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Study links antibiotics to asthma



March 14, 2006

Infants exposed to at least one course of antibiotics during their first year of life are twice as likely to develop asthma as children who do not take the medications, scientists report in a new analysis.

The study by researchers at the University of British Columbia is known as a meta-analysis, statistical research in which data from previous studies are pooled and re-analyzed. Some of the children in the studies had not been exposed to antibiotics while others had and those who had one course of the drug during their first year of life were more likely to develop the disorder.

"There are a number of important messages here, and as with any meta-analysis, it is best not to overinterpret the conclusion," said Dr. Carlo Marra, an assistant professor of pharmaceutical sciences at the University of British Columbia in Vancouver, the study's senior author. The research is reported in the journal Chest.

In one part of the analysis, Marra and his colleagues examined seven studies involving 12,000 children and found more than 1,800 instances of asthma among those treated with antibiotics. This suggested to Marra that children who got at least one course of the therapy were twice as likely to develop the asthma.

The odds of developing the disorder were even greater in another set of five studies that looked at children who received multiple courses of antibiotics. In this round of research, Marra studied the cases of 27,167 children and found 3,392 instances of asthma. The more courses of antibiotics the children had, the greater their risk of the disorder, Marra said.

He added that the purpose of a meta-analysis is to generate a hypothesis so additional scientific work can tease out a definitive answer. Marra and his team have begun such a study, analyzing the medical records of 200,000 children. Results are expected later this year.

Still unanswered is whether all classes of the drugs are linked to asthma, or just a few. But based on the current findings, Marra still urges a measure of caution. "Right now, this is the best evidence we have. So the take home message is that we should be judicious with our use of antibiotics." He said the drugs are prescribed too often to children, especially those with earaches.

Middle ear infections just as easily can be caused by viruses as bacteria.

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