Breathing lessons

For parents, a baby's first cold can prompt worries, a visit to the pediatrician, and, sometimes, a request for antibiotics.

But according to a study by epidemiologist and neurologist Michael B. Bracken '70MPH, '74PhD, and his colleagues, the early use of antibiotics may lead to an unfortunate outcome: a diagnosis, later in childhood, of asthma. In the American Journal of Epidemiology, the team reports that children who received the drugs before they were six months old were, in general, 52 percent more likely to develop asthma by the time they were six years old than those who hadn't taken antibiotics as infants.

About 8 percent of U.S. children—6 million—have asthma, and the numbers have climbed steadily since the early 1980s. Researchers point to a variety of possible causes, such as air pollution, exposure to allergens, certain lung infections, and genetics.

The new data help support another theory: the "hygiene hypothesis." A number of scientists have suggested that the correct development of the immune system requires exposure to diverse microbes in the infant's gastrointestinal system; antibiotics, by knocking out bacteria, may alter the system and even make it hypersensitive.

Tellingly, in the sample of 1,400 children in the Bracken study, researchers found that the largest effect was on infants who received antibiotics but whose parents did not have asthma. Those children had an almost 90 percent increase in their risk of developing the ailment by the time they turned six.

Bracken is quick to promote the lifesaving importance of antibiotics in infants, when the situation warrants them. But he urges physicians "to avoid unnecessary antibiotic use, especially in low-risk children."