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The Surprising Link Between Sleep and Pain Sensitivity

 The correlation between sleep deprivation and a heightened sensitivity to pain is not an apparent one, but it may exist. In a 2018 paper, researchers at the University of California, Berkeley established that our brains may turn off their “pain-protection” gear on days we don’t sleep enough.

Now let’s delve a little deeper into the findings of this paper and try to understand what makes us so irritable and grumpy when we sleep too little.
 

The Experiment
To examine the connection between pain and no sleep, the researchers conducted an experiment using functional magnetic-resonance imaging (FMRI), during which a number of participants’ brain activity was recorded as they were exposed to a growing heat on one of their legs.

Once the patient noted the heat becoming unbearable this point was established as the pain threshold and the experimenters stopped recording brain activity.

woman sleeping

Findings

1. How Did Participants React to Pain?
 
The findings surprised even the researchers themselves. Despite the small sample size (25 participants), the experimenters managed to establish that the threshold for thermal pain among the well-rested individuals was 111°F (44°C), whereas the sleep-deprived group could handle 4 degrees less.
 
2. What Brain Regions Could Account for The Different Pain Sensitivity? 
 
The region of the brain responsible for the perception of pain, the primary somatosensory cortex (highlighted in orange in the picture below), was significantly more responsive in the sleep-deprived individuals.
pain and sleep primary somatosensory cortex
The most interesting and surprising finding, however, was related to other parts of the brain, the striatum and the insula (schematically highlighted below in purple).
These regions are responsible for producing a hormone linked to pain tolerance, among other things, dopamine. The brains of the people who didn’t get enough sleep produced significantly less dopamine, which made them worse at tolerating painful stimuli than the control group.
Finally, the researchers conclude that the effect of sleep deprivation can last for several days, with the individuals who got less sleep continuing to be more sensitive to pain days after getting little sleep.
 
striatum and insula

3. What Conclusions Can We Make From This Study?

  • These findings opened our eyes to the problem of sleep deprivation-induced pain sensitivity. This is particularly important hospital patients, who can be experiencing more pain because of the noisy hospital rooms in which they have to stay.
  • The data can also be relevant to people suffering from painful chronic conditions, as a quality sleep could decrease their pain sensitivity.
  • Finally, it is yet to be discovered if the same pain and no sleep link can be extended to the psychological experiences we have when we don’t get enough sleep: irritability and nervousness.

What remains really clear, however, is that scientists found yet another reason for us to get a good night’s sleep every night. If you want to know more about the science and dangers of sleep deprivation, click on What Happens to Our Bodies When We Don’t Get Enough Sleep or The Link Between Sleep and Excellent Memory. If knowing about the importance of sleep is not enough for you and you’re looking for foolproof tips and techniques to get a better night’s sleep, read about The Breathing Exercises That Can Help Improve Your Sleep and Our Guided Sleep Meditation.

Good night!

H/T: newatlas.com

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