asa lowers MI but increases stroke

The role of aspirin in primary prevention remains uncertain. In a meta-analysis of five RCTs, Foster and colleagues found that aspirin slightly reduced the risk of a serious vascular event (odds ratio, 0.86; 95% CI: 0.80–0.90) and reduced the relative risk of myocardial infarction by about a third (OR, 0.71; 95% CI: 0.60–0.80], but had an uncertain effect on stroke (OR, 1.05; 95% CI: 0.90–1.20) [1]. The meta-analysis found that there were 0.1 excess intracranial bleeds per 1,000 patients treated per year with aspirin, and 0.7 major extracranial bleeds per 1,000 patients treated per year with aspirin. The authors found “insufficient evidence from RCTs to identify which individuals would benefit overall and which would be harmed by regular treatment with aspirin, although those at high and intermediate rather than low risk would be more likely to gain benefit.”