Differential effects of aspirin and non-aspirin nonsteroidal antiinflammatory drugs in the primary prevention of myocardial infarction in postmenopausal women

Abstract

The antiplatelet effect of aspirin reduces the risk of clinical manifestations of atherothrombosis by approximately 25% in secondary prevention settings. Data are limited in primary prevention of coronary heart disease, and even more in women. Here, we estimate the effects of aspirin and non-aspirin nonsteroidal antiinflammatory drugs in the primary prevention of myocardial infarction in postmenopausal women. We followed a cohort of 164,769 women, 50-74 years of age, registered in the General Practice Research Database in the United Kingdom, from January 1991 through December 1995. For aspirin and non-aspirin nonsteroidal antiinflammatory drugs, the risk of myocardial infarction associated with current use was compared with risk in non-users, using a nested case-control analysis. Overall, the relative risk of myocardial infarction associated with current use of aspirin of more than 1 month's duration was 0.56 [95% confidence interval (95% CI) = 0.26-1.21], and that of nonfatal myocardial infarction was 0.28 (95% CI = 0.08-0.91). Chronic use of nonsteroidal antiinflammatory drugs was not associated with a protective effect (relative risk = 1.32; 95% CI = 0.97-1.81). These findings indicate that incomplete and reversible inhibition of platelet cyclooxygenase by non-aspirin nonsteroidal antiinflammatory drugs is not sufficient to produce clinically detectable cardiovascular protection comparable with that achieved by low-dose aspirin through irreversible inactivation of platelet cyclooxygenase.