Lifestyle and endometrial cancer risk: A cohort study from the Swedish Twin Registry

Case-control studies of lifestyle factors have been inconclusive in the stu dy of endometrial cancer, and prospective data are scarce. Our aim was to e xamine the associations of physical activity, weight and weight change, fru it, vegetable, and alcohol consumption, socio-economic status, parity and p resence of diabetes mellitus with the risk of endometrial cancer in a cohor t study, In 1967, 11,659 women in the Swedish Twin Registry, born 1886-1925 , answered a 107-item questionnaire, including questions about diet, physic al activity and other lifestyle factors, Complete follow-up through 1992 wa s attained through record linkage to the Swedish Cancer and Death Registers . The relative risks for endometrial cancer were estimated in proportional hazards models that adjusted confidence limits for correlated outcomes. We observed 133 incident cases of endometrial cancer in the cohort. There was no clear pattern of risk over strata of alcohol or fruit and vegetable inta ke, although the data suggest an increased risk with very low fruit and veg etable intake, Increasing physical activity markedly decreased the risk of endometrial cancer (p for trend < 0.01), independently of weight and parity ; the risk in the highest quartile, relative to the sedentary category, was 0.2 (95% CI 0.3-0.8), As expected, higher weight in middle age increased t he risk (p for trend < 0.01), as did higher weight in early adulthood. Cont rary to previous findings, weight gain did not have an effect independent o f weight at enrollment. We did not find a genetic component to endometrial cancer. Our results confirm that environmental factors are the most importa nt, especially physical activity, parity, and weight in young and middle ag e. (C) 1999 Wiley-Liss, Inc.