title: Maternal and paternal age at delivery, birth order, and risk of childhood onset type 1 diabetes: population based cohort study.
abstract: OBJECTIVE
  To estimate the associations of maternal and paternal age at delivery and of birth order with the risk of childhood onset type 1 diabetes.
  
  
  METHODS
  Cohort study by record linkage of the medical birth registry and the national childhood diabetes registry in Norway.
  
  
  METHODS
  Norway.
  
  
  METHODS
  All live births in Norway between 1974 and 1998 (1.4 million people) were followed for a maximum of 15 years, contributing 8.2 million person years of observation during 1989-98. 1824 cases of type 1 diabetes diagnosed between 1989 and 1998 were identified.
  
  
  METHODS
  Incidence of type 1 diabetes.
  
  
  RESULTS
  There was no association between maternal age at delivery and type 1 diabetes among firstborn children, but among fourth born children there was a 43.2% increase in incidence of diabetes for each five year increase in maternal age (95% confidence interval 6.4% to 92.6%). Each increase in birth order was associated with a 17.9% reduction in incidence (3.2% to 30.4%) when maternal age was 20-24 years, but the association was weaker when maternal age was 30 years or more. Paternal age was not associated with type 1 diabetes after maternal age was adjusted for.
  
  
  CONCLUSIONS
  Intrauterine factors and early life environment may influence the risk of type 1 diabetes. The relation of maternal age and birth order to risk of type 1 diabetes is complex.
authors.affiliation: Diabetes Research Centre, Aker and Ullevål University Hospitals, Department of Paediatrics, Ullevål Hospital, N-0407 Oslo, Norway. lars.christian.stene@folkehelsa.no
authors.forename: L C
authors.initials: LC
authors.lastname: Stene
authors.forename: P
authors.initials: P
authors.lastname: Magnus
authors.forename: R T
authors.initials: RT
authors.lastname: Lie
authors.forename: O
authors.initials: O
authors.lastname: Søvik
authors.forename: G
authors.initials: G
authors.lastname: Joner
mesh_terms: D000328:Adult; D017668:Age of Onset; D001722:Birth Order; D015331:Cohort Studies; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D006801:Humans; D015994:Incidence; D007231:Infant, Newborn; D008297:Male; D008423:Maternal Age; D009664:Norway / Q000453:epidemiology; D010331:Paternal Age; D012306:Risk