Connections Between Deep Sleep And Cognition : A Wake-up Call

I'm not trying to spy on your privacy, but how long did you sleep last night? In the past week? I asked this question because the answer will have a significant impact on your future mental health.

More than 44 million people worldwide now suffer from Alzheimer's disease, and many members of the family may also have the disease. The impact of Alzheimer's disease on health, economy and personal life is staggering. With the increase of human life expectancy, there has been a significant increase in the number of people diagnosed with Alzheimer's disease. However, besides the longevity, the reduction of total sleep time is also a major cause.

Deep sleep can make people discharge toxic protein.
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As a sleep scientist, I became interested in the link between Alzheimer's disease and sleep several years ago. My findings are astounding: Sleep disorders are not only one of the hallmarks of the decline in cognitive function in Alzheimer's disease, but ensuring adequate sleep is an important factor in the future of people with Alzheimer's disease .

The impact of this finding is enormous. We will soon fill the missing part of the Alzheimer's study, and now we recognize that sleep provides a way to diagnose, treat, and even prevent the disease.

The myths, sleeping more makes silly

As we grow older, our sleep quality is getting worse. In particular, deep non-rapid eye movement (NREM) sleep is particularly susceptible. Unfortunately, this sleep mode is just one of the important patterns that helps us to incorporate new memories in brain structures and prevent you from forgetting.

However, if you evaluate a patient with Alzheimer's disease, you will find the deprivation of sleep more exaggerated. More to the point, the patient may have had a sleep disorder before the onset of Alzheimer's disease, indicating that it is an early warning sign of the disease and even a contributing actor. After diagnosis, the degree of patients with sleep disorders and the severity of the symptoms simultaneously, further revealing the relationship between the two.

However, until recently, we realized that the two are not just related. Although it remains to be seen, we now recognize that sleep disorders and Alzheimer's disease are the etiologies and accelerate each other's disease process.

a healthy sleep Architecture
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Alzheimer's disease is associated with the formation of a toxic protein called beta-amyloid, which accumulates in the brain as a sticky mass or as a clear blotch. Amyloid plaques are toxic to brain cells, impairing their function and eventually leading to nerve cell death. But the strange thing is that amyloid attacks only one part of the brain, not the rest, for reasons not yet clear.

It is this mode of amyloid-selective attack that shocks me: in the early stages of Alzheimer's disease, or late in the disease, the amyloid plaque accumulates in the brain in the middle of the frontal lobe. If you put your finger on the bridge of the nose and then move up 5 cm, the fingertips point to the middle of the frontal lobe. This finding is very much related to my research: this part of the brain is important for the electrical activity of deep NREM sleep.

As early as 2007, I wanted to know if NREM sleep damage in Alzheimer's patients is due to disease erosions in specific areas of the brain, as these are the key areas that regulate sleep. At the Sleep Research Center at the University of California, Berkeley, we started the study.

Through sleep testing, people at high risk of Alzheimer's disease are screened

Ten years after the idea was made, we evaluated the relationship between the sleep of hundreds of seniors aged 65 to 90 and varying degrees of amyloid formation in the brain and found that the amyloid in the frontal lobe The more protein deposition, the more severe the quality of the patient's deep sleep. Importantly, the association of Alzheimer's disease with amyloid plaques is not merely an overall loss of deep NREM sleep (which is common when we age), but also a serious deprivation of NREM sleep in patients Brain waves.

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This highly specific absence of deep sleep means that sleep disorders resulting from the accumulation of toxic amyloid in the brain are more than "normal aging." This is a specific phenomenon that belongs to the disease.

With that in mind, some of my research is now focused on diagnostics. In particular, we want to know whether this particular "indentation" in brainwave activity during sleep can be used to detect high-risk individuals who will develop Alzheimer's disease in the next few years or even decades. If sleep is indeed an early warning sign of illness, it is cheaper and more invasive than a brain scan and can be used for screening large numbers of people. Then through sleep monitoring, early intervention in Alzheimer's disease has become possible.

