1. The Department of Neurology, Hematology, Metabolism, Endocrinology and Diabetology (DNHMED), Yamagata University Faculty of Medicine, Yamagata 990-9585, Japan
2. Global Center of Excellence Program Study Group, Yamagata University School of Medicine, Yamagata 990-9585, Japan
3. Department of Social and Preventive Epidemiology, School of Public Health, The University of Tokyo, Tokyo 113-0033, Japan