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Abstract

Since the introduction of coronary artery bypass surgery (CABS) in the late sixties, the increase in the incidence rates has aroused controversy in the literature. Recent studies in the United States and Canada have documented both large rate increases in the elderly and geographic variations in incidence rates. This study was undertaken to discover whether similar patterns exist in British Columbia. Data from the British Columbia Hospital Morbidity Database, for fiscal years1979 through 1988, were used to calculate age-sex adjusted small-area incidence rates based on the school district of residence. Results showed a 1.2 fold increase in overall annual rate with a two-fold increase in the elderly. The greatest increase, almost nine-fold, was seen in the population aged 75 and over. In addition, the percentage of patients with either diabetes or chronic obstructive pulmonary disease increased from three to twelve percent of annual cases. Over the study period, extreme variability in annual rates was seen both within and among school districts. Within school districts, most variability was seen in districts with populations below 10,000. Poisson regression (which weighted school districts according to population size) showed that variation among school districts was highly significant (p