1. Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea
2. Department of Clinical Research Design and Evaluation, SAIHST, Sungkyunkwan University, Seoul, South Korea
3. Center for Health Promotion, Samsung Medical Center, Seoul, South Korea
4. Center for Clinical Epidemiology, Samsung Medical Center, Sungkyunkwan University, Seoul, South Korea
5. Departments of Epidemiology and Medicine and Welch Center for Prevention, Epidemiology and Clinical Research, Johns Hopkins Medical Institutions, Baltimore, MD, USA