Early respiratory infections and childhood asthma.

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.
Conclusion: 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.