A CASE-CONTROL STUDY OF PHYSICAL-ACTIVITY IN RELATION TO RISK OF CANCER OF THE RIGHT COLON AND RECTUM IN MEN

Background. Epidemiological data suggest that physical activity is modestly or moderately protective against colorectal cancer. Additional data are needed to define better the slope of the dose-response curve and to clarify the types of activities that appear most protective. Methods. We examined the relation between occupational and vigorous leisure time physical activity and risk of cancer of the right colon and rectum in data from a case-control study conducted in New England from 1986 to 1988. We interviewed 163 cases with cancer of the right colon, 242 cases with cancer of the rectum, and 703 community controls. Results. Vigorous leisure time physical activity was associated with a decreased risk of cancer of the right colon; for men exercising greater than or equal to 2 hours per week the odds ratio was 0.60 (95% confidence interval [Cl] : 0.35-1.00) compared with those who did not exercise. Adjustment for potentially confounding factors, including diet, had essentially no effect on the association. Self-reported occupational activity was less strongly related to risk of right colon cancer; the odds ratio for heavy work was 0.70 (95% Cl :0.32-1.51), Occupational activity coded according to job title was essentially unrelated to risk of right colon cancer. An association between physical activity and decreased risk of rectal cancer was not present in these data. Conclusions. Our data add weight to the evidence that physical activity is related to decreased risk of colon cancer.