Sleep is one of the body's most important restorative processes, with what's known as the glymphatic system using your snooze time to flush waste out of your noodle and keep it healthy. But now, scientists have discovered that a lack of sleep can hurt you way beyond not taking out your bio-trash. Skimping on your sleep literally can cause your brain to devour itself, according to research published in The Journal of Neuroscience.
Understanding your brain's housecleaning system
Your brain has two types of support cells--microglia and astrocytes--that help keep your brain in tip-top shape. Through a process called phagocytosis, microglial cells clear out other cells that are worn out or old. The astrocytes prune away synapses, or links between brain cells, that aren't necessary. These cells are cleaning away even when you're awake.
How sleep loss affects the cleaning process
Led by Michele Bellesi of the Marche Polytechnic University in Italy, researchers split mice into four groups to study their brains under varying levels of sleep deprivation. One group was allowed to be well-rested, getting 6 to 8 hours of slumber. The second group was woken up from time to time (spontaneously awake). The third group was kept awake for an extra 8 hours (sleep deprived). The last group was kept awake for five days straight (chronically sleep deprived).
The researchers compared astrocytic activity in all four groups and found that the amount of astrocytic activity seen in synapses increased as sleep loss went up. In the sleep-deprived and chronically-sleep deprived mice, the astrocytes moved into astrocytic phagocytosis, eating away at synapses. Fortunately, the synapses targeted tended to be larger, older ones, which the researchers compared to "old pieces of furniture" and which are more likely to need attention and cleaning anyway.
But then the researchers looked at the microglial activity. Microglial phagocytosis ramped up, too, but only in the chronically sleep deprived mice. That worries the research team because previous research already has confirmed that sustained microglial activity is observed in a range of brain disorders, including Alzheimer's and other neurodegenerative diseases.
You need your microglial and astrocytes to work for you and clean house in the brain. But this study suggests that failure to get enough sleep can send these cells into overdrive. That might increase your risk of certain types of dementia. The researchers plan to continue their work to confirm that the results seen in mice also happen in people, and whether the negative effects of too much phagocytosis are reversible. But until those results are in, the simple fix is to play it safe and stop burning so much midnight oil. No project is worth your brain.