1. International Healthcare Center, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Department of Clinical Epidemiology and Biostatistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
4. Diabetes Center Bochum-Hattingen, St. Josef-Hospital, Ruhr-University Bochum, Bochum, Germany.