Occupational and leisure-time physical activity and risk of colon cancer by subsite

Objective: Studies of physical activity and colon cancer risk by anatomic site have provided inconsistent results. Methods: We analyzed data from a population-based case-control study conducted in Iowa involving 685 colon cancer cases and 2434 control subjects. Results: Among those who reported recreational activity more than twice per week, a 30% risk reduction of colon cancer was observed for all sites with a 40% risk reduction for cancer of the right colon. Occupational physical activity was also associated with a reduced risk of colon cancer. The risk was the lowest for those with both high occupational and recreational physical activity (odds ratio, 0.5; 95% confidence interval, 0.3-0.8). Conclusions: Increased physical activity was inversely associated with colon cancer risk. The inverse associations were stronger for the right than for the left colon.