During sleep cerebrospinal fluid flushes through the brain to wash away harmful proteins and toxins that build up during the day.
The exact reason why we sleep has long been one of the greatest mysteries of modern science. Many different theories have been proposed, but the fact is that no one is entirely sure why we spend roughly a third of our lives asleep.
We’ve known for some time that sleep is important for the restoration and strengthening specific functions in the brain linked to memory, regulating emotions, decision-making, and even creativity. But scientists are now discovering the processes through which sleep also cleans the brain like a plumbing system, in the process changing its cellular structure.
A study suggests that sleep helps restore the brain by flushing out toxins that build up during waking hours. The results point to a potential new role for sleep in health and disease. Dr. Maiken Nedergaard and her colleagues at the University of Rochester Medical Center recently discovered a system that drains waste products from the brain. Cerebrospinal fluid, a clear liquid surrounding the brain and spinal cord, moves through the brain along a series of channels that surround blood vessels. The system is managed by the brain’s glial cells, and so the researchers called it the glymphatic system.
The study raises the possibility that certain neurological disorders might be prevented or treated by manipulating the glymphatic system. “These findings have significant implications for treating ‘dirty brain’ diseases like Alzheimer’s,” Nedergaard says. “Understanding precisely how and when the brain activates the glymphatic system and clears waste is a critical first step in efforts to potentially modulate this system and make it work more efficiently.”
Basically, the cerebrospinal fluid sits around your brain and spinal cord and “every six to eight hour period, filters through the brain while you’re asleep,” Tara Swart, a senior lecturer at MIT specializing in sleep and the brain, said. “The whole process takes six to eight hours.”
“If this waste-disposal system is under the body’s intrinsic regulation, there could be a pharmacological way to turn the system up or down,” says Jeffrey Iliff at the University of Rochester Medical Center in New York, one of the study authors. “Perhaps this is a biological pathway that could be co-opted to rescue us from or improve neurological degeneration.”
The reason for the increased flow, the researchers suggest, could be that the glial cells shrink away from the blood vessels during sleep. This leads to a 60 per cent increase in volume between the outer glymphatic pipes and the inner blood vessels, letting more fluid pass through the brain. “This work emphasises how we might want to think about ways our normal habits, even sleep, predispose us to certain problems later in life,” he says.
Much more important than your average cleaning system, this process clears neurotoxins out of your brain, specifically one called beta-amyloid, which has been found in clumps in the brains of people with Alzheimer’s disease. When this system can’t function properly due to lack of sleep, harmful remnants, like beta-amyloid, are allowed to build up.
A 2015 study published in the journal Nature Neuroscience was one of the first to look at humans rather than animal subjects when examining how sleep can fight against memory impairment. As it turns out, beta-amyloid also works to prevent your body from getting the rest it needs, creating something of a vicious cycle for the chronically sleep-deprived. As Matthew Walker, one of the neuroscientists who authored the study, wrote: “The more beta-amyloid you have in certain parts of your brain, the less deep sleep you get and, consequently, the worse your memory. Additionally, the less deep sleep you have, the less effective you are at clearing out this bad protein.”
As a result of these findings, Swart said she’s been “even more careful about [her] sleep.” In fact, as part of Swart’s Neuroscience For Leadership class at MIT in April, she discussed the serious health consequences that come from neglecting shut-eye. Swart, who is also a leadership coach, has been instructing executives to sleep for years. She promotes techniques related to diet and exercise, and warns that sleeping next to your smartphone—the one that emits 3G and 4G signals all night—affects your brain patterns, restructuring your brain cells and likely preventing you from allowing your brain to clean out waste material properly.
Research published in 2007 has already found that the electrical radiation emitted from smart devices is picked up by electrodes inside our brains. Scientists are still trying to figure out just how much damage the electromagnetic signals emitted from WiFi equipment can actually do to the human brain. But by potentially preventing our brains from flushing beta-amyloid—just by being in close proximity—it’s clear these devices already have the potential for serious damage.
Ultimately, how much sleep you think you need has little to do with it. CEOs have long bragged of their ability to only sleep four to five hours a night, but Swart says this bravado misses the point: even if you don’t feel sleepy, your brain needs those six to eight hours to cleanse itself every day. (Then there’s the multitude of research that shows a rested and resilient brain performs better, is better able to regulate emotions and think creatively.)
If having enough time to sleep is a challenge for you, Swart suggests naps. Taking even 20 minutes of shut-eye is comparable to “literally plugging in your phone battery,” says Swart, similar to a power boost. For 30 minutes of downtime, your brain will experience improved learning and memory. For those fortunate enough to snag 60 to 90 minutes of rest, “new connections can form which can unleash creativity in the brain.” “And that’s why Google has nap pods,” Swart explained.