Abstract
RATIONALE: In an observational cohort study, women who self-selected for frequent aspirin use developed less newly diagnosed asthma than women who did not take aspirin. OBJECTIVE: To explore whether low-dose aspirin decreased the risk of newly diagnosed asthma in a randomized, double-blind, placebo-controlled trial. METHODS: The Physicians' Health Study randomized 22,071 apparently healthy male physicians, aged 40-84 yr at baseline and tolerant of aspirin, over an 18-wk run-in period, to 325 mg aspirin or placebo on alternate days. The aspirin component was terminated after 4.9 yr due principally to the emergence of a statistically extreme 44% reduction in risk of first myocardial infarction among those randomly assigned to aspirin. MEASUREMENTS: Physicians could self-report an asthma diagnosis on questionnaires at baseline, 6 mo, and annually thereafter. Asthma was not an a priori endpoint of the trial. RESULTS: Among 22,040 physicians without reported asthma at randomization, there were 113 new asthma diagnoses in the aspirin group and 145 in the placebo group. The hazard ratio was 0.78 (95% confidence interval, 0.61-1.00; p = 0.045). This apparent 22% lower risk of newly diagnosed asthma among those assigned to aspirin was not modified by baseline characteristics including smoking, body mass index, or age. CONCLUSIONS: Aspirin reduced the risk of newly diagnosed adult-onset asthma in a large, randomized clinical trial of apparently healthy, aspirin-tolerant men. This result requires replication in randomized trials designed a priori to test this hypothesis; it does not imply that aspirin improves symptoms in patients with asthma.