1. Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
2. Department of Medicine, Nowon Eulji Medical Center, Eulji 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 Clinical Epidemiology, Samsung Medical Center, Sungkyunkwan University, Seoul, Korea
5. Departments of Epidemiology and Medicine and Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA