Sleep is essential. They have repeated it to us ad nauseam and we know it from our own experience. When we don’t sleep well, the next day we are sleepy, irritable, and our productivity plummets. However, we are not always fully aware of the importance of those 8 hours of sleep, especially for our brain.
Lack of sleep causes alterations in brain function that are not usually detected immediately but can have disastrous long-term consequences. In fact, it is known that during sleep our brain is freed from waste and toxic substances that are produced during daytime activity. If we don’t get enough sleep, our brain will still “cleanse” itself while we are awake, but it will go overboard, which can become a problem.
The cells that “clean” the brain
Researchers at the Università Politecnica delle Marche have discovered that little sleep can cause glial cells to destroy healthy neuronal connections; that is, the synapses, which are what allow the transmission of information. In the long term, this process could lead to the development of neurodegenerative disorders such as dementia.
Glial cells are very important for the proper functioning of the brain since they are responsible for maintaining the balance of neurons, being 5 to 10 times more abundant than these. Neuroglia, as they are also known, not only perform support, protection and nutrition functions, but also facilitate the connection between neurons and help eliminate waste from brain activity.
In addition, they are responsible for the repair and regeneration of injuries to the nervous system. As soon as damage occurs, these cells transform into reactive glia to solve the problem and normalize levels of nutrients and neurotransmitters. Astrocytes, in particular, eliminate unnecessary synapses to promote the regeneration of damaged tissues.
Basically, they are capable of phagocytosing; That is, “eating” waste products and damaged cells to protect neurons from pathogens and other threats. They are also responsible for “clearing” the path to establish more efficient neural connections, being in charge of deleting irrelevant information to “make space” that allows us to learn new things and create other memories.
The less you sleep, the more connections will be erased from your brain
Neuroscientists at the Università Politecnica delle Marche analyzed the effects of sleep deprivation in mice by comparing the brains of those who were able to sleep freely, those who were kept awake for the 8 hours they were supposed to sleep, and another group that was deprived of sleep for 5 days to simulate the effects of chronic sleep deprivation.
The research focused on studying the differences in the activity of glial cells depending on the degree of sleep deprivation, paying particular attention to the behavior of astrocytes since these have been related to brain degeneration.
Thus it was discovered an increase in the activity of glial cells. Phagocytosis increased proportionally to sleep deficit: astrocytes were active in 6% of the synapses in the sleep condition, 7% in the mild deprivation condition, and 13.5% in the chronic sleep-deprived group. That is, the less sleep, the greater the activity of astrocytes.
These results, which could be extrapolated to people as they fit with previous research, suggest that the activity of some glial cells is intensified under conditions of sleep deprivation, causing astrocytes to not only eliminate irrelevant connections and waste products, but also healthy synapses.
This process could worsen neuronal transmission, causing long-term damage to the brain. In fact, the intense activity of astrocytes for long periods of time could even end up causing secondary neuronal death, so it is not surprising that it could end up causing or accelerating neurodegenerative processes such as Alzheimer’s.
The good news? The researchers detected that this does not occur when sleep deprivation is punctual; that is, when we spend a single night without sleep, but it is a process that is triggered by chronic sleep deprivation.
Navarrete, M. et. Al. (2019) Astrocytic p38α MAPK drives NMDA receptor-dependent long-term depression and modulates long-term memory. Nature Communications; 10(1):2968.
Bellesi, M. et. Al. (2017) Sleep loss promotes astrocytic phagocytosis and microglial activation in mouse cerebral cortex. Journal of Neuroscience; 37(21): 5263-5273.