Assessing age at natural menopause from self-reported data in a long-running population-based cohort study

OBJECTIVES: To assess whether age at natural menopause could be determined through self-report, and evaluate consistency and reproducibility in self-reported age at natural menopause in a long-running population-based cohort study. METHODS: We used longitudinal data from 3394 women participating in the Doetinchem Cohort Study (1987-2017), who reported menstrual status and age at menopause up to seven times over 30 years. We assessed the proportion of women for whom age at natural menopause could be determined, within-person variation across repeated reports, and reproducibility defined as agreement within one year across increasing recall intervals. MAIN OUTCOME MEASURES: Proportion determination of age at natural menopause, within-person variation across reports, and reproducibility defined as agreement within one year across increasing recall intervals. RESULTS: Age at natural menopause could be determined in 57% of women who reached menopause during follow-up; in the remaining women, this was mainly precluded by hormone use and gynecologic surgery. Among women who had experienced natural menopause, 60% reported age differences of ≤2 years and 17% ≥4 years across reports. Variation increased with longer recall intervals, with underreporting among women already postmenopausal at baseline. Agreement within one year declined from 62% at 5 years to 45% at 30 years. CONCLUSION: For a substantial proportion of women, age at natural menopause is difficult to determine and inconsistently reported, especially over longer recall periods. Accurate documentation of menopausal status, hormone use, and surgical history are therefore crucial for both research and clinical care. Clear definitions and careful prospective documentation of hormone use can improve reproducibility and data quality, enhancing comparability across studies and supporting appropriate female-specific health care.