Medicine, Faculty of
Other UBC
Non UBC
Pediatrics, Department of
Population and Public Health (SPPH), School of
DSpace
Jin A, Lalonde CE, Brussoni M, McCormick R, George MA (2015) Injury Hospitalizations Due to Unintentional Falls among the Aboriginal Population of British Columbia, Canada: Incidence, Changes over Time, and Ecological Analysis of Risk Markers, 1991-2010. PLoS ONE 10(3): e0121694.
B.C. Injury Research and Prevention Unit
Child and Family Research Institute
Jin et al.
Jin, Andrew
Lalonde, Christopher E.
Brussoni, Mariana
McCormick, Rod
George, M. Anne
Background: Aboriginal people in British Columbia (BC) have higher injury incidence than the general population. Our project describes variability among injury categories, time periods, and geographic, demographic and socio-economic groups. This report focuses on unintentional falls. Results: During 1991 through 2010, the crude rate of hospitalization for unintentional fall injury in BC was 33.6 per 10,000 person-years. The Aboriginal rate was 49.9 per 10,000 and SRR was 1.89 (95% confidence interval 1.85-1.94). Among those living on reserves SRR was 2.00 (95% CI 1.93-2.07). Northern and non-urban HSDAs had higher SRRs, within both total and Aboriginal populations. In every age and gender category, the HSDA-standardized SRR was higher among the Aboriginal than among the total population. Between 1991 and 2010, crude rates and SRRs declined substantially, but proportionally more among the Aboriginal population, so the gap between the Aboriginal and total population is narrowing, particularly among females and older adults. These community characteristics were associated with higher risk: lower income, lower educational level, worse housing conditions, and more hazardous types of employment. Conclusions: Over the years, as socio-economic conditions improve, risk of hospitalization due to unintentional fall injury has declined among the Aboriginal population. Women and older adults have benefited more.
RESEARCH ARTICLEInjury Hospitalizations Due to UnintentionalFalls among the Aboriginal Population ofBritish Columbia, Canada: Incidence,Changes over Time, and Ecological Analysisof Risk Markers, 1991-2010Andrew Jin1☯, Christopher E. Lalonde2☯, Mariana Brussoni3,4,5☯¤a, Rod McCormick6☯,M. Anne George3,4,5☯¤b*1 Epidemiology Consultant, Surrey, British Columbia, Canada, 2 Department of Psychology, Faculty ofSocial Sciences, University of Victoria, Victoria, British Columbia, Canada, 3 Department of Pediatrics,Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada, 4 Child andFamily Research Institute, Vancouver, British Columbia, Canada, 5 School of Population and Public Health,University of British Columbia, Vancouver, British Columbia, Canada, 6 Faculty of Human, Social andEducational Development, Thompson Rivers University, Kamloops, British Columbia, Canada☯ These authors contributed equally to this work.¤a Current address: BC Injury Research & Prevention Unit, Vancouver, British Columbia, Canada¤b Current address: University of Northern British Columbia, Prince George, British Columbia, Canada* ageorge@mail.ubc.caAbstractBackgroundAboriginal people in British Columbia (BC) have higher injury incidence than the general pop-ulation. Our project describes variability among injury categories, time periods, and geo-graphic, demographic and socio-economic groups. This report focuses on unintentional falls.MethodsWe used BC’s universal health care insurance plan as a population registry, linked to hospi-tal separation and vital statistics databases. We identified Aboriginal people by insurancepremium group and birth and death record notations. We identified residents of specific Ab-original communities by postal code. We calculated crude incidence and Standardized Rel-ative Risk (SRR) of hospitalization for unintentional fall injury, standardized for age, genderand Health Service Delivery Area (HSDA), relative to the total population of BC. We testedhypothesized associations of geographic, socio-economic, and employment-related char-acteristics with community SRR of injury by linear regression.ResultsDuring 1991 through 2010, the crude rate of hospitalization for unintentional fall injury in BCwas 33.6 per 10,000 person-years. The Aboriginal rate was 49.9 per 10,000 and SRR wasPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 1 / 19OPEN ACCESSCitation: Jin A, Lalonde CE, Brussoni M, McCormickR, George MA (2015) Injury Hospitalizations Due toUnintentional Falls among the Aboriginal Populationof British Columbia, Canada: Incidence, Changesover Time, and Ecological Analysis of Risk Markers,1991-2010. PLoS ONE 10(3): e0121694.doi:10.1371/journal.pone.0121694Academic Editor: Dena L. Schanzer, Public HealthAgency of Canada, CANADAReceived: October 17, 2014Accepted: February 3, 2015Published: March 20, 2015Copyright: © 2015 Jin et al. This is an open accessarticle distributed under the terms of the CreativeCommons Attribution License, which permitsunrestricted use, distribution, and reproduction in anymedium, provided the original author and source arecredited.Data Availability Statement: The data that westudied are available on request, from PopulationData BC (https://www.popdata.bc.ca/data, contact:Kelly Sanderson, Researcher Liaison Unit Lead, e-mail: kelly.sanderson@popdata.bc.ca; specificationsin project file George 11–012) subject to approval bythe Data Stewards representing the British ColumbiaMinistry of Health Services, and the Vital StatisticsAgency of British Columbia, for ethical and privacyreasons, because the data pertain to individuals. Thedata may be accessed and statistically analysed only1.89 (95% confidence interval 1.85-1.94). Among those living on reserves SRR was 2.00(95% CI 1.93-2.07). Northern and non-urban HSDAs had higher SRRs, within both total andAboriginal populations. In every age and gender category, the HSDA-standardized SRRwas higher among the Aboriginal than among the total population. Between 1991 and 2010,crude rates and SRRs declined substantially, but proportionally more among the Aboriginalpopulation, so the gap between the Aboriginal and total population is narrowing, particularlyamong females and older adults. These community characteristics were associated withhigher risk: lower income, lower educational level, worse housing conditions, and more haz-ardous types of employment.ConclusionsOver the years, as socio-economic conditions improve, risk of hospitalization due to unin-tentional fall injury has declined among the Aboriginal population. Women and older adultshave benefited more.IntroductionAboriginal people in British Columbia (BC) have higher incidences of injuries than the generalpopulation [1–7]. Our project, Injury in British Columbia’s Aboriginal Communities: BuildingCapacity while Developing Knowledge [8–11], adds information about variability of incidencerates among injury categories, geographic regions, time periods, and demographic and socio-economic groups within the Aboriginal population. This report focuses on injuries due tounintentional falls.Studies of the economic burden of unintentional injuries in BC estimated that unintentionalfalls incident in 2004 cost the province $884 million: $650 million in direct costs (health care)and $235 million of indirect costs (productivity losses), altogether 31% of the $2.81 billion totalcosts attributed to all injuries. Unintentional falls caused 20% of deaths and 46% of hospitaliza-tions due to all injuries [12]. In 1998, 35% of total costs occurred among persons aged under 25years, and 25% occurred among the elderly (aged 65 years or older) [13]. The 2004 Special Re-port of the Provincial Health Officer noted that among the BC population aged 65 years orolder, during the period 1992 to 2001, 4.5% of all hospital separations and 11% of all person-days spent in hospital were attributable to injuries from unintentional falls. During the year2001–2002, among the population aged 65 years or older, 56% of emergency room visits were at-tributable to injuries from unintentional falls [14]. We think it relevant to measure unintentionalfalls injury among the Aboriginal population of BC, to help guide development of policies andprograms aimed at preventing and treating this condition among the Aboriginal population.We found one previously published study of the incidence of injury due to unintentionalfalls among the Aboriginal population of British Columbia [2]. During the period 1992 to2002 the Age-Standardized Mortality Rate (standardized to the 1991 population of Canada)due to unintentional falls among the Aboriginal population was 1.9 per 10,00 person-years,compared to 0.7 per 10,000 among other people in BC. The incidence of Potential Years ofLife Lost (under age 75) was 2.3 per 1,000 person-years among the Aboriginal population,and 0.5 per 1,000 among other people in BC. This study of mortality incidence used the prov-ince’s universal health care insurance program as a population registry, and identified Ab-original people (within the population, and among death records) by record linkage, using aFalls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 2 / 19on Population Data BC’s Secure ResearchEnvironment cloud server. BC Ministry of Health[creator], 2012: Consolidation File (MSP Registration& Premium Billing). V2012. Population Data BC[publisher]. Data extract. MOH (2012). BC VitalStatistics Agency [creator], 2011: Vital StatisticsBirths. Population Data BC [publisher]. Data extract.BC Vital Statistics Agency (2011). BC Vital StatisticsAgency [creator], 2011: Vital Statistics Deaths.Population Data BC [publisher]. Data extract. BC VitalStatistics Agency (2011). BC Ministry of Health[creator], 2011: Discharge Abstract Database(Hospital Separations). Population Data BC[publisher]. Data extract. MOH (2011).Funding: This work was funded by the CanadianInstitutes of Health Research, Institute of AboriginalPeoples Health [grant number AHR # 81043]. Salarysupport for authors was provided by the Child &Family Research Institute (MAG, MB), by a MichaelSmith Foundation for Health Research Scholar Award(MB), and the British Columbia Region, First Nationsand Inuit Health, Health Canada (AJ). The fundershad no role in study design, data collection andanalysis, decision to publish, or preparation of themanuscript.Competing Interests: The authors have declaredthat no competing interests exist.combination of insurance premium group, Indian status, and birth and death record nota-tions. However, left unanswered is the question as to how much of the difference in injuryrates between the Aboriginal and general populations is due to the higher proportion of theAboriginal population who reside in northern, rural or remote locations, where physical envi-ronments are more harsh and therefore more conducive to injuries. We adapted this study’smethods, and made three improvements. First, we studied a broader range of injury events(hospitalizations) instead of just deaths, thus enabling more description of variability in inci-dence rates among geographic regions, demographic groups and time periods. Also, to re-searchers wishing to estimate economic burden, hospitalizations are more relevant than aredeaths. Second, we standardized comparisons of injury rates between the Aboriginal and gen-eral populations, by age, gender and also region of the province, thus compensating for the ef-fects of northern location and degree of urbanization. Third, using an ecological approach,where the unit of observation is a geographic unit, we explored associations between stan-dardized incidence of injury due to unintentional falls, and a broad range of hypothesizedsocio-economic, geographic, and employment-related risk markers.MethodsEthics review and permission for data accessThe University of British Columbia Behavioural Research Ethics Board reviewed and approvedour methods (BREB file H06–80585). The Data Stewards representing the BC Ministry ofHealth and the BC Vital Statistics Agency approved the data access requests. We used existingdatabases, permanently linked by British Columbia Personal Health Number, maintained byPopulation Data BC [15–18]. Population Data BC rendered the client records anonymous be-fore our analysis. These data are available on request, from Population Data BC (https://www.popdata.bc.ca/data, contact: Kelly Sanderson, Researcher Liaison Unit Lead, e-mail: kelly.san-derson@popdata.bc.ca; specifications in project file George 11–012) subject to approval by theData Stewards representing the British Columbia Ministry of Health Services, and the VitalStatistics Agency of British Columbia, for ethical and privacy reasons, because the data pertainto individuals. The data may be accessed and statistically analysed only on Population DataBC’s Secure Research Environment cloud server.Population countsWe used the registration and premium billing files [15] of the Medical Services Plan of BC(MSP, the province’s universal health care insurance program) as a population registry,counting the total resident population of BC at the mid-points of fiscal years 1991–1992through 2009–2010. Within this population, we defined as “Aboriginal” any person with: (a)membership in MSP Premium Group 21 (indicating insurance premiums paid by First Na-tions and Inuit Health Program, Health Canada, for reason of Indian status, as defined by theIndian Act of Canada), OR (b) one or both parents with Indian status or resident on an Indi-an Reserve, as indicated on the linked Vital Statistics birth record [16], OR (c) Indian statusor resident of an Indian Reserve, as indicated on the linked Vital Statistics death record [17].We previously described this method, and discussed the quality of the population registry,and validity and limitations of the Aboriginal identification [11]. Our definition of “Aborigi-nal” is indirectly based on legally recognized Indian status, because for privacy reasons wecould not obtain direct access to the Indian Status Registry. However, our indirect methodhas the advantage of including children who are eligible for Indian status because of their pa-rents’ Indian status, but who have not yet applied to be included in the Indian Status Registry.Family accounts are included in MSP Premium Group 21 if the account’s primary registrantFalls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 3 / 19declares Indian status. Some persons with Indian status who are eligible to join MSP PremiumGroup 21 might not do so because another party (e.g., an employer) pays their premiums.However, this does not happen often because other potential payers have economic incentiveto identify people with Indian status so that they can shed the account. A study by the VitalStatistics Agency of BC, using the same method as ours, but with inclusion of additional per-sons found only in the Indian Status Registry, counted 151,783 Aboriginal persons in BC in2002 [2], modestly larger than our count of 135,076 