Insomnia among patients with chronic pain: A retrospective study.

Insomnia can coexist with chronic pain and is a major cause of rapidly increasing medical expenses. However, insomnia has not been fully evaluated in patients with chronic pain. This retrospective study aimed to identify the risk factors for insomnia in patients with chronic non-cancer pain. A total of 301 patients with chronic non-cancer pain were enrolled. Patients with the Athens insomnia scale scores ≥ 6 and < 6 were classified into insomnia (+) and insomnia (-) groups, respectively. All patients completed self-report questionnaires as part of their chronic pain treatment approach. Univariate and multivariate analyses were performed to predict insomnia. We found that 219 of 301 (72.8%) patients met the AIS criteria for insomnia. Significant differences were depicted between patients with and without insomnia in terms of body mass index, numeric rating scale, pain catastrophizing scale, hospital anxiety, and depression scale (HADS), pain disability assessment scale, EuroQol 5 dimension (EQ5D), and pain self-efficacy questionnaire. Multiple regression analysis identified the numeric rating scale, HADS, and EQ5D scores as factors related to insomnia in patients with chronic non-cancer pain. Anxiety, depression, and disability were associated with a greater tendency toward insomnia. HADS and EQ5D scores are useful screening tools for preventing insomnia in patients with chronic non-cancer pain.