title: Age at natural menopause in a population-based screening cohort: the role of menarche, fecundity, and lifestyle factors.
abstract: OBJECTIVE
  To verify whether a population-based hypothesis (age at menarche and age at natural menopause have an inverse relationship) also applies at the level of the individual and to investigate what other factors predict age at natural menopause.
  
  
  METHODS
  Prospective cohort study (the Doorlopend Onderzoek Morbiditeit/Mortaliteit [DOM] project).
  
  
  METHODS
  Prevention Breast Cancer Screening Centre, Utrecht, The Netherlands.
  
  
  METHODS
  A cohort of 3,756 Dutch women, born between 1911 and 1925, participating in a population-based breast cancer screening program, who experienced a natural menopause. Three samples of women were studied: a sample who did not use oral contraceptives (OCs) (n = 3,347), a sample of OC users (n = 409), and a combined sample of OC users and nonusers (n = 3,756).
  
  
  METHODS
  Age at menopause and menarche, fertility patterns, OC use, height, weight, smoking, and demographic variables.
  
  
  RESULTS
  No relation was found between age at menarche and age at natural menopause. The total percentage of variance in age at natural menopause explained by multiple regression including all factors was minimal, ranging from 1.3% to 9.7% in OC users. Linear regression analysis indicated a slight secular trend in age at menopause.
  
  
  CONCLUSIONS
  Frisch's hypothesis could not be corroborated at the individual level. These results suggest that age at menarche and menopause should be treated as independent risk factors for breast cancer. Modification of age at menopause by lifestyle factors (except possibly for OC use) appears minimal.
authors.affiliation: Utrecht University, The Netherlands.
authors.forename: P A
authors.initials: PA
authors.lastname: van Noord
authors.forename: J S
authors.initials: JS
authors.lastname: Dubas
authors.forename: M
authors.initials: M
authors.lastname: Dorland
authors.forename: H
authors.initials: H
authors.lastname: Boersma
authors.forename: E
authors.initials: E
authors.lastname: te Velde
mesh_terms: D000367:Age Factors; D000368:Aged; D015331:Cohort Studies; D003276:Contraceptives, Oral; D005260:Female; D005298:Fertility; D006801:Humans; D008019:Life Style; D016014:Linear Models; D017533:Marital Status; D008572:Menarche / Q000502:physiology*; D008593:Menopause / Q000502:physiology*; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies
chemical_list: D003276:Contraceptives, Oral