Lifetime physical activity and risk of endometrial cancer.

BACKGROUND The role of moderate physical activity and life patterns of activity in reducing endometrial cancer risk remains uncertain. METHODS We assessed lifetime histories of activity from recreation, transportation, chores, and occupation and other risk factors in a population-based case-control study of endometrial cancer conducted in the San Francisco Bay area. The analysis was based on 472 newly diagnosed cases ascertained by the regional cancer registry and 443 controls identified by random-digit dialing who completed an in-person interview. RESULTS Reduced risks associated with greater lifetime physical activity (highest versus lowest tertile) were found for both total activity [odds ratio (OR), 0.61; 95% confidence interval (95% CI), 0.43-0.87; Ptrend=0.01] and activity of moderate intensity (OR, 0.44; 95% CI, 0.30-0.64; Ptrend<0.0001). Compared with women with low lifetime physical activity (below median), those with greater activity throughout life had a higher reduction in risk (OR, 0.62; 95% CI, 0.44-0.88). Inverse associations were stronger in obese and overweight women, but differences were not statistically significantly different from those in normal-weight women. CONCLUSION These findings suggest that physical activity in adulthood, even of moderate intensity, may be effective in lowering the risk of endometrial cancer, particularly among those at highest risk for this disease. IMPACT The results emphasize the importance of evaluating lifetime histories of physical activity from multiple sources, including both recreational and nonrecreational activities of various intensities, to fully understand the relation between physical activity and disease risk.