Acetaminophen tied to teen asthma risk

Teenagers who take the painkiller acetaminophen monthly may have double the risk of asthma, compared with those who use none, according to a large new study.

But the findings don't mean people should clear out their medicine cabinets, because the study didn't prove whether acetaminophen helps cause asthma.

"In conclusion, the study findings add to the evidence that acetaminophen use in childhood may be an important risk factor for the development and/or maintenance of asthma," the study's authors said in Friday's online issue of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.

"However, it is not possible in a study of this design to determine whether the positive association observed was causal."

The study looked at nearly 323,000 children aged 13 and 14 in 50 countries, including Canada, who took part in the International Study of Asthma and Allergies in Childhood.

Dr. Richard Beasley, a professor of medicine at the Medical Research Institute of New Zealand, and his co-authors asked teens to report how much acetaminophen they took and their history of wheezing, nasal congestion and eczema rash.

Compared with non-users, recent use of acetaminophen was associated with:

• 1.43 times increased risk of asthma symptoms for medium users (once a year).
• 2.51 times or double the risk of asthma symptoms for high users (at least once a month).

Frequent use of acetaminophen was also associated with rhinoconjunctivitis, or allergic nasal congestion, and eczema.

Colds and fever

It is thought that acetaminophen may lower levels of an antioxidant called glutathione, which may lead to inflammation and suppress immune response, prolonging cold infections that commonly trigger severe asthma attacks in childhood.

Its possible that asthmatic teens may have had other conditions such as aches and pains that needed pain relief.

The researchers called for randomized, control trials that gives participants acetaminophen, another pain reliever like ibuprofen, or a placebo, to investigate the relationship and guide use of fever-relieving medications.

Doctors advise patients to follow the guidelines on the product label and use the drug as directed.

The frequency of acetaminophen use in the study varied among countries, from two per cent in Taiwan taking it more than once a month to 23 per cent in Canada, 42 per cent in the U.S. and 68 per cent in Nigeria.