DETERMINANTS OF AGE AT MENARCHE AS EARLY-LIFE PREDICTORS OF BREAST-CANCER RISK

Age at menarche is one of the few established risk factors for breast cancer; identification of its exogenous determinants could throw light on the origins of breast cancer. We have undertaken an epidemiologic study in Greece to ascertain whether: 1) energy intake, an indicator o f physical activity, is associated with later age at menarche; 2) ener gy-adjusted fat intake is related to earlier age at menarche; and 3) o ther macronutrients and anthropometric variables are predictors of age at menarche. Anthropometric, socio-economic, familiar, nutritional an d lifestyle predictors of age at menarche were studied by interviewing in person 345 female students 9 to 16 years old attending 8 schools o f Greater Athens. Menarche was the outcome variable in a proportional hazards model assessing the mutually adjusted incidence rate ratio by a series of predictor variables. In a complementary analysis, age at m enarche was the dependent variable among menstruating girls. Consisten t results were derived from the main and the complementary analysis. I ncreased height and body mass index accelerate the occurrence of menar che. Maternal and daughter's ages at menarche are correlated, but ther e is no evidence of an association with paternal education. Various me asures of moderate physical activity as well as increased total energy intake were associated with a delay in age at menarche. Energy-adjust ed macronutrients were not associated with age at menarche. It appears that an alteration of energy balance in early life through increased physical activity could delay age at menarche and reduce the risk for breast cancer in later life. (C) 1996 Wiley-Liss, Inc.