"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," said lead author Carlo Marra, Pharm D, PhD, University of British Columbia, Vancouver, BC, Canada.

Those babies under the age of one year who were treated with an antibiotic were twice as likely as those who received no antibiotics to become asthmatic later in childhood. The use of multiple antibiotics in infants appeared to further increase the asthma risk.

Identifying Potential Risk Factors

"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," he added.

Researchers at the University of British Columbia reviewed seven studies 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 meta-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.

Cautious Approach Advised

In a dose-response analysis, researchers analyzed the reporting data from 27,167 children, including 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.

"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 two receive an antibiotic for diagnosed ear infection. However, the majority of upper respiratory tract infections and bronchitis [are] viral, for which antibiotics are ineffective,” Dr. Marra pointed out.