Although we attempted to apply identical methods for the two surveys, it remains possible that minor sampling or measurement issues may have accounted for some of the difference in prevalence between the two years. Differences in survey methods, however, would likely not explain all of the increase in prevalence. While direct comparisons are not possible, our estimates and trends are similar to data from the National Health Interview Survey. In 2006, 8.3% (7.8–8.7) of adults 21 years and older reported difficulty with one or more of 12 functional activities (i.e., walking ¼ mile; climbing 10 steps; standing for 2 hrs; sitting for 2 hrs; stooping, bending, kneeling; reaching overhead; grasping small objects; lifting/carrying 10 lbs; pushing/pulling large objects; going out to events, participating in social activities; relaxing at home) because of chronic back or neck problems. In 1997 3.2% of adults reported difficulty with these activities because of chronic back or neck problems.(60) National data indicates that the proportion of Social Security Disability Income (SSDI) awardees claiming ‘musculoskeletal disease’ as their cause of disability has also increased markedly, from 15.2% in 1992 to 28.2% in 2006.(61) In 1983 musculoskeletal disorders were the fourth leading diagnostic group in disability awards; in 2003, they were the leading diagnostic group.(62). While the musculoskeletal disease classification includes conditions other than back pain, this national trend is consistent with our data on Medicare recipients under 62 years of age with chronic LBP.