A bidirectional relationship
Epidemiologic studies have found that, if you follow women who do not have pain, those with complaints about sleep are more than twice as likely to develop fibromyalgia.
Dr. Smith’s group and others have shown that if you deprive a healthy person of sleep, they become more sensitive to pain.
Inflammation could be one possible reason for this effect. In one study, participants who experienced forced awakening experienced less slow-wave sleep, which was tied to more inflammation in the morning. Increased inflammation was linked to greater pain sensitivity.
“We are starting to piece together some of the pathways. That’s just one,” Dr. Smith said.
A recent study by researchers at Harvard University and elsewhere investigated how sleep disturbances affected three pain pathways. In that study, the results varied by sex. The data indicate that optimal treatment approaches might differ for men and women, the researchers said.
Waking up to the problem
Sleep problems can be neglected in medical school and in the clinic. “People just have other things to focus on that they clearly know what they can do about it,” Dr. Smith said.
But clinicians should not hesitate to screen for conditions such as insomnia or OSA and refer patients to a specialist. If a patient has had pain for 6 months and treatments are not working, the chance that they have a treatable sleep disorder “is very high, above 50%,” Dr. Smith said. Many could have more than one sleep disorder, he added.
Continuous positive airway pressure for OSA and CBT for insomnia can improve sleep. Dr. Smith said he expects these measures will improve overall pain management as well.
If treating a sleep disorder fails to help with pain, however, it may still help prevent other sleep-related problems, such as depression, poor glucose control, and heart disease. It also could improve patients’ ability to function day to day, he said.
Evidence on whether treating sleep problems reduces pain has so far been mixed.
“We’ve done some studies showing that if you have CBT-I and you have knee arthritis, improvements in the amount of time you spend awake at night translate into improvements in pain at 6 months. There is a signal there, but it’s not as strong as we would like,” he said. “It may be that it takes longer than anyone would like” to have an effect.
A structured intervention such as CBT-I is likely more beneficial than education about sleep hygiene alone in resolving sleep disturbances, Dr. Whibley said. CBT-I includes active components such as sleep restriction therapy and stimulus control therapy and is recommended by the American Academy of Sleep Medicine as the first-line treatment for chronic insomnia (J Clin Sleep Med. 2008 Oct 15;4[5]:487-504).
Patients should consider the role that sleep may play in their chronic pain condition, he said.
“An increasing number of researchers and clinicians are becoming more interested in this as a foundational pillar of health, alongside activity and diet,” Dr. Whibley said. “Sleep is recognized as just as important but doesn’t seem to get the airtime.”
Clinicians, he added, should regularly assess their patients’ sleep and know where to refer those whom they feel would benefit from more advanced management: “They [should] know that they have at least got it on their radar to check as one of the important pillars of health that you should be able to control.”