INSOMNIA IN CHRONIC DISABLING MUSCULOSKELETAL PAIN DISORDERS IS INDEPENDENT OF PAIN AND DEPRESSION Early, Middle, and Late Insomnia. Additional validated

BACKGROUND CONTEXT— Insomnia is frequently experienced by patients suffering from chronic musculoskeletal disorders, but is often seen as simply a symptom of pain or depression, and not as an independent disorder. Compared to those who experience only chronic pain, patients with both chronic pain and insomnia report higher pain intensity, more depressive symptoms, and greater distress. However, insomnia has not yet been systematically studied in a chronic musculoskeletal pain with disability population. PURPOSES— This study assessed the prevalence and severity of patient-reported insomnia, as well as the relationship among insomnia, pain intensity, and depressive symptoms, in a chronic musculoskeletal pain with disability population. STUDY DESIGN/SETTING— A retrospective study of prospectively captured data. PATIENT SAMPLE— A consecutive cohort of 326 chronic musculoskeletal pain with disability patients (85% with spinal injuries) entered a functional restoration treatment program. All patients signed a consent form to participate in this protocol. MEASURES— Insomnia a Four groups formed: Moderate of No Clinically Significant Insomnia, Sub-threshold Insomnia, Moderate Clinical Insomnia and Severe Clinical Insomnia found in 5.5%, 21.2%, 39.6%, and 33.7% of the cohort, respectively. More than 70% of patients reported moderate to severe insomnia which is a considerably higher prevalence than found in most patient cohorts previously. A step-wise pattern was found, in which Severe Clinical Insomnia patients reported the highest pain, the most severe depressive symptoms, and the greatest disability. The Severe Clinical Insomnia patients also reported a higher number of sleep disturbance types (Early, Middle, and Late insomnia) than the other 3 groups. In fact, 62.9% of them reported all 3 disturbance types. Although correlations were found between insomnia and depressive symptoms, and between insomnia and pain, the shared variances were small (12.9% and 3.6%, respectively), indicating that depression and pain are separate constructs from insomnia.