Utilization of cardiovascular drugs (blood pressure lowering drugs, lipid lowering drugs and nitrates) and mortality from ischaemic heart disease and strokeAn ecological analysis based on Sweden's municipalities

Objective: To perform an ecological study in an effort to generate questions concerning the preventive impact of various cardiovascular drugs on mortality from stroke and ischaemic heart disease (IHD) in the community, and to explore the association between sales of nitrates and mortality from stroke and IHD. Methods: Out-patient drug utilization (sales) of blood pressure lowering drugs, lipid lowering drugs and nitrates were categorized in four groups of equal size by quartiles and compared with mortality from IHD and stroke, using the group of municipalities with the lowest utilization as reference, from 1989 to 1993 in 283 of Sweden's 288 municipalities, by Poisson regression. Adjustments were made for population size, age and gender proportions, the utilization rate of cardiovascular drugs other than the tested drug group and location of the municipality. Results: Compared with the group of municipalities with the lowest sales and adjusting only for population size, mortality from IHD and stroke increased with the extent of utilization of blood pressure lowering drugs and nitrates. In contrast, mortality decreased with increased utilization of lipid lowering drugs. After further adjustments by percentage of men, age structure, geographical location (mid-points) of the municipalities, and, as a proxy for cardiovascular disease, the sales of cardiovascular drugs other than the tested drug group, the increased risk associated with blood pressure lowering drugs disappeared, and there was a dose-response association between sales of diuretics and old antihypertensives and decreasing mortality, sales of nitrates continued to be associated with an increased risk, and the low mortality risk associated with sales of lipid lowering drugs persisted. Conclusion: Lipid lowering drugs may have a preventive impact in the general population, but the preventive impact of blood pressure lowering drugs, with the exception of diuretics and old antihypertensives, may be low in many municipalities. The safety of nitrates needs more investigation at the individual level. Received: 16 April 1998 / Accepted in revised form: 10 November 1998