general population sources cannot be considered in any sense equivalent to rates for background, reference, or unexposed groups nor, conversely, as rates for musculoskeletal disorders associated with any specific work or activity.
2. There are no comprehensive data available on occupationally unexposed groups. Given the proportion of adults now in the active workforce in the United States, any such nonemployed group would, by definition, be unrepresentative of the adult population.
Table 2.1 summarizes all available information regarding the rates in the general population from the six sources, organized by category: (1) all musculoskeletal disorders, (2) upper extremity disorders (including carpal tunnel syndrome), and (3) disorders of the back. Because there are relatively more data available in the latter category, Table 2.2 and Table 2.3 are included to provide the detailed findings in each of the relevant study groups. The overwhelming thrust of the data reveals that musculoskeletal disorders are very prevalent among adults in the United States, especially after the age of 50, and are a source of an extraordinary burden of disability.
According to the 1997 report from the National Arthritis Data Workgroup (Lawrence et al., 1998), a working group of the National Institute of Arthritis and Musculoskeletal and Skin Diseases, 37.9 million people, or 15 percent of the entire U.S. population, suffered from one or more chronic musculoskeletal disorders in 1990. Moreover, given the increase in disease rates and the projected demographic shifts, they estimate a rate of 18.4 percent or 59.4 million people with these disorders by the year 2020. Results of the National Health Interview Survey for 1995 showed a 13.9 percent prevalence of impairment from musculoskeletal disorders (Praemer, Furner, and Rice, 1999).
Other estimates were generated from the Health and Retirement Survey (1992-1994), which found a rate of 62.4 percent among men and women between ages 51 and 61 reporting one or more musculoskeletal disorders; 41 percent of these reported work disability as a consequence. Among all disabled workers in that age group, almost 90 percent reported one or more musculoskeletal disorders, making musculoskeletal disorders overwhelmingly the largest reason for disability. According to data from Supplemental Security Income, a program that covers chronically ill as well as previously employed persons, 7.7 percent of people under the age of 65 receiving assistance attribute it to musculoskeletal disorders. This proportion rises to 16.9 percent among adults in their 50s, and to 23.9 percent among adults 60 to 64 years old.
Data regarding upper extremity disorders and low back pain are consistent and show that both are important national concerns. Data regarding the former, available from the National Health Interview Survey, show