Age at menarche association with metabolic, reproductive, and sociodemographic factors: a population-based cross-sectional analysis using an outcome-wide framework in Geneva, Switzerland.

A global decline in age at menarche has raised concerns about its long-term health and social consequences. This study investigates temporal trends in age at menarche in a Swiss population born between 1936 and 1989 and assesses associations with sociodemographic, metabolic, and reproductive health factors. Age at menarche was examined across birth cohorts to assess temporal trends. Using an outcome-wide analytical framework, adjusted for age, survey year, and education, logistic and linear regression models examined the associations between menarche timing and sociodemographic, metabolic, and reproductive health factors. The sample included 6462 women aged 34-75. Mean age at menarche was 13.1 years, decreasing from 14.1 (born in 1936) to 12.9 (born in 1989). Early menarche (<12 years) was associated with lower income (aOR = 0.79; 95% CI: 0.67-0.93), higher odds of hypertension (aOR 1.41; 1.18-1.67), diabetes (aOR 1.40; 1.05-1.83), hypercholesterolemia (aOR 1.27; 1.07-1.49), shorter stature (-2.12 cm), higher BMI, increased hysterectomy prevalence (aOR 1.69; 1.33-2.13), and longer reproductive lifespan (+1.59 years). Late menarche (>14 years) was associated with increased stillbirth (aOR 1.80; 1.12-2.84) and ectopic pregnancy risks (aOR 1.45; 1.04-2.00) (however to be seen as exploratory as not significant after FDR correction), different menstrual patterns, reduced reproductive lifespan (-3.12 years), and lower education (aOR 0.81; 0.71-0.93). Age at menarche has declined in Geneva and is associated with various health outcomes. Including menarche timing in clinical assessments could improve risk stratification and preventive care.