Women on aspirin are less likely to get asthma

Summarized by Susan Aldridge, PhD, medical journalist
April 9, 2008

Summary

Taking a low dose of aspirin every day reduces the risk of developing adult-onset asthma, according to a new report from the Women's Health Study. This follows similar findings among men. However, the protection was not extended to those women who were obese.

Introduction

Asthma, a chronic inflammatory condition affecting the lungs, is a growing problem. Reasons may include obesity, environmental factors and the 'hygiene hypothesis' which suggests that the immune system is less exposed to common infections these days because standards of living have improved. One interesting factor is the role of aspirin. Use of the drug among the young has decreased because it was discovered that it could cause Reye's syndrome, a rare and potentially fatal condition affecting the liver and brain. Children are now given other analgesics, and their risk of asthma has increased. So could aspirin play a protective role against asthma? This has found to be so in the Physicians' Health Study in which a large group of healthy men were given either 325 mg aspirin or placebo each day. Those in the aspirin group had a 22 percent reduction in risk of developing asthma compared to the placebo group during follow up of five years. Furthermore, a large group of women reporting frequent use of aspirin had a decreased risk of asthma compared to those who never used it. Now researchers at Brigham and Women's Hospital, Boston, Massachusetts, and elsewhere, report similar findings from the Women's Health Study, a well known long term investigation of various factors affecting women's health.

What was done

A group of 39,876 female health professionals aged 45 or over entered the study between 1993 and 1996 and were assigned to aspirin or placebo. They took 100 mg aspirin or placebo every other day and were followed up for ten years, with new diagnoses of asthma being recorded.

What was found

Among the 37,270 women who completed the study, there were 872 new cases of asthma in the aspirin group and 963 in the placebo group. This amounts to a 10 percent decrease in risk of newly diagnosed asthma among those taking low dose aspirin. However, there was no protective effect among women who were obese, with a body mass index of greater than 30. The impact of aspirin was not modified by age, smoking status, exercise levels, or use of hormone replacement therapy. At the same time, the researchers were testing out vitamin E supplementation to see if it could protect against heart disease. They found that vitamin E had no protective effect against asthma.

What this study means

The protective effect of aspirin in this group of women was not as large as that found in the Physicians' Health Study, perhaps because the dose of aspirin was lower. The difference may also be due to gender. In the other previous study, women who used aspirin often had a 40 percent decreased risk of asthma. Again, the larger effect could have been due to higher doses. Those using aspirin as an analgesic tend to use higher doses than those using it in clinical trials to elicit a protective effect. Analysis shows the underlying protection afforded by aspirin to be quite similar between the three studies.

The researchers note that aspirin can actually precipitate an asthma attack among a minority of those with existing disease. The mechanism for this is not understood and, in fact, aspirin can actually improve the condition of some asthma patients. It is not known how it may protect healthy people from asthma, as has been found in the current study. There are several ways in which the drug could modify immune system activity that are likely to have an effect on asthma. These need further investigation with lab studies. Moreover, this study was not actually designed to investigate the link between aspirin and asthma, for aspirin was being explored for its impact on heart disease. However, the data look promising and need to be followed up by a trial designed specifically to explore the protective effect of aspirin in asthma. It is too soon to recommend the use of aspirin among the general public to prevent asthma.

Source

• Kurth T, Barr RG et al. Randomised aspirin assignment and risk of adult-onset asthma in the Women's Health Study Thorax online March 13, 2008 http://thorax.bmj.com/cgi/rapidpdf/thx.2007.091447v1

Related Links
Low Dose Aspirin Protects Against Asthma

Please take a moment to give us your comments. For questions about Health matters you may check our "Questions & Answers" Portal and Service.