It turns out that sleep serves a purpose other than just replenishing your energy. When you sleep your brain actually changes its state to clear away toxic byproducts that accumulate throughout the day.
A team led by Michele Bellesi from the Marche Polytechnic University in Italy examined the brain’s response to bad sleep habits and determined that there was a unique similarity between sleep-deprived and rested mice brains.
The researchers determined that getting persistently poor sleep leads to the brain clearing a large amount of neurons and synaptic connections that may not be reversible.
All cells in your body, including in the brain, are constantly refreshed by two different types of glial cells that are considered the glue that holds your nervous system together. Microglial cells clear your old and worn-out cells via phagocytosis – a process that means “to devour” in Greek.
The process occurs during sleep to clear away the damage that you accumulate during the day, but now we know that the same process happens when we’re chronically sleep-deprived. This might sound like a good thing, but it turns out that the sleep-deprived brain doesn’t know how to stop the process and ends up clearing out healthy cells as well.
How the study was conducted
Researchers divided the mice into three different groups:
- The first group slept for 6 to 8 hours (well-rested)
- The next group was periodically woken up from sleep (spontaneously awake)
- A third group was kept awake for an extra 8 hours (sleep-deprived)
- The final group was kept awake for five days straight (chronically sleep-deprived).
The researchers compared the activity of astroytes across the four groups and made some interesting findings. They found it in 5.7% of the synapses in well-rested brains and 7.3 in the spontaneously awoken group.
The sleep-deprived and chronically sleep-deprived groups showed something unexpected, however. The astrocytes increased their activity and were actually eating parts of the synapses. The sleep-deprived brains had active astrocytes in 8.4 % of the synapses while the chronically sleep-deprived group showed activity in 13.5% of the synapses.
That’s a problem, because unbridled microglial activity has been proven to be linked to diseases like Alzheimer’s and other types of neurodegenerative diseases.
“We find that astrocytic phagocytosis, mainly of presynaptic elements in large synapses, occurs after both acute and chronic sleep loss, but not after spontaneous wake, suggesting that it may promote the housekeeping and recycling of worn components of heavily used, strong synapses,” researchers stated in the report.
“By contrast, only chronic sleep loss activates microglia cells and promotes their phagocytic activity … suggesting that extended sleep disruption may prime microglia and perhaps predispose the brain to other forms of insult.”
The study hasn’t been conducted on humans yet, but the fact that Alzheimer’s has increased by 50 percent since 1999 means that this is definitely an important area to study.