Associations with menopause and menopausal transition in a nationally representative US sample.

OBJECTIVES: The purpose of this study was to assess sociodemographic and behavioral factors in relation to menopausal status in a representative sample of the United States population.
METHODS: Data were taken from the 1999 National Health Interview Survey (NHIS), limited to women aged 40-54 years who had not undergone surgical menopause. Menopausal transition was defined as absence of menstrual cycles for at least 3 but no more than 11 months or cycles that had become irregular in the past 12 months. Postmenopause was defined as absence of a menstrual cycle for 12 or more months. We used age-adjusted three-level logistic regression to examine the association between menopausal status and smoking, race/ethnicity, education, body mass index, exercise, and alcohol use.
RESULTS: Twenty percent of women in this sample had experienced natural menopause, 18% were in the menopausal transition and 61% were premenopausal. Using premenopause as the reference group, current cigarette smoking was strongly associated with being postmenopausal (odds ratio (OR) 2.2, 95% confidence interval (CI) 1.7, 3.0) and weakly associated with being in the menopausal transition (OR 1.4, 95% CI 1.1, 1.8). Education level was associated with being postmenopausal (OR 0.4, 95% CI 0.3, 0.6 comparing women with a college degree to women who had not completed high school), and alcohol use was weakly associated with being postmenopausal, with no evidence of a dose-response.
CONCLUSIONS: The associations with smoking were stronger for postmenopause than for the transition phase, suggesting that the effect of smoking may be to shorten the transition period. Education level may be a marker for other exposures that affect ovarian senescence.