Somatization as a predictor of outcomes following functional restoration of Chronic Disabling Occupational Musculoskeletal Disorders (CDOMD) patients

Abstract

Chronic disabling occupational musculoskeletal disorders (CDOMDs) result from both psychosocial and physical factors, and patients with CDOMD often have comorbid psychiatric conditions. The Patient Health Questionnaire (PHQ) was developed to simplify DSM-IV diagnoses. One module, the PHQ-15, was developed to measure common somatic symptoms and indicate probable Somatoform disorder. Somatization is present when somatic symptoms such as pain, dizziness, or nausea are medically unexplained. In a prospective cohort study, 1458 CDOMD patients from 2003-2010 completed functional restoration, consisting of quantitatively-directed exercise progression and multi-modal disability management. Patients were divided into 3 categories based upon a cluster analysis of pre-treatment PHQ-15 scores: low somatization (n = 501), moderate somatization (n=817), and high somatization (n=140). Somatization groups were compared on demographic, psychosocial, and one-year socioeconomic outcomes such as work return and work retention. Results found the PHQ-15 highly responsive to treatment, with a 45% decrease in the number of high somatizers at post-treatment, an 18% decrease in the number of moderate somatizers at post-treatment, and a 42% increase in the number of mild somatizers at post-treatment (indicating improvement). Patients with moderate or high levels of somatization at pre-treatment were more likely to be female, have longer disability, and have multiple injuries. Moderate or high somatizers also had significantly worse psychosocial outcomes: at both pre and post-treatment, they exhibited more depressive symptoms, self-reported disability and pain intensity, and lower health-related quality of life (p ≤ .02). One-year after discharge, those who continued to have somatization at post-treatment had lower work retention rates, and were more likely to have high health care utilization and surgery on the original injury (p ≤ .05). These results suggest that the PHQ-15 somatization subscale can act as a “red flag,” since somatization patients exhibit worse psychosocial and one-year objective socioeconomic outcomes, such as work retention and health-care utilization.