Children exposed to at least one course of antibiotics in their first year of life may have an increased risk of developing childhood asthma.

New research published in the March issue of CHEST, the peer-reviewed journal of the American College of Chest Physicians (ACCP), shows that children under age 1 who were treated with an antibiotic were twice as likely as untreated children to develop asthma in childhood. In addition, the use of multiple antibiotics in infants appeared to further increase the risk of developing asthma.

“Antibiotic use in children has been found to coincide with an increased incidence of childhood asthma,” said lead author Carlo Marra, Pharm D, PhD, University of British Columbia, Vancouver, BC, Canada. “Although the causal nature between antibiotics and asthma is still unclear, our overall results show that treatment with at least one antibiotic as an infant appears to be associated with the development of childhood asthma.”

Researchers from the University of British Columbia examined the association between antibiotic exposure during infancy and the development of childhood asthma. In a meta-analysis, researchers reviewed seven studies (four prospective and three retrospective) that compared exposure to at least one antibiotic to no exposure in the first year of life. Of the 12,082 children included in the analysis, 1,817 cases of childhood asthma were reported. Overall, infants who were exposed to at least one antibiotic were twice as likely as unexposed infants to develop asthma during childhood. The association between antibiotic use in the first year of life and asthma was significantly stronger in retrospective studies (odds ratio 2.82) than in prospective studies (odds ratio 1.12). Results also showed that high-risk infants, such as those with a family history of atopy, exposed to antibiotics had a lower risk of developing asthma than children in the general population, although the results were not significant.

In a dose-response analysis, researchers analyzed the reporting data from 27,167 children (3,392 asthma cases) from five studies to determine the effect that multiple courses of antibiotics in infants would have on the development of asthma. For each additional course of antibiotics taken during the first year of life, results showed a significant overall odds ratio of 1.16, suggesting that additional courses of antibiotics appeared to further increase the risk for asthma development. Again, this association was stronger for studies that were retrospective than for prospective studies.

“In children, antibiotics are commonly used to treat ear infections, upper respiratory tract infections, and bronchitis, but not every childhood infection requires an antibiotic,” said the study’s co-author Fawziah Marra, MD, University of British Columbia. “Current guidelines recommend that children under age 2 receive an antibiotic for diagnosed ear infection. However, the majority of upper respiratory tract infections and bronchitis is viral for which antibiotics are ineffective.”

“Asthma is one of the most common chronic childhood diseases, affecting millions of children in the United States,” said W. Michael Alberts, MD, FCCP, President of the American College of Chest Physicians. “By identifying potential risk factors for asthma and educating patients and families about risk factors, we may begin to see a reduction in the overall incidence of asthma.”

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