persons that year. Since we identifiedhospitalizations as Aboriginal (or not) by linking to the population registry, the undercount-ing applies to both the numerator (hospitalization counts) and the denominator (populationcounts), so there should be no bias in our calculated rates of hospitalization amongAboriginal people.For purposes of ecologic analysis (see below), within the population we identified Aborigi-nal “communities” [10]. In BC there are 199 First Nations and Indian Bands recognized by andregistered with the government of Canada, inhabiting about 498 reserves. Approximately 44%of the Aboriginal people in BC reside on a reserve and 56% do not. Conceptually, we defined acommunity as all the Aboriginal people residing on the reserves of one band. Operationally, weassigned Aboriginal people to communities according to postal code of residence. We couldthus identify 177 Aboriginal communities in BC. Because Indian reserves do not always haveunique and exclusive postal codes, the identified Aboriginal communities include both Aborig-inal reserve residents and off-reserve Aboriginal persons living near by, and some communitiescontain more than one band. This does not perfectly match our conceptual definition, but it isconsistent with our underlying intention, to identify culturally homogenous clusters of Aborig-inal people living close together.We aggregated the 177 identified Aboriginal communities to create a subcategory of the Ab-original population which we called “reserve”. We classified all other Aboriginal persons as“not reserve”.There are sixteen Health Service Delivery Areas (HSDAs) in BC. We classified each HSDA(and its residents) as “urban” or “not urban” according to the proportion of the population ofthe HSDA residing in an urban centre larger than 100,000 persons [11]. Fig. 1 is a map of BCshowing the 16 HSDAs in the province. The six urban HSDAs are marked with the ¶ symbol.The six urban HSDAs comprise metropolitan Vancouver and metropolitan Victoria, and ev-erywhere else in BC is “not urban” by our definition.We tabulated population counts by fiscal year, gender, 5-year age group, Aboriginal status,community, reserve residence, HSDA, and urban residence.Hospitalization countsWe tabulated counts of hospital separations [18] among residents of BC, occurring from April1, 1991 through March 31, 2010. We considered a hospitalization as “due to injury” if the levelof care was “acute” or “rehabilitation”, and the Most Responsible Diagnosis on the dischargerecord was an International Classification of Diseases Revision 9 (“ICD-9”) numeric code inthe range 800 through 999, or an International Classification of Diseases Revision 10 (“ICD-10”) code in the range S00 through T98. We considered an injury as “due to unintentional fall”if the first occurrence of the supplemental injury diagnosis code (indicating intention and ex-ternal cause) was an ICD-9 E-code in the range E880 through E888, or an ICD-10 code in therange W00 through W19.Linking individual hospitalization records to the population registry, we tabulated counts ofhospitalizations due to unintentional fall injury by calendar year, gender, 5-year age group, Ab-original status, reserve residence, HSDA, and urban residence.Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 4 / 19Incidence rates of hospitalizationAs in previously reported analyses [9–11], we calculated the crude rate of hospitalization asthe number of hospital separations divided by the person-years of observation (the sum of theannual population counts times the fraction of each year included in the observation period)during the same time period. We considered the crude rate to be a binomial proportion, andwe estimated standard errors of the proportion, and 95% confidence intervals of the proportionaccordingly. We calculated Standardized Relative Risk (SRR) of hospitalization relative to therisk of hospitalization in the reference population (78,256,306 person-years, the combinedtime-weighted total population of BC from April 1, 1991 through March 31, 2010) using themethod of indirect standardization [19], standardizing by gender, 5-year age group, andHSDA, or standardizing for just gender and 5-year age group when calculating SRRs for specif-ic HSDAs. We took the gender, age and HSDA (or gender and age) specific rates of hospitaliza-tion in the reference population, and multiplied them by the person-year counts within thecorresponding cells of the target population, summing to the indirectly standardized expectednumber of hospitalizations in the target population. We considered the expected rate (the ex-pected number divided by the number of person-years) to be a binomial proportion, and we es-timated standard errors and 95% confidence intervals accordingly. The Standardized RelativeRisk (“SRR”) (relative to the total population of BC) is the crude rate of hospitalizationsFig 1. Standardized Relative Risk of hospitalization for unintentional falls injury among Aboriginal populations of Health Service Delivery Areas.doi:10.1371/journal.pone.0121694.g001Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 5 / 19divided by the expected rate of hospitalizations. Since these rates have the same denominator(person-years) the SRR simplifies to the observed number of hospitalizations divided by the ex-pected number of hospitalizations. This is analogous to the Standardized Mortality Ratio (ifdeath is the event counted), and could also be called the Standardized Incidence Ratio.We assessed cumulative change in SRR over time as the proportional change between thefirst and last years of the observation period, i.e., (SRR2010/SRR1991) −1. To facilitate compari-sons, we converted proportional change over the entire period to an annualized change, usingthis formula.SRR2010SRR1991 1=ð20101991Þ 1Predictors of riskWe studied risk markers for hospitalization due to unintentional fall injury, using an ecologicalapproach, where the unit of observation was the Aboriginal “community” (as defined above).As hypothesized risk markers, we selected socio-economic, housing, and geographic indicatorspreviously developed by Statistics Canada and Aboriginal Affairs and Northern DevelopmentCanada. We previously published definitions and reasons for selection of the markers [9,10].From the 2001 and the 2006 Censuses of Canada, we measured the following hypothesizedsocio-economic markers of injury risk, for each community: (1) Total (annual) Income percapita, (2) Community Well-Being Income Score (i.e., total annual income per capita, logarith-mically scaled) [20], (3) proportion of population, age 25+ years with at least a high school cer-tificate, (4) proportion of population, age 25+ years with university degree, bachelors or higher,(5) average population per room (an index of the degree of crowding in the community’s hous-ing), (6) proportion of dwellings in need of major repairs, (7) proportion of population, age 25+ years, in the labour force, (8) proportion of population, age 25+ years, employed (for pay),(9) proportion of population who identified themselves as “an Aboriginal person, that is,North American Indian, Métis or Inuit (Eskimo)”, (10) proportion of population who gaveonly one response to the ethnic origin question, and it was a group that could be classified asNorth American Indian.We hypothesized that the hazardousness of employment among the community’s labourforce would be associated with risk of injury due to falls among the community