A Meta-Analysis of Aspirin for the Primary Prevention of Cardiovascular Diseases in the Context of Contemporary Preventive Strategies

The role of aspirin for primary prevention of cardiovascular diseases remains controversial, particularly in the context of contemporary aggressive preventive strategies.

Relevant randomized clinical trials were included, and risk ratios (RRs) were calculated using random-effects models. Additional moderator analyses were performed to compare the pooled treatment effects from recent trials (those reported after the guidelines of the National Cholesterol Education Program Third Adult Treatment Panel were published in 2001; thus, conducted on the background of contemporary preventive strategies) to the results of older trials.

Data from 14 randomized controlled trials involving 164,751 patients were included. Aspirin use decreased myocardial infarction risk by 16% compared with placebo (RR 0.84; 95% confidence interval [CI], 0.75-0.94); however, in the moderator analyses, aspirin was not associated with a decreased risk of myocardial infarction in recent trials, but was in older trials (P-interaction = .02). Overall, aspirin use significantly increased the occurrence of major bleeding (RR 1.49; 95% CI, 1.32-1.69) and hemorrhagic stroke (RR 1.25; 95% CI, 1.01-1.54). In moderator analyses, the risk of major bleeding (P-interaction = .12) or hemorrhagic stroke (P-interaction = .44) with aspirin was not significantly different between the older and new trials. Differences between aspirin and placebo in the risks for all-cause stroke, cardiac death, and all-cause mortality were not found.

In the context of contemporary primary prevention guidelines, the effect of aspirin on myocardial infarction risk was significantly attenuated, whereas its major bleeding and hemorrhagic stroke complications were retained. Therefore, in contemporary practice, routine use of aspirin for the primary prevention of cardiovascular events may have a net harmful effect.