PROSPECTIVE-STUDY OF CALCIUM-CHANNEL BLOCKER USE, CARDIOVASCULAR-DISEASE, AND TOTAL MORTALITY AMONG HYPERTENSIVE WOMEN - THE NURSES HEALTH STUDY

Background-In several observational studies, patients prescribed calci um channel blockers had higher risks of cardiovascular diseases and mo rtality than those prescribed other antihypertensive medications. We e xplored these associations in the Nurses' Health Study. Methods and Re sults-A total of 14 617 women who reported hypertension and regular us e of diuretics, beta-blockers, calcium channel blockers, ACE inhibitor s, or a combination in 1988 were included in the analyses. Cardiovascu lar events and deaths were ascertained through May 1, 1994. We documen ted 234 cases of myocardial infarction. Calcium channel blocker monodr ug users had an age-adjusted relative risk (RR) of myocardial infarcti on of 2.36 (95% CI, 1.43 to 3.91) compared with those prescribed thiaz ide diuretics. Women prescribed calcium channel blockers had a higher prevalence of ischemic heart disease. After adjustment for these and o ther coronary risk factors, the RR was 1.63 (95% CI, 0.97 to 2.77). Co mparing the use of any calcium channel blocker (monodrug and multidrug users) with that of any other antihypertensive agent, the adjusted RR was 1.42 (95% CI, 1.01 to 2.01). An association between calcium chann el blocker use and myocardial infarction was apparent among women who had ever smoked cigarettes (covariate-adjusted RR, 1.81; 95% CI, 1.20 to 2.72) but not among never-smokers (RR, 0.94; 95% CI, 0.48 to 1.84). Conclusions-In analyses adjusted only for age, we found a significant elevation in RR of total myocardial infarction among women who used c alcium channel blockers compared with those who did not. After adjustm ent for comorbidity and other covariates, the RR was reduced. Whether the remaining observed elevated risk is real, or a result of residual confounding by indication, or chance, or a combination of the above ca nnot be evaluated with certainty on the basis of these observational d ata.