Prospective study of body size throughout the life-course and the incidence of endometrial cancer among premenopausal and postmenopausal women.

Although adult obesity is known to increase endometrial cancer risk, evidence for childhood obesity is limited. We prospectively examined the association between body fatness throughout life and endometrial cancer risk. 47,289 participants in the Nurses' Health Study (NHS) and 105,386 of the Nurses' Health Study II (NHS II) recalled their body fatness at ages 5, 10 and 20 using a pictogram. Childhood and adolescent body fatness were derived as the average at ages 5 and 10 and ages 10 and 20, respectively. We obtained adult weight from concurrent questionnaires. We calculated hazard ratios (HR) of endometrial cancer using Cox proportional hazards models. During follow-up, 757 incident cases of endometrial cancer were diagnosed. Body fatness in childhood, at age 10, in adolescence and at age 20 were positively associated with endometrial cancer risk (HR for ≥ Level 5 versus ≤ Level 2 in adolescence: 1.83 (95% CI 1.41-2.37). After adjusting for most recent BMI, none of the associations persisted. Weight change since age 18 was positively associated with endometrial cancer risk [HR for ≥ 25 kg gain versus stable: 2.54 (95% CI 1.80-3.59). Adult BMI was strongly associated with endometrial cancer risk [HR BMI ≥ 35 kg/m(2) versus BMI ≤ 25 kg/m(2) : 4.13 (95% CI 3.29-5.16)]. In postmenopausal women, the association with BMI was significantly stronger among non-users of hormone therapy. In conclusion, obesity throughout life is positively associated with endometrial cancer risk, with adult obesity one of the strongest risk factors. Maintaining a healthy weight throughout life remains important.