Epidemiology of low-back pain in industry.

Low-back pain and back injuries are of such a complex nature that any one criterion cannot be applied by itself to give a valid assessment of the risk associated with manual materials-handling jobs. There is no question that low-back pain is an extremely significant cause of disability and has a major socioeconomic impact, but many different personal and job factors are associated with the incidence and prevalence of these complaints. There is a need for ongoing systematic investigations of the multiple risk factors that may be causally related to low-back pain and may possibly be amendable to preventive interventions. Knowledge of workplace and individual risk factors is far from complete. Prospective studies are needed so that factors contributing to the development of low-back pain can be separated from factors resulting from low-back pain. It is difficult to relate low-back pain to the workplace because it occurs quite often in workers employed in sedentary occupations. However, incidence, severity, and disability are all related to the physical demands of the job. In this regard, jobs involving lifting, lowering, pushing, pulling, carrying, and holding; body movements such as frequent bending, twisting, and sudden movements; and working in bent-over postures appear to have a significant potential for producing low-back pain. A combination of lifting, bending, and twisting appears to be most hazardous. It is concluded that lifting heavy loads contributes to increased frequency and severity rates for low-back pain. This is true regardless of whether the lifting is performed over a short period or throughout the day and whether it is performed a few times per day of repetitively. If, however, such lifting is performed repetitively, the medical hazard extends beyond low-back problems to other musculoskeletal strain and sprain injuries and to fatigue-related injuries, particularly for weaker workers. In this latter regard, gender, age, anthropometry, and previous history of back pain are known to modify these risks for populations of workers. The inherent variability between workers and within any worker over time precludes the use of such factors to assign risk to any particular individual.