Taking a small dose of aspirin every other day seems to reduce the risk of developing asthma among older women, concludes a study appearing in the on-line issue of Thorax.
The new study essentially mirrors a similar one in which men taking aspirin saw the same reduced risk.
The incidence of asthma is on the increase, possibly due to obesity, dietary factors, exposure to allergens and environmental factors.
But the trend also coincides with a decreased use of aspirin as people have switched to other over-the-counter pain relievers, or have avoided aspirin use in children due to concerns about Reye's syndrome (a condition characterized by swelling of the liver and brain, typically triggered by using aspirin to treat a virus).
That led some researchers to wonder whether the reduction in aspirin use was contributing to the rise of asthma.
This study, the first randomized trial in women, looked at nearly 40,000 healthy, female health care professionals, ages 45 and older, who were participating in the Women's Health Study.
Women were randomized to receive 100 milligrams (mg) of aspirin every other day, or a placebo. This dose was much lower than that taken by men in a previous study (325 mg).
Over the next decade, there were 10% fewer new cases of asthma in the women who had been taking aspirin regularly. However, aspirin had no effect in women who were obese, the researchers discovered.
"It could be due to the low dose, or there may be a biological reason," said Dr. Tobias Kurth, MD, ScD, an associate epidemiologist at Brigham and Women's Hospital and assistant professor of medicine at Harvard Medical School, both in Boston.
"It may be a dose-related issue," added Dr. Len Horovitz, MD, a pulmonary specialist with Lenox Hill Hospital in New York City. "It's basically like a baby aspirin."
According to the researchers, the effect of the regular aspirin dose in non-obese women was smaller than that seen in men (they saw a 22% risk reduction), but that may be at least partly attributable to the lower dose.
Interestingly, aspirin can exacerbate symptoms in 4% to 11% of people who have already been diagnosed with the condition.
"It's not usual for us to encourage people to take aspirin, because you don't know who does or does not have this sensitivity] until you have a problem," Dr. Horovitz said.
At this point, it's not clear exactly why aspirin has this effect.
The study authors warned that the research was still not enough to recommend taking aspirin regularly.
"These two studies are not sufficiently strong to make a recommendation for primary prevention of adult-onset asthma," said Dr. Kurth, who was involved in both studies.
For the many older adults already taking aspirin for its salutary effects on heart health, this could be an added benefit," he added.
To find out more about the health benefits and risks of aspirin, visit the MayoClinic.com Web site at www.mayoclinic.com. Type daily aspirin therapy" into the search box.