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Coronary revascularization in British Columbia, 1979-1988

University of British Columbia

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<0.0001). In an attempt to explain the variation in small area rates, the CABS rates for each school district from 1983 to 1988 were regressed on six ecological variables (distance from cardiologist, distance from internist, distance from centre, income, employment rate and graduation rate) with year and year-squared forced in. Income, distance from cardiologist, distance from centre and their first-order interactions were found to be important explanatory variables (R² = 0.21). While income and distance from cardiologist had a negative effect on the CABS rate, distance from centre had a surprising positive effect, which did not appear to be accounted for by colinearity with distance from cardiologist. The model was then refitted, using the CABS rate adjusted for morbidity in the school districts as the dependent variable. In this model distance from cardiologist and income changed in relative importance, and distance from centre and the interaction between variables were no longer important (R² = 0.30). Refitting this model to account for mobility to Alberta showed that distance from cardiologist and income explained more of the variation in rates (R² = 0.34). The presence of small-area variations in CABS rates, together with differences between centres in the number and type of procedures performed, suggest that there are inequities in cardiac care within B.C. These inequities appear to arise from complex relationships between distance from services and morbidity rates and average income in the school district of residence. In addition, it appears that the surgical centre referred to may also contribute to the variation in small-area rates, although this was not tested. It is clear that inequities in cardiac care cannot be redressed by simple solutions. Policy implications and suggestions for further research are discussed.

Thesis/Dissertation

application/pdf

2008-09-05

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http://hdl.handle.net/2429/1661

Health Care and Epidemiology

University of British Columbia

UBCV

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