Have you been sleeping well lately? We all know that getting enough sleep is an important part of living a healthy and engaged life. Of course, getting a good night’s sleep keeps you sharp during the day, and recent science has also shown how important it is in learning and memory. Sleep is not only good for helping you pay attention in class or remembering what you did yesterday though, it also helps keep your brain neat and tidy after a hard days work. Recent research has shown that sleep triggers the brain to clear out the toxins that build up while you’re awake.
In other parts of your body, waste management is the responsibility of a network of vessels known as the lymphatic system. This system picks up and flushes out toxic molecules and other waste products that build up in your body as you use energy. Strangely though, the brain does not contain any of these vessels. This has perplexed scientists for years, especially because the brain uses more energy than any other organ in the body. How could the brain clear out waste if it does not have access to lymphatic vessels?
It wasn’t until recently that a group of scientists began understanding the brain’s strategy for flushing out toxins. Researchers at the University of Copenhagen and the University of Rochester used an injectable dye and a specialized type of microscope to trace how fluid moves through the brain of a living mouse. They found that cerebrospinal fluid (CSF), the clear fluid in which the brain sits, enters the brain in the small spaces that surround blood-bringing arteries. This space is bound by a special type of brain cell called astroglia. These cells completely ensheath the blood vessels in the brain and have proteins, known as aquaporins, that allow CSF to move through brain tissue. As the fluid flows, it picks up toxic misfolded proteins and other metabolic waste that accumulate throughout the day. Finally, the fluid takes these toxins and flushes them out of the brain tissue and into outgoing blood vessels. Because these “glial” cells play such an important role, scientists have called this process the Glymphatic System (with the “G” standing for glial) (1).
What’s even more interesting though, is that this neural plumbing system isn’t always turned on. These same researchers performed a follow-up study published in Science and showed that the Glymphatic System “opens up” during sleep. They showed that while the mice were awake, the tracing dye barely flowed through the brain at all. However, when the mice were asleep or under anaesthesia, the dye moved rapidly through the brain tissue, suggesting that sleep allowed the flow of CSF through the brain to increase. The researchers even tested this directly by putting electrodes in the brain to measure the space between brain cells (3) while the mice were awake or asleep. They found that sleep caused the space to increase by 60%, allowing for increased volume and faster flow of CSF. The authors suggest that 40-80% of toxins are removed from brain tissue through this sleep-mediated toxin cleaning process.
Removing these toxins from the brain is critical. Many previous studies have shown that misfolded proteins can pile up in this space. Accumulation of some of these proteins is thought to lead to the development of neurodegeneration (2). The importance of sleep in clearing out these toxins is supported by studies that link lack of sleep with neurodegenerative diseases like Alzheimer’s (4). One study from the University of California San Francisco showed that people who suffered from disordered sleeping due to problems with breathing were significantly more likely to develop mild cognitive impairment or dementia than people with healthy sleep (5)
Researchers at the Washington University School of Medicine in St. Louis went a step further by measuring the concentration of amyloid-beta, a protein associated with Alzheimer’s Disease, in the CSF of sleep-deprived people. The researchers tested 8 healthy people between the ages of 30-60 who did not suffer from any sleep disorders. The participants were organized into three conditions. The participants in the first condition were allowed to have a normal night of sleep, while those in the second condition were sleep-deprived. The third condition consisted of participants having a night of drug-induced sleep. For each condition, CSF samples were taken every two hours to keep track of any changes in amyloid-beta concentration. The researchers found that the concentration of amyloid-beta was 25-50% higher in participants who were in the sleep deprivation group. They also did not see any differences in amyloid-beta between the participants who had a normal night of sleep versus those who had a drug-induced night of sleep (6). These results suggest that chronic sleep deprivation would likely result in consistently high levels of amyloid-beta, as lack of sleep prevents the cleaning crew from coming in at night to clear it out. This could increase the risk of forming clumps of amyloid-beta (known as plaques), which are a hallmark of Alzheimer’s disease.
Getting enough sleep is as important to your health as exercising and eating well. It’s important not only for maintaining high cognitive function day-to-day but also for flushing out toxins that build up over a lifetime of thinking. So tonight, consider going to bed a bit earlier than usual, your Glymphatic System will be happy to get started.
- Iliff et al. (2012). A paravascular pathway facilitates CSF flow through the brain parenchyma and the clearance of interstitial solutes, including amyloid β. Science Translational medicine. doi: 10.1126/scitranslmed.3003748.
- Frost & Diamond (2010). Prion-like mechanisms in neurodegenerative diseases. Nature Reviews Neuroscience. doi: 10.1038/nrn2786.
- Xie et al. (2013). Sleep drives metabolite clearance from the adult brain. Science. doi: 10.1126/science.1241224.
- Yaffe et al. (2011). Sleep-disordered breathing, hypoxia, and risk of mild cognitive impairment and dementia in older women. Journal of the American Medical Association. doi: 10.1001/jama.2011.1115.
- Tranah et al. (2011). Circadian activity rhythms and risk of incident dementia and mild cognitive impairment in older women. Annals of Neurology. doi: 10.1002/ana.22468.
- Lucey et al. (2018). Effect of sleep on overnight CSF amyloid-β kinetics. Annals of Neurology, doi: 10.1002/ana.2511.
Rebecca Williams grew up in England, where she studied medicine at Cambridge University, including obtaining degrees in Bachelor of Surgery and Experimental Psychology.
Having worked in General Practice and Community Paediatrics in London, she then relocated to Johannesburg, South Africa.
Rebecca has a passion for holistic community healthcare. She has helped to develop a community health training programme which she has taught in Mozambique, Zambia, Uganda and Nepal.
She is currently studying for a master’s degree in Disaster Management, her research interest being mechanisms for developing psychological resilience in first responders.
Married with four children, her spare time is spent enjoying tennis and water sports.
Before working with Brain Reference, Rebecca had previously published research in the field of complementary and alternative medicine which can be viewed on researchgate:
- Study of the Therapeutic Effects of Proximal Intercessory Prayer (STEPP) on Auditory and Visual Impairments in Rural Mozambique
- www.researchgate.net Rebecca Williams profile
Aside from her dedication to community health management and ongoing education to help first responders in medical crisis, Rebecca also enjoys playing the clarinet in the Rand Symphony Orchestra.
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