Antibiotic Use in First Year of Life Linked to l Risk of Developing Asthma

March 9, 2009 — Antibiotic use in the first year of life is linked to a small risk for the development of asthma, and this risk increases with the number of courses of antibiotics prescribed, according to the results of a study reported in the March issue of Pediatrics.

"Antibiotic exposure in early childhood is a possible contributor to the increasing asthma prevalence in industrialized countries," write Fawziah Marra, PharmD, from University of British Columbia in Vancouver, and colleagues. "Although a number of published studies have tested this hypothesis, the results have been conflicting."

The goal of this study was to evaluate the association between antibiotic exposure before age 1 year and development of childhood asthma, using administrative data from 1997 to 2003 birth cohorts. The investigators assessed antibiotic exposure during the first year of life in 251,817 infants, as well as the incidence of asthma after the first 24 months of life in both those exposed and not exposed to antibiotics in the first 12 months of life.

Cox proportional hazards models allowed adjustment for potential confounders (sex; socioeconomic status; urban or rural address; birth weight; gestational age; delivery method; frequency of clinician visits; hospital visit involving surgery; visits to an allergist, respirologist, or immunologist; congenital anomalies; and the presence of otitis media, acute bronchitis, or chronic bronchitis; and upper and lower respiratory tract infections) during the first year of life. Hazard ratios were calculated for the development of asthma associated with antibiotic exposure.

After adjustment, antibiotic exposure in the first year of life was associated with a small risk for the development of asthma in early childhood. The number of courses of antibiotics was associated with increased asthma risk, and this risk was highest in children treated with more than 4 courses of antibiotics. Except for sulfonamides, all antibiotics were associated with an increased risk for the development of asthma.

"This study provides evidence that the use of antibiotics in the first year of life is associated with a small risk of developing asthma, and this risk increases with the number of courses of antibiotics prescribed," the study authors write.

Limitations of this study include data not collected for the purposes of research, resulting in some problems with the data and coding inconsistencies; inability to adjust for all relevant variables; and inability to conclusively determine causality.

"We have shown that in a large, population-based cohort, after careful conducted analyses adjusting for many potential confounders and with multiple sensitivity analyses, the association between antibiotic exposure and the subsequent development of asthma remains," the study authors conclude.

The BC Lung Association (British Columbia, Canada) supported this study. The study authors have disclosed no relevant financial relationships.