population, asa direct effect on workers, or indirectly on the broader community population, as an indicatorof prevailing socio-economic conditions. Therefore, we calculated the following work-relatedstatistics of injury risk for each community, relative to the population of BC: (11) relative riskof work injury compensation claim, expected from occupational categories, and (12) relativerisk of work injury compensation claim, expected from industry categories. We defined thesetwo community-level markers as in a previous report focused on worker compensation injuries[10]. We took the numbers of worker compensation injuries, recorded in BC in 2006, withinoccupational [21] and industrial [22] categories, then divided by the census labour force popu-lation of BC aged 15 years or older in each category. We multiplied these rates of injury by thecategory-specific census labour force counts within each community, then summed to obtainthe community’s expected number of injury claims. We divided this expected number by thecommunity’s total census labour force population, then divided again by the rate of injuryclaims in BC, with all categories combined.The Government of Canada’s Department of Aboriginal Affairs and Northern Developmenthas a classification system for calculating funding allocations to First Nation bands [23]. Fromthe tables in this reference, we assigned to communities the following hypothesized geographicFalls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 6 / 19markers of injury risk: (13) Remoteness Index (higher score means more remote), and (14) Envi-ronmental Index (higher score means more environmentally challenging). These indices are nu-meric scores, based on geographic latitude, availability of year-round road access, and distanceto the nearest “service centre” (a city or town having government services, banks and suppliers).Ecological analysis. For each community, we calculated the age, gender and HSDA-stan-dardized SRR of hospitalization due to unintentional falls injury during the period 1999through 2003 (a 5-year period centred about the Census year 2001) and during the period 2004through 2008 (centred about the Census year 2006), relative to the total population of BC dur-ing the same time period. Logarithmic transformation approximately normalized the distribu-tion of the SRRs (Kolmogorov-Smirnov statistic 0.048, Shapiro-Wilk statistic 0.990, df = 292,p = 0.048); therefore we used the natural logarithm of SRR as the dependent (Y) variable forregression analysis.We tested hypotheses of association by performing least-squares linear regressions. We test-ed census year, hypothesized socio-economic, work-related and geographic markers, in turn asthe single independent variable. Variables that had statistically significant association (p<0.05)with SRR of worker compensation injury in univariate analysis were included in subsequentmultivariable regression analysis. We used stepwise backwards elimination of variables to ar-rive at the best-fitting multivariable model. At each step, the variable with the largest p-valuewas eliminated. Elimination stopped when all independent variables had regression coefficientssignificantly different from zero (p<0.05).The regression coefficient (“B”) of each independent variable represents the change in thedependent variable Ln(SRR) that is associated with a unit change in the independent variable.The relative risk associated with a change of one standard deviation (SD) in the independentvariable is calculated as the antilogarithm of B × SD. Repeating the calculation with the lowerand upper 95% confidence limits of B gives the confidence limits of the relative risk.ResultsAboriginal status and reserve residenceTable 1 shows crude rates and SRRs of hospitalization for injury due to unintentional falls, dur-ing the period 1991–2010, among the total population of BC (i.e., the reference population),the Aboriginal population, the Aboriginal population residing on reserve, and the Aboriginalpopulation residing off-reserve. Table 1 shows a pattern of higher crude incidence among theAboriginal population than among the total population of BC. The highest crude incidencerate is among the Aboriginal population residing on-reserve. The crude incidence among theAboriginal population off-reserve is lower, but still higher than among the total population ofBC. Standardization by age, gender and HSDA shows the same pattern among the three popu-lation groups, but the disparities between the Aboriginal population groups and the total popu-lation of BC are magnified.HSDAs and urban residenceTable 2 (and S1 Table and S2 Table) show crude rates and age and gender-standardized SRRsof hospitalization for injuries due to unintentional falls, during the period 1991–2010, withinthe total and Aboriginal populations of the HSDAs. Crude incidence rates and SRRs are highlyvariable among HSDAs, and this applies among both the Aboriginal population and amongthe total population of BC. Aggregating the HSDAs into categories of “urban” or “not urban”,one sees that, in general, urban HSDAs have lower crude rates and SRRs than do HSDAs thatare not urban, and this applies among both the Aboriginal population and among the totalpopulation of BC.Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 7 / 19Table 1. Hospital separations for injuries due to unintentional falls [1], British Columbia, 1991–2010 [2].P-years [3] Obs [4] Exp [5] Rate [6] 95% CI for Rate SRR [7] 95% CI for SRRBC, total population 78,256,306 262,819 262,818 33.6 33.5 - 33.7 1 [reference]BC, Aboriginal 2,541,060 12,683 6,710 49.9 49.1 - 50.8 1.89 1.85 - 1.94BC, Aboriginal, off-reserve 1,403,813 5,810 3,277 41.4 40.3 - 42.5 1.77 1.71 - 1.83BC, Aboriginal, on-reserve 1,131,862 6,839 3,421 60.4 59.0 - 61.9 2.00 1.93 - 2.07Notes:1. "Injury due to unintentional fall" defined as hospital separation with Most Responsible Diagnosis in the range ICD9:800–999 or ICD10:S00-T98, andsupplemental diagnosis in the range ICD9:E880-E888 or ICD10:W00-W19.2. Injuries occurring during the observation period 1991-Apr-01 to 2010-Mar-31.3. Person-years is the sum of the annual population counts times the fraction of each year included in the observation period.4. Observed number of injuries.5. Expected number, indirectly standardized, based on age, gender and HSDA-specific rates in the total population of BC.6. Crude Rate per 10,000 person-years.7. Standardized Relative Risk (compared to the total population of BC) = Observed/Expected.doi:10.1371/journal.pone.0121694.t001Table 2. Hospital separations for injuries due to unintentional falls [1], British Columbia, 1991–2010 [2], by Health Service Delivery Area.Total population Aboriginal populationHSDA Rate [3] 95% CI forRateSRR [4] 95% CI for SRR Rate [3] 95% CI forRateSRR [4] 95% CI for SRR11 45 44 - 47 1.37 1.34 - 1.41 48 41 - 56 1.96 1.57 - 2.4512 50 49 - 51 1.37 1.33 - 1.40 32 23 - 44 1.39 0.95 - 2.0413 41 41 - 42 1.02 1.00 - 1.03 38 35 - 41 1.65 1.47 - 1.8414 43 43 - 44 1.36 1.33 - 1.38 54 51 - 56 2.30 2.14 - 2.4621 32 31 - 32 0.92 0.91 - 0.94 34 31 - 37 1.55 1.40 - 1.7222 31 30 - 31 0.98 0.97 - 0.99 33 30 - 37 1.62 1.40 - 1.8623 29 29 - 29 0.92 0.91 - 0.93 27 24 - 30 1.34 1.17 - 1.5431 20 20 - 21 0.66 0.64 - 0.67 21 14 - 30 0.97 0.68 - 1.3932 27 27 - 27 0.80 0.79 - 0.81 43 41 - 46 2.09 1.90 - 2.2933 36 35 - 36 1.04 1.02 - 1.05 50 47 - 53 2.19 1.99 - 2.4141 40 40 - 41 0.96 0.95 - 0.97 45 41 - 49 2.08 1.85 - 2.3442 38 38 - 39 1.03 1.02 - 