title: Gestational age, birth weight, and the risk of hyperkinetic disorder.
abstract: OBJECTIVE
  To study the association between gestational age and birth weight and the risk of clinically verified hyperkinetic disorder.
  
  
  METHODS
  Nested case-control study of 834 cases and 20 100 controls with incidence density sampling.
  
  
  RESULTS
  Compared with children born at term, children born with gestational ages of 34-36 completed weeks had a 70% increased risk of hyperkinetic disorder (rate ratio (RR) 1.7, 95% confidence interval (CI) 1.2 to 2.5). Children with gestational ages below 34 completed weeks had an almost threefold increased risk (RR 2.7, 95% CI 1.8 to 4.1). Children born at term with birth weights of 1500-2499 g had a 90% increased risk of hyperkinetic disorder (RR 1.9, 95% CI 1.2 to 2.9), and children with birth weights of 2500-2999 g had a 50% increased risk (RR 1.5, 95% CI 1.2 to 1.8) compared with children born at term with birth weights above 2999 g. The results were adjusted for socioeconomic status of the parents, family history of psychiatric disorders, conduct disorders, comorbidity, and maternal smoking during pregnancy. Results related to birth weight were unchanged after adjusting for differences in gestational age.
  
  
  CONCLUSIONS
  Children born preterm, also close to term, and children born at term with low birth weights (1500-2499 g) have an increased risk of clinically verified hyperkinetic disorder. These findings have important public health perspectives because the majority of preterm babies are born close to term.
authors.affiliation: Perinatal Epidemiology Research Unit, Department of Obstetrics and Pediatrics, Aarhus University Hospital, Skejby, DK-8200 Aarhus N, Denmark. kmlinnet@ki.au.dk
authors.forename: K M
authors.initials: KM
authors.lastname: Linnet
authors.forename: K
authors.initials: K
authors.lastname: Wisborg
authors.forename: E
authors.initials: E
authors.lastname: Agerbo
authors.forename: N J
authors.initials: NJ
authors.lastname: Secher
authors.forename: P H
authors.initials: PH
authors.lastname: Thomsen
authors.forename: T B
authors.initials: TB
authors.lastname: Henriksen
mesh_terms: D000293:Adolescent; D017677:Age Distribution; D001724:Birth Weight / Q000502:physiology*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D019955:Conduct Disorder / Q000150:complications; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005865:Gestational Age; D006801:Humans; D006948:Hyperkinesis / Q000453:epidemiology / Q000209:etiology*; D008297:Male; D010375:Pedigree; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology; D012307:Risk Factors; D017678:Sex Distribution; D012907:Smoking / Q000009:adverse effects; D012959:Socioeconomic Factors