May lead to memory loss "culprit"

Based on these findings, we begin to look at another missing part of the mystery of Alzheimer's disease: How does accumulation of toxic protein plaques lead to loss of memory?

We know that amyloid deposits occur only in parts of the brain. The magic is that the hippocampus is a key memory storage area in the brain, largely unaffected. How do these toxic amyloid deposits cause loss of memory in Alzheimer's patients since they do not affect the memory area? This issue still plagues scientists today.

In my opinion, sleep disorders are the missing link in the study. We already know that slow, slow NREM sleep in young, healthy adults effectively pushes the "Save" button of the new memory to help us keep up with the latest lessons. Sleeping can also help us enter the memory, recalling past experiences.

If amyloid blocks deep NREM sleep in patients with Alzheimer's disease, can such an absence of deep sleep prevent older people from saving new memories and remembering only past experiences?

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To test this idea, we selected elderly patients with Alzheimer's who had varying levels of amyloid in their brains to learn a series of new things in the evening and record their sleep in the laboratory. The next morning, we tested these patients to see if their sleep was effective in consolidating these new memories.

We found that people who had the most amyloid deposits in the middle of the frontal lobe had the most profound loss of deep sleep and could not "save" these new memories. So there was overnight forgotten such a result. Therefore, deep NREM sleep disorders are a hidden intermediary, mediating between amyloid and memory disorders associated with Alzheimer's disease.

However, this is only half the story, and not too important half. Our study shows that amyloid plaques in Alzheimer's disease may be related to the loss of deep sleep, but does not enough sleep actually lead to the accumulation of amyloid in the brain? If the answer is "yes," we all have to accept a thought-provoking fact: Without enough sleep, night after night, year after year, amyloid accumulation in the brain will increase, which will directly increase the Alzheimer's disease Sickness risk.

Deep sleep helps brain "blowdown"

In parallel with our research, Maiken Nedergaard of the University of Rochester in New York also made the most dramatic discovery in the area of ​​sleep research that we can call the most recent decades. McCain found in the mouse brain a "blowdown" network called the glymphatic system, which consists of glial cells. These glial cells are located around the electrical pulse-generating neurons. Like the waste that the lymphatic system excretes, the lymphatic system uses cerebrospinal fluid to collect and decompose harmful metabolic waste from the hard work of neurons.

Although the lymphatic system is relatively more active during the day, Nedgod and his team found that this detoxification system activated high-speed operation during deep NREM sleep. With pulsating rhythms of deep NREM sleep, the brain discharges 10 to 20 times more waste. Think about it, it is a powerful night purifier.

If neither is enough, Nedold has a second finding that explains why cerebrospinal fluid is so efficiently discharged as metabolic waste at night. During deep NREM sleep, the volume of cerebral glia miraculously shrinks by 60%, creating more space for cerebrospinal fluid to clear metabolic waste. You can compare it to the architecture of a big city magically diminishing at night. Cleaners in the city can more easily remove rubbish from the day and then carry out high-pressure jet cleaning on every corner and gap.

What does this have to do with Alzheimer's disease? McCain found that a piece of toxic debris washed away by the lymphatic system during sleep was amyloid, which is the causative agent of Alzheimer's disease. The result of this study is consistent with another surprising finding. David Holtzman of Washington University in St. Louis and his team observed an immediate increase in amyloid levels in the mouse brain by preventing mice from getting into deep NREM sleep and keeping them awake.

Of course, there are some notable differences between mice and humans. The same thing happens if our sleep is affected? Worryingly, Holtzman proved this in July. His team conducted an experiment: depriving a healthy adult of a deep NREM sleep, but keeping the total sleep time unchanged. To do this, they waited until the subject went to sleep and then played a wake-up tone to take the brain out of deep sleep without waking the subject. After a night, they measured the amount of amyloid in their cerebrospinal fluid. The lack of cleaning with deep NREM sleep significantly increased Alzheimer's associated amyloid in subjects' cerebrospinal fluid.

The evidence is conclusive that a lack of deep sleep leads to a direct and immediate increase of amyloid in the human brain. Put simply, sleep is the savior of our nervous system or, in other words, the public health system.

