Issues in the early termination of the aspirin component of the Physicians' Health Study. Data Monitoring Board of the Physicians' Health Study

Ann Epidemiol. 1991 Aug;1(5):395-405. doi: 10.1016/1047-2797(91)90009-2.


The Physicians' Health Study is a randomized, double-blind, placebo-controlled prevention trial of 22,071 US physicians, using a factorial design to evaluate the role of aspirin in the prevention of cardiovascular mortality and beta carotene in the reduction of cancer incidence. After approximately 5 years of follow-up, the aspirin component was terminated, 3 years ahead of schedule. Several factors were considered in the decision to terminate, including a cardiovascular mortality rate markedly lower than expected in both aspirin and placebo subjects, precluding the evaluation of the primary aspirin hypothesis, and a highly significant (P < .00001) and impressive (44%) reduction in the risk of first myocardial infarction in the aspirin group. Issues in the decision to terminate are described in this report.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Aspirin / therapeutic use*
  • Cardiovascular Diseases / mortality
  • Cardiovascular Diseases / prevention & control*
  • Carotenoids / therapeutic use*
  • Double-Blind Method
  • Humans
  • Male
  • Middle Aged
  • Neoplasms / mortality
  • Neoplasms / prevention & control*
  • Physicians*
  • beta Carotene


  • beta Carotene
  • Carotenoids
  • Aspirin