Written by Dr. Jeffrey Durmer and Joe Burton.
We’re all familiar with sleep, and maybe all too familiar with how we feel when we don’t get enough of it. Healthy sleep, which for most people means at least 7 hours of minimally interrupted sleep per night, has been shown to provide a wide-ranging set of benefits, from maintaining a healthy appearance to optimizing metabolism to preserving mental ability and even ensuring the consistency of your personality. Insufficient sleep has been linked to poor long-term memory, impaired cognitive function and lack of creativity. While it’s possible to cut back on sleep, or even miss out for a night or two, a habit of regular unhealthy sleep can be devastating. The effects of poor sleep show up physically. It makes you look haggard and causes you to gain weight while dulling your capacity to pay attention and make good decisions. In fact, people who fail to prioritize sleep, or suffer from a chronic sleep disorder, are much more likely to suffer from, among other ailments, diabetes, cardiovascular disease and dementia.
Sleep does a number of things for your brain, including the consolidation of important new memories and the disposal of unnecessary experiences during deep REM sleep. Researchers have also long been aware that, during earlier stages of sleep, the brain replenishes its supply of neurotransmitters and hormones, stocking up for the next day. In fact, getting quality sleep helps you achieve many of the same benefits of mindfulness, such as focus, energy and improved mood. Until 2012, we had no idea that there existed an entire distinct and complex system, within the brain itself, that performed a daily task. A task as essential and as obvious as one we put ourselves through (or should put ourselves through) regularly: bathing.
By circulating a clear fluid known as lymph, the lymphatic system essentially washes the inside of the body, constantly removing and filtering out everything the body wants to get rid of. The presence of the lymphatic system throughout the body, and the fact that it doesn’t extend into the brain, created a sort of paradox. How does the central nervous system, which burns through energy much, much (10 to 15 times) faster than the rest of the body, remove all the waste it creates? Furthermore, how does it ensure a properly calibrated environment for the most sensitive biological process known to man: the reliable transmission of vast amounts of information between the 100 billion neurons in the human brain?
Turns out the answer was hiding under our noses, or more specifically, directly behind and slightly above our noses, the whole time. Cerebrospinal fluid (CSF), a mixture produced by specialized cells of the brain, has long been known to pass through the brain’s ventricles, or large open spaces, and then drain down the spinal cord and olfactory nerve in the nose on a one-way trip into the lymphatic system.
Why does that matter? In 2012, sleep researchers found that a network, now known as the glymphatic system, transports up to 10 times the volume of CSF during sleep than it does while you’re awake. While part of this increase is due to increased production of CSF, the spaces between brain cells also open up, expanding by over 50% to boost flow.
We’ve come to understand that the glymphatic system functions to remove waste from the brain, especially during sleep. The connection between sleep disorders, especially obstructive sleep apnea (OSA), and the development of general cognitive impairment and dementia in later life may well result from poor sleep limiting the activity of the glymphatic system. In fact, researchers have recently found significantly higher levels of the protein implicated in Alzheimer’s Disease in the brains of adult OSA patients. Treating obstructive sleep apnea can prevent and, to some degree, reverse the accumulation of this protein.
So, at the end of the day, a complex, and comprehensive, system exists to reach every neuron, transporting the supplies that the brain needs to function and removing the waste generated by a day full of thinking and learning. Your brain essentially washes itself every time you nod off!
You can enhance the cleansing activity of your glymphatic system by making sure you get healthy sleep. This means not only getting enough sleep, but getting healthy, uninterrupted sleep. One way to do this is to train your brain to become quieter. Mindfulness helps you focus on the present moment. In that space, your brain isn’t racing back and forth between regretting the past and worrying about the future. A simple body scan practice is very effective to help calm the chattering mind. Simply start from your feet and work your way up to your head by slowing focusing your attention on each part of your body and taking deep belly breaths. Often people don’t even make it all the way up because they are fast asleep.
In cancer patients with insomnia, mindfulness training produced significant differences in sleep quality. It took them 22 minutes less time to fall asleep, and their total sleep time increased by at least 30 minutes. Over time, that makes a huge difference in keeping your brain fresh. Additionally, long-term meditators show no apparent decrements in psychomotor vigilance task scores, even if sleep-deprived, when compared to the sleep-lacking control. This shows that consistently practicing mindfulness techniques aids cognitive function despite your ability to snooze well. Why? Mindfulness results in what scientists call the relaxation response — a physiological state of deep rest induced by practices like meditation and yoga. So even if you’re not getting enough sleep, you experience the kind of deep rest your body needs for processes like energy metabolism and immune function.
So, the next time you’re feeling groggy after missing out on sleep, remember that your dirty mind is basically wearing yesterday’s clothes and desperate for a shower and toothbrush. So get some rest, relax yourself and keep your brain fresh; you’ll prevent the accumulation of waste that, over time, can damage your grey matter while feeling and performing your best each day.
Dr. Jeffrey Durmer is a systems neuroscientist, neurologist and sleep medicine physician. He is an adjunct professor at Georgia State University Department of Health Professions and co-founder of FusionHealth. Prior to FusionHealth, he directed the Emory University Sleep Laboratory program. He is a three-term member of the Medical & Scientific Advisory Board for the Restless Legs Foundation and serves as the Sleep Performance Director for the Atlanta Falcons. Dr. Durmer is also an appointed Sleep Medicine advisor to the Federal Aviation Administration.