Exercise-induced bronchoconstriction in children with asthma: An observational cohort study.

BACKGROUND/PURPOSE: The diagnosis of exercise-induced bronchoconstriction (EIB) was established by changes in lung function after exercise challenge. The prevalence of EIB and factors related to EIB were not fully described in children with asthma. The aim of this study was to investigate the prevalence and predictors of EIB in children with asthma. METHODS: A total of 149 children with physician-diagnosed asthma above 5 years of age underwent standardized treadmill exercise challenge for EIB and methacholine challenge for airway hyper-responsiveness from October 2015 to December 2016. RESULTS: EIB presented in 52.5% of children with asthma. Compared with children without EIB, there were more patients with atopic dermatitis in children with EIB (p = 0.038). Allergic to Dermatohagoides pteronyssinus and Dermatophagoides farinae were also found more in children with EIB (p = 0.045 and 0.048 respectively). Maximal decrease in forced expiratory volume in 1 s (FEV1) were highest in patients who were most sensitive to methacholine provocation (provocation concentration causing 20% fall in FEV1 [PC20] ≤ 1 mg/mL). Patients, who were more sensitive to methacholine challenge (with lower PC20 levels), develop EIB with more decline in FEV1 after exercise challenge (p = 0.038). Among patients with EIB, airflow limitation development in patient with methacholine-induced airway hyper-responsiveness was more abrupt and severe compared with patients without airway hyper-responsiveness (p = 0.045 and 0.033 respectively). CONCLUSION: EIB presented in 52.5% of children with asthma. The more severe methacholine-induced hyper-responsiveness, the higher prevalence of EIB as well as the severity.