1. Musashikoganei Clinic, Japanese Health and Welfare Co-operative Federation, Honcho, Koganei-shi, Tokyo, Japan
2. Division of Clinical Epidemiology, Jikei University School of Medicine, Nishishimbashi, Minato-ku, Tokyo, Japan
3. Okinawa Chubu Hospital, Miyazato, Uruma-shi, Okinawa, Japan
4. National Hospital Organization Nagasaki Medical Center, Kubara, Omura-shi, Nagasaki, Japan
5. Unnan City Hospital, Iida, Daito-cho, Unnan-shi, Shimane, Japan
6. Teine Family Medicine Clinic, Maeda, Teine-ku, Sapporo-shi, Hokkaido, Japan
7. Okinawa Miyako Hospital, Shimozato, Hirara, Miyakojima-shi, Okinawa, Japan