Effects of Psychological Symptoms on Sleep in Chronic Musculoskeletal Pain

Sleep disturbances are more common in patients with chronic musculoskeletal pain, but there are differences between subjective and objective sleep measures, according to study results published in The Clinical Journal of Pain. In addition, the study revealed a close relation between mental distress and sleep quality.

On one hand, sleep disturbances may adversely affect chronic musculoskeletal pain, and on the other hand, pain catastrophizing and mental distress may contribute to impaired sleep patterns. The goal of the current cross-sectional, case-controlled, observational study was to assess the impact of psychological factors on sleep quality and parameters in chronic musculoskeletal pain.

The study cohort included patients aged 18 to 65 years with musculoskeletal pain, treated at the outpatient clinics at the Rehabilitation Department and the Pain Clinic at the University Hospital of North Norway. A control group included healthy and pain-free controls, matched by age, sex, and season of investigation.

Several self-report questionnaires were used to assess subjective sleep measures. Pain severity was assessed using the Norwegian version of the Brief Pain Inventory (BPI), and the 25 item version of the Hopkins Symptoms Checklist (HSCL) was used to assess mental distress. Additional measures included the Norwegian version of the Pain Catastrophizing Scale (PCS), Insomnia Severity Index (ISI) and the Pittsburgh Sleep Quality Index (PSQI).  Actigraphy used for a week with accompanying sleep diary and one night of polysomnography were used to assess objective sleep measures.

The final study sample included 56 patients (mean age 41.7 years, 75% women) and 53 participants serving as controls (mean age 41.8 years, 72% women). 

Subjective measures revealed significant group differences between patients with chronic musculoskeletal pain and healthy controls, as those with chronic pain had significantly more pain symptoms (BPI mean 4.12 vs 0.81, respectively), pain catastrophizing (PCS mean 12.32 vs 3.58, respectively) and mental distress (HSCL mean 1.73 vs 1.24, respectively).

Similarly, insomnia (ISI mean 11.9 vs 4.1, respectively) and sleep quality (PSQI 9.7 vs 4.5, respectively) were worse in those with chronic pain, compared with controls.

However, objective measures revealed only moderate differences between the groups in sleep continuity according to the actigraphy results and minor differences between groups in sleep architecture, based on the polysomnography data.

While there was no association between HSCL with the objective sleep measures used in this study, the analyses revealed a strong association between mental distress and subjective sleep measures, as increased psychological distress according to HSCL was associated with increased symptoms of insomnia (ISI) and reduced sleep quality (PSQI).

The researchers suggest that the differences between the groups in the subjective sleep measures are partially explained by the differences in mental distress.

Pain catastrophizing according to PCS was not significantly associated with sleep efficiency, but there was a significant association between PCS and slow wave sleep on polysomnography in patients with chronic pain, as more pain catastrophizing predicted less slow wave sleep.

The study had several limitations, including the cross-sectional design, relatively small sample size, and additional unmeasured confounders.

“The differences in subjective and objective sleep measures indicate that they probe different aspects of sleep functioning in patients with musculoskeletal pain, and their combined application may be valuable in clinical practice,” concluded the study researchers.

Reference

Abeler K, Friborg O, Engstrøm M, Sand T, Bergvik S. Sleep characteristics in adults with and without chronic musculoskeletal pain: the role of mental distress and pain catastrophizing [published online Jun 15, 2020]. Clin J Pain. doi:10.1097/AJP.0000000000000854