Lifetime Cigarette Smoking and Colorectal Cancer Incidence in the Physicians' Health Study I

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Colorectal cancer ranks fourth in incidence and second in cause of death from cancer in the United States (1). Although virtually every study has reported a positive association between cigarette smoking and adenomatous polyps, the evidence regarding smoking and colorectal cancer is less clear, probably because of a long induction period (2). We, therefore, examined lifetime smoking history and incidence of colorectal cancer in a large cohort of men followed for more than 12 years.

In 1982, a total of 22 071 U.S. male physicians, 40–84 years of age, who did not have a history of myocardial infarction, stroke, cancer, liver or renal disease, gout, peptic ulcer, or contraindications to aspirin were randomly assigned in the Physicians' Health Study I, after written informed consent was obtained from them (3,4). The study was approved by the institutional review board of the Brigham and Women's Hospital, Boston, MA. Twice in the first year and once yearly thereafter, the participants completed a short questionnaire that asked about the occurrence of relevant health outcomes. The analysis is based on all self-reported and confirmed reports of colorectal cancer until December 31, 1995.