Assessment of sleep in patients with chronic pain

Patients with chronic pain commonly complain about poor sleep and likewise people with poor sleep report worse pain. In NHS Grampian Patients attending chronic pain clinics are routinely assessed using the Brief Pain Inventory (BPI). This is a short questionnaire capturing the severity of patients' pain and the extent to which pain interferes with daily functioning, including one question about interference of pain with sleep. There are several dedicated validated tools available for the subjective assessment of sleep. In this pilot study we asked patients with chronic pain to complete the Pittsburgh Sleep Quality Index (PSQI), the Pain and Sleep 3-Item Questionnaire (PSQ-3) and the Verran-Snyder Halpern (VSH) sleep scale in addition to the BPI, to assess whether the sleep interference score in the BPI was able to accurately capture sleep quality. Following ethical approval and written informed consent, unselected participants were recruited from pain clinics following provision of information about the study a week before the clinic visit. Fifty-one patients (aged 18–88 years) were recruited. BPI pain scores (patients' assessment of their average pain) were subsequently divided into tertiles of mild (scoring 0–4), moderate (5–6) or severe pain (7–10). Thirteen participants scored their average pain as mild, 16 as moderate and 22 as severe. BPI sleep interference scores correlated significantly with pain scores (r=0.78, p<0.0001). Sleep disturbance and poor sleep efficiency/quality were identified by the dedicated sleep assessment tools, with significant associations with pain severity tertile. Using the VSH scale which describes sleep over the previous 24h, we found greater sleep disturbance (p=0.014) and poorer sleep efficiency (p=0.012) as pain severity increased (Fig. 2). Likewise using the PSQ-3 which records sleep interference over the last week, sleep disturbance was greater (p<0.0001) and using the PSQI, which assesses sleep over the previous month, the index of poor sleep quality was higher (p<0.0001) as pain increased. We conclude that more severe pain is associated with worse subjective sleep quality and that the BPI may be useful for rapid initial assessment of sleep in patients with chronic pain. We thank the NIAA for a John Snow Intercalated Bursary award to Rachel Vaughan.