1. Department of Clinical Studies; Radiation Effects Research Foundation; Hiroshima; Japan
2. Department of Statistics; Radiation Effects Research Foundation; Hiroshima; Japan
3. International University of Health and Welfare Clinic; Ohtawara; Japan
4. Department of Radiation Biology and Molecular Epidemiology; Radiation Effects Research Foundation; Hiroshima; Japan
5. Department of Clinical Studies; Radiation Effects Research Foundation; Nagasaki; Japan
6. Department of Gastroenterology and Metabolism; Applied Life Sciences; Institute of Biomedical and Health Sciences; Hiroshima University; Hiroshima; Japan