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 ≥ 26 units, those highly active (energy expenditure ≥ 2,500 kcal [≥ 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.
©1994The American College of Sports Medicine