Physical activity, weight change and endometrial cancer risk: The multiethnic cohort

AACR Annual Meeting-- Apr 12-16, 2008; San Diego, CA 3073 Obesity, adult weight gain, and physical inactivity are known or suspected risk factors for endometrial cancer. We examined the associations of these related factors with endometrial cancer risk among 37,884 postmenopausal African-American, Japanese-American, Latina, Native-Hawaiian, and White women recruited to the prospective Multiethnic Cohort Study from 1993 to 1996 who had natural menopause and complete risk factor data. During an average of 8.2 years of follow-up, 311 cases of invasive endometrial cancers were identified among these women. Information on physical activity, weight at age 21, and weight at time of recruitment was obtained from the baseline questionnaire. In our analysis, “change in weight” was defined as the percentage weight change from the age of 21 years to the time of recruitment; and total physical activity was analyzed as metabolic equivalents of energy expenditure (METs) per day based on participants’ responses to various physical activity questions. Hazard rate ratios (RRs) and 95% confidence intervals (CIs) for endometrial cancer incidence associated with each risk factor were estimated using log-linear (Cox) proportional hazard models stratified by age at and year of recruitment, race/ethnicity, and study area, and adjusted for potential confounders. No association between physical activity and endometrial cancer risk was observed; the RR was 0.97 (95% CI: 0.65, 1.48) among women in the highest compared with the lowest quartile of physical activity (≥1.764 METs/day versus ≤1.418 METs/day). However, adult weight gain was associated with an increased risk (P trend <0.001) of malignancy. Women in the highest quartile of weight change (≥35% weight gained from the age of 21 years) had a RR of 3.52 (95% CI: 2.13, 5.83) compared to women in the lowest quartile (< 8.5% weight gain or any percentage weight loss). In conclusion, a 35% adult weight gain increased the risk of endometrial cancer by 3.5 fold among postmenopausal women in the Multiethnic Cohort Study.