1.05 50 47 - 53 2.28 2.10 - 2.4743 40 39 - 41 1.27 1.24 - 1.30 68 64 - 73 3.06 2.73 - 3.4451 41 40 - 42 1.62 1.57 - 1.67 62 59 - 64 2.57 2.41 - 2.7452 33 33 - 34 1.30 1.27 - 1.33 61 58 - 64 2.82 2.58 - 3.0853 29 28 - 30 1.17 1.13 - 1.21 54 49 - 59 2.51 2.16 - 2.91Urban [5] 30 30 - 31 0.91 0.90 - 0.91 41 40 - 43 1.94 1.85 - 2.04Not [6] 39 39 - 39 1.15 1.14 - 1.16 54 53 - 55 2.36 2.29 - 2.43All HSDAs 34 34 - 34 1 [reference] 50 49 - 51 2.24 2.18 - 2.30Notes:1. "Injury due to unintentional fall" defined as hospital separation with Most Responsible Diagnosis in the range ICD9:800–999 or ICD10:S00-T98, andsupplemental diagnosis in the range ICD9:E880-E888 or ICD10:W00-W19.2. Injuries occurring during the observation period 1991-Apr-01 to 2010-Mar-31.3. Crude Rate per 10,000 person-years.4. Standardized Relative Risk (indirectly standardized by age and gender, compared to the total population of BC) = Observed/Expected.5. Urban: aggregation of HSDAs 22, 23, 31, 32, 33 and 41, where > 62.3% of the HSDA population live in a large population centre.6. Not urban: aggregation of HSDAs 11, 12, 13, 14, 21, 42, 43, 51, 52, 53.doi:10.1371/journal.pone.0121694.t002Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 8 / 19Comparing HSDA-specific crude incidence rates, one sees that in most, but not all HSDAs,Aboriginal people have a higher rate of hospitalization for unintentional fall injury than do thetotal population of BC. Comparing HSDA-specific SRRs, one sees that in every HSDA, stan-dardized for age and gender, Aboriginal people have a higher risk of hospitalization for uninten-tional fall injury than do the total population. Urban-dwelling Aboriginal people have a higherrisk of hospitalization for unintentional fall injury than do the urban dwelling total populationof BC. Aboriginal people residing in non-urban HSDAS also have a higher risk of hospitalizationfor unintentional fall injury than do the total population of BC residing in non-urban HSDAs.Age and genderTable 3 (and S3 Table and S4 Table) show crude rates and age and gender-specific, HSDA-stan-dardized SRRs of hospitalization for injuries due to unintentional falls, during the period 1991–2010, within specific age and gender categories of the total and Aboriginal populations of BC.Among those aged less than 50 years, males have higher incidence rates of hospitalization for un-intentional fall injury than do females, but among those aged 50 years and older, females havehigher incidence rates, and the excess among females is even larger among persons aged 70 yearsor older. This pattern applies both among the total population and among the Aboriginal popu-lation of BC. Among the total population of BC, the incidence rate is lowest in the 20 to 29 yearsof age group, and increases with age, this pattern occurs both among males and among females.Table 3. Hospital separations for injuries due to unintentional falls [1], British Columbia, 1991–2010 [2], by gender and age.Total population Aboriginal populationGender Age Rate [3] 95% CI for Rate SRR [ref] Rate [3] 95% CI for Rate SRR [4] 95% CI for SRRF 0–9 17 17 - 18 1 29 27 - 31 1.51 1.39 - 1.65F 10–19 10 10 - 10 1 21 19 - 23 1.67 1.49 - 1.88F 20–29 7 7 - 8 1 26 24 - 29 2.65 2.31 - 3.04F 30–39 10 9 - 10 1 35 33 - 38 2.78 2.47 - 3.14F 40–49 14 13 - 14 1 46 43 - 50 2.76 2.46 - 3.10F 50–59 26 26 - 27 1 91 85 - 97 2.86 2.56 - 3.19F 60–69 49 48 - 49 1 152 142 - 162 2.50 2.25 - 2.78F 70–79 119 117 - 120 1 283 264 - 303 2.05 1.86 - 2.27F 80+ 355 352 - 358 1 481 447 - 517 1.17 1.08 - 1.27M 0–9 23 22 - 23 1 38 35 - 40 1.54 1.43 - 1.66M 10–19 24 24 - 25 1 35 33 - 38 1.25 1.16 - 1.35M 20–29 17 17 - 17 1 36 33 - 39 1.73 1.57 - 1.91M 30–39 17 17 - 17 1 42 39 - 45 1.99 1.81 - 2.19M 40–49 19 19 - 20 1 52 48 - 55 2.18 1.97 - 2.41M 50–59 24 24 - 24 1 70 65 - 75 2.46 2.18 - 2.78M 60–69 34 34 - 35 1 109 100 - 118 2.52 2.20 - 2.88M 70–79 64 63 - 65 1 169 153 - 187 2.27 1.95 - 2.64M 80+ 186 184 - 189 1 241 213 - 273 1.14 1.00 - 1.30Notes:1. "Injury due to unintentional fall" defined as hospital separation with Most Responsible Diagnosis in the range ICD9:800–999 or ICD10:S00-T98, andsupplemental diagnosis in the range ICD9:E880-E888 or ICD10:W00-W19.2. Injuries occurring during the observation period 1991-Apr-01 to 2010-Mar-31.3. Crude Rate per 10,000 person-years.4. Standardized Relative Risk (indirectly standardized by age, gender and HSDA, compared to the total population of BC) = Observed/Expected.doi:10.1371/journal.pone.0121694.t003Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 9 / 19Among the Aboriginal population of BC, the incidence rate is lowest in the 10 to 19 years of agegroup, and increases with age, this pattern occurs both among males and among females.Comparing age and gender-specific crude incidence rates, one sees that all age and gendercategories, Aboriginal people have a higher rate of hospitalization for unintentional fall injurythan do the total population of BC. Comparing age and gender-specific, HSDA-standardizedSRRs, one sees that in every age and gender category, Aboriginal people have a higher risk ofhospitalization for unintentional fall injury than do the total population of BC. The increasedrelative risk among Aboriginal people is less severe among the young (less than 20 years of age)and the very elderly (80 years or older).Changes over timeTables 4 and 5 (and S5 Table and S6 Table) show crude rates and SRRs of hospitalizationsfrom injuries due to unintentional falls, during the period 1991–2010, among the total and Ab-original populations of BC (Table 4), and demographic categories within these populationsTable 4. Hospital separations for injuries due to unintentional falls [1], British Columbia, 1991–2010 [2], by calendar year.Total population Aboriginal populationYear Rate [3] 95% CI forRateSRR [4] 95% CI for SRR Rate [3] 95% CI forRateSRR [4] 95% CI for SRR1991 39 39 - 40 1.28 1.25 - 1.31 73 67 - 79 2.88 2.51 - 3.301992 39 39 - 40 1.26 1.24 - 1.29 72 67 - 77 2.83 2.52 - 3.181993 39 38 - 40 1.26 1.23 - 1.28 65 60 - 70 2.53 2.26 - 2.831994 37 36 - 37 1.18 1.16 - 1.20 60 56 - 65 2.33 2.09 - 2.611995 36 35 - 36 1.14 1.12 - 1.16 56 52 - 61 2.21 1.97 - 2.471996 35 35 - 36 1.11 1.09 - 1.13 52 48 - 56 2.04 1.83 - 2.271997 35 34 - 35 1.08 1.06 - 1.10 55 51 - 59 2.14 1.92 - 2.381998 33 33 - 34 1.03 1.01 - 1.05 52 48 - 56 2.01 1.81 - 2.241999 33 33 - 34 1.02 1.00 - 1.03 52 48 - 56 2.00 1.80 - 2.232000 34 34 - 35 1.03 1.01 - 1.04 54 50 - 58 2.07 1.86 - 2.302001 33 32 - 33 0.98 0.96 - 0.99 47 43 - 51 1.79 1.61 - 1.992002 31 31 - 32 0.91 0.90 - 0.93 45 41 - 49 1.70 1.54 - 1.892003 31 30 - 31 0.90 0.88 - 0.91 42 39 - 45 1.58 1.43 - 1.752004 31 31 - 32 0.90 0.88 - 0.91 47 44 - 51 1.78 1.61 - 1.962005 31 30 - 31 0.88 0.86 - 0.89 41 37 - 44 1.51 1.37 - 1.662006 32 32 - 33 0.91 0.89 - 0.92 42 38 - 45 1.53 1.38 - 1.682007 31 31 - 32 0.87 0.86 - 0.88 43 40 - 46 1.56 1.41 - 1.712008 31 31 - 32 0.87 0.85 - 0.88 39 36 - 43 1.42 1.29 - 1.562009 32 31 - 32 0.87 0.86 - 0.89 39 36 - 42 1.40 1.28 - 1.542010 31 30 - 32 0.83 0.81 - 0.86 41 35 - 48 1.47 1.22 - 1.771991–2010 34 33 - 34 1 [reference] 50 49 - 51 1.89 1.85 - 1.94Notes:1. "Injury due to unintentional fall" defined as hospital separation with Most Responsible Diagnosis in the range ICD9:800–999 or ICD10:S00-T98, andsupplemental diagnosis in the range ICD9:E880-E888 or ICD10:W00-W19.2. Injuries occurring during the observation period 1991-Apr-01 to 2010-Mar-31.3. Crude Rate per 10,000 person-years.4. Standardized