disorders is higher among individuals who perform activities that exceed tissue tolerances. Generally speaking, the more that they perform those activities, the greater are their risks for such disorders.

Question 5: What is the incidence of such conditions in (a) the general population; (b) specific industries; and (c) specific occupational groups?

Current knowledge about the incidence of each of the conditions described in Question 1 in the general adult population is limited because (1) the conditions are clinically diagnosed, typically in doctors' offices; (2) diagnostic criteria for these conditions are not uniformly applied; (3) there are no data collection systems to capture such diagnoses in the health care system; and (4) two-thirds of the adults in the general population are employed, with variable occupational risks. Those who are not employed, including those with various chronic conditions and disabilities, are not a suitable reference population. Data on industry and occupational groups are based on a wide variety of methods that have been collected for different purposes. It is the steering committee's judgment that it is not possible to make useful comparisons on the basis of these data.

Question 6: Does the literature reveal any specific guidance to prevent the development of such conditions in (a) the general population; (b) specific industries; and (c) specific occupational groups?

Specific interventions can affect the reported rate of musculoskeletal disorders in specific industries and for specific occupations. Interventions can also reduce reports of musculoskeletal disorders, the presence of risk factors, and the reporting of comfort and pain associated with work. It is also clear that the effectiveness of interventions can be improved if they are tailored to specific occupations and work settings. There is a dearth of data on interventions in the general population.

Question 7: What scientific questions remain unanswered, and may require further research, to determine which occupational activities in which specific industries cause or contribute to work-related musculoskeletal disorders?

Looking at this web of evidence, we have reached three major conclusions:

• Musculoskeletal disorders are a serious national problem: estimates of costs range from $13 to $20 billion annually.

• These problems are caused by work and non-work activities.

• There are interventions that can reduce the problems.

We have also identified some focused research projects, the results of which could increase the efficacy of interventions. Some of these projects would produce useful results