Background: Early menarche is associated with early menopause and other adverse health outcomes, but the association with vasomotor symptoms (VMS, including hot flushes and night sweats) is unclear. This study aimed to examine the association between age at menarche and the risk of hot flushes and night sweats and investigate whether the association is modified by body mass index (BMI) in midlife.
Methods: We conducted a pooled analysis using data from 18,555 women in six studies from the International collaboration on the Life course Approach to reproductive health and Chronic disease Events (InterLACE). VMS frequency data (never, rarely, sometimes, and often) were self-reported and harmonised from two studies (n=13,602); severity data (never, mild, moderate, and severe) from the other four studies (n=4,953). Multinominal logistic regression models with four categories of frequency/severity for the outcome of VMS were used to estimate relative risk ratios (RRRs) and 95% confidence intervals (CIs) adjusted for covariates and incorporated study as random effects.
Results: Frequency data showed that early menarche ≤11 years was associated with an increased risk of ‘often’ hot flushes (RRR 1.48, 1.24-1.76) and night sweats (RRR 1.59, 1.49-1.70) compared with menarche at ≥14 years. Severity data showed similar results, but appeared less conclusive, with RRRs of 1.16 (0.94-1.42) and 1.27 (1.01-1.58) for ‘severe’ hot flushes and night sweats, respectively. BMI significantly modified the association as the risk associated with early menarche and ‘often’ VMS was stronger among women who were overweight or obese than those of normal-weight, while this gradient across BMI categories was not as strong with the risk of ‘severe’ VMS.
Conclusions: Early menstruation is a risk factor for VMS, particularly for frequent VMS, but midlife BMI may play an important role in modifying this risk.