1. Department of Gastroenterology; Hokkaido University Graduate School of Medicine; Sapporo Japan
2. Health Sciences University of Hokkaido; Tobetsu-cho Japan
3. National Hospital Organization Hakodate Hospital; Hakodate Japan
4. Health Administration and Policy; Tohoku University School of Medicine; Sendai Japan
5. Department of Public Health; Aichi Medical University School of Medicine; Aichi Japan