PHYSICAL-ACTIVITY AND ITS RELATION TO CANCER RISK - A PROSPECTIVE-STUDY OF COLLEGE ALUMNI

Previous investigations regarding the influence of physical activity on cancer risk generally have utilized a single assessment of activity, thus failing to account for changes over time. Additionally, one assessment may be somewhat imprecise. We attempted to overcome these problems in a study of 17,607 men (aged 30-79 yr), followed from 1962 or 1966 (1962/1966) through 1988. We assessed physical activity (based on self-reported stair climbing, walking and participation in sports or recreational activities) twice: in 1962/1966 and again in 1977. A total of 280 colon, 53 rectal, 454 prostatic, 262 lung, and 88 pancreatic cancers developed during follow-up. Among alumni with Quetelet's index greater than or equal to 26 units, those highly active (energy expenditure greater than or equal to 2,500 kcal [greater than or equal to 10,460 kJ].wk(-1)) had 0.19 (95% confidence interval, 0.02-1.52) to 0.56 (0.29-1.09) times the colon cancer risk of those inactive (<1,000 kcal [<4,184 kJ].wk(-1)). Colon cancer risk was unrelated to level of activity among alumni with Quetelet's index < 26 units. Highly active alumni also had 0.39 (95% confidence interval, 0.18-0.85) to 0.62 (0.45-0.85) times the lung cancer risks of their inactive colleagues. Physical activity was not significantly associated with risks of rectal, prostatic, or pancreatic cancers. The biologic basis for a protective effect of increased activity on cancer risk appears plausible.