Associations of physical activity and diet with the onset of menopause in Japanese women.

OBJECTIVE: Prospective studies on physical activity and diet and the onset of natural menopause are scarce. The aim of this study was to examine the association of physical activity and dietary factors potentially related to endogenous estrogen levels such as fats, dietary fiber, soy isoflavones, and alcohol with the onset of menopause in a cohort of premenopausal women. METHODS: Study participants were 3,115 premenopausal Japanese women aged 35 to 56 years derived from the participants in the Takayama Study. Physical activity was assessed by a validated questionnaire at baseline, and the metabolic equivalent score was calculated. The dietary intakes were estimated by a validated food frequency questionnaire at baseline and adjusted for total energy. Menopause status was defined as the absence of menstruation for 12 months or more. The Cox proportional hazard model was used to estimate the hazard ratio of the occurrence of menopause after controlling for age, parity, body mass index, smoking status, years of education, and lifelong irregular menstrual cycle. RESULTS: During the 10-year follow-up, 1,790 women experienced natural menopause. A high physical activity level and a high intake of polyunsaturated fat were moderately but significantly associated with the earlier onset of menopause; the hazard ratios for the highest versus lowest quartile were 1.17 (95% CI, 1.02-1.34) for physical activity and 1.15 (95% CI, 1.01-1.31) for polyunsaturated fat intake. Total fat, other types of fat, dietary fiber, soy isoflavones, and alcohol were not associated with the onset of menopause. CONCLUSIONS: These data suggest that high levels of physical activity and polyunsaturated fat intake are associated with earlier onset of menopause.