title: Gestational age-specific associations between infantile acute bronchiolitis and asthma after age five.
abstract: BACKGROUND
  Infantile acute bronchiolitis (AB) is a risk factor for the development of paediatric asthma. The associations might differ according to gestational age.
  
  
  METHODS
  Data sets of emergency department (ED) visits (January 2002 to June 2010) and livebirth records (January 2002 to December 2004) from the state of Georgia were linked for all children who survived 1 year. Exposure was an ED visit for AB during infancy, and the outcome was an ED visit for asthma after age 5 years. The risk of asthma among children with AB (n = 11 564) was compared with the risk of asthma among children who did not have an ED visit for AB but who utilised the ED for another reason during infancy (n = 131 694). Associations were estimated using log-binomial regression models that controlled for several plausible confounders. Effect measure modification of the risk ratio by gestational age was investigated.
  
  
  RESULTS
  Unadjusted asthma risks (per 100 children) through June 2010 were 4.5 for children with AB and 2.3 for children without AB. The adjusted risk ratio for the overall association was 1.9 [95% confidence interval 1.7, 2.1]. We did not observe effect modification of the risk ratio by gestational age.
  
  
  CONCLUSIONS
  A positive association was observed between ED visits for AB and subsequent asthma ED visits after age 5; associations did not vary meaningfully by gestational age. Sensitivity analyses did not suggest large biases due to differences in ED utilisation across sociodemographic groups or loss to follow-up from residential migration.
authors.affiliation: Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA; Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Strickland
authors.forename: Caitlin A
authors.initials: CA
authors.lastname: Marsh
authors.forename: Lyndsey A
authors.initials: LA
authors.lastname: Darrow
mesh_terms: D000367:Age Factors; D001249:Asthma / Q000453:epidemiology*; D001988:Bronchiolitis / Q000453:epidemiology*; D002648:Child; D015331:Cohort Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D005865:Gestational Age; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016015:Logistic Models; D008297:Male; D012307:Risk Factors; D013548:Sweden / Q000453:epidemiology
keywords: asthma; bronchiolitis; cohort; emergency department; gestational age; premature; preterm