1. Department of Clinical Studies, Radiation Effects Research Foundation (RERF), Nagasaki 850-0013, Japan
2. Department of Statistics, Radiation Effects Research Foundation (RERF), Hiroshima 732-0815, Japan
3. Faculty of Rehabilitation, Hiroshima International University, Hiroshima 739-2695, Japan
4. Department of Clinical Studies, Radiation Effects Research Foundation (RERF), Hiroshima 732-0815, Japan
5. Iseikai Hospital, Osaka 533-0022, Japan
6. Department of Neurology and Strokology, Nagasaki University Hospital, Nagasaki 852-8501, Japan