A new study finds that a good night’s sleep literally clears your head.
How often have you used the expression, “I just need to clear my head”? It’s an excuse to step away from your desk when you can’t focus on a project or to get out of the house for a long walk after a particularly stressful day. You come back feeling refreshed, though likely still with a head full of thoughts.
But a new study, published in the journal Cell, found that there may be a way to clear your head — literally — and it involves going to bed. The study, conducted in mice, found that deep sleep allows the body to get to work, flushing out waste from the brain. Come morning, after a night of deep, restorative sleep, you wake up not only re-energized but potentially cleared of toxic proteins, as well. Consider it brainwashing for the modern age.
"It's like turning on the dishwasher before you go to bed and waking up with a clean brain," senior author Maiken Nedergaard of the University of Rochester and University of Copenhagen, Denmark, said in a press release.
How Deep Sleep Clears Out Your Brain
Scientists have known for some time that the body has a waste-removal process for the brain and spinal cord, known as the glymphatic system. Specifically, it circulates fluid to clear out toxic proteins that can build up to form plaque, which research shows is linked to neurological disorders such as Alzheimer’s disease. However, this study may have unlocked the exact mechanism triggering this essential waste removal.
While studying mice experiencing deep sleep, the researchers zoomed in on the role of a molecule called norepinephrine, also known as noradrenaline. The molecule is best known for its role in the flight-or-fight response, but the researchers also discovered that norepinephrine plays an essential role in this overnight garbage pick-up process: It triggers blood vessel contractions, which create slow pulses that keep waste moving out of the brain and spinal cord.
It’s a “rhythmic flow” driven by a “harmony in the constriction and dilation of the arteries,” according to study co-author Natalie Haughland of the University of Copenhagen and the University of Oxford. The process ushers cerebrospinal fluid through the brain, removing waste products as it travels. If the glymphatic system were an orchestra, norepinephrine would be the conductor, she said.
This process occurs specifically during deep sleep, suggesting that a good night’s rest is as vital as ever to well-being — but there’s a catch.
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How to Get Deep-Cleaning Slumber
Not all deep sleep is created equal. The researchers discovered some nuances regarding restorative brainwashing. In a follow-up experiment, the researchers gave mice zolpidem (a common medication used to treat insomnia). While they found that the mice on the sleep aid fell asleep faster, their norepinephrine waves were 50 percent lower than that of mice sleeping naturally. Fluid transport into the brain — the part of the process that clears out the junk, so to speak — also dropped more than 30 percent.
More research is needed to determine why medication-induced sleep may not support the brain’s waste-removal process as much as “natural” deep sleep. It’s important to take these findings with a grain of salt, too, as further studies are needed to support the results in human participants.
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Still, the findings pave the way for deeper exploration — and potential discoveries — into how you can maximize sleep for your brain’s benefit. For now, practice good sleep hygiene to prime yourself for deep-cleaning slumber: Stick with a consistent bedtime and wake-up schedule, turn off electronics at least 30 minutes before bed, and keep a cool and quiet sleep environment.