Reproductive, lifestyle, socioeconomic and anthropometric correlates of early menopause.

OBJECTIVE: This study aimed to identify lifestyle, reproductive and socioeconomic correlates of early menopause (age <45 years) in a cross-sectional analysis of a population-based cohort of Japanese women. METHOD: The study analyzed data from 6313 naturally menopausal women in the Yamagata Cohort Study (2009-2015). Women were classified as having early menopause (age <45 years; n = 239) or menopause at age 45-54 years (n = 6074). Data included age at menarche, menstrual pattern at age 20 years, educational attainment, marital status, parity, breastfeeding, smoking and body mass index (BMI). Multivariable logistic regression estimated odds ratios (ORs) with 95% confidence intervals (CIs). RESULTS: Lower educational attainment (OR 1.84, 95% CI 1.32-2.57) and never-married status (OR 2.52, 95% CI 1.24-5.11) were associated with early menopause. Low BMI was associated with early menopause in univariate analysis but not after multivariable adjustment. An interaction was observed between menstrual pattern at age 20 years and BMI: among women with menstrual irregularity, obesity (BMI ≥25 kg/m2) was associated with higher odds of early menopause (OR 3.49, 95% CI 1.91-6.37). CONCLUSION: In this cross-sectional analysis of a population-based cohort of Japanese women, lower educational attainment and never-married status were associated with early menopause. Women with menstrual irregularity and obesity may be at increased risk of early menopause.