B58-05 Silent Small Airway Dysfunction and Clinical Implications

Rationale Small airway dysfunction (SAD) is increasingly recognized as a critical component of respiratory diseases. This study aimed to evaluate the prevalence of SAD in subjects without airway obstruction (AO) and its associated risk factors. Methods This cross-sectional study included participants from high altitude in western China using a multistage stratified sampling procedure. All participants underwent a standardized questionnaire and pulmonary function. SAD was diagnosed when at least two of the following indicators were less than 65% of predicted values: maximal mid-expiratory flow, forced expiratory flow (FEF) at 50% of vital capacity, and FEF at 75% of vital capacity. Airway obstruction (AO) was also defined as a post-BD forced expiratory volume in 1s (FEV1 ) /forced vital capacity (FVC) of < 0.70. Multivariate logistic regression was used to analyze risk factors for SAD. Results In total, 4912 participants living at high altitude in China were included in the analysis. The overall prevalence of SAD in subjects without AO was 25.1% (95% CI 23.9%-26.4%). Compare to non-SAD subjects, SAD without AO subjects experience more cough, sputum, wheezing and dyspnea, and their post-BD FEV1%pred and post-BD FEV1/FVC decreased. In the multivariate logistic regression analysis, post-tuberculosis (TB) (OR 1.68, 95%CI 1.26-2.24) and exposure to household air pollution (HAP) (OR 1.33, 95% CI 1.14-1.56) were two major risk factors for SAD without AO compared to healthy controls. Conclusion Our study revealed a high prevalence of SAD in subjects without AO at high altitude. This kind of people with silent SAD had more symptoms and lower lung function compared to non-SAD subjects, which was s a type of pre-COPD and might have the risk of developing into COPD. Post-TB and HAP were risk factors for SAD without AO, providing evidence for prevention and control of chronic airway diseases. Figure. Forest plot showing OR for participants of SAD without AO compare to healthy controls. Each spot represents an OR. The horizontal lines indicate 95% CIs. Abbreviations: SAD, small airway dysfunction; AO, airway obstruction; BMI, body mass index; TB, tuberculosis; HAP, household air pollution.