Sleep and Chronic Pain – Research Update – March 2014

The association between poor sleep and chronic pain is an interesting subject.

For those interested, I previously posted on Sleep and Chronic Pain back in September 2012.

I had the following fantastic article forwarded to me by a colleague, and I thought it apt to provide a research update on this topic.

Finan PH, Goodin BR, Smith MT. The association of sleep and pain: an update and a path forward. J Pain. 2013 Dec;14(12):1539-52.

For those of you just wanting the key abstract info…….

A key trend emerging from population-based longitudinal studies is that sleep impairments reliably predict new incidents and exacerbations of chronic pain.

Microlongitudinal studies employing deep subjective and objective assessments of pain and sleep support the notion that sleep impairments are a stronger, more reliable predictor of pain than pain is of sleep impairments.

Recent experimental studies suggest that sleep disturbance may impair key processes that contribute to the development and maintenance of chronic pain, including endogenous pain inhibition and joint pain.

For those wanting more detail…….

The paper was designated as a “Critical Review”. Its purpose, according to the authors, was to “critically examine the recent prospective and experimental literature (2005-present) in an attempt to update the field on emergent themes pertaining to the directionality and mechanisms of the association of sleep and pain”.

It is a very extensive article that I would encourage you all to read if you can access it. Given the extensive nature of it, I have tried to pull out some of the key conclusions that the authors reached from their synthesis/review of the data. Here we go:

On Sleep Disturbance and Development of Pain:

• Elevated insomnia symptoms increase the risk of exacerbating existing headache and developing new incident headache.
• Insomnia symptoms at baseline significantly increased the risk of developing chronic musculoskeletal pain (both widespread and regional).
• Prospective studies indicate that sleep disturbance:
  • Increases the risk for new-onset cases of chronic pain in pain-free individuals.
  • Worsens the long-term prognosis of existing headache and chronic musculoskeletal pain
  • Influences daily fluctuations in clinical pain.
• Insomnia symptoms significantly increase the risk of developing future chronic pain disorders in previously pain-free individuals.
• Existing pain is not a strong predictor of new incident cases of insomnia.
• Deeper assessments of sleep disturbance tend to suggest that sleep disturbance is a stronger predictor of future pain than pain of sleep disturbance.
• In a series of analyses involving associations between depression, fatigue, sleep, and pain, the best-fitting structural equation model included a path in which sleep predicted pain.

On Quality/Good Sleep. It has been shown to:

• Predict chronic widespread pain symptom resolution over 15 months.
• Improve the long-term prognosis of individuals with tension-type headache, migraine, and chronic musculo-skeletal pain.

On Poor Sleep and Increased Pain Sensitivity:

• Tentative support for the notion that sleep deprivation increases pain sensitivity.
  • Healthy subjects report spontaneous bodily pain after 2 nights of partial (4 hours) sleep deprivation, and this effect increases as the number of nights of partial sleep deprivation increases.
  • Partial sleep deprivation may produce hyperalgesia.
  • Continuous 4-hour sleep restriction for only 1 night resulted in elevations in self-reported pain, fatigue, depression, and anxiety in rheumatoid arthritis patients but not controls. In addition:
    • Disease-specific measures of pain severity and painful joint counts were elevated in the rheumatoid arthritis patients following partial sleep deprivation.
    • Partial sleep deprivation altered both psychosocial symptoms and disease-specific markers of rheumatoid arthritis.

On Impact of Sleep Disturbance on Pain Inhibition:

• Conditioned Pain Modulation (CPM) is a measure of endogenous opioid-mediated pain inhibition. Reduced CPM efficacy results in impaired pain inhibition.
  • Sleep disturbance and/or poor sleep efficiency were significantly associated with diminished CPM efficacy in Temporomandibular disorder, fibromyalgia and rheumatoid arthritis patients (relative to healthy controls).
• Research suggests that total sleep deprivation selectively augments the activity of nociceptive pathways without altering the perception of non-nociceptive somatosensory stimuli.
  • Patients have demonstrated reductions in heat pain threshold following total sleep deprivation, whereas detection thresholds (e.g. touch) remained unchanged.
• Sleep deprivation appears to dysregulate endogenous opioid systems. This may increase vulnerability to central sensitization and persistent pain.

Other Conclusions:

• It remains to be determined if the association of sleep and pain varies across different chronic pain disorders. The present review synthesizes findings from a wide range of disorders, including neuropathic, musculoskeletal, headache/migraine, and idiopathic pain disorders.
• Efforts to prevent and treat chronic pain may be well served to target sleep disturbance as a point of primary prevention and intervention.
• The biopsychosocial model provides an excellent framework through which to integrate these and other potential mechanisms of the association of sleep and pain, such as inflammation and neuroendocrine factors.
• The past decade of research has allowed us to move past the question of whether sleep and pain are related.

Fascinating stuff!

Just before I throw in my musings on the above I thought I would highlight a couple of other recent sleep related studies I found when further looking into this research update.

Haack et al (2007) conducted a study to investigate the effects of reduced sleep duration on peripherally circulating inflammatory mediators (e.g. plasma interleukin levels). The study involved 18 volunteers who were randomly assigned to either 12 days of sleeping 8 hours per night or 4 hours per night. The patients sleeping 4 hours per night demonstrated elevated Interleukin levels versus the 8 hour per night sleepers.  Key conclusions being:

• Insufficient sleep quantity may facilitate and/or exacerbate pain through elevations of interleukin.
• In disorders where sleep disturbances are common, insufficient sleep quantity itself may establish and maintain its co-occurrence with pain and increased inflammation.