• Robb G. Best

Accessing Your Body's Natural Painkillers

Welcome back to our Sleep Series, a string of blog posts about the role of sleep in our lives, including the benefits of achieving enough slumber and tips to help make it happen. As life grows increasingly stressful and complicated, it becomes more and more important to perform the necessary steps to take care of yourself, sleep being key among them.

If you have an injury or a chronic pain issue, relaxing enough to get seven to nine hours of nightly sleep can be tough. A 2015 poll from the National Sleep Foundation found that two out of three people suffering from chronic pain experience regular sleep disturbances. But at the same time, it’s vital; sleep plays a key role in managing pain, in a variety of ways.

Scientists at the University of California, Berkeley, recently completed an experiment which demonstrates just that. Senior study author Professor Matthew Walker and PhD student Adam Krause applied safe but uncomfortable levels of heat to the legs of 25 healthy young volunteers after a night of sleep and scanned their brains. They then repeated the process after a night during which the volunteers had experienced a sleepless night.

While everyone’s pain threshold is a little different, Walker and Krause started by figuring out the baseline level of discomfort for each volunteer, the point at which the temperature began to read as pain. For most volunteers on a good night of sleep, this was around 111 degrees Fahrenheit (about 44 degrees Celsius).

However, after a restless, wakeful night, the tipping point itself changed for the vast majority of the volunteers: on average, the temperature where discomfort began slipped down to 107 degrees Fahrenheit. Lack of sleep made the subjects more sensitive to pain.

“Across the group, they were feeling discomfort at lower temperatures, which shows that their own sensitivity to pain had increased after inadequate sleep,” said Krause. “The injury is the same, but the difference is how the brain assesses the pain without sufficient sleep.”

The brain scans showed an increase of activity at the somatosensory cortex, which made sense for the increased pain sensitivity. What surprised Walker and Krause, however, was a drop of activity in another brain region, the nucleus accumbens. This area is involved with the brain’s reward circuitry, including the release of reward chemical dopamine to soften pain. In other words, a sleepless night didn’t just make people more sensitive to discomfort, it also dulled the brain’s natural ability to soothe.

Also hit by a slowdown in the sleep-deprived brain was the insula, in charge of evaluating pain signals and placing them in context so that the body can respond. This mutes the body’s ability to correctly deploy its own natural painkillers.

The researchers also surveyed over 230 people of all ages concerning their nightly hours of sleep and their daily pain levels. Even minor fluctuations in sleep showed a direct relationship with increased pain sensitivity.

“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,” said Krause.

“The optimistic takeaway here is that sleep is a natural analgesic that can help manage and lower pain,” said Walker. “Yet ironically, one environment where people are in the most pain is the worst place for sleep — the noisy hospital ward.” Walker hopes to work with hospitals to create environments more conducive to getting a good night’s sleep.

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