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Confounding familial factors could influence link between antibiotics, childhood asthma

Researchers found no causal link between antibiotics in early life and childhood asthma, but confounding factors shared within families could influence such an association, according to recent study results.

“Our results indicate that there is no causal link between antibiotics treatment and childhood asthma,” researcher Catarina Almqvist Malmros, MD, PhD, pediatrician and professor at the department of medical epidemiology and Biostatistics, Karolinska Institutet, Stockholm, said in a press release. “We also want to emphasize the importance of correctly diagnosing children with airway symptoms, where suspected symptoms of asthma should be separated from respiratory infection.”

In a prospective population-based study, Malmros and colleagues identified 493,785 children born to women who were pregnant between July 2005 and December 2010. Controls included 180,894 children who were eligible for sibling analyses.

Asthma was defined as having been diagnosed with the disease and being prescribed asthma drugs. Cox proportional hazard regression was used to study the association between antibiotic exposure and asthma. Analyses showed an association between antibiotic exposure in fetal life and increased asthma risk in the study cohort (HR=1.28; 95% CI, 1.25-1.32) but not in the control group (HR=0.99; 95% CI, 0.92-1.07%).

“In cohort analyses, antibiotics used to treat respiratory infections in childhood were associated with more pronounced increased risk of asthma (HR=4.12; 95% CI, 3.78-4.5) than antibiotics used for urinary tract and skin infections (HR=1.54; 95% CI, 1.24-1.92),” the researchers wrote.

Excess risks for respiratory infections after exposure to antibiotics decreased (HR=2.36; 95% CI, 1.78-3.13) and “disappeared” for antibiotics used to treat urinary tract and skin (HR=0.85; 95% CI, 0.47-1.55).

“Our study suggests that the association between antibiotics and asthma is caused by confounding factors shared within families, in addition to confounding by indication or reverse causation because of respiratory infections,” the researchers concluded.

Disclosure: See the study for a full list of relevant financial disclosures.