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If you have been diagnosed with asthma, you had better get used to it, researchers say. A new study suggests it is a life-long affliction.

Some earlier research involving relatively small groups of patients found many people are symptom-free for long periods of time, raising the possibility that the condition may disappear. Indeed, it's commonly believed children can outgrow asthma.

But the new study, based on more than 600,000 patients including both children and adults, has all but dashed such hopes. Asthma may go into remission, but it comes back in the vast majority of cases, according to findings published in the Journal of Allergy and Clinical Immunology.

"This evidence supports the hypothesis that once you have asthma, you have it for life," said the lead author, Andrea Gershon, a researcher at the Institute for Clinical Evaluative Sciences in Toronto.

Asthma is a chronic lung disorder in which the airways become inflamed and narrow, making it difficult to breathe. Environmental triggers ranging from pollen to cold air can make asthma symptoms worse. Patients are prescribed inhaled steroids and other mediations to keep the condition under control.

The researchers analyzed 15 years of medical records for patients in Ontario who in 1993 had an existing asthma diagnosis. During the period under review, more than 75 per cent of patients had gaps of time when their asthma became inactive, and many stopped seeking medical treatment.

"You may go for years without having any symptoms, but the evidence shows it does eventually come back in most people," said Dr. Gershon. "And my guess is that the only reason why we didn't find that it returned in 100 per cent of cases is because the study didn't cover a longer period of time."

The findings of the study ring true for physicians who routinely treat asthma patients. "There is a myth that kids outgrow their asthma," said Kenneth Chapman, director of the Asthma and Airway Centre at University Health Network in Toronto. "Some will go through an adolescent honeymoon when their asthma seems to disappear, but if you were to do some careful measurements, you would discover that there are still laboratory signs of asthma."

For some asthmatic adults, occupational exposures to certain lung irritants can aggravate their symptoms. If they change jobs, their asthma seems to go away. "But if they went back to the original job, the asthma would flare up again," noted Dr. Chapman.

Dr. Gershon says she isn't sure why asthma sometimes goes into remission. But patients should keep in mind it will likely come back and the proper management of the condition, including regular use of medications, can minimize breathing problems.

"My research may be a downer for people ... but I think they should know what to expect," added Dr. Gershon.

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