Frequent use of the popular painkiller acetaminophen may increase a person's risk for developing asthma, a study says. But experts caution that it's far too early to tell consumers to avoid it.
Women who were taking acetaminophen at least 15 days a month for six years had a 63% higher risk of developing asthma compared with women who didn't use the analgesic, according to researchers.
Individual reactions to pain relievers vary. "'We are not trying to say that all asthmatics should stop using acetaminophen," says study author Dr. R. Graham Barr, assistant professor of medicine and epidemiology at Columbia University.
Soaring rates of asthma across the United States have alarmed public health officials and puzzled asthma experts.
Scientists estimate that in the past 30 years, asthma cases approximately doubled in younger children, says Susan Redline, an asthma expert at Case Western Reserve University in Cleveland.
However, the exact cause of this steep climb remains unclear.
Rising rates of obesity—which can impair lung function—have been cited by experts as a possible culprit, as have indoor pollutants, such as dust mites and mold.
But the upswing in new asthma cases also coincided with the increasing popularity of over-the-counter acetaminophen, the researchers say. According to the American Medical Association, approximately 200 over-the-counter drugs contain acetaminophen.
In their study, Barr and his colleagues examined data from the Nurses Health Study, which included nearly 722,000 adult women. As part of the study, each participant kept a record of her analgesic use, as well as the development of any new medical conditions, including asthma.
Among women who used acetaminophen for more than half of the days in a given month, "there was a significant increase—63%—in the risk of a new diagnosis of asthma," Barr says.
Scientists know that acetaminophen lowers blood levels of a natural compound called glutathione. "Glutathione has an antioxidant effect in the body, particularly in the lungs," Barr explains. When glutathione levels plummet, "that may reduce the antioxidant defenses in the body and increase the possibility of developing asthma."
However, the study only demonstrates an association between acetaminophen and increased asthma-not a cause-and-effect relationship. And Barr notes that other analgesics such as aspirin, ibuprofen and nonsteroidal anti-inflammatory drugs (NSAIDs), such as celecoxib (Celebrex), have also been shown to affect asthmatics in various ways.
"If individuals happen to notice that their asthma gets worse after they take aspirin or non steroidals or acetaminophen, it's worth reassessing that usage," Barr says. "But we're not making any blanket statements."
For information on controlling asthma symptoms, visit the Asthma and Allergy Foundation of America at uuw.aafa.org.