title: Early respiratory infections and childhood asthma.
abstract: OBJECTIVE
  To assess the role of early respiratory infections in the development of bronchial obstruction in the first 2 years of life, and asthma by the age of 4 years in the Oslo Birth Cohort, established in 1992-1993. Having older siblings and attendance to a day care center were also considered as proxy measures of early infections.
  
  
  METHODS
  A total of 2531 children were followed from birth to 4 years of age. Experiences of respiratory infections were recorded in the follow-up surveys at 6 and 12 months of age, and children with symptoms and signs of bronchial obstruction during the first 2 years of life were identified and examined. The presence of current asthma was recorded when the children were 4 years old.
  
  
  RESULTS
  Children with respiratory infections during infancy had a higher risk of having bronchial obstruction during the first 2 years of life and of having asthma at 4 years of age. In logistic regression adjusting for confounders including other infections, the risk of asthma at 4 years of age was related to lower respiratory tract infection (odds ratio [OR]: 3.4; 95% confidence interval [CI]: 2.3-7.0), otitis media (OR: 1.8; 95% CI: 1.2-2.6), croup (OR: 2.1; 95% CI: 1.2-3.7) in the first year and related to the common cold (OR: 2.0; 95% CI: 1.3-3.1) in the first 6 months of life. The risk of current asthma was inversely related to older siblings after controlling for early respiratory infections.
  
  
  CONCLUSIONS
  Early respiratory infections indicate increased, rather than decreased, risk of developing bronchial obstruction during the first 2 years of life and of having asthma at 4 years of age.
authors.affiliation: Section of Epidemiology, Department of Population Health Sciences, National Institute of Public Health, Oslo, Norway. per.nafstad@folkehelsa.no
authors.forename: P
authors.initials: P
authors.lastname: Nafstad
authors.forename: P
authors.initials: P
authors.lastname: Magnus
authors.forename: J J
authors.initials: JJ
authors.lastname: Jaakkola
mesh_terms: D001249:Asthma / Q000150:complications*; D001982:Bronchial Diseases / Q000209:etiology*; D002675:Child, Preschool; D015986:Confounding Factors, Epidemiologic; D003251:Constriction, Pathologic; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D016015:Logistic Models; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000150:complications*; D012307:Risk Factors; D011795:Surveys and Questionnaires