Background
No consistent conclusion on the association between body mass index (BMI) and age at natural menopause was established.
Aim
To examine the relationship between BMI and age at menopause, we pooled individual-level data from 11 prospective studies.
Methods
Over 24 000 women who experienced menopause after recruitment were included. Baseline BMI was categorised according to the WHO criteria. Natural menopause is recognised to have occurred after 12 consecutive months of amenorrhea. Age at menopause was categorised as <45 years (early menopause), 45-49, 50-51 (reference category), 52-53, 54-55, and ≥56 years (late menopause). Multinomial logistic regression models were used to estimate multivariable relative risk ratios (RRRs) and 95% confidence intervals (CI) for the associations between BMI and menopause age.
Results
The mean (standard deviation) age at menopause was 51.4 (3.3) years, with 1.6%, 26.5%, and 12.8% of the women underweight, overweight, and obese, respectively. Compared with normal BMI group (18.5-24.9 kg/m2), underweight women had over 2-fold risk of early menopause (RRR 2.15, 95% CI 1.50-3.06), while overweight (1.52, 1.31-1.77) and obese women (1.54, 1.18-2.01) were at higher risk of late menopause. Overweight and obesity were also significantly associated with 20% increased risk of menopause at ages 52-53 and 54-55 years. No association between underweight and late menopause was observed. A higher risk (1.23, 0.89-1.71) for early menopause among obese women was suggested but not significant.
Conclusion
Overweight and obese women had more than 50% higher risk of late menopause, while underweight women had over twice the risk of early menopause.