The rhythmic waves of blood and cerebrospinal fluid (CSF) that occur when we are sleeping, appear to function much like a washing machine’s rinse cycle, which may help to clear the brain of toxic waste on a regular basis.
Every 20 seconds, a wave of fresh cerebrospinal fluid rolls into the sleeping brain. These slow, rhythmic blasts, described for the first time in the Nov. 1 Science, may help explain why sleep is so important for brain health.
Studies on animals have shown that the fluid, called CSF, can wash harmful proteins, including those implicated in Alzheimer’s disease, out of the brain. The new results give heft to the idea that a similar power wash happens in sleeping people.
The findings, published recently in the journal Science, are the first to suggest that the brain’s well-known ebb and flow of blood and electrical activity during sleep may also trigger cleansing waves of blood and CSF. While the experiments were conducted in healthy adults, further study of this phenomenon may help explain why poor sleep or loss of sleep has previously been associated with the spread of toxic proteins and worsening memory loss in people with Alzheimer’s disease.
From Science News via YouTube »
During non-REM sleep, oxygen-rich blood (colored red) flows out of the brain just before a wave of cerebrospinal fluid (blue) rolls in, entering from a lower part called the fourth ventricle. That cerebrospinal fluid may help clean harmful proteins out of the brain.
A third of people in the UK get less than the recommended 7-9 hours a night, according to the National Sleep Foundation. But ostrich pillows, nap pods, wearable devices and sleep robots can all supposedly help. The FT’s Daniel Garrahan tests out some of the latest sleep solutions.
How well we sleep impacts how we think and feel, as well as our alertness, memory, and concentration. “Sleep quality and quantity are directly related to the health of the brain,” says Beth A. Malow, MD, MS, FAAN, professor of neurology and director of the sleep disorders division at Vanderbilt University Medical Center in Nashville. Several studies have demonstrated an association between sleep disturbances such as insomnia, fragmented sleep, sleep apnea, and even excessive napping and an increased risk of cognitive decline over time, says Brendan P. Lucey, MD, assistant professor of neurology and director of the sleep medicine section at Washington University School of Medicine in St. Louis.
In 2009, a series of studies on mice conducted at Washington University were among the first to suggest that chronically sleep-deprived subjects develop higher levels of harmful amyloid beta and tau proteins—considered, along with neurofibrillary tangles, to be hallmarks of Alzheimer’s disease. “Think of tau and amyloid as the waste produced by typical nerve function,” says Charlene Gamaldo, MD, FAAN, associate professor of neurology and medical director of the Johns Hopkins Sleep Disorders Center. “Normally, the brain clears these metabolic waste products away.”
And it may clear away these proteins during sleep, according to a landmark 2013 rodent study in Science by researchers at the University of Rochester Medical Center, who showed that during deep sleep, when neural activity quiets down, cerebrospinal fluid (CSF) bathes the brain, washing away excess amyloid beta and tau proteins. A more recent study, published in the November 2019 issue of iScience, provided further insight into CSF’s function. MRI scans taken while subjects were sleeping showed that during deep sleep, blood flow in the brain diminished as pulsing waves of CSF flushed out excess amyloid beta and tau, presumably girding the brain against cognitive decline. So while it has been known that sleep has some value for survival, these reports seem to put sleep front and center in terms of protecting us from cognitive decline.
Long-term sleep disruptions may raise the risk of some cancers. But sleep and cancer are intertwined in other ways too. Getting a good night’s sleep is difficult during cancer treatment and can be a lifelong challenge for survivors.
“In our research, nearly one in four survivors of childhood cancer had difficulty falling asleep and staying asleep,” says cancer expert Kathryn Ruble, M.S.N., Ph.D. , of the Johns Hopkins Kimmel Cancer Center . “Helping cancer survivors improve their sleep might help them perform at school, on the job, and throughout their lives.”
Disruptions in the body’s “biological clock,” which controls sleep and thousands of other functions, may raise the odds of cancers of the breast, colon, ovaries and prostate. Exposure to light while working overnight shifts for several years may reduce levels of melatonin, encouraging cancer to grow.
