Findings of two randomized, placebo controlled clinical trials challenged the role of aspirin in primary prevention in a low-risk population and in patients of diabetes. A randomized, double-blind, placebo-controlled, multicenter study was done in seven countries. Between July 5, 2007, and Nov 15, 2016, 12 546 eligible patients aged 55 years (men) or 60 years (women) and older and had an average cardiovascular risk were randomly assigned to receive enteric-coated aspirin (100 mg daily, n=6270) or placebo (n=6276). During median follow-up of 60 months, in the intention-to-treat analysis, the primary endpoint (a composite outcome of time to first occurrence of cardiovascular death, myocardial infarction [MI], unstable angina, stroke, or transient ischemic attack [TIA]) occurred in 269 (4.29%) patients in the aspirin group versus 281 (4.48%) patients in the placebo group (hazard ratio [HR] 0.96). Gastrointestinal bleeding events (mostly mild) occurred in 61 (0.97%) patients in the aspirin group versus 29 (0.46%) in the placebo group (HR 2.11). Documented deaths and the overall incidence rate of adverse events was similar in both groups. Another total of 15,480 participants with diabetes but no evident cardiovascular disease (CVD) were randomized to receive aspirin at a dose of 100 mg daily or matching placebo in the UK. During a mean follow-up of 7.4 years, serious vascular events (i.e., MI, stroke or TIA, or death from any vascular cause, excluding any confirmed intracranial hemorrhage) occurred in a significantly lower percentage of participants in the aspirin group than in the placebo group (658 participants [8.5%] vs. 743 [9.6%]; HR 0.88). In contrast, major bleeding events occurred in 314 participants (4.1%) in the aspirin group, as compared with 245 (3.2%) in the placebo group (HR 1.29), with most of the excess being gastrointestinal bleeding and other extracranial bleeding. There was no significant difference between the aspirin and the placebo groups in the incidence of gastrointestinal tract cancer or all cancers. The benefits of aspirin for patients with CVD are well established but not in primary prevention. Source: https://www.thelancet.com/; https://www.nejm.org/
