1. 1Division of Gastroenterology, Department of Internal Medicine, Sapporo Shirakaba-dai Hospital, Sapporo, Japan.
2. 2Department of Gastroenterology and Hepatology, Sapporo Medical University, Sapporo, Japan.
3. 3The Institute of Medical Science Hospital, The University of Tokyo, Tokyo, Japan.
4. 4Hokkaido Chitose College of Rehabilitation, Chitose, Japan.
5. 5Department of Public Health, Aichi Medical University School of Medicine, Nagakute, Japan.
6. 6Division of Health Administration and Promotion, Faculty of Medicine, Tottori University, Yonago, Japan.
7. 7Department of Preventive Medicine, Nagoya University, Graduate School of Medicine, Nagoya, Japan.
8. 8Department of Public Health, Hokkaido University Faculty of Medicine, Sapporo, Japan.