Want to know one of the most reliable ways to protect your brain from dementia (and many other ailments)? Matthew Walker, PhD, an author and professor of neuroscience and psychology at the University of California, Berkeley, wrote:
“Scientists have discovered a revolutionary new treatment that makes you live longer. It enhances your memory and makes you more creative. It makes you look more attractive. It keeps you slim and lowers food cravings. It protects you from cancer and dementia. It wards off colds and the flu. It lowers your risk of heart attacks and stroke, not to mention diabetes. You’ll even feel happier, less depressed, and less anxious. Are you interested?”
Well, are you? It’s not a pill, it’s not a procedure, and it’s not some wacky, unproven alternative medicine. What is this mystery treatment?
It’s sleep, and according to tons of robust data, it really does have the potential to do all the amazing things listed above—and is likely to be essential for anyone looking to avoid dementia.
Sleep and the brain
Many of us think of sleep as a period where the mind and body shut down. But according to the science, it’s quite the opposite—sleep is an active period where tons of important biological processes take place. One of the most vital is memory consolidation—the process by which the tremendous amount of experiences and information we receive every day are processed, stored, and converted from short-term to long-term memory.
Ever wonder why babies and toddlers need so much sleep (11-14 hours) while adults can get by on shorter periods (7-9 hours)? Research suggests it’s probably due to the fact that very young children are so busy assessing new inputs and acquiring new skills like language and sociability. All that information takes time to sort and process, so it requires a heavy dose of slumber.
But what happens when you don’t get enough sleep? Sure, you’ll feel groggy the next day, but the consequences can extend far beyond that. According to new research published in The Laryngoscope, obstructive sleep apnea (OSA)—a disorder that occurs when the throat muscles intermittently relax during sleep, blocking the airway—can wreak havoc on the brain. Investigators found that having OSA and neglecting treatment increased a person’s odds of being diagnosed with Alzheimer’s disease by more than twofold.
Sleep deprivation can lead to other types of dementia, too. A systematic review and meta-analysis of the association between sleep disorders and cognitive impairment in older adults found that insomnia was associated with a 53% higher risk for all-cause dementia. Another study conducted in more than 50,000 patients with insomnia in Taiwan found that they were at a 2.14-fold increased risk for dementia. This large insomnia cohort had a higher prevalence of diabetes, dyslipidemia, hypertension, coronary heart disease, chronic liver disease, and chronic kidney disease at baseline, too.
Sleep and waste disposal
What is it about sleep that keeps our brains in tip-top shape? Researchers think that when we sleep, cerebrospinal fluid—the fluid that flows in and around the hollow spaces of the brain and spinal cord and is responsible for cushioning the brain and transporting nutrients—flushes out toxic metabolic waste that accumulates while we’re awake. That waste includes β-amyloid, the sticky protein that is thought to be one of the primary drivers of Alzheimer’s disease.
It may seem obvious, but this cleansing process could be the reason why we sleep. That’s big news because scientists have never arrived at a consensus to explain sleep’s primary purpose.
“The discovery that sleep, but not wakefulness, allows removal of waste metabolites from the brain defines a new and interesting hypothesis for explaining the biological necessity of sleep,” wrote the authors of a recent study published in Current Opinion in Physiology. “Sleep is for clearing the brain from the potential neurotoxic waste products that accumulate during wakefulness,” a process that’s driven by cerebrospinal fluid transport.
Scientists have dubbed this brain waste removal pathway the glymphatic system, which appears to be much more active during sleep. Research spotlights a well-established relationship between sleep, glymphatic clearance of waste, and β-amyloid washout. But our understanding of this process is imperfect, for a number of reasons.
First, scientists haven’t pinpointed the mechanism that inhibits the flow of cerebrospinal fluid during wakefulness but promotes its entry during sleep. In other words, they generally know that the glymphatic system is most active during sleep, but not why or what triggers this activity.
It also remains a mystery why wakefulness seems incompatible with cerebrospinal fluid clearance. “If waste removal from the brain is necessary for its health and function, it would seem more intuitive that these clearance processes should work continuously during the wake period to avoid build-up of toxic waste,” study authors wrote.
In all, the glymphatic system has emerged as an exciting new pathway that not only could help answer the age-old question of why we sleep, but can help us move closer to a better explanation of why a lack of quality sleep is so closely associated with a neurodegenerative disease like dementia.
Sleep on it
There’s no shortage of research to illustrate the links between good sleep and good health. There’s just as much to show that poor sleep quality is linked to poor health, too—particularly when it comes to dementia.
Still, so much about sleep remains a mystery, including one of the most basic questions of all—“why?” Fortunately, scientists are busy plumbing the depths of this medical, scientific, and philosophical question, and emerging evidence is helping us get closer to a consensus.
Until then, keep in mind this advice from Dr. Walker: “Sleep is the single most effective thing we can do to reset our brain and body health each day—Mother Nature’s best effort yet at contra-death.”