Bjelland EK, et al. - Researchers sought to investigate if age at menarche is associated with age at menopause or with duration of the reproductive period (interval between menarche and menopause). Observations suggested age at menarche to be a strong indicator for the duration of women’s reproductive period. Association between age at menarche and age at menopause was weak and non-linear.

Methods

• During the years 2006–2014, researchers performed a retrospective cohort study of 336,788 women, aged 48–71 years, in the BreastScreen Norway.
• Self-administered questionnaires were used to obtain information about age at menarche and menopausal status.
• Time to event approaches were used to estimate the associations.

Results

• In most menarche groups, median age at menopause was 51 years.
• In this study, women with menarche at age 16 years or age ≥ 17 years reported menopause 1 year later [median: 52 years, interquartile range (IQR): 49–54 years] than women with menarche at age 13 years (median: 51 years, IQR: 49–54 years, reference) (crude hazard ratio (HR) = 0.95; 95% CI: 0.93–0.97 and 0.95; 95% CI: 0.92–0.99, P_{non-linearity} < 0.001).
• Reduction in the reproductive period was noted with increasing age at menarche (P_{non-linearity} < 0.001); women with menarche at age ≤ 9 years had 9 years longer median reproductive period than women with menarche at age ≤ 17 years (median: 43 vs 34 years).
• No notable influence of adjustment for year of birth on HR estimates was observed.