Pain and sleep have one obvious connection. When we’re in pain, we have a hard time sleeping. But, new research indicates that lack of sleep also makes pain worse.
The research, conducted at the University of California, Berkeley, helps explain the self-perpetuating cycles of sleep loss, chronic pain and even opioid addiction. A 2015 National Sleep Foundation poll found that two in three chronic pain patients suffer from reoccurring sleep disruptions.
“If poor sleep intensifies our sensitivity to pain, as this study demonstrates, then sleep must be placed much closer to the center of patient care, especially in hospital wards,” said study senior author Matthew Walker, a UC Berkeley professor of neuroscience and psychology.
By applying uncomfortable levels of heat to the legs of two dozen healthy young adults — while scanning their brains — Walker and UC Berkeley Ph.D. student Adam Krause found that the neural mechanisms that pick up on pain signals, evaluate them and activate natural pain relief are disrupted when operating on insufficient sleep.
While researchers proved their hypothesis that sleep deprivation would increase pain sensitivity — as demonstrated by an amped-up response in the brain’s somatosensory cortex — what surprised them was ramped-down activity in the nucleus accumbens, a region of the brain’s reward circuitry that, among other functions, increases dopamine levels to relieve pain.
“Sleep loss not only amplifies the pain-sensing regions in the brain, but blocks the natural analgesia centers, too,” Walker said.
Another key brain region found to slow down in the sleep-deprived brain was the insula, which evaluates pain signals and places them in context to prepare the body to respond.
“This is a critical neural system that assesses and categorizes the pain signals and allows the body’s own natural painkillers to come to the rescue,” said Krause, lead author of the study and a doctoral student in Walker’s Center for Human Sleep Science lab at UC Berkeley.
To further test the sleep-pain connection in more common daily-life scenarios, researchers surveyed more than 230 adults of all ages nationwide via Amazon’s Mechanical Turk online marketplace.
Respondents were asked to report their nightly hours of sleep as well as their day-to-day pain levels over the course of a few days. The results showed that even minor shifts in their sleep and wake patterns were correlated with pain sensitivity changes.
“The results clearly show that even very subtle changes in nightly sleep — reductions that many of us think little of in terms of consequences — have a clear impact on your next-day pain burden,” Krause said. “The optimistic takeaway here is that sleep is a natural analgesic that can help manage and lower pain. Yet ironically, one environment where people are in the most pain is the worst place for sleep — the noisy hospital ward.”
Walker’s goal is to work with hospitals to create more sleep-friendly inpatient facilities.
“Our findings suggest that patient care would be markedly improved, and hospital beds cleared sooner, if uninterrupted sleep were embraced as an integral component of healthcare management,” he said.
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