"The risk of asthma relapse in adulthood may be of concern with regard to employment in occupations where asthma would pose a risk, such as aviation or fire fighting," said lead researcher Robin Taylor, M.D., of the University of Otago School of Medicine in Dunedin, New Zealand.
"It is likely that during adolescence, the asthma subsides to the point where airway inflammation is minimal and does not cause symptoms," Dr. Taylor said. "Patients who have a relapse likely have had a change in environment that provokes airway inflammation to the point where asthma symptoms recur."
Dr. Taylor noted that this study focused on 18-year-olds because they are often being assessed medically for employment reasons. "Often employers wish to know whether someone who has a past history of asthma and who is in remission is likely to experience a relapse and by doing so may be unable to continue with their occupation,"
Dr. Taylor said. "Particularly when employers invest a great deal of resources in training a young individual, this may be critical. For example, someone being recruited into the Army may be perfectly fit at the time of recruitment, but all their training might go to waste if, at a later stage, they develop asthma symptoms which prevent them from being involved in strenuous physical activity. Such individuals may need to be discharged from military service as a consequence."
Dr. Taylor has followed a group of 1,037 New Zealanders to age 26, with detailed respiratory histories done every two years to age 15, then at ages 18, 21 and 26. Of that group, 176 had doctor-diagnosed asthma at ages 9, 11, 13 or 15. Of those, 68 had no asthma symptoms at age 18, but 16, or 24% of this group had asthma symptoms when they were 21, and these symptoms persisted in 8 of them at age 26. Of the 52 who had no symptoms at 21 years, 8 reported symptoms of asthma at age 26. Therefore, a total of 24 of the 68 (35%) of those who did not have asthma symptoms at age 18 experienced relapses by age 21 or 26.
Those who are at greatest risk of relapsing are those who are highly allergic (also called atopic), or who have "twitchy" airways, known as "bronchial hyper-responsiveness," which can be measured in a pulmonary function laboratory. "However, even this test is not terribly satisfactory," Dr. Taylor said. "Only 26 % of those who relapsed were positive for bronchial hyper-responsiveness in our study."