c a c i d Blood Sugar : f a s t i n g : glucose tolerance : diabetes m e l l i t u s Blood Pressure : s y s t o l i c : d i a s t o l i c Smoking Mental s t r e s s - 87 -se v e r a l s t u d i e s have shown no change i n w e i g h t 3 1 ' ^ ' . However, since two of these l a t t e r s t u d i e s a l s o showed a reduction i n o b e s i t y * ^ ' , t h i s probably s i g n i f y i n g t h a t as e x e r c i s e pro-gresses, f a t t i s s u e i s used up at approximately the same rate that muscle t i s s u e i s synthesized (thereby seemingly confirming the f o l k l o r e t h a t muscle replaces f a t , and v i c e v e r s a ) . Other . ,. 117,120,158,190,269,300,359,419,497 , . . stu d i e s ' ' ' ' ' , however, have shown a reduction of both body weight and o b e s i t y w i t h aerobic exer-. 88,94,166,199,202,211,218,286,351, c i s e . S t i l l other studies ' ' t i i t , i i 4 9 ^ , not l o o k i n g at f a t t i s s u e , have merely shown a reduction i n body weight. O v e r a l l , these e f f e c t s give e x e r c i s e a c l e a r r o l e . _p i .. 21,23,83,303, 304,316,425,427,432,459 i n the therapy of o b e s i t y > > i > > > > ' > ^ I t should be emphasized t h a t with respect to o b e s i t y , as opposed to the other r i s k f a c t o r s , i t i s the amount of aerobic a c t i v i t y , r a t h e r than the l e v e l , t h a t i s most imp o r t a n t 1 . ( i i ) Serum T r i g l y c e r i d e s Another r i s k f a c t o r uniformly reported as reduced by 4 . - • 4 . • , -A 46,117,120,158,174, aerobic a c t i v i t y i s serum t r i g l y c e r i d e s 190,205,209,270,287,300,348,388,479,486,489,497_ Q n l y Q n e s t u d y 294 482 showed t h a t t r i g l y c e r i d e s increased, and one that i t 190 remained unchanged. Studies of t r i g l y c e r i d e s i n runners ' 490 491 ' have shown that the l e v e l of t r i g l y c e r i d e s i s propor-490 t i o n a l t o the distance run, even when c o n t r o l l e d f o r o b e s i t y Most of the other s t u d i e s have not c o n t r o l l e d f o r o b e s i t y , which i s very c l o s e l y a s s o c i a t e d w i t h serum l i p i d s . Indeed, one study has shown that the e f f e c t s of an e x e r c i s e program - 88 -on t r i g l y c e r i d e s disappeared a f t e r c o n t r o l l i n g f o r concomitant 185 weight l o s s , although another study showed t h a t the two were p a r t i a l l y independent. Moreover, the e f f e c t s of e x e r c i s e on 326 348 t r i g l y c e r i d e s l a s t only from three to four days ' a f t e r e x e r c i s e ceases. This time i s i n s u f f i c i e n t to c r e d i t the e f f e c t s on t r i g l y c e r i d e s s o l e l y to subsequent weight gain. 359 I n t e r e s t i n g l y , one study found t h a t t r i g l y c e r i d e s were reduced i n t i a l l y but returned to pre - e x e r c i s e l e v e l s a f t e r two years, despite the p e r s i s t e n c e of e x e r c i s e . ( i i i ) Serum C h o l e s t e r o l s The reported e f f e c t s on serum c h o l e s t e r o l s are not so c o n s i s t e n t . There are numerous reports of a lowering of cho l e s -t e r o l w i t h aerobic a c t i v i t y31,H7,158,190,233,234,294,353,367 f 384 423 486 491 ' ' ' . On the other hand, other authors have reported a s i g n i f i c a n t r e d u c t i o n only w i t h concomitant d i e t a r y r e s t r i c -174 t i o n s , while s t i l l others have reported n o n - s i g n i f i c a n t 120 489 reductions or reductions that were v a r i a b l e . Wilhelmsen 32 6 and a s s o c i a t e s reported the e f f e c t s disappearing when c o n t r o l -490 l e d f o r o b e s i t y , although Wood and associates reported t h a t 45 46 269 they p e r s i s t e d when so c o n t r o l l e d . Numerous studi e s ' ' ' 359 454 455 479 482 ' - ' i i have reported no a s s o c i a t e d lowering of c h o l e s t e r o l . P a r t of these c o n t r a d i c t i o