Stressed to the max? Deep sleep can rewire the anxious brain

A sleepless night can trigger up to a 30 percent rise in emotional stress levels, new study shows

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Deep sleep concept (stock image). Credit: © stokkete / Adobe Stock

November 4, 2019

Science Daily/University of California - Berkeley

Researchers have found that the type of sleep most apt to calm and reset the anxious brain is deep sleep, also known as non-rapid eye movement (NREM) slow-wave sleep, a state in which neural oscillations become highly synchronized, and heart rates and blood pressure drop.

When it comes to managing anxiety disorders, William Shakespeare's Macbeth had it right when he referred to sleep as the "balm of hurt minds." While a full night of slumber stabilizes emotions, a sleepless night can trigger up to a 30% rise in anxiety levels, according to new research from the University of California, Berkeley.

UC Berkeley researchers have found that the type of sleep most apt to calm and reset the anxious brain is deep sleep, also known as non-rapid eye movement (NREM) slow-wave sleep, a state in which neural oscillations become highly synchronized, and heart rates and blood pressure drop.

"We have identified a new function of deep sleep, one that decreases anxiety overnight by reorganizing connections in the brain," said study senior author Matthew Walker, a UC Berkeley professor of neuroscience and psychology. "Deep sleep seems to be a natural anxiolytic (anxiety inhibitor), so long as we get it each and every night."

The findings, published today, Nov. 4, in the journal Nature Human Behaviour, provide one of the strongest neural links between sleep and anxiety to date. They also point to sleep as a natural, non-pharmaceutical remedy for anxiety disorders, which have been diagnosed in some 40 million American adults and are rising among children and teens.

"Our study strongly suggests that insufficient sleep amplifies levels of anxiety and, conversely, that deep sleep helps reduce such stress," said study lead author Eti Ben Simon, a postdoctoral fellow in the Center for Human Sleep Science at UC Berkeley.

In a series of experiments using functional MRI and polysomnography, among other measures, Simon and fellow researchers scanned the brains of 18 young adults as they viewed emotionally stirring video clips after a full night of sleep, and again after a sleepless night. Anxiety levels were measured following each session via a questionnaire known as the state-trait anxiety inventory.

After a night of no sleep, brain scans showed a shutdown of the medial prefrontal cortex, which normally helps keep our anxiety in check, while the brain's deeper emotional centers were overactive.

"Without sleep, it's almost as if the brain is too heavy on the emotional accelerator pedal, without enough brake," Walker said.

After a full night of sleep, during which participants' brain waves were measured via electrodes placed on their heads, the results showed their anxiety levels declined significantly, especially for those who experienced more slow-wave NREM sleep.

"Deep sleep had restored the brain's prefrontal mechanism that regulates our emotions, lowering emotional and physiological reactivity and preventing the escalation of anxiety," Simon said.

Beyond gauging the sleep-anxiety connection in the 18 original study participants, the researchers replicated the results in a study of another 30 participants. Across all the participants, the results again showed that those who got more nighttime deep sleep experienced the lowest levels of anxiety the next day.

Moreover, in addition to the lab experiments, the researchers conducted an online study in which they tracked 280 people of all ages about how both their sleep and anxiety levels changed over four consecutive days.

The results showed that the amount and quality of sleep the participants got from one night to the next predicted how anxious they would feel the next day. Even subtle nightly changes in sleep affected their anxiety levels.

"People with anxiety disorders routinely report having disturbed sleep, but rarely is sleep improvement considered as a clinical recommendation for lowering anxiety," Simon said. "Our study not only establishes a causal connection between sleep and anxiety, but it identifies the kind of deep NREM sleep we need to calm the overanxious brain."

On a societal level, "the findings suggest that the decimation of sleep throughout most industrialized nations and the marked escalation in anxiety disorders in these same countries is perhaps not coincidental, but causally related," Walker said. "The best bridge between despair and hope is a good night of sleep."

https://www.sciencedaily.com/releases/2019/11/191104124140.htm

Not all sleep is equal when it comes to cleaning the brain

February 27, 2019

Science Daily/University of Rochester Medical Center

New research shows how the depth of sleep can impact our brain's ability to efficiently wash away waste and toxic proteins. Because sleep often becomes increasingly lighter and more disrupted as we become older, the study reinforces and potentially explains the links between aging, sleep deprivation, and heightened risk for Alzheimer's disease.

