title: Birth asphyxia measured by the pH value of the umbilical cord blood may predict an increased risk of attention deficit hyperactivity disorder.
abstract: OBJECTIVE
  Although birth asphyxia is a major risk factor for neonatal and childhood morbidity and mortality, it has not been investigated much in relation to attention deficit hyperactivity disorder (ADHD). We examined whether birth asphyxia measured by the pH of the blood in the umbilical artery cord was associated with childhood ADHD.
  
  
  METHODS
  A population-based cohort of 295 687 children born in Finland between 1991 and 2002 was followed until December 31, 2007. ADHD was identified by the International Classification of Diseases, 10th edition, as a diagnosis of hyperkinetic disorder. We examined the risk of ADHD with varying pH values using Cox regression, taking time trends into consideration.
  
  
  RESULTS
  When compared to the reference group, a pH value below 7.10 was significantly associated with an increased risk of ADHD. The strongest risks were observed among children with a pH value <7.15 and a gestational age of <32 weeks. The pH value did not contribute much to the risk among children with an Apgar score of 0-3.
  
  
  CONCLUSIONS
  Birth asphyxia, defined by low pH value, may predict an increased risk of ADHD in childhood. The association between the pH value and ADHD was homogenous when stratified by gestational age and the Apgar score.
authors.affiliation: Department of Public Health, Section for General Medical Practice, Aarhus University, Aarhus C, Denmark.
authors.forename: Susanne Hvolgaard
authors.initials: SH
authors.lastname: Mikkelsen
authors.affiliation: Clinical Epidemiology, Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark.
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
authors.affiliation: Department of Public Health, Section for Epidemiology, Aarhus University, Aarhus C, Denmark.
authors.forename: Bodil Hammer
authors.initials: BH
authors.lastname: Bech
authors.affiliation: Department of Obstetrics and Gynaecology, Odense University Hospital, Odense, Denmark.
authors.forename: Chunsen
authors.initials: C
authors.lastname: Wu
authors.affiliation: Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), Los Angeles, CA, USA.
authors.forename: Zeyan
authors.initials: Z
authors.lastname: Liew
authors.affiliation: National Institute for Health and Welfare, Helsinki University, Helsinki, Finland.
authors.forename: Mika
authors.initials: M
authors.lastname: Gissler
authors.affiliation: Department of Public Health, Section for General Medical Practice, Aarhus University, Aarhus C, Denmark.
authors.forename: Carsten
authors.initials: C
authors.lastname: Obel
authors.affiliation: Department of Epidemiology, Fielding School of Public Health, University of California, Los Angeles (UCLA), Los Angeles, CA, USA.
authors.forename: Onyebuchi
authors.initials: O
authors.lastname: Arah
mesh_terms: D001034:Apgar Score; D001238:Asphyxia Neonatorum / Q000097:blood*; D001289:Attention Deficit Disorder with Hyperactivity; D002648:Child; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D005865:Gestational Age; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male
keywords: Apgar score; Attention deficit hyperactivity disorder; Birth asphyxia; Gestational age; Umbilical artery cord blood pH value