title: Variability of reproductive history across the Swiss SAPALDIA cohort--patterns and main determinants.
abstract: 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.
  
  
  OBJECTIVE
  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 (<52 years) than older (>52 years) menopausal age.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Institute of Social and Preventive Medicine, University of Basel, Switzerland. julia.dratva@unibas.ch
authors.forename: Julia
authors.initials: J
authors.lastname: Dratva
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Zemp
authors.forename: Patricia
authors.initials: P
authors.lastname: Staedele
authors.forename: Christian
authors.initials: C
authors.lastname: Schindler
authors.forename: Michael C
authors.initials: MC
authors.lastname: Constanza
authors.forename: Michael
authors.initials: M
authors.lastname: Constanza
authors.forename: Margaret
authors.initials: M
authors.lastname: Gerbase
authors.forename: Nicole
authors.initials: N
authors.lastname: Probst-Hensch
authors.forename: Thierry
authors.initials: T
authors.lastname: Rochat
authors.forename: Ursula
authors.initials: U
authors.lastname: Ackermann-Liebrich
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D001723:Birth Rate; D015331:Cohort Studies; D005260:Female; D006306:Health Surveys; D006801:Humans; D053208:Kaplan-Meier Estimate; D008572:Menarche / Q000208:ethnology* / Q000502:physiology; D008593:Menopause / Q000208:ethnology* / Q000502:physiology; D008875:Middle Aged; D010298:Parity; D011247:Pregnancy; D016016:Proportional Hazards Models; D012907:Smoking; D013557:Switzerland / Q000453:epidemiology; D019371:Topography, Medical