Brains do a lot of work while we sleep—far from being a passive behavior, sleep is actually critical to brain health, and as a result, mental and cognitive health. A few new studies in recent weeks underline how important sleep is, and how detrimental lack of sleep can be. And not just chronic lack of sleep, but a single night of lost sleep.
While many people may have heard that sleep deprivation can affect things like metabolism and memory, research is also showing that it can strongly affect anxiety, Alzheimer’s risk, and even chronic health at the level of our genes.
An interesting study from the University of California at Berkeley looked at one night’s loss of sleep on anxiety and emotion regulation in 18 healthy young adults. After a night of total sleep deprivation, participants reported a 30% rise in anxiety levels, compared to how they’d felt the night before—people who were allowed a full night’s sleep had no such flood of anxiety.
And the difference was reflected in their brain scans: Those who were sleep deprived had more activity in their amygdalae, the brain center of fear and anxiety. And in response to watching an emotionally charged video clip, the sleep-deprived participants also had much less activity in their medial frontal cortices, which help govern emotional reactivity. This suggests that sleep may help us keep rein of our emotions. If you’ve ever felt like an emotional basket case after a night of poor sleep, this may be why.
“Deep sleep provides a nocturnal soothing balm, taking the sharp edges off our lives and lowering our anxiety,” said study author Matthew Walker in a statement. “It’s a form of nocturnal therapy that many of us shortchange in this modern era of insufficient sleep.”
Another study built upon the growing consensus that sleep is a big protector against dementia, clearing away the brain gunk that can accumulate and eventually lead to the amyloid-beta plaques associated with Alzheimer’s. But the new study, from Washington University School of Medicine, focused on the protein tau, which forms the “tangles” also seen in Alzheimer’s-affected brains.
The researchers studied both mice and humans, depriving them of sleep in several experiments. In one, mice, who are nocturnal, showed a doubling of tau levels when they were kept awake during their normal daytime slumber. And in humans, kept awake for one whole night, their tau levels rose by 50%. Finally, when the team injected mice with tau, those who were allowed to sleep normally had much less of it four weeks later than mice who were sleep-deprived—in these mice, it had spread notably, and to parts of the brain known to be affected in humans with Alzheimer’s.
"The interesting thing about this study is that it suggests that real-life factors such as sleep might affect how fast the disease spreads through the brain," said study author David Holtzman in a statement. "We've known that sleep problems and Alzheimer's are associated in part via a different Alzheimer's protein - amyloid beta - but this study shows that sleep disruption causes the damaging protein tau to increase rapidly and to spread over time."
He also suggests that sleep is a necessary part of brain maintenance.
"Getting a good night's sleep is something we should all try to do," Holtzman said. "Our brains need time to recover from the stresses of the day. We don't know yet whether getting adequate sleep as people age will protect against Alzheimer's disease. But it can't hurt, and this and other data suggest that it may even help delay and slow down the disease process if it has begun."
CHANGING OUR GENES
Finally, another study, from the University of Hong Kong, looked at the genes of young doctors who either worked during the day or worked the night shift. Doctors who had just one night of sleep loss had more breaks in their DNA and a reduction in DNA repair genes, compared to rested participants.
The authors suggest that these molecular changes may help explain why sleep deprivation is known to be linked to increased risk for cancer, as well as cardiovascular, neurodegenerative, and metabolic diseases.
"Although this work is very preliminary, it is clear from the results that even a single night of sleep deprivation can trigger events that may contribute to the development of chronic disease," said study author Siu-Wai Choi in a news release.
Again, what's interesting about all three studies is that sleep loss on a small scale can lead to significant changes. Most people might not lose an entire night of sleep so often, but losing even half of one regularly might also have an effect in the long-term. And it's pretty logical that chronic sleep loss could have lasting effects—research has definitely suggested this. At any rate, the new studies add to the growing evidence that sleep shouldn't be considered an indulgence, but a necessity.