More than 40 million Americans take aspirin for the primary or secondary prevention of myocardial infarction and stroke, including approximately half of all those aged 65 years or more.(1) The daily dose varies from 81 mg (1 baby aspirin) to 325 mg (1 adult aspirin). The efficacy of aspirin for the secondary prevention of myocardial infarction and stroke has been validated by multiple randomized clinical trials.(2)
The first randomized clinical trial to establish the efficacy of aspirin for primary prevention was the US Physicians Health study published in 1989.(3) More than 22,000 male US physicians were randomized to 325 mg of aspirin every other day versus placebo and followed for 5 years. The incidence of fatal or nonfatal myocardial infarction was 44% lower in those taking aspirin (odds ratio = 0.56; 95% confidence interval, 0.45-0.70; P
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— James E. Dalen, MD, MPH
This article originally appeared in the February 2010 issue of The American Journal of Medicine.
