Bronchial Hyperresponsiveness, Airway Inflammation, and Airflow Limitation in Endurance Athletes

BackgroundWhereas a high prevalence of bronchial abnormalities has been reported in endurance athletes, its underlying mechanisms and consequences during exercise are still unclear.Study objectivesThe purpose of this study was to assess the following: (1) bronchial responsiveness to methacholine and to exercise; (2) airway inflammation; and (3) airflow limitation during intense exercise in endurance athletes with respiratory symptoms.DesignCross-sectional observational study.SettingLung function and exercise laboratory at a university hospital.Patients and measurementsThirty-nine endurance athletes and 13 sedentary control subjects were explored for the following: (1) self-reported respiratory symptoms; (2) bronchial hyperresponsiveness (BHR) to methacholine and exercise; (3) airflow limitation during intense exercise; and (4) bronchial inflammation using induced sputum and nitric oxide (NO) exhalation.ResultsFifteen athletes (38%) showed BHR to methacholine and/or exercise in association with bronchial eosinophilia (mean [± SD] eosinophil count, 4.1 ± 8.5% vs 0.3 ± 0.9% vs 0%, respectively), higher NO concentrations (19 ± 10 vs 14 ± 4 vs 13 ± 4 parts per billion, respectively), a higher prevalence of atopy, and more exercise-induced symptoms compared with nonhyperresponsive athletes and control subjects (p < 0.05). Furthermore, airflow limitation during intense exercise was observed in eight athletes, among whom five had BHR. Athletes with airflow limitation reported more symptoms and had FEV1, FEV1/FVC ratio, and forced expiratory flow at midexpiratory phase values of 14%, 9%, and 29%, respectively, lower compared with those of nonlimited athletes (p < 0.05).ConclusionBHR in endurance athletes was associated with the criteria of eosinophilic airway inflammation and atopy, whereas airflow limitation during exercise was primarily a consequence of decreased resting spirometric values. Both BHR and bronchial obstruction at rest with subsequent expiratory flow limitation during exercise may promote respiratory symptoms during exercise in athletes.