Objectives: To determine the association between antibiotic exposure in the first year of life and the development of childhood asthma.
Design: Metaanalysis of observational studies retrieved through systematic search of all available electronic data sources. Studies included in the metaanalyses were those with populations exposed to one or more courses of antibiotics during the first year of life, and asthma diagnosis was defined as diagnosis by a physician between the age of 1 to 18 years.
Setting: Retrospective and prospective studies published in the English-language literature from 1966 to present.
Results: Eight studies (four prospective and four retrospective) examined the association between exposure to at least one course of antibiotics and development of childhood asthma. The total number of subjects for the analysis comparing exposure to at least one antibiotic to no exposure in the first year of life was 12,082 children and 1,817 asthma cases. In the dose-response analysis, we included data from a total of 27,167 children and 3,392 asthma cases. The pooled odds ratio (OR) for the eight studies was 2.05 (95% confidence interval [CI], 1.41 to 2.99). The association was significantly stronger in the retrospective studies (OR, 2.82; 95% CI, 2.07 to 3.85) than the prospective studies (OR, 1.12; 95% CI, 0.88 to 1.42). Five of the eight studies examined whether the association was related to the number of courses of antibiotics taken in the first year of life. The overall OR for the dose-response analysis was 1.16 (95% CI, 1.05 to 1.28) for each additional course of antibiotics; however, this association was not significantly stronger in the retrospective studies (OR, 1.37; 95% CI, 1.18 to 1.60) relative to the prospective studies (OR, 1.07; 95% CI, 0.95 to 1.20).
Conclusions: Exposure to at least one course of antibiotics in the first year of life appears to be a risk factor for the development of childhood asthma. Because of the limitations of the studies conducted to date, additional large-scale, prospective studies are needed to confirm this potential association.