Advancing epidemiologic studies of occupational injury--approaches and future directions.

Despite increased attention to the epidemiology of occupational injuries and work-related musculoskeletal disorders, little is known about the relative contribution of risk factors for specific injuries and diseases and effective ways to prevent them. Building on the knowledge and ideas presented in the previous papers in this special issue, this paper describes the salient issues regarding the needs and the opportunities in design, conduct, and analysis of epidemiologic research on occupational injury. There is a clear need for standardization of definitions on exposure variables and health outcomes, since basic terminology is not used consistently across studies. Improved surveillance systems with linkage to other databases offer excellent opportunities to evaluate trends in risk factors and occupational injuries. New opportunities for etiologic studies include the case-crossover design, which focuses on relations between intermittent exposures and injuries, as well as several hybrid designs that combine advantages and strength of the traditional case-control and cohort study designs. Various suggestions are presented to capture the dynamics of exposure, including both intermittent and continuous factors in the assessment strategy. The importance of cohort studies is emphasized to clarify the temporal relations between causes and effects in work-related injury research. Finally, intervention studies are much needed and a hierarchical approach is suggested, starting with observational surveys, continuing with quasi-experimental studies and concluding with randomized controlled experiments of those interventions that hold the largest promise.