A new study shows that national parks worldwide are worth an estimated $6 trillion—with a “T”— in mental health benefits. A team from Australia’s Griffith University, comprised of ecologists, psychologists, and economists, looked at the psychological benefits of national park visits and compared them to the costs of poor mental health. They sampled 20,000 people in three groups, looking at improved cognition, sleep, stress relief, and reduced anxiety and depression. Overwhelmingly, parks made things better.
The researchers were able to attach an economic value on the mental health benefits of national parks, and open spaces in general, by factoring in how much countries spend on mental health treatment and care, while taking into account poor workplace productivity and antisocial behavior. They also examined the quality-adjusted life years of the three groups under study, an economic tool that experts use to measure the value of medical care by reducing a person’s pain, whether mental or physical.
Dr. Ram Randhawa, a psychiatrist at the University of British Columbia’s Sleep Disorders Program, says about 30 per cent of Canadians struggle with getting to or staying sleep at any given time. The prevalence of insomnia does seem to be higher among women, he said.
For most people, sleep issues are a temporary problem brought on by stress or worry. For some, they can be a debilitating, life-long problem.
Getting a consistent seven- to nine-hours of sleep each night is the single most effective thing each of us can do for our health and wellbeing.
Matthew Walker, writing for The Guardian:
Related is the association between plentiful slumber and athletic performance. Sleep is perhaps the greatest legal performance-enhancing “drug” that few people are taking advantage of. Obtain less than eight hours of sleep a night, and especially less than six hours a night, and the following happens: time to physical exhaustion drops by 10 to 30%, as does aerobic output; limb extension force and vertical jump height are reduced; peak and sustained muscle strength decrease. Add to this the cardiac, metabolic and respiratory effects: higher rates of lactic acid buildup and reductions in blood oxygen saturation with converse increases in carbon dioxide, due in part to a reduction in the amount of air that the lungs can expire in a sleep-deficient state. And then there is injury risk. Relative to sleeping nine hours a night, sleeping five to six hours a night will increase your chances of injury across a season by more than 200%.
Routinely sleeping less than six hours a night also compromises your immune system, significantly increasing your risk of cancer. So much so, that recently the World Health Organization classified any form of night-time shiftwork as a probable carcinogen.
Inadequate sleep – even moderate reductions of two to three hours for just one week – disrupts blood sugar levels so profoundly that you would be classified as pre-diabetic. Short sleeping increases the likelihood of your coronary arteries becoming blocked and brittle, setting you on a path towards cardiovascular disease, stroke and congestive heart failure.
All it takes is one hour of lost sleep, as demonstrated by a global experiment performed on 1.6 billion people across more than 60 countries twice a year, otherwise known as daylight saving times. In the spring, when we lose one hour of sleep, there is a 24% increase in heart attacks the following day. In the autumn, we gain an hour of sleep opportunity, and there is a 21% reduction in heart attacks.
It’s been repeatedly shown that sleep is essential to how we form memories.
The human brain requires we sleep roughly one third of every day to properly process and store thoughts so they can be remembered at a later time. Depriving ourselves of sleep, especially over the long term, can disrupt this process. And it can make learning more difficult.
Researchers at the Sleep Research Laboratory at the University of Ottawa have found that once you drift off, your brain shifts information from the hippocampus, which is only used to store recent memories, to the prefrontal cortex. It’s how we learn new things, and remember them for the future.
A short night of sleep may translate into learning less. Our brain requires suffecient time to store everything it took in during the day. Researchers say it’s clear that if you want to be smarter, you may need to sleep more.
The waking brain is optimized for collecting external stimuli, the sleeping brain for consolidating the information that’s been collected. At night, that is, we switch from recording to editing, a change that can be measured on the molecular scale. We’re not just rotely filing our thoughts—the sleeping brain actively curates which memories to keep and which to toss.
It doesn’t necessarily choose wisely. Sleep reinforces our memory so powerfully—not just in stage 2, where we spend about half our sleeping time, but throughout the looping voyage of the night—that it might be best, for example, if exhausted soldiers returning from harrowing missions did not go directly to bed. To forestall post-traumatic stress disorder, the soldiers should remain awake for six to eight hours, according to neuroscientist Gina Poe at the University of California, Los Angeles. Research by her and others suggests that sleeping soon after a major event, before some of the ordeal is mentally resolved, is more likely to turn the experience into long-term memories.
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