n s i n r e s u l t s concerning c h o l e s t e r o l and aerobic a c t i v i t y may be accounted f o r by v a r i a -t i o n s i n type, d u r a t i o n , i n t e n s i t y and frequency of e x e r c i s e . - 89 -For example, c h o l e s t e r o l - l o w e r i n g seems r e s t r i c t e d to l e i s u r e -4 - - - 4 - 202,300 „ . , . , 190 time a c t i v i t y . Moreover, Hartung and as s o c i a t e s report that the e f f e c t i s dependent on the distance run f o r 49 7 runners, t h a t i s , the duration of e x e r c i s e . Other authors have reported that the e f f e c t depended on the number of e x e r c i s e sessions attended, that i s , on the frequency of e x e r c i s e . 419 Shephard and coworkers , r e p o r t i n g on t h e i r i n d u s t r i a l f i t n e s s program, found few favorable changes i n serum l i p i d s , i n s p i t e of decreased percent body f a t and body weight. However, n o t i n g there was only a 3.3 ml/kg.min change i n V0 2 max, the authors concluded that the l e v e l of e x e r c i s e was p o s s i b l y too low to a f f e c t the l i p i d s s i g n i f i c a n t l y . This c o n c l u s i o n i s supported 8 9 by the work of Cooper and ass o c i a t e s who showed c o n s i s t e n t l y s i g n i f i c a n t c o r r e l a t i o n s of c h o l e s t e r o l w i t h V0 2 max only i n those w i t h values i n the highest q u i n t i l e . 494 However, Wyndham , i n h i s review, concludes that the evidence i s i n c o n c l u s i v e , p r i n c i p a l l y because the st u d i e s showing no e f f e c t seemed to have b e t t e r designs and thus c a r r i e d more weight. In the l i g h t of the dis c r e p a n c i e s i n type, d u r a t i o n , frequency and i n t e n s i t y of e x e r c i s e mentioned p r e v i o u s l y , I do not e n t i r e l y agree. For example, Wyndham st r e s s e s the impor-219 tance of Ilmarinen and a s s o c i a t e s ' study due to i t s design. However, not only d i d the program f a i l to,maintain the de s i r e d l e v e l of p h y s i c a l f i t n e s s to the end of "the study p e r i o d - the l e v e l a c t u a l l y decreased i n the study group - but the c o n t r o l group increased t h e i r l e v e l of a c t i v i t y . Moreover, both groups - 90 -reduced t h e i r smoking and f a t consumption. (This i s another example of p o s i t i v e behavioural change i n a c o n t r o l group o f a 462 c l i n i c a l t r i a l .) L i t t l e wonder then t h a t there was no d i f f e -rence between the groups. I do agree w i t h Wyndham's recommenda-t i o n f o r more randomized, c o n t r o l l e d s t u d i e s . Such a recommen-dation i s a p p l i c a b l e t o the whole of the a s s o c i a t i o n between a c t i v i t y and both r i s k f a c t o r s and CHD. P a r t of the v a r i a b l e e f f e c t of e x e r c i s e on c h o l e s t e r o l l e v e l s may a l s o be r e l a t e d to the var y i n g e f f e c t s of e x e r c i s e on the components c o n s t i t u t i n g t o t a l serum c h o l e s t e r o l (TSC) that i s , on VLDL, LDL and HDL c h o l e s t e r o l . Aerobic e x e r c i s e has been 209 489 as s o c i a t e d w i t h a lowering of VLDL ' , a not s u r p r i s i n g f i n d i n g since VLDL i s mostly t r i g l y c e r i d e s produced by the l i v e r , w i t h only a r e l a t i v e l y s m a ll amount of c h o l e s t e r o l . However, LDL-C, accounting f o r the bulk of c h o l e s t e r o l , has a l s o K i ' 4_ J • 205,388,489,490 ,491 been shown to decrease w i t h e x e r c i s e , p a r t i -8 c u l a r l y when accompanied by a low f a t d i e t . By f a r the most i n t e r e s t i n g , and p o t e n t i a l l y the most s i g n i f i c a n t a s s o c i a t i o n i s the accompanying increase i n HDL-C. HDL-C has been reported to increase w i t h regular aerobic p h y s i -, . . ., 312,341,367,388,491 m, . „ . , , c a l a c t i v i t y ' ' ' ' . This