The prevalence of bronchial hyperresponsiveness in elementary school children and its associated factors

Abstract

Purpose: We investigated the prevalence of bronchial hyperresponsiveness (BHR) and its associated factors in population-based elementary school children. Methods: Methacholine bronchial provocation tests were performed on 1,151 elementary school children and BHR was defined as PC20 (provocative concentration of methacholine causing a 20% fall in forced expiratory volume in 1 second [FEV1]) ≤8 mg/mL. We analyzed the prevalence of BHR according to age and sex. The Korean version of International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, skin prick test, pulmonary function test, and blood tests were performed to determine associated factors for BHR. Results: A total of 1,106 students eligible for provocation tests were included in the analysis. The overall prevalence of PC20 ≤8 mg/mL was 11.5% (95% confidence interval, 10.6-13.4) and BHR decreased with age (P-value for trend <0.001). Younger age (adjusted odds ratio [aOR], 0.860; P=0.032), higher blood eosinophil % (aOR, 1.151; P=0.001), lower predictive % of FEV1 (aOR, 0.977; P=0.029), fraction of exhaled nitric oxide (FeNO) ≥25 ppb (aOR, 2.118; P=0.025), and sensitization to mites (aOR, 1.705; P=0.034) were associated with BHR. Preterm birth (aOR, 2.056; P=0.068) showed borderline significance. The associated factors for BHR with atopy were lower body mass index (aOR, 0.838; P=0.005), preterm birth (aOR, 4.361; P=0.003), and FeNO ≥25 ppb (aOR, 2.161; P=0.043). Younger age (aOR, 0.810; P=0.037) and higher blood eosinophil % (aOR, 1.296; P<0.001) were associated with BHR without atopy. Conclusion: The prevalence of BHR decreased with age in elementary school children. Younger age, preterm birth, eosinophilia, sensitization to mites, lower lung function, and higher FeNO level were independently associated with BHR.(Allergy Asthma Respir Dis 2014;2:171-178)