Variability of reproductive history across the Swiss SAPALDIA cohort - Patterns and main determinants

Background: Reproductive characteristics play an aetiological role for many diseases, including reproductive cancers. They have been shown to vary internationally and nationally, but have not yet been described for the whole Swiss population. Aim: The study investigated the variability of reproductive characteristics, their patterns, and main determinants across a population-based female study population in Switzerland. Methods: Reproductive characteristics obtained from 3119 women ( 28-72 years) participating in the SAPALDIA cohort survey in 2001-2003 are described across birth cohorts, study areas, language regions, and levels of urbanization. Determinants of age at menopause were analysed by Cox regression. Results: Reported median age at menarche was 13 years and median age at natural menopause was 52 years. The prevalence of nulliparity was 27%, and the fertility rate 1.6. Across birth cohorts there was a decline of menarcheal age and fertility rates, and an increase of nulliparity and age at last pregnancy. All characteristics varied across study areas, language regions, and levels of urbanization. Smoking, parity, and physical exercise were stronger predictors of earlier ( 552 years) than older ( 452 years) menopausal age. Conclusion: Reproductive events show secular and geographic variation within Switzerland. Smoking, parity and physical activity significantly predict age at natural menopause, particularly before age 52. The secular trend of earlier menarche and increased nulliparity may result in a higher risk of reproductive cancers in younger generations.