Relative Risk (indirectly standardized by age, gender and HSDA, compared to the total population of BC, 1991 to 2010) = Observed/Expected.doi:10.1371/journal.pone.0121694.t004Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 10 / 19(Table 5), by year. SRRs have been standardized for age, gender, and HSDA. Recall that the ref-erence population is the combined total population of BC during the entire period (1991through 2010). Thus, the SRR for the total population of BC in a particular year can be higheror lower than one, but the average of the SRRs for the total population of BC, over all the years,will be one. Table 4, and Figs. 2 and 3, show that in every year, the Aboriginal population had ahigher crude rate and a higher SRR than did the total population of BC, but over the period1991–2010, reductions in crude rates and standardized risks have been sustained, and substan-tial, among both populations. Table 5 shows that reductions have also been substantial amongmales, females, and youth (age under 25 years) within both the Aboriginal and total popula-tions of BC. Standardized by age, the reductions in SRR are independent of any changes overtime in the age distributions of the populations. Among the Aboriginal population of BC, theproportion residing in urban HSDAs increased from 28.7% in 1991 to 30.1% in 2010. Amongthe total population of BC, the proportion increased from 60.0% in 1991 to 62.4% in 2010.Table 5. Hospital separations for injury due to unintentional fall [1], British Columbia, 1991–2010 [2], by calendar year and demographic category.Demographic category Year Person-years[3] Obs [4] Exp [5] Rate [6] 95% CI forRateSRR [7] 95% CI for SRRAboriginal 1991 81,353 590 205 73 67 - 79 2.88 2.51 - 3.30Aboriginal 2010 39,871 164 112 41 35 - 48 1.47 1.22 - 1.77Aboriginal, Male 1991 39,605 284 107 72 64 - 81 2.64 2.19 - 3.19Aboriginal, Male 2010 19,739 89 55 45 37 - 55 1.62 1.24 - 2.11Aboriginal, Female 1991 41,281 298 93 72 64 - 81 3.21 2.62 - 3.93Aboriginal, Female 2010 20,052 75 56 37 30 - 47 1.35 1.04 - 1.76Aboriginal, age under 25 years 1991 41,961 231 85 55 48 - 63 2.71 2.19 - 3.35Aboriginal, age under 25 years 2010 18,972 36 38 19 14 - 26 0.94 0.69 - 1.30BC 1991 2,566,094 10,109 7,894 39 39 - 40 1.28 1.25 - 1.31BC 2010 1,158,039 3,561 4,268 31 30 - 32 0.83 0.81 - 0.86BC, Male 1991 1,261,517 4,527 3,428 36 35 - 37 1.32 1.28 - 1.37BC, Male 2010 573,085 1,412 1,738 25 23 - 26 0.81 0.78 - 0.85BC, Female 1991 1,298,489 5,459 4,379 42 41 - 43 1.25 1.21 - 1.28BC, Female 2010 584,475 2,147 2,523 37 35 - 38 0.85 0.82 - 0.88BC, age under 25 years 1991 880,765 2,501 1,565 28 27 - 30 1.60 1.52 - 1.68BC, age under 25 years 2010 330,130 345 557 10 9 - 12 0.62 0.57 - 0.67BC 1991–2010 78,256,306 262,819 262,693 34 33 - 34 1 [reference]BC, Male 1991–2010 38,715,563 110,420 110,420 29 28 - 29 1 [reference, male]BC, Female 1991–2010 39,474,907 151,295 151,294 38 38 - 39 1 [reference,female]BC, age under 25 years 1991–2010 24,727,465 43,114 43,113 17 17 - 18 1 [reference, under25]Notes:1. "Injury due to unintentional fall" defined as Most Responsible Diagnosis in the range ICD9:800–999 or ICD10:S00-T98, and supplemental diagnosis inthe range ICD9:E880-E888 or ICD10:W00-W19.2. Separations occurring during the observation period 1991-Apr-01 to 2010-Mar-31.3. Person-years is the annual population count times the fraction of the year included in the observation period.4. Observed number of hospital separations (acute or rehabilitation care).5. Expected number, indirectly standardized, based on age, gender and HSDA-specific rates in the total population of BC during the entireobservation period.6. Crude Rate per 10,000 person-years.7. Standardized Relative Risk (compared to the total population of BC during the same observation period) = Observed/Expected.doi:10.1371/journal.pone.0121694.t005Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 11 / 19Having standardized by HSDA, we can say that the reductions in SRR are independent of anyeffect from the increasing concentration of the populations into urban areas.Table 6 shows proportional changes in SRR between 1991 and 2010, among the Aboriginaland total populations of BC, and demographic categories within these populations As we de-scribed in an earlier report comparing time trends among various injury categories [11], between1991 and 2010 there was 49.0% decline in SRR of hospitalization due to unintentional fallsamong the Aboriginal population (annualized change of −3.5%, 95% confidence interval: −4.6%to −2.3%), compared to 34.8% decline among the total population of BC (annualized change of−2.2%, 95% CI −2.4% to −2.0%). The disparity between the Aboriginal and total populations wasstatistically significant (p = 0.039, 2-sided). Among Aboriginal females there was 57.9% declinein SRR, substantially more than the 31.7% decline among females in the total population of BC(p = 0.005, 2-sided). But among Aboriginal males, and among Aboriginal youth (age under 25years), the declines in SRR were practically same as the declines among the same demographicgroups within the total population of BC. The greater decline in SRR means that the gap betweenthe Aboriginal and total populations of BC is shrinking, but the comparisons among demograph-ic categories indicates that the closing gap is occurring due to more rapid improvements amongfemales and older adults.Fig 2. Hospitalizations due to unintentional falls, British Columbia, 1991–2010, crude rate by year.doi:10.1371/journal.pone.0121694.g002Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 12 / 19Ecological analysis of predictors of riskTable 7 shows statistics from regression models with a single independent (X) variable. We iden-tified the following variables as statistically significant (p<0.05 for the null hypothesis that theregression coefficient “B” is zero) predictors of a community’s injury hospitalization risk: (1) an-nual income per capita (measured in $): increase of one standard deviation ($5,900) was associ-ated with a reduction in SRR of hospitalization from injury due to unintentional fall by a factorof 0.915; (2) annual income per capita (measured on a logarithmic scale): increase of one stan-dard deviation was associated with a reduction in SRR by a factor of 0.909; (3) proportion of theadult population who had completed high school: increase of one standard deviation (17.4%)was associated with a reduction in SRR by a factor of 0.908; (4) proportion of dwellings in needof major repair: increase of one standard deviation (19.2%) was associated with an increase inSRR by a factor of 1.089; (5) relative risk of worker compensation claim based on the occupa-tional distribution of the community’s labour force: increase of one standard deviation (0.36)was associated with an increase in SRR by a factor of 1.087; (6) relative risk of workerFig 3. Hospitalizations due to unintentional falls, British Columbia, 1991–2010, standardized relative risk by year.doi:10.1371/journal.pone.0121694.g003Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 13 / 19Table 6. Standardized Relative Risks of hospitalization for injury due to unintentional fall, British Columbia, 1991–2010.Demographic category SRR 1991 SRR 2010 1991 to 2010% change p* Annual % change L95CL U95CLAboriginal 2.88 1.47 -49.0% 0.039 -3.5% -4.6% -2.3%Aboriginal, Male 2.64 1.62 -38.9% 0.969 -2.6% -4.2% -0.9%Aboriginal, Female 3.21 1.35 -57.9% 0.005 -4.5% -6.1% -2.8%Aboriginal, age under 25 years 2.71 0.94 -65.2% 0.592 -5.4% -7.3% -3.5%BC 1.28 0.83 -34.8% -2.2% -2.4% -2.0%BC, Male 1.32 0.81 -38.5% -2.5% -2.8% -2.2%BC, Female 1.25 0.85 -31.7% -2.0% -2.2% -1.7%BC, age under 25 years 1.60 0.62 -61.2% -4.9% -5.3% -4.4%Notes:* probability (2-sided, z-test) that Ln((SRR 2010)/(SRR 1991)) Aboriginal = Ln((SRR 2010)/(SRR 1991)) BCSRR: Standardized Relative Risk (indirectly standardized by age, gender and HSDA, compared to the total population of BC, 1991 to 2010) = Observed/ExpectedL95CL: lower limit of the 95% confidence interval for the annualized % change.U95CL: upper limit of the 95% confidence interval for the annualized % change.doi:10.1371/journal.pone.0121694.t006Table 7. Ecologic analysis of risk of hospitalization due to unintentional falls injury among BC First Nations communities, 1999–2008; regression[1] statistics frommodels with one independent (X) variable.X Variable units min max mean[2]SD[2]N R2 B[3] SE[4]p[5] RR Ratio per SD[6]L95CL[7]U95CL[8]Census 1 year 2001 2006 2003.5 2.5 292 0.007 -0.017 0.011 0.147 0.959 0.907 1.015IncomePerCapita1000 $1,000 5.3 50.9 13.1 5.9 139 0.030 -0.015 0.007 0.042 0.915 0.841 0.997IncomeScore 1 32.6 108.1 60.2 12.7 139 0.041 -0.008 0.003 0.017 0.909 0.841 0.983HighSchool 1% 0.0 116.7 55.7 17.4 240 0.032 -0.006 0.002 0.005 0.908 0.848 0.971UniversityDegree 1% 0.0 34.3 3.9 5.8 240 0.009 -0.008 0.005 0.133 0.954 0.897 1.015PopPerRoom 1 0.30 1.11 0.53 0.11 240 0.016 0.644 0.327 0.050 1.074 1.000 1.154NeedMajorRepairs 1% 0.0 120.0 32.7 19.2 240 0.022 0.004 0.002 0.022 1.089 1.013 1.172LabourForce 1% 9.9 100.0 61.7 12.3 240 0.000 0.000 0.003 0.965 0.998 0.926 1.077Employed 1% 7.7 77.3 47.3 11.0 240 0.004 -0.003 0.003 0.312 0.964 0.897 1.035OccupationRisk RR 0.00 2.71 1.12 0.36 240 0.018 0.234 0.113 0.040 1.087 1.004 1.177IndustryRisk RR 0.00 3.92 1.11 0.34 240 0.019 0.300 0.139 0.032 1.106 1.009 1.212Remoteness 1 0.08 1.35 0.23 0.22 290 0.003 0.111 0.123 0.367 1.024 0.972 1.080EnvironIndex 1 0.40 3.00 0.65 0.38 290 0.000 0.015 0.074 0.842 1.006 0.951 1.064Aboriginal 1% 5.7 100.0 84.7 23.2 240 0.014 0.002 0.001 0.069 1.058 0.996 1.124NAIndian 1% 5.6 103.1 81.5 23.8 240 0.009 0.002 0.001 0.138 1.048 0.985 1.114Notes:1. The dependent (Y) variable is Ln(SRR of hospitalization due to unintentional falls injury), and regression is weighted by person-years.2. Unweighted mean and standard deviation (SD) of the independent (X) variable3. B = regression coefficient4. SE = standard error of the regression coefficient5. p = probability that B = 06. Relative Risk Ratio per SD = exp(BxSD). One SD change in the independent variable is associated with a change in the Standardized Relative Risk ofinjury by this factor. E.g., one SD change in Income Per Capita ($5,900) is associated with reduction is SRR by a factor of 0.915.7. Lower limit of the 95% confidence interval for the Relative Risk Ratio per SD.8. Upper limit of the 95% confidence interval for the Relative Risk Ratio per SD.doi:10.1371/journal.pone.0121694.t007Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 14 / 19compensation claim based on the industry distribution of the community’s labour force: increaseof one standard deviation (0.34) was associated with an increase in SRR by a factor of 1.106.After step-wise regression, one independent variable remained in the best-fitting model: theproportion of the adult population who had completed high school (p = 0.005). We did notfind any multivariable model in which all of the independent variables were statistically signifi-cantly associated with SRR of hospitalization from unintentional fall injury.DiscussionAboriginal people have higher incidence of hospitalization due to unintentional falls than thetotal population. Standardizing for age increases the disparity, because the Aboriginal popula-tion are on average younger than the total population of BC, and hospitalization for uninten-tional falls injury is most frequent among the elderly. Standardizing for geographic area ofresidence (HSDA) reduces the disparity, because the Aboriginal population are more likely toreside in northern or non-urban HSDAs, where hospitalization for unintentional falls injuryoccurs more frequently. Standardizing for both age and HSDA, Aboriginal people have abouttwice the risk of hospitalization due to unintentional falls injury as do the total population ofBC. The disparity is greater comparing Aboriginal people living on-reserve to the total popula-tion of BC, than comparing Aboriginal people living off-reserve to the total population of BC.Having standardized for HSDA, we can say that this difference is not simply because most re-serve communities are located in northern or non-urbanized areas, where unintentional fallsinjuries occur more frequently, there may be less contention for hospital beds, and physiciansmay be more likely to admit injured persons to hospital because of a lack of outpatient or com-munity-care options. There must be other factors related to living on a reserve, indeed to theAboriginal condition, that increase risk of unintentional falls injury. Whatever these factorsmay be, they are historically long-standing, but they are diminishing with time. Changes overtime in risk of hospitalization from unintentional falls injury suggest that the gap between theAboriginal population and the total population of BC is narrowing.We found an interesting pattern with respect to age, gender and time. Among people aged50 years and over, risk of hospitalization due to unintentional fall injury is higher among fe-males than males, but among those under 50 years, the risk is higher among males. Among fe-males and adults over 25 years of age, risk is declining faster among the Aboriginal populationthan among the general population of BC, but among males and youth under 25 years, risk isdeclining at the same rate as among the general population. One might hypothesize that unin-tentional fall injuries among women and older adults are mostly related to osteoporosis andother age-related physical frailties, whereas fall injuries among males and youth are morestrongly influenced by behaviours such as employment, recreational activities and substanceuse. The hospital discharge record can have as many as 25 diagnostic codes (maximum 16prior to 2001), but the present analysis used just two: the most responsible diagnosis, and thefirst occurrence of an external cause of injury code. Further analysis of additional diagnosticcodes may help elucidate factors contributing to the fall injury.Our ecological analysis of hypothesized socio-economic, employment-related, and geographicrisk markers may help explain disparities of risk among Aboriginal reserve communities. We ob-served that lower income, lower educational level, worse housing conditions and more hazardoustypes of employment are associated with increased risk of hospitalization from unintentionalfalls injury. All of these factors could be classified as socio-economic disadvantages. Multivariableregression analyses, intended to elucidate the relative importance of these factors, their relation-ships and the pathways by which they might exert their effects were not informative, because weencountered problems of low statistical power. First, hospitalization from unintentional fallsFalls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 15 / 19injury is a very narrow category of injury (crude incidence among the on-reserve Aboriginal pop-ulation is 60.4 per 10,000 per year), and with the small communities