title: Risk of childhood asthma in relation to the timing of early child care exposures.
abstract: OBJECTIVE
  To examine whether early child care exposure influences the risk for development of asthma.
  
  
  METHODS
  Longitudinal data from 939 children and their families from the National Institute of Child Health and Development Study of Early Child Care and Youth Development were analyzed. Exposure to other children in the primary child care setting as an infant (before 15 months) and as a toddler (16-36 months) were assessed as risk factors for persistent or late-onset asthma by age 15 via logistic regression.
  
  
  RESULTS
  The number of children in the child-care environment when the child was a toddler was significantly associated with odds of asthma, even after adjusting for respiratory illnesses and other risk factors (P < .05). The fewer the children exposed to as toddlers, the higher the probability of persistent or late-onset asthma by age 15.
  
  
  CONCLUSIONS
  This study supports the theory of a protective effect of exposure to other children at an early age, especially as a toddler, on the risk of asthma. This effect appears to be independent of the number of reported respiratory tract illnesses, suggesting that other protective mechanisms related to the number of children in the child care environment may be involved.
authors.affiliation: Department of Public Health Sciences, University of Virginia School of Medicine, Charlottesville, VA 22908-0717, USA. mgurka@virginia.edu
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Gurka
authors.forename: James A
authors.initials: JA
authors.lastname: Blackman
authors.forename: Peter W
authors.initials: PW
authors.lastname: Heymann
mesh_terms: D000293:Adolescent; D000367:Age Factors; D017668:Age of Onset; D001249:Asthma / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D002654:Child Care / Q000706:statistics & numerical data*; D002656:Child Day Care Centers / Q000706:statistics & numerical data*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D012307:Risk Factors; D014481:United States
references.citation: J Allergy Clin Immunol. 1997 Jan;99(1 Pt 1):6-12
references.pmid: 9003205
references.citation: Child Dev. 2003 Jul-Aug;74(4):976-1005
references.pmid: 12938694
references.citation: Am J Respir Crit Care Med. 2003 May 1;167(9):1239-43
references.pmid: 12446273
references.citation: Pediatrics. 1999 Apr;103(4 Pt 1):753-8
references.pmid: 10103298
references.citation: Respir Med. 2007 Jul;101(7):1431-8
references.pmid: 17350816
references.citation: Arch Pediatr Adolesc Med. 2001 Apr;155(4):481-8
references.pmid: 11296076
references.citation: BMJ. 1989 Nov 18;299(6710):1259-60
references.pmid: 2513902
references.citation: Arch Pediatr Adolesc Med. 2002 Feb;156(2):121-6
references.pmid: 11814371
references.citation: Lancet. 1999 Feb 6;353(9151):450-4
references.pmid: 9989715
references.citation: J Allergy Clin Immunol. 1999 Mar;103(3 Pt 1):355-61
references.pmid: 10069865
references.citation: Am J Respir Crit Care Med. 1999 Nov;160(5 Pt 1):1617-22
references.pmid: 10556130
references.citation: Am J Epidemiol. 2009 Jan 15;169(2):195-205
references.pmid: 19033160
references.citation: Am J Respir Crit Care Med. 1998 Aug;158(2):352-7
references.pmid: 9700106
references.citation: Pediatrics. 2004 Sep;114(3):e327-32
references.pmid: 15342893
references.citation: BMJ. 2001 Feb 17;322(7283):390-5
references.pmid: 11179155
references.citation: Thorax. 1999 Aug;54(8):664-9
references.pmid: 10413716
references.citation: Am J Respir Crit Care Med. 1997 Jan;155(1):156-61
references.pmid: 9001305
references.citation: Am J Public Health. 1995 Aug;85(8 Pt 1):1109-12
references.pmid: 7625505
references.citation: Am J Respir Crit Care Med. 2006 Jan 15;173(2):143-63
references.pmid: 16210666
references.citation: N Engl J Med. 1995 Jan 19;332(3):133-8
references.pmid: 7800004
references.citation: Arch Dis Child. 1998 Oct;79(4):328-33
references.pmid: 9875043
references.citation: N Engl J Med. 2000 Aug 24;343(8):538-43
references.pmid: 10954761