title: Infectious exposure in the first years of life and risk of central nervous system tumours in children: analysis of birth order, childcare attendance and seasonality of birth.
abstract: BACKGROUND
  An infective, mostly viral basis has been found in different human cancers. To test the hypothesis of a possible infectious aetiology for central nervous system (CNS) tumours in children, we investigated the associations with proxy measures of exposure to infectious disease.
  
  
  METHODS
  In a large case-control study nested in the populations of Denmark, Norway, Sweden, and Finland of 4.4 million children, we studied the association of birth order and seasonal variation of birth with subsequent risk for CNS tumours. We identified 3983 children from the national cancer registries, and information on exposure was obtained from the high-quality national administrative health registries. We investigated the association between childcare attendance during the first 2 years of life and the risk for CNS tumours in a subset of Danish children with CNS tumours, using information from the Danish Childcare database.
  
  
  RESULTS
  We observed no association between birth order and risk of CNS tumours overall (odds ratio (OR) for second born or later born vs first born, 1.03; 95% confidence interval (CI), 0.96-1.10) or by histological subgroup, and children with CNS tumours did not show a seasonal variation of birth that was distinct from that of the background population. Childcare attendance compared with homecare showed a slightly increased OR (1.29; 95% CI, 0.90-1.86) for CNS tumours, with the highest risk observed in children attending a crèche. The strongest association was observed for embryonal CNS tumours. We found no effect of age at enrolment or duration of enrolment in childcare.
  
  
  CONCLUSIONS
  These results do not support the hypothesis that the burden of exposure to infectious disease in early childhood has an important role in the aetiology of paediatric CNS tumours.
authors.affiliation: Institute of Cancer Epidemiology, Danish Cancer Society, Strandboulevarden 49, DK-2100 Copenhagen, Denmark. samsoe@cancer.dk
authors.forename: L S
authors.initials: LS
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Kamper-Jørgensen
authors.forename: K
authors.initials: K
authors.lastname: Schmiegelow
authors.forename: C
authors.initials: C
authors.lastname: Johansen
authors.forename: P
authors.initials: P
authors.lastname: Lähteenmäki
authors.forename: C
authors.initials: C
authors.lastname: Träger
authors.forename: T
authors.initials: T
authors.lastname: Stokland
authors.forename: K
authors.initials: K
authors.lastname: Grell
authors.forename: G
authors.initials: G
authors.lastname: Gustafson
authors.forename: P
authors.initials: P
authors.lastname: Kogner
authors.forename: A
authors.initials: A
authors.lastname: Sehested
authors.forename: J
authors.initials: J
authors.lastname: Schüz
mesh_terms: D000293:Adolescent; D001254:Astrocytoma / Q000453:epidemiology / Q000209:etiology*; D001722:Birth Order; D016022:Case-Control Studies; D016543:Central Nervous System Neoplasms / Q000453:epidemiology / Q000209:etiology*; D002648:Child; D002654:Child Care / Q000379:methods / Q000706:statistics & numerical data; D002675:Child, Preschool; D003141:Communicable Diseases / Q000150:complications* / Q000453:epidemiology; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009664:Norway / Q000453:epidemiology; D036801:Parturition / Q000502:physiology*; D012306:Risk; D012621:Seasons; D013548:Sweden / Q000453:epidemiology
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