Objective: We examined the associations of leisure-time physical activity and adiposity with endometrial cancer risk.
Methods: Eligible subjects were 32,642 healthy US women, >or=45 years, from the Women's Health Study. Women reported on questionnaires about their weight, height, and physical activity at baseline (1992-1995) and waist and hip circumference at 72 months. During an average follow-up of 8.8 years, 264 women developed endometrial cancer, confirmed using medical records.
Results: The heaviest women (body mass index, BMI >or= 30 kg/m(2)) had more than twice the risk of endometrial cancer as those who were least heavy (BMI < 22.5 kg/m(2)) [multivariable-adjusted relative risk, RR = 2.49 (95% confidence interval (CI) = 1.73, 3.59)]. Neither waist nor waist/hip ratio predicted risk in multivariate analyses. Leisure-time physical activity and walking were also unrelated to risk. Women reporting any vigorous activity had lower risk than those reporting none (multivariable-adjusted RR = 0.74 [0.56, 0.97]) independent of BMI, but there was no trend of declining risk with increasing energy expended in such activities. In examining the joint effects of BMI and physical activity, compared with active (>or=15 MET-h/week), normal weight (BMI < 25) women, those who were both inactive (<15 MET-h/week) and overweight (BMI >or= 25) had higher risk (multivariable-adjusted RR = 1.85 [1.26, 2.72]), as did women who were overweight and active (multivariable-adjusted RR = 1.60 [1.01, 2.54]), whereas normal weight, inactive women (multivariable-adjusted RR = 1.17 [0.77, 1.77]) did not.
Conclusions: This study confirms BMI as a strong predictor of endometrial cancer risk. Central adiposity did not independently predict risk after adjustment for BMI; there also was no clear evidence of an inverse relation with leisure-time physical activity.