The sleep debt collectors will come. They want you to know that there is no such thing as forgiveness, only a shifting expectation of how and when you are going to repay them in kind. You think about them when you lie in bed at night. How much will they ask? Are you solvent? You fall asleep, and an hour later you wake up in a cold sweat. You fall asleep, and then wake up, losing consciousness until the morning.
As almost everyone knows, a couple of nights of bad sleep is often followed by lethargy, difficulty concentrating, irritability, mood swings, and drowsiness. For years, it was thought that these effects, accompanied by cognitive impairments such as poor performance on short-term memory tests, could be primarily due to a chemical called adenosine, a neurotransmitter that suppresses electrical impulses in the brain. Bursts of adenosine have been consistently observed in sleep-deprived rats and humans.
However, adenosine levels can be quickly restored after a few nights of good sleep. This has led to a scientific consensus that a lack of sleep can be forgiven with a couple of quality naps, as reflected in casual statements like “I’ll get enough sleep” or “I’ll be awake tomorrow.”
But a review article recently published in the journal Trends in Neurosciences argues that the popular notion of sleep as something that can be accumulated and repaid is nonsense. The review, which analyzes the last couple of decades of research on the long-term neural effects of sleep deprivation in both animals and humans, points to a growing body of evidence that sleep deprivation is likely to lead to long-term brain damage and an increased risk of neurodegenerative diseases. disorders like Alzheimer’s disease.
“This is very, very important in setting the stage for what needs to be done in sleep health and the science of sleep,” said Mary Ellen Wells, a sleep researcher at the University of North Carolina who was not involved in the review.
“ Back to recommendation stories
It has long been known that intense periods of sleep deprivation are unhealthy. Forced insomnia has been used as punishment and torture for centuries. In the first experimental study of sleep deprivation, published in 1894 by the Russian scientist Maria Manaseina, puppies were kept awake by constant stimulation; they died within five days. Subsequently, examining their bodies, Manasseina noticed that “the brain was the seat of propensity for the most serious and most irreparable changes.” Blood vessels bled, fatty membranes degenerated. “A complete lack of sleep is more detrimental to animals than a complete lack of food,” Manaseina concluded.
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But there are many ways to not get enough sleep. You can go completely without sleep for long periods of time, which scientists call acute sleep deprivation. (In 1963, a high school student managed to stay awake for 264 hours.) You may experience chronic sleep deprivation—chronic sleep deprivation. You can lie awake chasing your thoughts or relax by watching TV all night. Studies such as Manaseina’s were considered extreme to the point of being irrelevant to humans.
Research continued, but “that’s where they were kind of classified,” said Fabian Fernandez, a neuroscientist at the University of Arizona who was not involved in the new review. “When are you going to keep an animal or a person awake until they are dead?”
However, over the past couple of decades, animal sleep deprivation research has become more subtle, precise, and possibly applicable to humans, according to Dr. Sigrid Vizey, a neuroscientist at the University of Pennsylvania, and Zachary Zamora, a researcher. in Vesey’s lab, authors of a new review.
Looking at past studies of sleep-deprived mice, many of which were conducted by Vesey, the researchers found that when the animals were awake just a couple of hours more than usual every day, two key parts of the brain were noticeably affected: the coeruleus locus, which is responsible for feelings of alertness and arousal, and the hippocampus, which plays an important role in memory formation and learning. These areas, which in humans play a central role in maintaining conscious experience, slow down the production of antioxidants in animals, which protect neurons from unstable molecules that are constantly produced, like exhaust gases, by functioning cells. When antioxidant levels are low, these molecules can build up and attack the brain from within, destroying proteins, fats, and DNA.
“Waking the brain even under normal circumstances carries penalties,” Fernandez said. “But when you stay awake for too long, the system overloads. At some point, you can’t beat a dead horse. If you ask your cells to stay active 30% more each day, the cells die. .”
In the brains of mice, sleep deprivation resulted in cell death after several days of sleep restriction — a much lower threshold for brain damage than previously thought. It also caused inflammation in the prefrontal cortex and increased levels of tau and amyloid proteins, which have been linked to neurodegenerative diseases such as Alzheimer’s and Parkinson’s, in the locus coeruleus and hippocampus.
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After a full year of regular sleep, the previously sleep-deprived mice were still suffering from nervous system damage and brain inflammation. For Veezy and Zamora, this meant that the effects were long lasting and possibly permanent.
However, many scientists said the new study should not cause panic. “It’s possible that sleep deprivation damages the brains of rats and mice, but that doesn’t mean you should be stressed out about not getting enough sleep,” said Jerome Siegel, a sleep researcher at the University of California, Los Angeles. contribute to the review.
Siegel noted that damage to the nervous system appears gradually, and that the extent to which sleep deprivation affects the human brain is still largely unknown. He also expressed concern that over-anxiety about the long-term effects of sleep deprivation could lead people to try to sleep more unnecessarily and with the help of medication.
“The simplest message is sleep deprivation is bad, but that doesn’t mean sleep is monotonously good,” he said.
There is currently no ethical way to measure the extent and type of sleep deprivation-induced cell damage in the locus coeruleus and hippocampus of a living person. Instead, longitudinal studies published over the past 15 years have relied on behavioral changes and self-reported sleep data to link chronic poor sleep to dementia, depression, metabolic problems, cardiovascular disease, poor immune response, and more. low average scores. These experiments can be difficult to confirm, but taken together with the results of animal studies, they hint that there is some long-term link between lack of sleep and physical and cognitive impairment.
“Sleep loss can damage the brain, and if it happens in mice, and it has been shown to happen in other species, then it probably happens in humans as well,” Vesey said. “The question always arises: how much lack of sleep can lead to injury? But looking at all that literature together, about one week of chronic sleep deprivation, it really does suggest that you’ve damaged your brain to some degree.”
If a link can be made between mice and humans, it could change our understanding of sleep, which is usually associated with drowsiness rather than damage to the nervous system. There is already a well-known gap between how people perceive their cognitive abilities after sleep deprivation and how they actually perform on tests of memory and reaction time. People can feel good when their brains are in turmoil, and they can feel exhausted when their brains are fine. “The perception and reality of your dream can be very, very different,” Wells said.
This gap, in turn, “really prevents us from asking the right questions,” Vesey added. She hopes that people and scientists will come to a better understanding of sleep. And then, knowing that we, no doubt, will still get into sleep debt.