we studied (mean popula-tion 351, SD 419), the expected number of injury events per 5-year observation period is small(11). Consequently, the rate of hospitalization in a community, which is a proportion, will have avery high standard error, simply on the basis of random sampling variability. The ecological mul-tivariable analysis method worked better with broader, more frequent outcome categories, for ex-ample, hospitalizations from all injuries combined (crude incidence 252 per 10,000 per year [9]),or worker compensation injury claims with all injury categories combined (crude incidence 105per 10,000 per year [10]). Second, the ecological characteristics of the communities were derivedmostly from custom tabulations of the Census of Canada, aggregating data pertaining to the pop-ulations of specific reserves. Census geography is more precise than postal codes, so these datapertain only to residents of reserves. On the other hand, they include all residents of the reserves,even those who do not meet our definition of “Aboriginal”. Thus, the community populationamong whom we calculated injury risks is not exactly the same as the community populationamong whom we ascertained the ecological predictors of risk. This mismatch probably increasedthe component of random variability in our regression models, thus making the coefficient of de-termination (R2) smaller, and making it less likely that we would find statistically significant asso-ciations between injury risk and the hypothesized ecological predictors of risk. But this is all themore reason to take seriously the associations that we did find.A limitation of all ecological studies is the fallacy that associations observed at the commu-nity level apply also at the individual level. For example, we found that a preponderance ofmore hazardous types of employment among the community’s labour force is associated withincreased risk of hospitalization due to unintentional falls among the community’s population.It is plausible that individuals employed in hazardous occupations or industries would be morelikely to suffer injury from falls. But it is also possible that more hazardous employment is anindicator of a higher prevalence of socio-economic disadvantage among the community’s pop-ulation, and the injurious consequences are borne mostly by those in the community who arenot employed at all.Our ecological analysis of risk markers did not include off-reserve Aboriginal or non-Ab-original communities. Therefore, the findings say nothing about disparities of unintentionalfall injury risk between the on-reserve and off-reserve Aboriginal populations, or between theAboriginal and total populations of BC. Those questions invite further research, and will be ex-plored in a future report.In this study we did not count injuries, we counted hospitalizations due to injury. Hospitali-zations indicate injury burden, but are also influenced by utilization factors such as availabilityof hospital beds, outpatient and community care options, and patterns of medical practice.These factors vary among regions of the province, and we standardized risks by HSDA, so thecomparison between the Aboriginal and the total populations of BC should not be biased. How-ever, acting within HSDAs there may be other factors that affect Aboriginal people differentlyfrom the general population. Hospitalizations do not include all injuries: excluded are milder in-juries, and also extremely severe injuries resulting in immediate death. Some injuries may lead tomore than one hospitalization. Hospitalizations [9,11], worker compensation claims [10], pri-mary care visits (the subject of a future report), and deaths [2–7] are pieces of a larger picture.The magnitude of the disparity in risk of hospitalization due to unintentional falls (SRR of1.89) was somewhat less than the disparity in risk of death. During the period 1991 to 2002,people with Indian status residing on-reserve experienced 2.85 times more, and those residingoff-reserve experienced 1.76 times more Potential Years of Life Lost (PYLL) due to uninten-tional falls than did other Canadians [7]. During the period 1992 to 2002, people with Indianstatus experienced an Age Standardized Mortality Rate due to unintentional falls 2.7 timesFalls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 16 / 19higher, and suffered 4.6 times more PYLL than other people in BC [2]. Aboriginal people mayhave more severe falls than the general population. Alternatively, Aboriginal people mayunder-utilize health care services, relative to the severity of their falls. But in general, our find-ings are consistent with the mortality experience. This suggests that our observations reflectreal disparities and changes in the underlying incidence of unintentional falls injury, and arenot merely artefacts related to hospital utilization.In this analysis, the main outcome of interest was SRR of hospitalization (standardized byage, gender and HSDA), because this was useful for testing hypotheses of association with Ab-original ethnicity, reserve residence, urban residence and time period. However, the crude ratereflects the true burden of injury. Further analysis, incorporating time series modelling andforecasting of rates, population and demographic forecasting, and the resource-intensity ofhospitalization categories could provide more information about the burden of unintentionalfalls injury among our target population.ConclusionsAboriginal people need culturally appropriate programs to mitigate unintentional falls injuryeven more than the general population do. As socio-economic conditions improve [24], risk ofunintentional fall injury has declined among the Aboriginal population. Females and olderadults seem to have benefited more. To improve health and safety, and to close the gap betweenthe Aboriginal and the general populations require that we also address the socio-economic de-terminants of health [25].Supporting InformationS1 Table. Hospital separations for injuries due to unintentional falls [1], British Columbia,1991–2010 [2], by Health Service Delivery Area.(DOC)S2 Table. Hospital separations for injuries due to unintentional falls [1], Aboriginal BC,1991–2010 [2], by Health Service Delivery Area.(DOC)S3 Table. Hospital separations for injuries due to unintentional falls [1], British Columbia,1991–2010 [2], by gender and age.(DOC)S4 Table. Hospital separations for injuries due to unintentional falls [1], Aboriginal BC,1991–2010 [2], by gender and age.(DOC)S5 Table. Hospital separations for injuries due to unintentional falls [1], British Columbia,1991–2010 [2], by calendar year.(DOC)S6 Table. Hospital separations for injuries due to unintentional falls [1], Aboriginal BC,1991–2010 [2], by calendar year.(DOC)AcknowledgmentsThe authors thank Anna Low, Sherylyn Arabsky and Kelly Sanderson (née Alke) of PopulationData BC for assistance with data access and linkage.Falls Injury among Aboriginal People in BC, CanadaPLOSONE | DOI:10.1371/journal.pone.0121694 March 20, 2015 17 / 19Author ContributionsConceived and designed the experiments: AJ MBMAG CEL RM. 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Injury inequities
Fall-related injury
Indigenous injury
Injury risks
Injury Hospitalizations Due to Unintentional Falls among the Aboriginal Population of British Columbia, Canada : Incidence, Changes over Time, and Ecological Analysis of Risk Markers, 1991-2010
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