Aspirin for the prevention of cardiovascular events in patients without clinical cardiovascular disease: A meta-analysis of randomized trials

Background The benefit of aspirin to prevent cardiovascular events in subjects without clinical cardiovascular disease relative to the increased risk of bleeding is uncertain. Methods A meta-analysis of randomized trials of aspirin versus placebo/control to assess the effect of aspirin on major cardiovascular events (MCEs) (nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death), individual components of the MCE, stroke subtype, all-cause mortality, and major bleeding. Nine trials involving 102,621 patients were included: 52,145 allocated to aspirin and 50,476 to placebo/control. Results Over a mean follow-up of 6.9 years, aspirin was associated with a reduction in MCE (risk ratio [RR] 0.90, 95% CI 0.85-0.96, P < .001). There was no significant reduction for myocardial infarction, stroke, ischemic stroke, or all-cause mortality. Aspirin was associated with hemorrhagic stroke (RR 1.35, 95% CI 1.01-1.81, P = .04) and major bleeding (RR 1.62, 95% CI 1.31-2.00, P < .001). In meta-regression, the benefits and bleeding risks of aspirin were independent of baseline cardiovascular risk, background therapy, age, sex, and aspirin dose. The number needed to treat to prevent 1 MCE over a mean follow-up of 6.9 years was 253 (95% CI 163-568), which was offset by the number needed to harm to cause 1 major bleed of 261 (95% CI 182-476). Conclusions The current totality of evidence provides only modest support for a benefit of aspirin in patients without clinical cardiovascular disease, which is offset by its risk. For every 1,000 subjects treated with aspirin over a 5-year period, aspirin would prevent 2.9 MCE and cause 2.8 major bleeds. (Am Heart J 2011;162:115-124.e2.)