Women’s Health
Cohort-based estimates of natural menopause timing in the US using competing risk models Alison Gemmill* Alison Gemmill Gemmill University of California, Los Angeles
Menopause is a major but underexamined determinant of women’s health and population aging. Although prior studies suggest that the age at menopause has increased over time, recent US estimates rely largely on period-based prevalence measures that obscure birth cohort dynamics and do not account for competing reproductive endpoints, including bilateral oophorectomy and hysterectomy. Using repeated cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) from 2000-2020, we estimated birth cohort differences in the timing of natural menopause using competing risk survival models and compared results to censoring-based estimates. By age 50, the cumulative incidence of natural menopause declined across birth cohorts, falling from 41.6% (95% CI: 36.6–46.6) in the 1914–1924 cohort to 26.5% (95% CI: 23.4–29.6) in the 1965–1974 cohort (Figure 1). The median age at natural menopause was 53 years (95% CI: 52–54) in the 1914–1924 cohort and occurred at older ages in more recent cohorts. The cumulative incidence of premature natural menopause (<40 years) fell from 8.6% (95% CI: 6.9–10.5) to 1.9% (95% CI: 1.4–2.3), and the cumulative incidence of early menopause (ages 40–44) declined from 11.1% (95% CI: 9.1–13.1) to 4.0% (95% CI: 3.1–5.0). In contrast, estimates that treated surgical menopause as censoring overstated cumulative incidence at older ages and implied earlier menopause timing. Together, these findings indicate that period-based approaches and censoring of surgical menopause underestimate the timing of natural menopause relative to cohort-based competing risk analyses. The population age at natural menopause in the US has increased more than previously recognized, with particularly large declines in early and premature menopause across successive birth cohorts.