e f f e c t has been reported to be obtainable w i t h even moderate e x e r c i s e a f t e r only one T209 . , , . ,. . ,190,489 , . , , , _ week , appears t o be dose-related ' and independent of a 490 reduction i n body f a t (which d i d account f o r some of the 19 3 i n c r e a s e ) , of sex and of changes i n t o t a l c h o l e s t e r o l and - 91 -4 82 t r i g l y c e r i d e s . One o v e r a l l e f f e c t i s an e l e v a t i o n i n the HDL/TSC r a t i o 1 9 0 ' 4 9 1 . Since an ele v a t e d HDL and HDL/TSC r a t i o are apparently p r o t e c t i v e against CHD, t h i s e f f e c t of e x e r c i s e may w e l l be a key component i n i t s p o s s i b l e r o l e i n the athero-genic process. Coupled w i t h the o v e r a l l favorable e f f e c t on 468 19 3 the l i p i d p r o f i l e of both men and women undertaking r e g u l a r aerobic e x e r c i s e , such f i n d i n g s could w e l l endow e x e r c i s e w i t h a c e n t r a l r o l e i n CHD prevention, p a r t i c u l a r l y i n the l i g h t of the concomitant reduction i n ob e s i t y and tendency t o change d i e t a r y 117 h a b i t s . C e r t a i n l y , such a • l i p i d - n o r m a l i z i n g e f f e c t i s mainly r e s p o n s i b l e f o r aerobic e x e r c i s e being a t h e r a p e u t i c modality f o r the treatment of h y p e r l i p i d e m i a s , e s p e c i a l l y 159 185 494 Type IV ' ' , p a r t i c u l a r l y when combined w i t h a low f a t A ' 4- - 4 - U U - U U • 4 - - « 4.159, 422,494 d i e t w i t h which e x e r c i s e has a s y n e r g i s t i c e f f e c t (iv) Blood Pressure Programs of r e g u l a r aerobic e x e r c i s e have been shown 4- K - l . T , . , . , , , 45,199 ,294 ,497 to be r e l a t e d to a decrease i n blood pressure ' , 53 being e f f e c t i v e on hypertensive people as w e l l . In f a c t , 79 Choquette and Ferguson reported t h a t hypertensive p a r t i -c i p a n t s i n an e x e r c i s e program r e a l i z e d a much greater b e n e f i t than normotensives d i d . The e f f e c t s have been reported f o r both 4 . , • 45,46,117,120,211,359 , ,. . ,. 31,46 ,117,158 the s y s t o l i c ' ' and d i a s t o l i c ' ' ' components. However, the r e s u l t s have been v a r i a b l e . C e r t a i n authors have reported a d e f i n i t e lowering of s y s t o l i c blood pressure but a v a r i a b l e 4 5 or n o n - s i g n i f i c a n t 1 2 0 , 2 1 1 - 92 -158 e f f e c t on d i a s t o l i c , and the reverse has a l s o been reported 53 Moreover, Boyer and Kasch reported that both components were lowered i n hypertensive p a r t i c i p a n t s , whereas, i n normotensive p a r t i c i p a n t s only the d i a s t o l i c component was lowered. Paolone 359 and a s s o c i a t e s reported a c o n s i s t e n t lowering e f f e c t on s y s t o l i c ; but on d i a s t o l i c reported a decrease a f t e r one year w i t h a retu r n to pre- e x e r c i s e l e v e l s a f t e r two years. Cooper 89 and colleagues , on the other hand, reported that d i a s t o l i c blood pressure was only s i g n i f i c a n t l y lower i n those men i n • 31 the upper q u i n t i l e of VG^ max. Barnard and Anthony , on the con t r a r y , reported a c o n s i s t e n t e f f e c t on d i a s t o l i c , but an e f f e c t on s y s t o l i c only i n men over 50 years of age. Some authors have reported no a s s o c i a t i o n of blood 454 455 pressure w i t h e i t h e r e x e r c i s e programs ' or s e l f - r e p o r t e d 384 479 a c t i v i t y ' , qu i t e p o s s i b l y due to the problems of type, d u r a t i o n , i n t e n s i t y and frequency mentioned e a r l i e r . The study 454 455 of T a y l o r and colleagues ' was indeed confounded by the f a c t that both t h e i r c o n t r o l and experimental groups showed 494 improvement i n p h y s i c a l f i t n e s s l e v e l s . Wyndham , i n h i s review, concluded that e x e r c i s e does lead to lowered blood pressure, a conclusion supported by the r o l e of e x e r c i s e as a 53 79 427 459 thera p e u t i c modality f o r high blood pressure ' ' ' . (v) Smoking The reported r e l a t i o n s h i p of aerobic e x e r c i s e t o smo^ king behaviour has been q u i t e v a r i a b l e . The st u d i e s which show - 93 -. . . . . . , . , . . 