1. Department of Internal Medicine, Korea University Anam Hospital, Korea University College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Seoul National University Boramae Medical Center, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Biostatistics, Seoul National University Boramae Medical Center, Seoul, Korea.
4. Department of Preventive Medicine, Ajou University School of Medicine, Suwon, Korea.
5. Division of Endocrinology and Metabolism, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.