1. Department of Public Health, Graduate School, Yonsei University, Seoul, Korea
2. Division of Gastroenterology, Department of Internal Medicine, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea
3. Department of Internal Medicine and Institute of Gastroenterology, Yonsei University College of Medicine, Seoul, Korea
4. Department of Biostatistics, Graduate School of Public Health, Yonsei University, Seoul, Korea