Key Point:

Acetaminophen use, particularly frequent use, may increase the risk of newly diagnosed asthma in women.

NEW YORK CITY—Acetaminophen is considered a relatively safe drug for pain and fever relief. In the United States, use of the drug increased during the 1970s and 1980s following reports linking aspirin administration and Reye’s syndrome in children. Although this rise in acetaminophen use coincided with an increase in the prevalence and severity of asthma in the US, no link between the two was considered likely—until recently. New evidence suggests that the drug may increase the risk of newly diagnosed adult-onset asthma in women.[1]

R. Graham Barr, MD, DrPH, and colleagues assessed asthma prevalence and acetaminophen use among 73,321 women enrolled in the Nurses’ Health Study. The authors adjusted for confounders, such as body mass index, smoking history, other analgesic use, and anxiety. According to Dr. Barr, who is an Assistant Professor of Medicine and Epidemiology at the Columbia University Medical Center, “the development of asthma appears to be related to frequent acetaminophen use, at least in some populations.”

During 352,719 person-years of follow-up, there were 346 participants who were given a new diagnosis of asthma. The risk of having newly diagnosed asthma rose linearly as acetaminophen use increased. In particular, women who used the drug for more than 14 days per month had a multivariate rate ratio for asthma of 1.63 (CI, 1.11 to 2.39) compared with nonusers. In women who used it less often, an increase in asthma risk was also seen, but the difference did not quite reach statistical significance.

The association between acetaminophen and asthma appears to be independent of aspirin use. What are the mechanisms behind this increased risk? Dr. Barr hypothesized that acetaminophen reduces levels of the antioxidant glutathione in the lung. This, in turn, predisposes the lung to oxidative injury. “Oxidative stress is implicated in the pathophysiology of asthma,” he noted.

Although his study did not involve participants with preexisting asthma, Dr. Barr said that other evidence suggested that “acetaminophen seems to trigger asthma among a subgroup of asthmatics—but it’s a small subgroup.” It is also not known if there are women who are at increased risk for acetaminophen-related asthma. Therefore, Dr. Barr and his group believe that it is premature to advise women or asthmatic patients to avoid acetaminophen.

He and his team did not find any interaction with hormone exposure, a potential culprit for asthma in women. However, he acknowledged that such a link is possible. He believes that his findings may even be generalizable to men. “Many of the women in this study were postmenopausal, so we anticipate that the findings would be similar among men also,” said Dr. Barr. In the meantime, he and his group advocate further research on pulmonary responses to acetaminophen to identify subgroups whose asthma may be modified by the drug.

—Tamara Gibb