Exercise-Induced Bronchoconstriction in Chinese Elite Athletes from Olympic Summer Sports:An Epidemiological Study

Objective: To investigate the incidence of exercise-induced bronchoconstriction(EIB) in Chinese elite athletes from Olympic Summer Games, and then analyse the characteristics of key indicators related to respiratory inflammation and ventilatory function in EIB athletes. Methods: 411 athletes(female 235, male 176; 19 high level athletes, 148 elite athletes and 244 sub-elite athletes) were recruited from 15 different summer sports, and they were divided into indoor(pool-or land-based) or outdoor sport group(road-or venue-based) according to sports environment, and they were also categorized into endurance, skill, speed & strength,or team sport discipline according to sport characteristics. The respiratory symptoms during exercise, asthma history and EIB information were obtained through questionnaire. Pulmonary function data(i.e., forced expiratory volume in the first second(FEV1),maximum ventilation, forced vital capacity, expiratory peak air flow rate, etc.) were collected during bronchial exercise provocation test, and the reduction rate of FEV1was used to diagnose EIB. The inflammatory responses were evaluated through venous blood sample. The chi-square test, independent sample t-test and repeated measures method were used to do data analysis. Results: Three athletes(2.7%) have been diagnosed EIB before participation, and a total of 109 athletes(female 71, male 38) were diagnosed with EIB in this study, the overall incidence rate was 26.5%. The top 5 EIB incidence sports was swimming(51.5%), hockey(40.7%),synchronized swimming(40.0%), rugby(38.5%) and track and field(33.3%), and judo(11.1%), rhythmic gymnastics(10.5%),badminton(9.5%), weightlifting(9.5%) and wrestling(6.5%) were ranked in the last five. The EIB incidence rate was higher in female athletes than that of male athletes(30.2% vs 21.3%, P=0.049); the endurance event was higher than speed & strength event(37.3% vs 20.0%, P=0.038); the outdoor event was higher than indoor event(33.1% vs 21.6%, P=0.05), and the indoor swimming pool-based event was higher than land-based event(47.2% vs 14.2%, P<0.001), but there was no significant difference between the venue-and road-based events in outdoor environment. In addition, all pulmonary function parameters were significantly decreased in EIB athletes, which were lower than healthy athletes. The blood indictors including eosinophil count, neutrophil count, IL-6, IL-8and CC16 levels were higher in EIB athletes than that of healthy athletes. Conclusions: The Chinese elite athletes from Olympic Summer Games are suffering from severe EIB problems, and the reduced lung ventilation and severe airway inflammation are observed in EIB athletes. All athletes, coaches, and sports authorities are recommended to pay highly attention to EIB problems, and it is suggested that the inflammatory factors(i. e., IL-8, CC16) and non-pharmacological measures(i. e., chlorine-free swimming pool, anti-haze venue, nutritional supplements) can be sued to prevent and treat EIB.