Veterans of insomnia know in their bones what science says about sleep deprivation and pain: that both are traveling together, one is feeding the other.
For example, people who experience chronic pain often lose the ability to sleep well and quickly indicate back pain, sciatica or arthritis as a reason. The loss of sleep, in turn, can make the back feel worse, and sleeping the next night is even more difficult.
The reason why sleep deprivation strengthens pain is not fully resolved, but has to do with the way the body responds to injuries, such as bent or ankle wounds. First, it hurts, because the nerve sends an explosion to the spinal cord and brain. There, the regional network of neurons becomes inflamed in reaction to injury and works to control, or respond to, sensations.
Think of experience as a kind of physiological dialogue between basic units that take a hit and a command control center that tries to hold back damage. In a new study, the team of neuroscientists has clarified the nature of the top-down part of the exchange, and how it is influenced by sleep.
In sleep laboratory experiments, the researchers found that one night of sleep deprivation reduced a person's pain threshold by more than 15 percent and left a clear signature in brain pain control centers.
In a separate trial, the team determined that small deviations in the average amount of sleep from one day to the next predicted the general level of pain felt the next day.
"What's interesting about these findings is that they will stimulate and justify, do more research to complete this system," said Michael J. Twery, director of sleep disorders at National Heart, Lung and Blood Institute, which I was not involved in in the new study . "Once we understand how sleep deprivation changes the way these pathways work, we must be able to handle pain more effectively, all kinds of pain."
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Other researchers caution that this study is small and requires more replication. But, they said, when chronic pain conditions and drug addiction increase, the new work warns that the body's ability to control pain can be increased without a doctor's prescription.
The study team, led by Adam J. Krause and Matthew P. Walker from the University of California at Berkeley, had 25 adults who entered the laboratory twice to measure their heat pain threshold. Two measurements of each subject were taken, one in the morning after a full night's sleep, and one in the morning after staying up all night. Two visits occurred at least one week apart and included measurements on the brain imaging machine.
Subjects assess the sensation of pain from small hot pads that stick to their skin, near the ankles. By gradually adjusting the temperature up and down, the researchers identified the level of pain each person rated 10, or "irresistible," on a scale of 1 to 10.
Attractive twilight increases everyone's sensitivity to heat the next morning, by 15 to 30 percent on the pain scale. Previous research has produced similar results, for various painful sensations.
But brain images add a new dimension: for each participant, activity jumps in the area of pain perception and sinks in areas believed to help control or reduce pain. The largest peak is in the somatosensory cortex, a neural network that flows through the top of the brain like a headphone band.
This is the seat of the so-called homunculus, a distorted map of the neuronal "small human" body; it seems that the perception of pain becomes conscious. The lowest level of activity occurs in deeper brain regions, such as the thalamus and nucleus accumbens.
Intentional sleep deprivation is rare in the natural world (robins and squirrels don't usually stay up late to watch "Saturday Night Live"), so there is a possibility that there is no developing backup system to help restore or restore Adjust the brain pain control system, Dr. Walker.
In a separate trial, the research team recruited 60 online adults who reported daily pain. The participants assessed their sleep and pain for two days, noted sleep the night before in the morning and their level of pain at night.
For each individual, poor sleep quality estimates a higher score on the daily pain scale. Sleep duration is not a critical factor, according to research; the important thing is a deep sleep disorder, a period largely without dreams of deep sleep.
The implications of this new work are very broad, perhaps starting with hospitals, where the noise level is high and disturbances often occur. Providing earplugs and sleep masks, as airlines do, will be an inexpensive way to speed up recovery and shorten hospital stays, the study authors suggest.
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