1. van Tulder M, Koes B, Bombardier C. Low back pain. Best Pract Res Clin Rheumatol. 2002;16:761–75.
2. Suka M, Yoshida K. Musculoskeletal pain in Japan: prevalence and interference with daily activities. Mod Rheumatol. 2005;15:41–7.
3. Ikegami N, Fukuhara S, Shimozuma K, Ikeda S, editors. Handbook for assessment of QOL (in Japanese). Tokyo: Igaku-Shoin; 2001.
4. Japanese Ministry of Health, Labour, and Welfare, Minister’s Secretariat, Department of Statistics and Information (eds.). The 2004 National Life Survey (in Japanese). Tokyo: Health and Welfare Statistics Association; 2006.
5. Japanese Ministry of Internal Affairs and Communications, Statistics Bureau. Current Population Estimates as of October 1, 2004. Available at: http://www.stat.go.jp/english/data/jinsui/2004np/index.htm .