Background: In 1988, the aspirin component of the Physicians' Health Study, a randomized, double-blind, placebo-controlled trial of 22 071 apparently healthy men was terminated early, due principally to a statistically extreme (P<.00001) 44% reduction in the risk of a first myocardial infarction (MI). The Cardio-Renal Drugs Advisory Committee recommended that the US Food and Drug Administration approve professional labeling of aspirin to prevent first MI. The agency did not act on this recommendation because the only other trial, the British Doctors' Trial of 5139 men, showed no significant benefits. Since that time, 3 additional randomized trials (which included men and women) of aspirin in the primary prevention of MI have been published.
Methods: A computerized search of the English literature from 1988 to the present revealed 5 published trials: the Physicians' Health Study (22 071 participants), the British Doctors' Trial (5139), the Thrombosis Prevention Trial (5085), the Hypertension Optimal Treatment Study (18 790), and the Primary Prevention Project (4495).
Results: Among the 55 580 randomized participants (11 466 women), aspirin was associated with a statistically significant 32% reduction in the risk of a first MI and a significant 15% reduction in the risk of all important vascular events, but had no significant effects on nonfatal stroke or vascular death.
Conclusions: The current totality of evidence provides strong support for the initial finding from the Physicians' Health Study that aspirin reduces the risk of a first MI. For apparently healthy individuals whose 10-year risk of a first coronary event is 10% or greater, according to the US Preventive Services Task Force and the American Heart Association, the benefits of long-term aspirin therapy are likely to outweigh any risks.