title: Maternal age at birth and childhood type 1 diabetes: a pooled analysis of 30 observational studies.
abstract: OBJECTIVE
  The aim if the study was to investigate whether children born to older mothers have an increased risk of type 1 diabetes by performing a pooled analysis of previous studies using individual patient data to adjust for recognized confounders.
  
  
  METHODS
  Relevant studies published before June 2009 were identified from MEDLINE, Web of Science, and EMBASE. Authors of studies were contacted and asked to provide individual patient data or conduct prespecified analyses. Risk estimates of type 1 diabetes by maternal age were calculated for each study, before and after adjustment for potential confounders. Meta-analysis techniques were used to derive combined odds ratios and to investigate heterogeneity among studies.
  
  
  RESULTS
  Data were available for 5 cohort and 25 case-control studies, including 14,724 cases of type 1 diabetes. Overall, there was, on average, a 5% (95% CI 2-9) increase in childhood type 1 diabetes odds per 5-year increase in maternal age (P = 0.006), but there was heterogeneity among studies (heterogeneity I(2) = 70%). In studies with a low risk of bias, there was a more marked increase in diabetes odds of 10% per 5-year increase in maternal age. Adjustments for potential confounders little altered these estimates.
  
  
  CONCLUSIONS
  There was evidence of a weak but significant linear increase in the risk of childhood type 1 diabetes across the range of maternal ages, but the magnitude of association varied between studies. A very small percentage of the increase in the incidence of childhood type 1 diabetes in recent years could be explained by increases in maternal age.
authors.affiliation: Centre for Public Health, Queen's University Belfast, Belfast, UK. c.cardwell@qub.ac.uk
authors.forename: Chris R
authors.initials: CR
authors.lastname: Cardwell
authors.forename: Lars C
authors.initials: LC
authors.lastname: Stene
authors.forename: Geir
authors.initials: G
authors.lastname: Joner
authors.forename: Max K
authors.initials: MK
authors.lastname: Bulsara
authors.forename: Ondrej
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authors.lastname: Cinek
authors.forename: Joachim
authors.initials: J
authors.lastname: Rosenbauer
authors.forename: Johnny
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authors.lastname: Ludvigsson
authors.forename: Mireia
authors.initials: M
authors.lastname: Jané
authors.forename: Jannet
authors.initials: J
authors.lastname: Svensson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Goldacre
authors.forename: Thomas
authors.initials: T
authors.lastname: Waldhoer
authors.forename: Przemyslawa
authors.initials: P
authors.lastname: Jarosz-Chobot
authors.forename: Suely G A
authors.initials: SG
authors.lastname: Gimeno
authors.forename: Lee-Ming
authors.initials: LM
authors.lastname: Chuang
authors.forename: Roger C
authors.initials: RC
authors.lastname: Parslow
authors.forename: Emma J K
authors.initials: EJ
authors.lastname: Wadsworth
authors.forename: Amanda
authors.initials: A
authors.lastname: Chetwynd
authors.forename: Paolo
authors.initials: P
authors.lastname: Pozzilli
authors.forename: Girts
authors.initials: G
authors.lastname: Brigis
authors.forename: Brone
authors.initials: B
authors.lastname: Urbonaite
authors.forename: Sandra
authors.initials: S
authors.lastname: Sipetic
authors.forename: Edith
authors.initials: E
authors.lastname: Schober
authors.forename: Gabriele
authors.initials: G
authors.lastname: Devoti
authors.forename: Constantin
authors.initials: C
authors.lastname: Ionescu-Tirgoviste
authors.forename: Carine E
authors.initials: CE
authors.lastname: de Beaufort
authors.forename: Denka
authors.initials: D
authors.lastname: Stoyanov
authors.forename: Karsten
authors.initials: K
authors.lastname: Buschard
authors.forename: Chris C
authors.initials: CC
authors.lastname: Patterson
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology*; D005260:Female; D006801:Humans; D008423:Maternal Age; D015201:Meta-Analysis as Topic; D016017:Odds Ratio; D012044:Regression Analysis; D015203:Reproducibility of Results