The government-funded study is one of the largest to delve into the biology of asthma.
Most of the studies followed patients over time and collected samples of mucus from the lower part of the lungs.
Surprisingly, researchers found that nearly half (47%) of asthma sufferers did not have eosinophils in their mucus, indicating that something else was causing asthma in these patients.
They also found that people with this so-called non-eosinophilic asthma did not respond well to treatment with oral and inhaled corticosteroids, like prednisone, Aerobid, Azmacort, Flovent, and Symbicort, which fight inflammation.
“The currently used anti-inflammatories didn’t seem to be that effective, at least over a two-week period, in a subgroup of patients who had non-eosinophilic disease,” says researcher John V. Fahy, MD, a professor of medicine and director of the Airway Clinical Research Center at the University of California at San Francisco.
Patients with non-eosinophilic asthma also did respond to the drug albuterol. Albuterol works by relaxing the muscles around the airways, which helps them open up so the person can breathe easier. It’s usually prescribed as a rescue medication.
The study is published in the American Journal of Respiratory and Critical Care Medicine.
Search for Answers in Asthma Is Urgent
Asthma experts who were not involved in the study said it was “impressive and comprehensive.”
“It just confirms what a lot of us have felt,” that there are different kinds of asthma, says Erwin W. Gelfand, MD, chairman of the department of pediatrics at National Jewish Health, a hospital in Denver that specializes in lung diseases.
“It points out how desperate we are for additional asthma medications,” Gelfand says.
The search for a better understanding of asthma is an urgent one.
Twenty-five million people have asthma in the U.S., and that number is rising, according to the CDC, though researchers don’t know why.
A Link to Obesity?
One theory is that obesity is behind the steady increase.
This study lends some support to that theory.
When researchers tried to tease out differences between the groups with eosinophilic asthma vs. non-eosinophilic asthma, they discovered that people with eosinphilic asthma, which is associated with more severe disease, tended to be much leaner than people with the non-eosinophilic kind of asthma.
People with non-eosinophilic asthma were generally older when their asthma was diagnosed, had less severe disease, and were more likely to be overweight.
“You can’t tell in a ... study like this, but it is known that obesity is associated with asthma, and it seems like the obesity comes first,” Fahy says.
Advice to Patients
While the biology behind asthma is a hot area of research, experts say the findings really haven’t found a way into the doctor’s office.
There’s still no test that can easily distinguish one kind of asthma from another, for example.
“What patients should take away is if they’re taking a medication, and they’re not benefiting from it, then they should question it,” Gelfand says. They should ask whether they might not need to try a different drug.