Adherence to Aspirin in the Prevention of Myocardial Infarction The Physicians' Health Study

Background: The primary aim of this article was to explore, in subgroup analyses, whether participants with differing frequencies of aspirin consumption in a randomized, double-blind, placebo-controlled, primary prevention trial had different magnitudes of benefit in the prevention of myocardial infarction. Secondary aims were to identify factors associated with adherence and to examine the relationship of adherence with cardiovascular outcomes in the placebo group. Methods: The Physicians' Health Study randomized 22 071 US male physicians who were free of myocardial infarction and cerebrovascular disease at baseline. The average follow-up during the aspirin component of the trial was 60.2 months. Baseline cardiovascular risk factors and adherence to therapy during the trial were assessed by questionnaire; cardiovascular outcomes were reported by questionnaire and confirmed by record review by an Endpoints Committee. Results: Several cardiovascular disease risk factors assessed at baseline were related to poor adherence (taking Conclusions: These subgroup data raise the possibility that a less than alternate day aspirin regimen may yield lower benefits in the prevention of myocardial infarction. Alternate explanations are that these analyses reflect either the play of chance or effects of uncontrolled confounding since comparisons were no longer randomized. Randomized trials are necessary to address the question of frequency of administration of aspirin to achieve optimal benefits in primary prevention of myocardial infarction. (Arch Intern Med. 1994;154:2649-2657)