Early Antibiotic Use Linked to Childhood Asthma

Children who received antibiotics in their first year of life were significantly more likely to develop transient wheezing and persistent asthma, and the risk increased with each course of antibiotics.

Children who are given antibiotics as infants may be at increased risk for developing asthma as toddlers, the results of a new study suggest.

The study, published in the May 2014 issue of the Annals of Allergy, Asthma, and Immunology, explored 2 hypotheses that explain the increasing prevalence of childhood asthma in the United States. The hygiene hypothesis suggests that because children today are exposed to fewer microbes than in the past, they are more susceptible to atopic disorders, while the microbiota hypothesis suggests that perturbations in children’s gastrointestinal microbiota disrupt the immune system.

To assess the explanatory power of these hypotheses, the retrospective study evaluated the association between antibiotic use during the first year of life and the development of asthma in children through the age of 7 years. To eliminate inconsistent results, the association was tested separately for 3 asthma phenotypes: transient wheeze (asthma that does not persist after 3 years of age), late-onset asthma (asthma that begins after 3 years of age), and persistent asthma (asthma that begins in the first 3 years of life and persists through 4 to 7 years of age). Children included in the study were covered under a nationwide employer-provided health insurance plan.

Overall, 18.5% of children developed wheezing or asthma between infancy and 7 years of age, and 42.7% had been exposed to at least 1 course of antibiotics during their first year of life. The results indicated that antibiotic use during infancy was associated with an increased risk of transient wheezing (odds ratio of 2.0) and persistent asthma (odds ratio of 1.6). These associations remained significant after excluding children who had experienced asthma or respiratory infections during infancy, premature infants, and those with cystic fibrosis. The association between antibiotic use and persistent asthma peaked when children were 3 years old (odds ratio of 2.5) and weakened as they grew older. However, there was no association between antibiotic use and late-onset asthma.

The results also indicated a dose-response relationship. The risk of developing asthma increased with each course of antibiotics, and the risk for transient wheeze and persistent asthma doubled when infants received 5 or more courses. In addition, children who had experienced a lower or upper respiratory tract infection during their first year of life were significantly more likely to develop each of the asthma phenotypes.

Although the results do not prove that antibiotic use during infancy causes the development of childhood asthma, they do support the hygiene and microbiota hypotheses, the study authors suggest. “A second interpretation is that antibiotic exposure in infancy is an indirect marker of asthma risk, without playing direct causal roles,” they note.

Nonetheless, the authors conclude that unnecessary use of antibiotics in infants should be avoided.