7 7 , 1 1 7 , 1 9 9 , 2 7 4 , 3 5 1 , 4 7 9 an a s s o c i a t i o n with smoking reduction ' ' are v. i A K 4.1. . . i i . , . . 5 6 , 1 4 2 , 3 2 8 , 3 8 4 , balanced by those which show no such reduction ' ' 454 4 5 5 4 9 7 ' . Some studies have shown a s t a t i s t i c a l l y n o n - s i g n i -2 0 2 f i c a n t r e d u c t i o n , while others have reported a reduction only i n those l e s s than s i x t y , and only i n a s s o c i a t i o n w i t h l e i s u r e -2 86 time a c t i v i t y . In s p i t e of such v a r i a b i l i t y , Long concludes that aerobic e x e r c i s e i s ass o c i a t e d w i t h reduced smoking. (vi) Serum U r i c A c i d The a s s o c i a t i o n of aerobic a c t i v i t y w i t h serum u r i c a c i d i s the most v a r i a b l e of a l l . Authors have reported that 52 32 7 " r e g u l a r aerobic e x e r c i s e lowers and r a i s e s , has a v a r i a b l e 2 9 4 359 4 9 7 e f f e c t and no e f f e c t at a l l ' . P a r t of the expl a n a t i o n may once again r e s t i n the extent of t r a i n i n g . For example, 89 Cooper and as s o c i a t e s reported an a s s o c i a t i o n between decreased l e v e l s and e x e r c i s e only i n those i n the upper q u i n t i l e of f i t n e s s . The r e s u l t s remain i n c o n c l u s i v e . ( v i i ) Blood Sugar S i m i l a r l y v a r i a b l e r e s u l t s are seen i n a s s o c i a t i o n w i t h f a s t i n g blood sugar l e v e l s . Some studies have shown an increase 4 9 7 i n blood sugar w i t h an ex e r c i s e program , e s p e c i a l l y a f t e r two 359 2 9 1 years . Others have shown a decrease e s p e c i a l l y i n those 2 70 w i t h h y p e r l i p i d e m i a (Type IV) . Once again, the answer to such c o n f l i c t i n g r e s u l t s may l i e i n the t r a i n i n g l e v e l , s i n c e 89 Cooper and associates found that blood sugar was s i g n i f i c a n t l y d i f f e r e n t only between those i n the two extreme q u i n t i l e s of - 94 -f i t n e s s l e v e l . The e f f e c t s of aerobic e x e r c i s e i n enhancing glucose 4 - i v, 4. 4. -.158 ,461,486 ., . c c . t o l e r a n c e , however, are not contested ' , t h i s e f f e c t undoubtedly being p a r t l y r e s p o n s i b l e f o r the use of e x e r c i s e i n 138 427 459 the management of diabetes m e l l i t u s ' ' . However, the e f f e c t of e x e r c i s e on i n c r e a s i n g the number of i n s u l i n b i n d i n g ., 432 , n ... ., . n. 41,181 , , s i t e s and c e l l u l a r s e n s i t i v i t y to i n s u l i n a l s o plays a r o l e i n the therapeutic choice of e x e r c i s e , as i t does i n the 432 treatment of other i n s u l i n - r e s i s t a n t s t a t e s such as o b e s i t y ' ( v i i i ) F i b r i n o l y s i s Aerobic a c t i v i t y has a l s o been reported to enhance . , . 24,114,479 ,482 . . .. • , ...114,479 f i b r i n o l y s i s ' ' , an e f f e c t with a t h r e s h o l d which has been reported to be i n excess of 40% of the VG^ max 479 The e f f e c t does not occur i n a l l people, and occurs unequally i n others: the response i s poor i n insulin-dependent 2 4 diabetes and Type IV l i p o p r o t e m e m i a (ix) Mental Stress Regular aerobic e x e r c i s e r e p o r t e d l y reduces mental 45,82,154,162,234,372,378,461,486 _. . . .. .. s t r e s s i > i ' i ' ' > Since aerobic a c t i v i t y counterbalances the p h y s i o l o g i c consequences of s t r e s s , E l i o t 127 and colleagues recommend i t as a the r a p e u t i c and p r o p h y l a c t i