1. Department of Gastroenterology University of Ulsan College of Medicine, Asan Medical Center Seoul Korea
2. Department of Clinical Epidemiology and Biostatistics, Asan Medical Center University of Ulsan College of Medicine Seoul Korea
3. Digestive Diseases Research Center University of Ulsan College of Medicine Seoul Korea
4. Inflammatory Bowel Disease Center University of Ulsan College of Medicine, Asan Medical Center Seoul Korea