Clinical Question: Is aspirin beneficial in the primary prevention of adverse cardiovascular events in women and men?

Setting: Various (meta-analysis)

Study Design: Meta-analysis (randomized controlled trials)

Synopsis: Although aspirin reduces the risk of adverse cardiovascular events in high-risk adults, it is uncertain if women derive the same benefits as men. The investigators searched MEDLINE, the Cochrane Registry, bibliographies of retrieved trials, and reports presented at major scientific meetings for randomized trials evaluating the risks and benefits of aspirin treatment for the primary prevention of cardiovascular events. Six randomized trials with a total of 95,456 individuals, including 51,342 women, were identified. Follow-up occurred for an average of 6.4 years among the various studies.

In women, aspirin therapy was associated with a 12 percent reduction in cardiovascular events (odds ratio [OR] = 0.88; 95% confidence interval [CI], 0.70 to 0.97; number needed to treat [NNT] = 316; 95% CI, 180 to 3,805) and a 17 percent reduction in stroke (OR = 0.83; 95% CI, 0.70 to 0.97; NNT = 457; 95% CI, 259 to 2,597). There was no significant benefit of aspirin in reducing the risk of myocardial infarction or cardiovascular mortality. In men, there was a similar 14 percent reduction in cardiovascular events (OR = 0.86; 95% CI, 0.78 to 0.94; NNT = 155, 95% CI, 98 to 364) and a 32 percent reduction in myocardial infarction risk (OR = 0.68; 95% CI, 0.54 to 0.86; NNT = 114; 95% CI, 79 to 261). There was no significant beneficial effect of aspirin in reducing the risk of stroke or cardiovascular mortality. Aspirin treatment significantly increased the risk of major bleeding in men and women, and all-cause mortality was unchanged. There was no evidence of publication bias, and the outcomes of the various trials were homogenous.

Bottom Line: Primary prevention with aspirin reduces the risk of adverse cardiovascular events in women and men. In particular, aspirin reduces the risk of stroke in women and the risk of myocardial infarction in men. The risk of major bleeding is significantly increased with regular aspirin therapy in both sexes, and overall mortality is unchanged. Patients and their physicians should weigh their independent risks and benefits before deciding on regular aspirin use. (Level of Evidence: 1a)