1. Department of Medicine, Samsung Medical Center; Sungkyunkwan University School of Medicine; Seoul Korea
2. Center for Clinical Epidemiology, Samsung Medical Center; Sungkyunkwan University School of Medicine; Seoul Korea
3. Department of Clinical Research Design and Evaluation, Samsung Advanced Institute for Health Science and Technology; Sungkyunkwan University School of Medicine; Seoul Korea
4. Center for Health Promotion; Samsung Medical Center; Seoul Korea
5. Departments of Epidemiology and Medicine and Welch Center for Prevention, Epidemiology and Clinical Research; Johns Hopkins Medical Institutions; Baltimore Maryland USA