1. Howden LM, Meyer JA. Age and sex composition: 2010–2010 census briefs. 2011.
http://www.census.gov/prod/cen2010/briefs/c2010br-03.pdf
2. He W, Muenchrath MN. 90+ in the United States: 2006–2008-American Community Survey Reports. 2011.
http://www.census.gov/prod/2011pubs/acs-17.pdf
3. Bressler HB, Keyes WJ, Rochon PA, et al. The prevalence of low back pain in the elderly: a systematic review of the literature. Spine. 1999;24:1813–9.
4. Koch H, Smith MC, DHHS publication (PHS). Office-based ambulatory care for patients 75 years old and over, National Ambulatory Medical Care Survey, 1980 and 1981. Hyattsville: Advance Data from Vital and Health Statistics, National Center for Health Statistics (NCHS); 1985. p. 85–1250.
5. Dagenais S, Caro J, Haldeman S. A systematic review of low back pain cost of illness studies in the United States and internationally. Spine J. 2008;8:8–20.