Exercise-induced bronchospasm among healthy elite cross country skiers and non-athletic students

Abstract

Regular exercise in cold, dry air is believed to be a predisposing factor for exercise-induced bronchospasm (EIB). The aim of this study was to compare the occurrence of EIB among previously healthy elite cross country skiers and their non-athletic control subjects. Twenty healthy elite cross country skiers and 18 non-asthmatic controls were challenged by a standardized free exercise test. Thereafter, subjects' respiratory function was followed by flow-volume spirometry up to 30 min. EIB was defined in the post-exercise spirometry as at least one of the following: a >or=10% decrease in forced expiratory volume in 1 s (FEV1), a >or=20% decrease in mean maximal expiratory flow (MMEF) or a >or=25% decrease in peak expiratory flow rate (PEF). EIB was found in two skiers and one control according to FEV1, for seven skiers and two controls according to MMEF. Two skiers and one control had exercise-induced asthma (EIA) according to both parameters. The largest decrease in PEF was 13%, that did not result in additional diagnoses. All nine of the subjects with a positive test result reported asthma-like symptoms (dyspnea, cough or increased mucus excretion) after the exercise challenge. Accordingly, seven previously healthy skiers (35%) and two controls (11%) were diagnosed as having EIB. In addition, three skiers of the original cohort were excluded because of an earlier asthma diagnosis, making the total asthma prevalence 10/23 (42%) among the elite skiers. It was concluded that EIB is more common in elite cross country skiers than in non-athletic controls. The bronchoconstriction induced by exercise is usually mild or moderate, and flow-volume spirometry with sensitive flow parameters is needed for it to be diagnosed. Even a mild asthma decreases minute ventilation and maximal performance of winter sport athletes. Therefore, skiers with long-term respiratory symptoms or decreased performance should be studied for EIA and treated adequately.