1. Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Japan
2. Department of Gastroenterology, The Japan Association for Development of Community Medicine Nerimahikarigaoka Hospital, Japan
3. Department of Biostatistics, School of Public Health, Graduate School of Medicine, The University of Tokyo, Japan
4. Department of Endoscopy and Endoscopic Surgery, The University of Tokyo Hospital, Japan