Many adults diagnosed with asthma may not actually have the disease, a new study from Canada suggests.
Researchers found that about one-third of adults in the study who were previously diagnosed with asthma did not meet the criteria for an asthma diagnosis when they were retested several years later. This group continued to test negative for asthma over multiple retests in the study, and they showed no signs of worsening symptoms when they stopped taking asthma medications.
These findings may mean that these people were originally misdiagnosed, or that their asthma went away on its own, the researchers said. [8 Strange Signs You're Having an Allergic Reaction]
The results show that, for some adult patients diagnosed with asthma, "reassessing that diagnosis may be warranted," the researchers wrote in today's (Jan. 17) issue of the journal JAMA.
The findings also suggest that some people may be taking asthma medications when they don't need to be, meaning they are unnecessarily paying for a medication, and putting themselves at the risk of possible side effects from the drugs, the researchers said. "Use of asthma medications in these patients presumably provided only risks for medication adverse effects, and cost," without clear benefit, they wrote in their study.
Asthma is a condition in which people's airways become inflamed and narrowed, which can lead to coughing, chest tightness, wheezing and trouble breathing, or a combination of these symptoms.
In the study, researchers analyzed information from more than 600 adults in 10 Canadian cities who had been diagnosed with asthma in the past five years. About 45 percent of participants said they were taking daily medications to control their asthma, according to the study, which was led by Dr. Shawn Aaron, a respirologist at the Ottawa Hospital Research Institute and a professor at the University of Ottawa in Ontario.
To see if these patients really did have asthma, participants first underwent a lung function test used to diagnose asthma, called spirometry. This test measures how much air people are able to blow out of their lungs, and how quickly they do this.
If patients tested negative on this first test, they then underwent a second test used to diagnose asthma. During this test, they inhaled a chemical called methacholine, which is a common trigger for asthma.
Patients who still tested negative for asthma were asked to lower the dose of their asthma medications, and were tested again three weeks later. Those who had a third negative test were asked to stop taking all of their asthma medications, and undergo a fourth and final test in another three weeks.
People who had negative results on all of these tests were then assessed by a doctor to determine whether they had a condition other than asthma.
The study found that about 200 of the participants, or 33 percent, didn't have asthma, because they had negative results on the diagnostic tests, and didn't show a worsening of symptoms when they stopped taking medications. About 35 percent of these 200 participants were taking daily asthma medications at the start of the study. [9 Myths About Seasonal Allergies]
To see if asthma might return, these 200 participants were followed for an additional year, but more than 90 percent continued to show no signs of asthma, despite not taking any medications for it, the researchers said.
More than half of these participants had not undergone a lung function test when they were originally diagnosed with asthma, the researchers said. Still, about 12 percent of participants did have medical records showing a previous positive test for asthma using a lung function test, and so these patients may have experienced a spontaneous remission of the disease, the researchers said.
When the participants without asthma were evaluated by the study doctors, about 60 percent were diagnosed with other conditions, such as seasonal allergies, acid reflux or breathing difficulties that were due to obesity. But a fraction of participants — 2 percent of the overall study group — were diagnosed with serious conditions, such ischemic heart disease and bronchiectasis, a condition in which the lungs' airways are damaged and become enlarged, making it harder to clear mucus.
The researchers noted in their study that some people with asthma may experience long periods of remission before they have a recurrence of their asthma. This means that, even though the study participants were followed for 15 months, it's still possible that some could experience a recurrence of their asthma after the study ended, they said.
Original article on Live Science.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.