New York - Exposure to antibiotics in the first year of life may increase the risk of developing asthma later in childhood, researchers report. In fact, there may even be a higher risk with each additional course of antibiotics.
However, the investigators say they cannot exclude the possibility of "reverse causation" - in which the presence of asthma leads to more frequent respiratory tract infections, which in turn increases the rate of antibiotic use.
The prevalence of asthma in western countries has increased over the last three decades, Dr Carlo Marra and colleagues at the University of British Columbia in Vancouver note in the medical journal Chest. In the same period there has been a greater exposure of infants to antibiotics, but epidemiological evidence linking antibiotic use with asthma risk is conflicting.
To review the available evidence, Marra's group identified seven studies that specifically examined the relationship between being given at least one prescription for an antibiotic in the first year of life and the development of physician-diagnosed asthma between the ages of one and 18 years.
According to the team's report, the studies included 12 82 children and 1 817 asthma cases.
Overall, the pooled data showed that the likelihood of developing asthma was doubled among children with antibiotic exposure before one year of age.
Marra's group also combined data from five studies analysing a potential dose-response relationship, which included 27 167 children and 3 392 asthma cases. The chances of having asthma increased 16 percent with every additional course of antibiotics given during the first year of life.
The researchers suggest that the concerns they encountered - including reverse causation and type of antibiotics used - will need to be overcome in further large-scale, database-related studies to definitively answer whether or not antibiotic use early in life is associated with later asthma risk.
Meanwhile, it is possible to safely reduce the number of antibiotics that infants receive, co-author Dr Fawziah Marra notes in a press release. Although antibiotics are commonly used to treat upper respiratory tract infections and bronchitis, she notes that most of these infections are viral - and antibiotics are ineffective.
SOURCE: Chest, March 2006.