Procedures
NDD
THORACIC, LUNG
A professional questionnaire was implemented to collect information about demographic characteristics, respiratory symptoms, and exposure to COPD-related risk factors (Lung function was examined by EasyOne Spirometer (NDD Medizintechnik AG, Switzerland) following the operation of the American Thoracic Society and the European Respiratory Society (The questionnaire and the spirometry examination were performed by trained staff from local medical systems.