1. Department of Internal Medicine; Environmental Health Center; Kangwon National University Hospital; School of Medicine; Kangwon National University; Chuncheon Korea
2. Institute of Health and Environment; Seoul National University; Seoul Korea
3. Department of Pulmonary and Critical Care Medicine; Clinical Research Center for Chronic Obstructive Airway Diseases; Asan Medical Center; University of Ulsan College of Medicine; Seoul Korea
4. Division of Pulmonary and Critical Care Medicine; Department of Internal Medicine; Korea University Ansan Hospital; Ansan Korea
5. Department of Preventive Medicine; Ajou University School of Medicine; Suwon Korea
6. Complex Disease Genetic Epidemiology Branch; Department of Epidemiology; Graduate School of Public Health; Seoul Korea