I wrote recently about the relationship between sleep and fibromyalgia, a chronic pain syndrome, and the about important—and complicated—relationship between sleep and pain. Now there’s news that one of the most effective remedies for sleep apnea—CPAP therapy—may also have the benefit of reducing sensitivity to pain. A recent study found consistent use of the CPAP could reduce pain sensitivity in patients with severe OSA. The study tested 12 patients—7 men and 5 women—with severe obstructive sleep apnea. They found that six to eight weeks of regular CPAP use led to significantly reduced pain sensitivity and also to improved continuity of sleep.
The relationship between sleep and pain is one we don’t yet fully understand. What we do know—and what anyone who suffers from chronic pain can attest to—is that each can have a significant effect on the other. The presence of pain can make it hard to fall asleep and stay asleep, and being sleep deprived can make a person feel more sensitive to aches and pains. Studies that have examined the relationship between sleep and pain found these links to be true—and also found that it doesn’t take a lot of lost or disrupted sleep to have an effect on how we experience pain:
- One study showed 12 women who were deprived of sleep for only 3 consecutive nights experienced increased sensitivity to pain. Pain sensitivity began to increase after a single night of disrupted sleep and grew worse each night.
- Another study tested healthy men for pain sensitivity after a short period of total sleep deprivation. Researchers found that total sleep deprivation dramatically decreased the men’s threshold for pain. A recovery sleep period after sleep deprivation restored the men’s pain threshold.
- Recent research info fibromyalgia showed that women who were sleep deprived had as much as 5 times higher a risk of developing the chronic pain syndrome, over a 10-year period, as women who were not sleep deprived.
- A sleep-pain study performed on rats showed that when deprived of REM sleep, the rats experienced a significant increase in sensitivity to several types of pain stimuli.
The type of sleep we get—or don’t get—may be significant when it comes to pain. Researchers are increasingly focusing on stages of sleep that occur in the later stages of the sleep cycle--REM sleep and delta, or slow wave, sleep—as being critical in protecting pain thresholds. Throughout the night, your sleep unfolds in a recurring and progressive cycle. Over the course of a night, the cycle shifts so that you spend more time in REM sleep and in the later sleep stages that are considered slow wave sleep. If you are sleep deprived, or your sleep is constantly being interrupted, your body does not reach the REM and slow wave-rich sleep that occurs in these later periods.
Here’s where the CPAP may be playing its role in helping reduce pain sensitivity. CPAP works by pushing a constant stream of air through the sleeper’s airway, to keep it from closing. Sleep apnea occurs when muscles in the back of the throat collapse, closing off the airway. This causes a person to stop breathing. It also interrupts a person’s sleep cycle, since those who suffer from sleep apnea are awakened, however briefly, often many times throughout the night by their breathing problem.
It’s possible that the CPAP allows a person to sleep through their full sleep cycle, achieving those later stages of sleep that are so restorative, and also appear to help decrease our sensitivity to pain. This study is just a beginning—we don’t yet know why CPAP might be effective in reducing pain sensitivity. But these results are promising and intriguing, and this is a topic that deserves additional inquiry.
For millions of people who suffer from obstructive sleep apnea, and perhaps other independent conditions that bring about chronic or intermittent pain, the possibility that CPAP could help reduce sensitivity to pain is welcome and important news. It’s also another reason to make sure that patients who have been prescribed CPAP as a treatment actually follow through with the therapy. The CPAP can work very effectively, but only if it’s actually used! This latest research provides yet another very good reason for people with OSA to make sure that the CPAP is part of their nightly routine—every night. The benefits may be even broader than we previously thought.
Michael J. Breus, PhD
The Sleep Doctor™