title: Parental age and autism spectrum disorders.
abstract: OBJECTIVE
  We sought to study the possible association between parental age and autism spectrum disorder (ASD) by using both a cohort design and a sibling design.
  
  
  METHODS
  Our cohort included all singleton births in Denmark from January 1, 1980, through December 31, 2003, a total of 1,311,736 children. Cases of ASDs were obtained from the Danish National Psychiatric Register using International Classification of Diseases (ICD)-8 and ICD-10.
  
  
  RESULTS
  A total of 9556 children were diagnosed with an ASD. Both maternal and paternal age were associated with a greater risk of ASD in the offspring (hazard ratios ranging from 1.21 (1.10-1.34) to 1.65 (1.09-2.48) depending on combinations of parental age categories; <35, 35-39, and 40+ years). For mothers younger than 35 years, the risk of ASD increased with increasing father's age group. For fathers younger than 35 years, the risk of ASD increased with increasing maternal age.
  
  
  CONCLUSIONS
  We found an association between parental age and ASD in the cohort study, but the combined underlying mechanisms through which paternal and maternal age impact ASD risk do not seem to act synergistically. The results of the sibling analysis suggest that the association between parental age and ASD found in the cohort study cannot be accounted for by common genetic and environmental factors.
authors.affiliation: School of Public Health, Department of Biostatistics, University of Aarhus, Bartholins Allé 2, Aarhus C, Denmark. parner@biostat.au.dk
authors.forename: Erik Thorlund
authors.initials: ET
authors.lastname: Parner
authors.forename: Simon
authors.initials: S
authors.lastname: Baron-Cohen
authors.forename: Marlene B
authors.initials: MB
authors.lastname: Lauritsen
authors.forename: Meta
authors.initials: M
authors.lastname: Jørgensen
authors.forename: Laura A
authors.initials: LA
authors.lastname: Schieve
authors.forename: Marshalyn
authors.initials: M
authors.lastname: Yeargin-Allsopp
authors.forename: Carsten
authors.initials: C
authors.lastname: Obel
mesh_terms: D000328:Adult; D002659:Child Development Disorders, Pervasive / Q000453:epidemiology / Q000209:etiology*; D015331:Cohort Studies; D003718:Denmark; D005260:Female; D005865:Gestational Age; D006801:Humans; D007223:Infant; D008297:Male; D008423:Maternal Age; D010331:Paternal Age; D015995:Prevalence; D012042:Registries; D012307:Risk Factors; D012737:Sex Factors; D035781:Siblings; D055815:Young Adult