Acetylsalicylic acid (or aspirin) has numerous biological effects, including anti-inflammatory properties and reduced platelet activation. These mechanisms explain the benefits of aspirin for prevention of atherosclerotic cardiovascular disease (CVD) and its propensity to cause unwanted bleeding.
While older studies suggested that aspirin was associated with a relative reduction of first cardiovascular events by up to 20%, 3 clinical trials published in 2018 suggest at most modest reductions in cardiovascular outcomes of a magnitude comparable with the risk of clinically significant bleeding.1-3 These trials were designed to clarify earlier doubts, but have fueled continuing controversy. Recommendations accounting for these studies range from continued cautious use to abandonment of aspirin for primary prevention. Recent American Heart Association/American College of Cardiology prevention guidelines suggest that “aspirin should be used infrequently in the routine primary prevention” of CVD and limited to selected high-risk patients with low bleeding risk.4