These findings demonstrate that the lack of sleep interacts with the pathogenesis of Alzheimer's disease and creates a vicious circle. Without adequate sleep, amyloid accumulates in the brain, affecting areas of the brain that cause deep sleep. The resulting loss of depth of NREM sleep further prevents amyloid clearance in the nighttime brain, resulting in amyloid accumulation. The more amyloid protein, the less deep sleep; the less deep sleep, amyloid will accumulate more, this is an endless loop.

Sleeping well is the scientific truth

This evidence brings with it a prognostic puzzle: Too little sleep during your lifetime can significantly increase the risk of developing Alzheimer's disease. This is true no matter whether you are ready to accept it or not. Unfortunately, for people with sleep disorders, this association has been confirmed and reported by many epidemiological studies: If you have sleep disorders such as insomnia or sleep apnea and are not treated, do you suffer from Alzheimer's The risk of illness will be higher.

However, looking back on these findings, we can get a promising prediction that by improving sleep we should be able to reduce the risk of the disease or at least postpone it.

To this idea, clinical studies have given early support, and middle-aged and elderly people with sleep disorders have not yet transitioned to Alzheimer's disease. When their sleep problems are resolved, their cognitive decline slows, which can delay the onset of Alzheimer's disease for as long as 10 years.

Therefore, increasing the length and quality of sleep helps fight the disease. For those who are healthy and have no sleep problems, this means freeing up more time for sleep, preferably 8 hours a night.

But those with sleep problems, or people who do not have adequate sleep due to aging and dementia? Drugs are not a good choice. The current sleeping pills do not produce spontaneous sleep, and cause increased cancer and lethality.

Scientists are now developing some electrical stimulation of the brain to enhance NREM sleep in the elderly and in patients with dementia. Just like when the lead singer does not give chorus, then you need teamwork to make up. They tried to make the "singing voice" formed by electrical stimulation resonate with the weak sleeping brain wave to artificially enhance sleep brain waves. We hope to save the learning and memory functions of the elderly and people with dementia by restoring some deep sleep.

This is a cure, but our goal is to better prevent it. If we succeed in a small-scale clinical trial, we hope to develop a more cost-effective way to scale it up to groups for reuse. Ideally, deep sleep in susceptible individuals should begin to take place during the middle decades of human life, decades before the inevitable cut-off point of Alzheimer's disease. We admit that this is a lofty aspiration and even a reckless ambition, but this has become a top priority when people see their family members struggle with the disease.

Obviously, lack of sleep is just one of several risk factors associated with Alzheimer's disease. Sleep itself is not a miracle cure for dementia. However, priority sleep is an unambiguous method of reducing the risk of developing Alzheimer's disease, regardless of age. This fact has sounded the alarm for us.

How long to sleep to be enough?

Adequate sleep plays a crucial role in protecting your brain from Alzheimer's disease. But how long do you need to sleep?

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According to the US National Sleep Foundation, most adults require seven to nine hours of sleep per night. But as we grow older, the amount of sleep we need will change. For example, an 18-year-old may take 6 to 11 hours. Older people need sleep time seems to be no different from young people, but it is difficult to achieve.

In general, you should not set the alarm to wake yourself up. If you do this, you may not get enough sleep time. More importantly, lying in bed does not mean sleeping time, set himself an 8-hour goal, sleep well.

References for Text and Images:

• https://www.webmd.com/sleep-disorders/ss/slideshow-sleep-disorders-overview
• https://www.npr.org/sections/health-shots/2016/01/04/460620606/lack-of-deep-sleep-may-set-the-stage-for-alzheimers
• https://www.slideshare.net/ashrafeladawy/normal-sleep-architecture
• https://www.aafp.org/afp/1999/0501/p2551.html
• http://slideplayer.com/slide/10020731/
• http://www.kurzweilai.net/how-sleep-deprivation-poses-risks-to-physical-and-mental-health
• https://en.wikipedia.org/wiki/Sleep

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