Salve for the lungs: aspirin might prevent asthma.

Regular use of aspirin may prevent healthy adults from developing asthma, according to a 5-year study of male doctors.

Inflammation in the lungs characterizes asthma. During an attack, inflamed airways constrict, obstructing air flow. The disease affects about 5 percent of men and more than 8 percent of women and children. It most frequently develops during childhood, and some kids outgrow it.

For the current study, epidemiologist Tobias Kurth of Brigham and Women's Hospital in Boston and his colleagues analyzed data on some 22,000 male physicians who had participated in a study between 1982 and 1988. Although the original trial was focused on heart disease, its records contained information on asthma.

None of the participants initially had asthma. Half of them received placebos during the study, while the others took 325 milligrams of aspirin every other day.

After an average of 4.9 years, 145 men in the placebo group had developed asthma, but only 113 aspirin takers had the disease. This finding suggests that aspirin use cuts asthma incidence by 22 percent, Kurth's team reports in the Jan. 15 American Journal of Respiratory and Critical Care Medicine.

In a 2004 study conducted by a group including two of Kurth's collaborators, women who frequently took aspirin developed asthma only 60 percent as often as did women who never took aspirin.

Indirect evidence also suggests that aspirin reduces asthma incidence. Since about 1980, most doctors have considered aspirin too risky to give to children, even for such purposes as cold-symptom relief, because it increases risk of Reye's syndrome. Aspirin use in children fell dramatically in the early 1980s, and the use of the alternative painkiller acetaminophen rose.

The shift away from aspirin contributed to a subsequent rise in childhood asthma, allergist Arthur Varner, who practices at Allergy Diagnostic in Beachwood, Ohio, and two colleagues proposed in 1998.

Acetaminophen doesn't reduce inflammation as do aspirin, ibuprofen, and naproxen, which are called nonsteroidal anti-inflammatory drugs. These NSAIDs may reduce the risk that a viral respiratory infection will precipitate asthma in susceptible children and adults, Varner suggests.

He notes that a 2005 study linked acetaminophen, but not the NSAIDs aspirin or ibuprofen, to increased risk of adult-onset asthma.

"When a person first gets cold symptoms, if they reach for aspirin or ibuprofen, they maybe protected against asthma," he speculates. "If they reach for acetaminophen, it enhances the chance that that virus will lead to asthma."

The finding of a protective effect of aspirin is "quite interesting," says American Lung Association spokesman Norman Edelman, a pulmonologist at the State University of New York at Stony Brook.

The evidence is too preliminary to encourage habitual aspirin use for asthma prevention, Kurth and Edelman caution.

"Aspirin is certainly not a treatment for asthma," Kurth adds. The drug triggers attacks in some people with existing asthma.