Treating 1,000 people with preventive aspirin for five years prevents 2.9 major cardiovascular events (nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death) and causes 2.8 major bleeds, according to a meta-analysis.
Nine primary prevention trials compared results for aspirin alone for the primary prevention of cardiovascular disease, and reported data on myocardial infarction, stroke and cardiovascular deaths. Aspirin doses ranged from 100 mg every other day to 500 mg/d, and seven of them studied doses from 75 mg/d to 162.5 mg/d. No dose-dependent effects were noted, the researchers said. Results appeared in the July issue of the American Heart Journal.
A total of 2,029 major cardiovascular events occurred among 52,145 (3.86%) patients allocated to aspirin compared with 2,099 major cardiovascular events among 50,476 (4.16%) patients assigned to placebo or control. Over a mean follow-up of nearly 7 years, aspirin was associated with a reduction in major cardiovascular events (risk ratio [RR] 0.90; 95% confidence interval [CI], 0.85 to 0.96, P less than .001). There was no statistically 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 less than .001).
The absolute risk reduction was 0.39% (95% CI, 0.18% to 0.61%) over a mean follow-up of 6.9 years, for a number needed to treat of 253 (95% CI, 163 to 568) to prevent a single major cardiovascular event.
A total of 458 major bleeding events occurred among 52,145 (0.88%) patients allocated to aspirin compared with 278 major bleeding events among 50,421 (0.55%) patients assigned to placebo or control. Pooled results demonstrated a significant 62% increase in the risk of major bleeding (RR 1.62; 95% CI, 1.31 to 2.00, P less than .001). In aggregate, the absolute risk was 0.38% (95% CI, 0.21% to 0.55%) over the mean follow-up of 6.9 years, which corresponds to a number needed to harm of 261 (95% CI 182-476) to cause a single major bleeding event. For gastrointestinal hemorrhage, there was a significant 29% increase in events with aspirin versus placebo or control (RR 1.29; 95% CI, 1.24 to 1.47, P less than .001).
*This blog post was originally published at ACP Internist*