In combination, the risk factors can predict the risk of chronic disability after back injury and may help in targeting workers for special attention to prevent disability, according to lead author Judith A. Turner, Ph.D., of University of Washington, Seattle.
Researchers performed interviews with 1,885 workers who submitted a workers' compensation claim for lost work time an average of 3 three weeks after experiencing a back injury on the job. A range of medical, job-related and psychological factors was analyzed as possible risk factors for disability at one year after the injury.
Not surprisingly, workers with more severe back injury were more likely to be on disability after 1 year. Workers with pain spreading down into the leg – indicating involvement of the spinal nerve roots, or radiculopathy –were at particularly high risk.
Disability risk also was higher for workers who rated their initial disability higher, who had pain at more sites and who had previous injuries resulting in more than 1 month off work. Another significant predictor was the specialty of the first doctor seen after back injury. Workers who saw a chiropractor were less likely to be disabled at one year.
Certain job characteristics also affected disability risk. Risk was lower when employers offered accommodations (such as light duty) for workers recovering from back injuries. In contrast, risk was higher for workers who rated their jobs as "very hectic."
The researchers combined the significant factors into a statistical model to predict which workers were at highest risk of long-term disability after back injury. The model was 88 percent accurate in identifying workers who would and would not be disabled after one year.
Work-related back injuries are common, researchers noted. Although only a small fraction of workers with back injuries develop long-term disability, this group accounts for most of the costs related to back pain. Knowing the early risk factors for long-term disability could help in understanding why some workers do become disabled and, more importantly, allow them to be targeted for interventions to prevent disability.
The new study is the largest so far to examine risk factors for chronic disability after back injury. Although more severe back injury is one important factor, other risk factors are significant independent of injury severity.
"This confirms clinical impressions that patients with similar examination and imaging findings vary in pain and disability outcomes, likely because of factors other than biologic ones," said Turner and colleagues.
Current approaches to chronic pain emphasize the interrelationships between biological and psychological factors. However, in the new study, most of the psychological factors thought to contribute to chronic pain were not significant risk factors for disability. The researchers call for expanded approaches to prevention and treatment that will account for the many different factors that can affect disability, including "health care provider, employer and family responses, and work and economic factors."