Respiratory Infections May Be Cause of Analgesic-Asthma Link

The association between use of analgesics in infancy and increased likelihood of developing asthma may actually be due to respiratory infections that prompt analgesic use, a new study indicates.

A number of studies have found a link between use of analgesics such as acetaminophen and ibuprofen in infancy and later development of asthma. However, a new study finds that the true culprit in causing asthma appears to be respiratory infections that prompt the use of analgesics rather than the analgesic use itself. The study, conducted by researchers at Brigham and Women’s Hospital and Harvard Medical School, is scheduled to be presented on May 20, 2013, at the American Thoracic Society 2013 International Conference in Philadelphia.

The study included 1139 mother-child pairs who took part in Project Viva, a research study investigating potential links between lifestyle factors and development of asthma and other childhood conditions. The researchers found that 70% of the mothers used acetaminophen during their pregnancies and 16% used ibuprofen. During the first year of life, 95% of infants in the study took acetaminophen at least once, with 28% taking it 1 to 5 times, 25% 6 to 10 times, and 43% more than 10 times. In addition, 70% of infants took ibuprofen at least once during the first year of life, with 28% taking it 1 to 5 times, 17% 6 to 10 times, and 25% more than 10 times.

By the age of 3 years, 36% of the children in the study had at least 1 wheezing episode, 18% had recurrent wheeze, and 21% had been diagnosed with asthma. Use of analgesics in infancy was associated with an increased likelihood of developing asthma and asthma symptoms, but when the researchers controlled for respiratory infections and ear infections in the first year of life, this association disappeared in most cases. (A slight association between ibuprofen use in infancy and likelihood of developing recurrent wheeze or asthma remained.)

“These results suggest that respiratory infections in infancy, and not analgesic use, are the actual underlying risk factor for asthma and wheeze in children,” said lead study author Joanne Sordillo, ScD, instructor of medicine at Brigham and Women's Hospital in Boston, in a press release.

Prenatal exposure to analgesics was associated with an increased likelihood of developing asthma and wheeze after controlling for various demographic and health factors. However, the researchers had no information on why the mothers took analgesics during pregnancy, so they could not adjust for these potentially confounding factors.

“Future studies will need to carefully collect information regarding the reasons for taking such over-the-counter drugs as analgesics during pregnancy,” said Dr. Sordillo in the press release.