"Sleep is critical to the function of the brain's waste removal system and this study shows that the deeper the sleep the better," said Maiken Nedergaard, M.D., D.M.Sc., co-director of the Center for Translational Neuromedicine at the University of Rochester Medical Center (URMC) and lead author of the study. "These findings also add to the increasingly clear evidence that quality of sleep or sleep deprivation can predict the onset of Alzheimer's and dementia."

The study, which appears in the journal Science Advances, indicates that the slow and steady brain and cardiopulmonary activity associated with deep non-REM sleep are optimal for the function of the glymphatic system, the brain's unique process of removing waste. The findings may also explain why some forms of anesthesia can lead to cognitive impairment in older adults.

The previously unknown glymphatic system was first described by Nedergaard and her colleagues in 2012. Prior to that point, scientists did not fully understand how the brain, which maintains its own closed ecosystem, removed waste. The study revealed a system of plumbing which piggybacks on blood vessels and pumps cerebral spinal fluid (CSF) through brain tissue to wash away waste. A subsequent study showed that this system primarily works while we sleep.

Because the accumulation of toxic proteins such as beta amyloid and tau in the brain are associated with Alzheimer's disease, researchers have speculated that impairment of the glymphatic system due to disrupted sleep could be a driver of the disease. This squares with clinical observations which show an association between sleep deprivation and heightened risk for Alzheimer's.

In the current study, researchers conducted experiments with mice that were anesthetized with six different anesthetic regimens. While the animals were under anesthesia, the researchers tracked brain electrical activity, cardiovascular activity, and the cleansing flow of CSF through the brain. The team observed that a combination of the drugs ketamine and xylazine (K/X) most closely replicated the slow and steady electrical activity in the brain and slow heart rate associated with deep non-REM sleep. Furthermore, the electrical activity in the brains of mice administered K/X appeared to be optimal for function of the glymphatic system.

"The synchronized waves of neural activity during deep slow-wave sleep, specifically firing patterns that move from front of the brain to the back, coincide with what we know about the flow of CSF in the glymphatic system," said Lauren Hablitz, Ph.D., a postdoctoral associate in Nedergaard's lab and first author of the study. "It appears that the chemicals involved in the firing of neurons, namely ions, drive a process of osmosis which helps pull the fluid through brain tissue."

The study raises several important clinical questions. It further bolsters the link between sleep, aging, and Alzheimer's disease. It is known that as we age it becomes more difficult to consistently achieve deep non-REM sleep, and the study reinforces the importance of deep sleep to the proper function of the glymphatic system. The study also demonstrates that the glymphatic system can be manipulated by enhancing sleep, a finding that may point to potential clinical approaches, such as sleep therapy or other methods to boost the quality of sleep, for at-risk populations.

Furthermore, because several of the compounds used in the study were analogous to anesthetics used in clinical settings, the study also sheds light on the cognitive difficulties that older patients often experience after surgery and suggests classes of drugs that could be used to avoid this phenomenon. Mice in the study that were exposed to anesthetics that did not induce slow brain activity saw diminished glymphatic activity.

"Cognitive impairment after anesthesia and surgery is a major problem," said Tuomas Lilius, M.D., Ph.D., with the Center for Translational Neuromedicine at the University of Copenhagen in Denmark and co-author of the study. "A significant percentage of elderly patients that undergo surgery experience a postoperative period of delirium or have a new or worsened cognitive impairment at discharge."

https://www.sciencedaily.com/releases/2019/02/190227173111.htm

Deep sleep may act as fountain of youth in old age

Restorative, sedative-free slumber can ward off mental and physical ailments, suggests research

April 5, 2017
Science Daily/University of California - Berkeley
As we grow old, our nights are frequently plagued by bouts of wakefulness, bathroom trips and other nuisances as we lose our ability to generate the deep, restorative slumber we enjoyed in youth. But that does not mean the elderly need less sleep, according to neuroscientists.

