Bronchodilator responses in Chinese children from asthma index families and the general population

Background: Although airway hyperresponsiveness to bronchoconstrictors has been extensively investigated, epidemiologic studies on airway hyperresponsiveness to bronchodilators are limited. Objective: Our goal was to characterize the distribution and determinants of bronchodilator response (BDR) and bronchodilator hyperresponsiveness (BDHR) in rural Chinese children age 8 to 15 years. Methods: Our study included children with and without asthma from asthma index families (1131 boys, 1143 girls) and subjects without asthma from general population controls (457 boys, 377 girls). BDR was calculated as [(post bronchodilator FEV ₁ - baseline FEV ₁)/baseline FEV ₁] × 100. BDHR was defined as BDR greater than 12%. We investigated the distributions and major determinants of BDR and BDHR using scatterplots and multiple linear and logistic regression models. Results: There was a gradient in BDR by asthma status and family history. The mean (±SD) BDR was 7% ± 9% in subjects with asthma, 4% ± 5% in subjects without asthma from index families, and 3% ± 5% in controls. This trend was also seen for BHDR. BDR generally decreased with age. There was a notable sex difference in BDR around puberty in subjects with asthma. Sex difference was also seen in the relationship of BDR with body mass index. Additional variables correlated with BDR included height and prebronchodilator FEV ₁. Atopy was not correlated with BDR. In models accounting for these variables, chronic respiratory symptoms were associated with BDR and BDHR. Conclusion: In these Chinese children, multiple factors affected BDR, including age, sex, height, body mass index, asthma status, and family history of asthma. Clinical implications: Because BDR can be affected by multiple factors, interpretation of clinical or research findings on BDR needs to take these factors into consideration.