Figure 1

Flow diagram for study subject. COPD chronic obstructive pulmonary disease, KNHANES Korea National Health and Nutrition Health Examination Survey, FEV1 forced expiratory volume in one second, FVC forced vital capacity.

Flow diagram for study subject. COPD chronic obstructive pulmonary disease, KNHANES Korea National Health and Nutrition Health Examination Survey, FEV1 forced expiratory volume in one second, FVC forced vital capacity.