Although sleep disorders and disturbances are associated with worse chronic pain outcomes, both pharmacologic and nonpharmacologic treatment interventions can improve pain outcomes. This is according to research results published in Sleep Medicine Reviews.
Researchers conducted a systematic scoping review to examine the current literature relating to the influence of sleep disorders and sleep disturbance on pain outcomes among US veterans with chronic nonmalignant pain.
In total, 1450 records were retrieved and 26 were reviewed in the analysis. Overall, the studies included 923,434 participants (average age, 53.3±12.9 years; 82.1% males, primarily White); 84.6% of studies included fewer than 700 participants. Studies were primarily prospective, cross-sectional, or observational in design, and the majority had low quality evidence or major flaws (42.3%); in 38.5%, the evidence quality was considered good.
Fifteen studies evaluated sleep disturbances, and 11 evaluated sleep disorders. The most common disorder diagnoses were insomnia and obstructive sleep apnea (54.5% and 27.3%, respectively). Across all studies, the most frequently assessed pain outcomes were self-reported and included pain severity or intensity (73.1%), pain interference (38.5%), pain disability (7.7%), and the likelihood or odds of a chronic pain diagnosis (7.7%). Ten studies reported on chronic pain duration at study onset.
Nine of the studies that assessed the influence of diagnosed sleep disorders on chronic pain outcomes used an observational or nonexperimental design. Across these studies, the presence of either a sleep disorder or a worsening of sleep disorder-related symptoms resulted in worse pain outcomes.
Insomnia was associated with greater pain interference with sleep and greater pain-related disability. Insomnia was also associated with a nearly 2-fold increase in the odds of being diagnosed with headache (adjusted odds ratio [aOR], 1.97) and significantly increased odds of persistent headache (aOR, 1.19).
In veterans with both insomnia and chronic pain, self-reported sleep quality and disturbances and greater symptom severity for insomnia were associated with worse pain severity and interference. Researchers in one study found that insomnia “partially mediated the relationship between PTSD [posttraumatic stress disorder] and pain severity and pain interference.”
Ten studies examined the influence of sleep disturbance on pain outcomes using an observational design. Worse pain responses were observed across 7 studies. Poor sleep was associated with higher chronic pain severity, pain interference, and greater overall pain. Self-reported sleep disturbances were also significantly associated with worsened pain outcomes, even after controlling for PTSD, anxiety, depression, and use of analgesic or sleep medications.
Two studies evaluated patient samples that treated patients with sleep-disordered breathing with continuous positive airway pressure (CPAP). A randomized, sham-controlled pilot trial of veterans with Gulf War illness and sleep-disordered breathing found a 34% reduction in pain severity among those who used CPAP for at least 5 hours per night, 3 nights per week.
Finally, 5 studies evaluated samples of patients who received treatment. Across these studies, treatment-induced improvements in sleep disturbance were associated with improved pain outcomes. Treatment modalities included cognitive behavioral therapy, morning bright-light therapy, and oral prazosin. Study results suggest that both pharmacologic and nonpharmacologic interventions resulted in improved pain outcomes.
Study limitations include an inability to directly compare results across studies due to heterogeneity and mixed evidence quality, methodological limitations in each study, and an inability to generalize results outside of a population of predominantly middle-aged, white, male US veterans. Uncontrolled variables may have also introduced bias.
“Preliminary evidence suggests that treatment-induced sleep improvements ameliorate pain,” the researchers concluded. “Thus, the relationship of sleep and pain should be considered for the management of chronic pain outcomes in veterans.”
Further research should expand the current understanding of how sleep disturbances and disorders influence pain, allowing for the development of targeted interventions.
Disclosure: This clinical trial was supported in part by Pacira Pharmaceuticals. Please see the original reference for a full list of authors’ disclosures.
Saconi B, Polomano RC, Compton PC, McPhillips MV, Kuna ST, Sawyer AM. The influence of sleep disturbances and sleep disorders on pain outcomes among veterans: a systematic scoping review. Published online November 30, 2020. Sleep Med Rev. doi:10.1016/j.smrv.2020.101411