A meta-analysis on the benefits and risks of aspirin treatment in the primary prevention of cardiovascular disease by sex included six trials, with a total of 95 456 individuals. Three trials included only men, one included only women, and two included both sexes. Among 51 342 women with 1 285 major cardiovascular events (625 strokes, 469 MIs, 364 cardiovascular deaths), aspirin therapy was associated with a significant 12% reduction in cardiovascular events (odds ratio [OR], 0.88; 95% confidence interval [CI], 0.79–0.99) and a 17% reduction in stroke (OR, 0.83; 95% CI, 0.70–0.97), which was a reflection of reduced rates of ischemic stroke (OR, 0.76; 95% CI, 0.63–0.93). There was no significant effect on MI or cardiovascular mortality. Among 44 114 men with 2 047 major cardiovascular events (597 strokes, 1 023 MIs, 776 cardiovascular deaths), aspirin therapy was associated with a significant 14% reduction in cardiovascular events (OR, 0.86; 95% CI, 0.78–0.94) and a 32% reduction in MI (OR, 0.68; 95% CI, 0.54–0.86). There was no significant effect on stroke or cardiovascular mortality. Aspirin treatment increased the risk of bleeding in women (OR, 1.68; 95% CI, 1.13–2.52) and in men (OR, 1.72; 95% CI, 1.35–2.20).
A technology assessment report on aspirin for the primary prevention of cardiovascular events was abstracted in the Health Technology Assessment Database. Five trials were included in a meta-analysis and modelling. Aspirin reduced the risk for the combined endpoint of nonfatal myocardial infarction and fatal coronary heart disease (CHD) by 28% (summary OR, 0.72; 95% CI, 0.60 to 0.87). Aspirin increased the risk of hemorrhagic strokes (OR 1.4; 95% CI, 0.9 to 2.0) and major gastrointestinal bleeding (OR 1.7; 95% CI, 1.4 to 2.1). All-cause mortality (OR, 0.93; 95% CI, 0.84 to 1.02) was not significantly affected over this time period. For 1,000 patients with a 5 percent risk of CHD events over 5 years, aspirin would prevent 14 myocardial infarctions (range 6 to 20) but would cause 1 hemorrhagic stroke (range 0 to 2) and 3 major gastrointestinal bleeds (range 2 to 4). For patients with CHD risk of 1 percent over 5 years, aspirin would prevent 3 myocardial infarctions (range 1 to 4) but would cause 1 hemorrhagic stroke (range 0 to 2) and 5 major gastrointestinal bleeding events (range 2 to 4).
The decision about whether to use aspirin chemoprevention requires consideration of the patient's cardiovascular risk as well as the patient's relative utility for the different clinical outcomes prevented or caused by its use.
The following decision support rules contain links to this evidence summary: