To investigate the bronchial response to exercise, we studied a random sample of 494 children and adolescents, aged 7–16 years, from Copenhagen. Exercise challenge consisted of steady running on a 10% sloping treadmill for 6 min in a climate chamber. Furthermore, in 464 subjects a histamine challenge test was also performed. Of the 494 subjects studied, 81 (16%) had at least 10% and 30 (6%) at least 15% reduction in FEV1 within 15 min after exercise. Twenty-nine (6%) subjects had bronchial hyperresponsiveness to both histamine and exercise, 48 (10%) subjects had bronchial hyperresponsiveness to exercise, but histamine responsiveness within the normal range, whereas 340 (73%) subjects had neither bronchial hyperresponsiveness to exercise nor inhaled histamine. With regard to the presence of asthma defined as substantial exercise induced bronchoconstriction (Δ-FEV1≥10%), exercise testing may not be appropriate for identifying clinical asthma in a random sample, because the highest predictive value of a positive lest was 25%. On the other hand, a history of clinical asthma was frequently associated with increased bronchial responsiveness to exercise (77%). In conclusion, 16% of a random sample of children and adolescents had abnormal bronchial responsiveness to exercise (ΔFEV1≥10%), 6% of the subjects had a ΔFEV1≥15%. Furthermore, because of a low predictive value of a positive test, the exercise challenge test has only a supplementary role in the detection of clinical asthma in population samples.
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