0329 GMT December 08, 2019
Multiple studies have found associations between pain and poor sleep, including a study published in 2018 in the journal Frontiers in Psychiatry that suggested that the relationship is bidirectional — people report having worse pain after a poor night of sleep and people report sleeping worse when in pain, everydayhealth.com wrote.
Now new research published in The Journal of Neuroscience suggests for the first time that part of the explanation behind this link is because sleep deprivation makes certain pain centers of the brain more active than they otherwise would be after a good night of sleep.
“Our findings provide the first evidence that the previously known effect of poor sleep on pain relates to changes in the pain-sensing and pain-modulating regions of the brain caused by sleep loss,” said study coauthor Adam Krause, a doctoral student with the Center for Human Sleep Science at the University of California in Berkeley.
Krause and his colleagues measured pain sensitivity in a group of 25 healthy young adults ages 18 to 30. Using functional magnetic resonance imaging (fMRI), the scientists scanned the participants’ brains under two conditions — once after they had a healthy eight hours of sleep and once after they had a night of sleep deprivation. During both fMRIs, participants received uncomfortable levels of heat to their legs.
Restricting sleep lowered the participant’s threshold for pain compared with what they reported after a good night of sleep, and the fMRI scans showed that parts of the brain responsible for sending pain signals were markedly more active after a night of sleep restriction compared with after a night of adequate sleep.
“We were not surprised to find that sleep deprivation amplified pain sensitivity because anyone with chronic pain knows this,” Krause said.
“But we were surprised by how strong the effect was.”
After the study participants were sleep-deprived, researchers recorded a 120 percent rise in activity in the somatosensory cortex among them. The somatosensory cortex is the part of the brain that processes sensory input, interpreting for the brain what something (like pain) feels like. These results indicate the pain signal was therefore amplified after sleep deprivation.
Lack of sleep blunted response, however, in the striatum and insula, two areas of the brain involved in processing pain, including evaluating its severity and controlling our emotional response to it. The data showed there was a 60 to 90 percent drop in activity in these regions after a night without rest, suggesting the brain was worse equipped to manage a pain response after poor sleep.
“I like to think of the striatum and insula as the master gatekeepers of pain,” Krause said. They initiate the brain’s natural painkilling mechanisms and provide relief from that discomfort. But that doesn’t appear to happen as well (or nearly at all) after poor sleep, he explained. “It’s as if the sleep-deprived brain has left the floodgates open in the middle of a deluge of pain signals.”
Subjects also rated their level of pain in response to the heat. After being sleep-deprived individuals reported reaching their threshold at a lower temperature than after they had had a good night’s sleep.
To supplement the fMRI tests, investigators conducted an online survey of 236 individuals (recruited via the crowdsourcing marketplace Amazon Mechanical Turk). Over the course of a few days, respondents reported nightly hours of sleep and next-day pain levels. The findings revealed that even minor shifts in sleep and wake patterns affected pain sensitivity: Decreased sleep quality from one night to the next was linked to worse pain, as was increased awakenings during the night.
What Do the Results Mean for Pain Sufferers?
The data clearly reinforces that pain and sleep have an intimate relationship, suggesting that if you can get a good night’s sleep, pain will likely not be so severe as if you had slept poorly. From a public health standpoint the data underscore that even modest improvements in sleep quality among individuals in pain may have the potential to significantly reduce the burden of pain, as well as some healthcare costs.
“It is our hope that this research encourages medical practitioners to bring sleep much closer to the core of patient care,” said Krause.
Taking steps to enhance sleep may be especially useful in hospitals, too.
“The hospital setting, where pain is often at its worst, is also where sleep is most disrupted,” said Krause.
“For example, waking a patient up repeatedly to perform various tests may not be as important as allowing a patient to sleep uninterrupted throughout the night.”
If sleep can reduce pain to a great enough extent, patients may not need as many narcotic analgesics, such as morphine, heroin, oxycodone, or fentanyl, which remain a standard treatment for pain, Krause adds.
“These drugs are effective at reducing pain, but they come with a broad set of side effects, including, but not limited to, addiction and dependency,” he said.
“Perhaps an approach to pain that includes healthy sleep habits will reduce the need to rely on such drugs.”
Steven Feinsilver, MD, director of the Center for Sleep Medicine at Lenox Hill Hospital in New York City, agreed that hospitals might take action based on these results.
“Humans sleep better when it’s dark, cool, quiet, and comfortable, but we don’t do a very good job of that in the hospitals,” he said.”
These are things we might be able to fix. Sleep is a powerful biological drug — if you don’t mess it up, it tends to work.”
Feinsilver, who was not involved in the study, said that cognitive behavioral therapy is the gold standard for helping individuals develop good sleep habits and is recommended as a first-line treatment before trying medication for sleep.
The study authors noted some limitations to the research, including that the in-lab experiments were performed on healthy young adults despite the fact that those who tend to more frequently suffer from pain are older. Furthermore, pain was only gauged according to heat levels, so results may differ with different types of pain. The online portion of the study was also limited because all of the information was self-reported.
Krause anticipates future research that will further analyze which aspects of sleep are most important for managing pain. What properties of sleep seem to protect people from the worst effects of sleep deprivation? Because the immune system plays a central role in pain sensitivity, he also would like to examine how immune function may tie in with sleep problems to affect pain.