MONDAY, June 11, 2007 (HealthDay News) -- Giving antibiotics for a non-respiratory tract infection to an infant younger than 1 greatly increases the odds that the child will develop asthma, according to new research.
The study found that the risk was highest for those infants who received multiple courses of antibiotics and those who received prescriptions for broad-spectrum antibiotics. Broad-spectrum antibiotics tend to kill a wide range of bacteria -- both good and bad.
"Asthma is a multi-factorial disease, and we've found evidence of an association with first-year-of-life antibiotic use and asthma," said the study's lead author, Anita Kozyrskyj, an associate professor at the University of Manitoba in Winnipeg, Canada.
One hypothesis, Kozyrskyj added, is that broad-spectrum antibiotics are killing off too many good bacteria.
"It may be that you need the presence of good bacteria during the first year of life for the immune system to develop normally, and the antibiotics are killing off some of the natural microflora in the gut," she said.
The study findings are published in the June issue of the journal Chest.
Each year, about 4 million American children have active asthma, resulting in about 14 million missed school days, according to the American Lung Association. Because asthma can't currently be cured, only controlled, researchers are focusing on factors that may play a role in the initial development of the lung disease.
For the new study, Kozyrskyj and her colleagues followed almost 14,000 children from birth in 1995 until 2003, when all of the children had reached 7 years of age. Data came from the Manitoba Health Services Insurance Program and included information on physician visits, prescriptions, hospitalizations and health diagnoses.
Additionally, the researchers linked this data to data on the mothers of these children to see if there was a maternal history of asthma. Parents also completed surveys on home and environmental exposures.
All of the children were from Manitoba. Half were male, and 57 percent lived in urban areas. One-quarter of the children were from low-income families; 90 percent had siblings; 5 percent had a maternal history of asthma, and 6 percent developed asthma by age 7, the researchers found.
Two-thirds of the youngsters had received at least one antibiotic prescription during their first year of life, many of them for broad-spectrum antibiotics, according to the study. And, the more antibiotics received, the greater the risk of asthma.
Kids who received one to two courses of antibiotics had a 21 percent increased risk of asthma; those given three to four courses of antibiotics had a 30 percent rise in risk; while youngsters given more than four courses of antibiotics had a 46 percent increased risk of asthma.
Children given antibiotics for non-respiratory tract infections, such as urinary-tract infections, were as much as 86 percent more likely to develop asthma than those treated for respiratory infections.
Other factors that increased the risk of asthma included a family history, living in an urban area and being male. Having a sibling conferred a slight protective effect, as did having a dog for children who received multiple courses of antibiotics. In kids who had more than four courses of antibiotics before age 1, having a dog decreased the risk of asthma by 28 percent. However, in kids who received fewer antibiotics, that protective effect wasn't there.
Dr. Alan Khadavi, a pediatric asthma specialist at New York University Medical Center, said that prevention of asthma isn't a reason to get a dog. "If you already have a dog, that's fine, but the studies are conflicting about whether they're helpful or harmful," he added.
As for antibiotic use, Khadavi said, "If your child under 1 year is sick, have him or her evaluated. Don't push for antibiotics. But. on the other hand, if it's a serious infection that needs to be treated, I wouldn't worry too much about the asthma risk. If it's a mild infection, a watch-and-wait approach won't be harmful if they're under a physician's care."
Dr. Sai Nimmagadda, an attending physician in the division of allergy at Children's Memorial Hospital in Chicago, said this study points to the need for "more judicious use of antibiotics, especially broad-spectrum antibiotics in kids under a year."
"Once wheezing has developed, it's difficult to alter the course of asthma, so now we're looking back to see if there are any risk factors we can change," he said.
Kozyrskyj recommended that physicians start by prescribing narrow-spectrum antibiotics, such as amoxicillin, for their youngest patients, and then if necessary, try a broad-spectrum medication.
To learn more about childhood asthma, visit the American Lung Association.