1. Health Services Research and Development Center, University of Tsukuba, Tsukuba City 305-8575, Japan
2. Hinohara Memorial Peace House Hospital, Nakai 259-0151, Japan
3. Department of Post-Graduate Education, Kameda Medical Center, Kamogawa City 296-0041, Japan
4. Department of Medicine, Division of Geriatrics, University of California, San Francisco, CA 94143, USA
5. Department of Health Services Research, Institute of Medicine, University of Tsukuba, Tsukuba 305-8575, Japan
6. Diabetes and Metabolism Information Center, Research Institute, National Center for Global Health and Medicine, Tokyo 162-8655, Japan
7. Institute for Global Health Policy Research, Bureau of International Health Cooperation, National Center for Global Health and Medicine, Tokyo 162-8655, Japan