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several industrial sectors and are not limited to the traditional heavy labor environments represented by agriculture, mining, and manufacturing. It was reported, for example, that the service sector accounted for 26 percent of sprains/strains, carpal tunnel syndrome, or tendinitis, while the manufacturing sector accounted for 22 percent. Another database, National Center for Health Statistics, using self-reports provided estimates for back pain among those whose pain occurred at work (approximately 11.7 million) and for those who specifically reported that their pain was work-related (5.6 million). In this survey, the highest-risk occupations among men were construction laborers, carpenters, and industrial truck and tractor equipment operators; among women, the highest-risk occupations were nursing aides/orderlies/attendants, licensed practical nurses, maids, and janitor/cleaners. Other high-risk occupations were hairdressers and automobile mechanics. Many such workers often are employed in small businesses or are self-employed.

The focus of the panel's work has been the review and interpretation of the scientific literature characterizing musculoskeletal disorders of the low back and upper extremities and their relationship to work. Here we provide an integration of the studies that have been reviewed in the chapters on observational epidemiology, biomechanics, basic sciences, and workplace interventions. As noted in the chapter on epidemiology, there are significant data to show that both lower back and upper extremity musculoskeletal disorders can be associated with workplace exposures. Across the epidemiologic studies, the review has shown both strength and consistency of association. Concerns about whether the associations could be spurious have been considered and reviewed. Biological plausibility has been demonstrated in biomechanical and basic science studies, and further evidence to build causal inferences has been demonstrated by intervention studies that demonstrate reduction in the occurrence of musculoskeletal disorders following implementation of interventions.

The purpose of this discussion is to extend beyond the summaries of each of the chapters, and to integrate information among the chapters relevant to the model presented in Figure 10.1 (which reproduces Figure 1.2 for the reader's convenience). Also, with the acknowledgment that each set of studies has inherent limitations that affect the confidence about conclusions, another purpose is to consider the patterns of evidence that emerge across the different types of studies, as noted earlier in the report.

The integration of findings associated with musculoskeletal disorder risk and the workplace can best be addressed by considering the evidence for the presence of linkages representing the various pathways to injury shown in Figure 10.1. There is a large and diverse body of literature addressing the work-relatedness of musculoskeletal disorders, with different aspects of the literature suggesting different mechanisms of injury.



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