c t o o l f o r s t r e s s d i s o r d e r s . - 95 -(x) Fundamental B i o l o g i c a l Factors P h y s i c a l a c t i v i t y i s a l s o a s s o c i a t e d w i t h other r i s k f a c t o r s which are e i t h e r not m o d i f i a b l e or e s s e n t i a l l y not. E x e r c i s e decreases as socioeconomic and e d u c a t i o n a l s t a t u s 8 3 336 decrease ' In a d d i t i o n , Canadian women are not as p h y s i -8 3 c a l l y a c t i v e as men 13 Age i s n e g a t i v e l y c o r r e l a t e d w i t h p h y s i c a l a c t i v i t y ' 83 437 448 ' l e a d i n g to what Stoedefalke c a l l s the middle-aged t r o i k a : weak musculature, l a c k of f l e x i b i l i t y and low endurance. The decrease i n a c t i v i t y w i t h age may be one f a c t o r r e l a t e d to the increased r i s k of CHD seen w i t h aging. However, age a f f e c t s aerobic e x e r c i s e as a r i s k f a c t o r . For example, M o r r i s and 329 colleagues reported that the b e n e f i t s of l e i s u r e - t i m e a c t i -v i t y on CHD increased w i t h age, e s p e c i a l l y a f t e r age 50 years. 385 S i m i l a r r e s u l t s were reported by Rosenman and colleagues i n t h e i r Western C o l l a b o r a t i v e Group Study. I n t e r e s t i n g l y , T i b b l i n and a s s o c i a t e s 4 ^ 0 reported no a s s o c i a t i o n of l e i s u r e - t i m e exer-c i s e h a b i t s and f a t a l heart attack at age 50. Concerning occu-355 p a t i o n a l a c t i v i t y , Paffenbarger and coworkers found that t h e i r longshoremen w i t h high energy outputs on the job had decreased f a t a l CHD events only i n the age range 35 to 54 years. Although t h i s r e p o r t seems at odds with the previous s t u d i e s , the e x p l a -n a t i o n appears to l i e i n the nature of the a c t i v i t y . Wilhelmsen 4 78 and cohorts found t h a t occupational p h y s i c a l a c t i v i t y was e f f e c t i v e during youth, but t h a t l e i s u r e - t i m e a c t i v i t y was i n l a t e r years. The e f f c t s of aerobic a c i v i t y thus - 96 -seem age-dependent. (xi) Summary In summary, ex e r c i s e i s ass o c i a t e d with other CHD r i s k f a c t o r s . Regular aerobic e x e r c i s e leads t o a reduction i n body f a t (and u s u a l l y body weight) and has a general favorable i n f l u e n c e on serum l i p i d s , p a r t i c u l a r l y lowering VLDL, LDL-C and r a i s i n g HDL-C and the HDL-C/TSC r a t i o . Aerobic a c t i v i t y a l s o counterbalances the p h y s i o l o g i c a l e f f e c t s of p s y c h o l o g i c a l s t r e s s , enhances f i b r i n o l y s i s , lowers blood pressure ( e s p e c i a l l y i n hypertensives) and improves glucose metabolism ( e s p e c i a l l y i n d i a b e t i c s ) . I t has a v a r i a b l e e f f e c t on serum u r i c a c i d and smoking behaviour, and i t not only decreases w i t h age, but i s v a r i a b l e with age i n i t s r o l e as a p r o t e c t i v e f a c t o r . The asso-c i a t i o n of aerobic a c t i v i t y with other r i s k f a c t o r s i s dependent on the type, i n t e n s i t y , duration and frequency of e x e r c i s e , as i s i t s a s s o c i a t i o n w i t h CHD i t s e l f . f. Conclusions This s e c t i o n on p h y s i c a l a c t i v i t y and ex e r c i s e has shown that r e g u l a r , l i f e l o n g aerobic p h y s i c a l a c t i v i t y has many p o s i t i v e e f f e c t s on the body's metabolism, biochemistry, anatomy and physiology. In a d d i t i o n i t has many s a l u b r i o u s p s y c h o l o g i -c a l e f f e c t s . Such e f f e c t s are the b a s i s of the e f f e c t s on h e a l t h g e n e r a l l y , and CHD s p e c i f i c a l l y . C e r t a i n l y the e f f e c t s on the c a r d i o v a s c u l a r - r e s p i r a t o r y system go a long way i n e x p l a i n i n g the p r o t e c t i v e e f f e c t of aerobic a c t i v i t y f o r