But does that mean older people just need less sleep?

Not according to UC Berkeley researchers, who argue in an article published April 5 in the journal Neuron that the unmet sleep needs of the elderly elevate their risk of memory loss and a wide range of mental and physical disorders.

"Nearly every disease killing us in later life has a causal link to lack of sleep," said the article's senior author, Matthew Walker, a UC Berkeley professor of psychology and neuroscience. "We've done a good job of extending life span, but a poor job of extending our health span. We now see sleep, and improving sleep, as a new pathway for helping remedy that."

Unlike more cosmetic markers of aging, such as wrinkles and gray hair, sleep deterioration has been linked to such conditions as Alzheimer's disease, heart disease, obesity, diabetes and stroke, he said.

Though older people are less likely than younger cohorts to notice and/or report mental fogginess and other symptoms of sleep deprivation, numerous brain studies reveal how poor sleep leaves them cognitively worse off.

Moreover, the shift from deep, consolidated sleep in youth to fitful, dissatisfying sleep can start as early as one's 30s, paving the way for sleep-related cognitive and physical ailments in middle age.

And, while the pharmaceutical industry is raking in billions by catering to insomniacs, Walker warns that the pills designed to help us doze off are a poor substitute for the natural sleep cycles that the brain needs in order to function well.

"Don't be fooled into thinking sedation is real sleep. It's not," he said.

For their review of sleep research, Walker and fellow researchers Bryce Mander and Joseph Winer cite studies, including some of their own, that show the aging brain has trouble generating the kind of slow brain waves that promote deep curative sleep, as well as the neurochemicals that help us switch stably from sleep to wakefulness.

"The parts of the brain deteriorating earliest are the same regions that give us deep sleep," said article lead author Mander, a postdoctoral researcher in Walker's Sleep and Neuroimaging Laboratory at UC Berkeley.

Aging typically brings on a decline in deep non-rapid eye movement (NREM) or "slow wave sleep," and the characteristic brain waves associated with it, including both slow waves and faster bursts of brain waves known as "sleep spindles."

Youthful, healthy slow waves and spindles help transfer memories and information from the hippocampus, which provides the brain's short-term storage, to the prefrontal cortex, which consolidates the information, acting as the brain's long-term storage.

"Sadly, both these types of sleep brain waves diminish markedly as we grow old, and we are now discovering that this sleep decline is related to memory decline in later life," said Winer, a doctoral student in Walker's lab.

Another deficiency in later life is the inability to regulate neurochemicals that stabilize our sleep and help us transition from sleep to waking states. These neurochemicals include galanin, which promotes sleep, and orexin, which promotes wakefulness. A disruption to the sleep-wake rhythm commonly leaves older adults fatigued during the day but frustratingly restless at night, Mander said.

Of course, not everyone is vulnerable to sleep changes in later life: "Just as some people age more successfully than others, some people sleep better than others as they get older, and that's another line of research we'll be exploring," Mander said.

Meanwhile, non-pharmaceutical interventions are being explored to boost the quality of sleep, such as electrical stimulation to amplify brain waves during sleep and acoustic tones that act like a metronome to slow brain rhythms.

However, promoting alternatives to prescription and over-the-counter sleep aids is sure to be challenging.

"The American College of Physicians has acknowledged that sleeping pills should not be the first-line kneejerk response to sleep problems," Walker said. "Sleeping pills sedate the brain, rather than help it sleep naturally. We must find better treatments for restoring healthy sleep in older adults, and that is now one of our dedicated research missions."

Also important to consider in changing the culture of sleep is the question of quantity versus quality.

"Previously, the conversation has focused on how many hours you need to sleep," Mander said. "However, you can sleep for a sufficient number of hours, but not obtain the right quality of sleep. We also need to appreciate the importance of sleep quality.

"Indeed, we need both quantity and quality," Walker said.
Science Daily/SOURCE :
https://www.sciencedaily.com/releases/2017/04/170405144431.htm