Age at natural or surgical menopause, all-cause mortality, and lifespan among postmenopausal women in the United States

OBJECTIVE: This study investigated the association of age at natural menopause with or without undergoing hysterectomy and/or bilateral oophorectomy after menopause and age at surgical menopause with all-cause mortality and lifespan in postmenopausal women. METHODS: The data stemmed from the National Health and Nutrition Examination Survey (NHANES) (1999-2018) and NHANES III (1988-1994), including 14,161 postmenopausal women over 40. Cox proportional hazard models were used to estimate unadjusted and adjusted hazard ratios (HRs) (95% confidence intervals [CIs]). We also used Cox proportional hazard models with penalized splines to depict the association between continuous age at menopause and all-cause mortality and nonparametric regression with smoothing splines to illustrate the association between age at menopause and lifespan in deceased participants. RESULTS: The adjusted HRs (95% CIs) for age at natural menopause of <40, 40 to 44, and 55+ years in women without undergoing hysterectomy or bilateral oophorectomy after menopause were 1.48 (1.15-1.91), 1.16 (1.00-1.35), and 0.91 (0.77-1.07) compared with age at natural menopause of 45 to 54, respectively. The respective HRs (95% CIs) for age at surgical menopause were 1.39 (1.11-1.75), 1.09 (0.86-1.38), and 0.83 (0.53-1.32). However, no significant association was found between age at natural menopause and all-cause mortality among women undergoing hysterectomy and/or bilateral oophorectomy after menopause. When treated as continuous variables, age at natural menopause without undergoing hysterectomy or bilateral oophorectomy after menopause presented inverse and nonlinear associations with all-cause mortality, whereas age at surgical menopause was linearly inversely associated with all-cause mortality. The association between age at menopause and lifespan was linearly positive regardless of menopausal type. CONCLUSION: Young age at menopause was associated with increased risks of all-cause mortality. The later menopause age was related to a longer lifespan.