Even a single night without sleep is enough: If our brain does not get a night’s rest, it ages prematurely. Its fine structure then shows changes that would otherwise only occur a year or two later, a study reveals. Fortunately, these signs of aging are reversible: If you catch up on sleep, the brain also “rejuvenates” itself. This underscores the importance of a night’s sleep in brain regeneration and flushing out waste.
Sleep is essential for us: Our brain needs the break to flush out waste , recalibrate synapses and store what we have learned. When we lack sleep, we become more irritable, antisocial, sensitive to pain, less concentrated, and prone to distorted memories. In children, a lack of sleep can even impair brain development in the long term.
Sleep deprivation for the sake of science
But how does short-term sleep deprivation affect the brain? Can you see the stress that the lack of rest causes? This has now been investigated by Congying Chu from Forschungszentrum Jülich and his colleagues. To do this, they first determined the biological age of the brains of 134 young, healthy test subjects using magnetic resonance imaging (MRI). This can be seen, among other things, in the volume and shape of different areas of the brain.
The actual test then began in the sleep laboratory of the German Aerospace Center in Cologne: Some of the test subjects were kept awake all night and stayed awake for more than 24 hours. A second group was only allowed to sleep for three hours at night. The third group suffered from chronic sleep deprivation: they only slept for five hours a day for five consecutive nights. All test persons were then examined again in the brain scanner.
Aged a year or two
The result: if we fail to sleep at night, this has measurable consequences for our brain. After just one sleepless night, the test subjects’ brain scans showed structural changes that would normally not be expected until a year or two later. In other words, in just one night, her brain’s biological age had increased by one to two years. “These changes were consistent across three independent experiments,” report Chu and his colleagues.
However, the experiment also showed that the brain suffers less if it is only deprived of part of the night’s sleep. In the two groups that were allowed to sleep at least part of the night, the premature aging of the brain did not occur. “Overall, the consistent results suggest that only total sleep loss changes brain morphology in young participants in an age-like direction,” says Elmenhorst.
Catching up on sleep reverses aging
Fortunately, these signs of aging are not permanent: After the test subjects had slept normally again for a night, their brain condition also normalized, as the brain scans showed. “Brain features no longer differed from baseline after a night of restful sleep. The brain ‘rejuvenated’, so to speak,” explains Chu’s colleague David Elmenhorst.
These findings are also interesting because they provide more insight into the connection between age, sleep and the brain. Older people usually sleep less well than they did when they were young, and such sleep disorders are particularly pronounced in people with dementia. Conversely, a sleep disorder can accelerate the aging process of the brain and promote the progression of dementia.
The now uncovered reversible changes in short-term sleep deprivation could now help to learn more about the biological roots of these relationships. (Journal of Neuroscience, 2023; doi:10.1523/JNEUROSCI.0790-22.2023 )