The association of adolescent to midlife weight change with age at natural menopause: a population study of 263,586 women in Norway.

Age at menopause varies considerably among women and is linked to health after menopause. Body mass index is associated with age at natural menopause, but the influence of weight change remains unclear. Thus, we studied associations of adolescent to midlife weight change with age at natural menopause. We performed a retrospective population-based cohort study of 263,586 women aged 50-69 years attending BreastScreen Norway (2006-2015). The associations were estimated as hazard ratios (HRs) for having reached menopause using Cox proportional hazard models. We included nine categories of weight change based on recalls of adolescent weight compared to peers and quartiles of midlife weight in kilograms. We adjusted for year and country of birth, education, number of childbirths, height, smoking, and exercise. Women with the largest estimated weight loss had highest hazard of reaching menopause (adjusted HR 1.11, 95% CI: 1.06-1.17) compared to women with estimated stable average weight. Conversely, women with the largest estimated weight gain had lower hazard (adjusted HR 0.96, 95% CI: 0.93-0.99). Women with estimated stable high weight had lowest hazard of reaching menopause (adjusted HR 0.93, 95% CI: 0.90-0.95). Our findings suggest that changes in body weight across the life course may influence the timing of menopause.