ATS 2013 Report – Underlying respiratory illnesses in infancy, rather than early analgesic use, appear to drive asthma development

by Peter Mas Mollinedo – Investigators report that the link between asthma and early childhood use of acetaminophen or ibuprofen could be the result of underlying respiratory infections, and not use of these the drugs.

They presented the findings on May 20, 2013 at the American Thoracic Society 2013 International Conference.

As background, the researchers noted that infants with fever are routinely treated with ibuprofen and acetaminophen, and prior research shows a link between the use of analgesics during infancy and the subsequent development of asthma and asthma symptoms, including wheeze. But these earlier studies did not evaluate the possible role of underlying respiratory infection in development of asthma and asthma symptoms.

“Many children are given over-the-counter analgesics to treat the fever that accompanies respiratory infections, so it seemed unclear to us whether asthma and wheeze were really linked to the use of these drugs or perhaps to the respiratory infection itself,” said lead investigator Joanne Sordillo, ScD., instructor of medicine at Brigham and Women’s Hospital in Boston. “In our study, we wanted to try to determine if accounting for early life respiratory infections mitigated the relationship between analgesic use and development of wheeze and asthma in children,” she added.

The researchers retrospectively evaluated data from 1,139 mother-child pairs from Project Viva, a research study of pregnant women and their children examining lifestyle factors during pregnancy and after birth, analyzing for effects on eventual development of asthma and other childhood conditions.

Mothers completed questionnaires during early pregnancy, at mid-pregnancy and at one year post-partum. The questionnaires included acetaminophen and ibuprofen-use. During the first 3 years post-partum, mothers reported any ensuing doctor’s diagnosis of asthma or wheezing symptoms.

The researchers divided prenatal acetaminophen exposure into three categories: non-exposure, exposure of less than 10 times, and exposure over 10 times.

Since ibuprofen was used much less than acetaminophen, exposure was divided by two categories, exposed and non-exposed. Ibuprofen use beyond the first trimester was rare and was not included.

For exposure during the first 12 months post-partum, the researchers divided the children into four groups for each drug: non-exposed, exposed one to five times, exposed six to 10 times and exposed more than 10 times.

The researchers found a higher exposure to acetaminophen prenatally and during the first 12 months of life compared to ibuprofen exposure, with 70 percent of mothers reporting acetaminophen use during pregnancy and 16 percent reporting using ibuprofen while pregnant.

The investigators reported that 95 percent of children received at least one dose of acetaminophen during infancy versus 70 percent of children who received at least one dose of ibuprofen.

About 43 percent of children received 10 doses of acetaminophen post-partum and before they were a year old compared to 25 percent of children who received more than 10 doses of ibuprofen.

The investigators evaluated for a correlation between drug use and asthma and asthma-like symptoms, adjusting the analysis for respiratory infections up to age three. Such infections included bronchiolitis, pneumonia, bronchitis, croup or any other respiratory infection.

They found that, while use of the drugs was associated with wheeze and asthma in unadjusted models, after adjusting for respiratory infections, the association between medication use and development of asthma symptoms was substantially reduced.

They concluded, “The majority of increased wheeze and asthma risk associated with early life acetaminophen and ibuprofen was diminished after adjustment for respiratory infections. These results suggest that respiratory infections, a main cause of fever in infancy, rather than the analgesics themselves, underlie the asthma-related outcomes.”