Log in
Have you ever wondered, "Why do people sleep?" or "What does quality sleep really mean?"
Many people vaguely understand that sleep is for resting, but few truly grasp the essence of sleep. Many probably think it's just about resting the body.
Indeed, opportunities to learn about sleep are scarce, and it's so commonplace that we rarely feel the need to investigate it. Up until about 70 years ago, sleep was considered a passive behavior and state of consciousness.
That is, it was believed that when a room darkened or became quiet, humans and animals would react to the external environment and naturally fall asleep.
However, animal experiments actively conducted around that time revealed that animals did not sleep or wake in response to external conditions. It was discovered for the first time that sleep and wakefulness are states of behavior and consciousness controlled by the brain, regulated by the brain's spontaneous activity.
It was found that nerve cells exist in the brain that increase their activity during wakefulness and sleep, and that sleep and wakefulness occur due to the increase or decrease in their activity.
Furthermore, around the same time, REM sleep was discovered, and it was also found that
sleep is not merely rest; during sleep, the brain performs maintenance on itself and the body that it cannot do when awake
.
This marked the beginning of modern sleep research, so to speak.
We focused on the idea that "sleep is not merely physical rest; the brain, while spontaneously sleeping, carries out important physiological functions during sleep." We proposed the term "brain sleep" (ブレインスリープ) to describe the brain's self-induced sleep, and we even named the company we founded in the first year of Reiwa after it.
This time, we will focus on this new concept of sleep, "brain sleep," and explain the meaning of sleep.
By reading this article, you will be able to understand the true meaning of sleep and manage it effectively!
1. Sleep: A largely unknown field with much left to discover
Recently, interest in sleep has grown, and we're seeing more books and resources on the topic. It's a field receiving significant attention, as many people struggle with sleep-related issues.
However, despite ongoing research into sleep in modern times, much remains unknown. This is understandable, given that sleep only began to be considered a field of research about 70 years ago.
During REM sleep, the brain's motor and visual cortices are actively working, similar to when awake, and we experience dreams. We've also learned that sleep is crucial for memory consolidation and erasure, and that growth hormones, vital for physical development and repair, are secreted during deep non-REM sleep right after falling asleep.
Sleeping children not only grow, but they may also become smarter. Furthermore, as the functions of sleep have become clearer, it has also become apparent that various sleep disorders exist, such as insomnia, hypersomnia, and sleep apnea syndrome.
In recent years, the number of patients with sleep disorders has increased, and in Japan, sleep disorders are even referred to as a national disease.
While much about sleep has been clarified, sleep medicine is still a young field. Therefore,
from the perspective of a sleep researcher, I believe that what we definitively know about sleep is less than 10% of the whole.
Indeed, new discoveries are still emerging, and the mystery only deepens. Sleep research is advancing daily, yet it remains a field with many unknowns.
2. "Brain Sleep": The new common sense about sleep?
The main topic here, "Brain Sleep," refers to the brain actively functioning even while asleep, playing vital roles that can only be fulfilled during sleep.
In other words, "Brain Sleep" describes quality, deep sleep that refreshes both the brain and body.
The term "sleep" often implies simply being asleep, but that doesn't necessarily mean you're getting proper rest, does it?
Many of you have probably experienced the difference between feeling refreshed after the same amount of sleep and not. This difference stems from the quality of sleep. Sleep has both good and bad quality, and those who experience good quality sleep tend to feel more satisfied when they wake up the next day.
Sleep quality is explained in more detail in a separate article, so please refer to that.
While we tend to focus on sleep resting the body, resting the brain, or rather, the brain sleeping, is extremely important for improving sleep quality.
There's a significant difference between getting this "brain sleep" and not. I'll explain "brain sleep" in more detail later.
Before delving into "brain sleep," let's review the basic roles of sleep!
Some roles may be surprisingly unknown, so pay attention.
3. Why is sleep (brain sleep) necessary? Let's review its 5 roles.
There are five main reasons why sleep is necessary, related to both the brain and the body.
Have you ever felt your body light and your mind clear the day after a good night's sleep?
The reason for this feeling is that the quality of your sleep was high, and both your brain and body were thoroughly rested.
When sleep quality improves, so does your performance the next day.
The first 90 minutes of sleep are particularly important. Since it's the deepest sleep you get during the entire period, it's called "the golden 90 minutes."
By making the most of these golden 90 minutes, you can improve the quality of your sleep.
Getting quality sleep not only improves your performance the next day but also contributes to your long-term brain, body, and mental health.
So, why is it good to get quality sleep? The answer lies in understanding the roles sleep plays.
Let's take a look at the five roles!
3-1. Rest for the brain and body: The primary function of sleep!
The most crucial role of sleep is rest.
Many people believe that sleeping is essential for recovering from fatigue. And they are right.
However, please remember that "sleep" is not just "rest."
In the human body, the autonomic nervous system is constantly working unconsciously, and understanding this system is crucial for sleep.
Many people are familiar with the terms "sympathetic nervous system" and "parasympathetic nervous system."
Each has a dominant period of activity, with the sympathetic nervous system known for its "activity mode" and the parasympathetic nervous system for its "relaxation mode."
During the day, the sympathetic nervous system is dominant, while the parasympathetic nervous system becomes dominant during non-REM sleep and after meals.
While REM sleep is a state of physical rest, non-REM sleep is a valuable time for the brain to also rest.
Therefore, a smooth transition to the parasympathetic nervous system before sleep is crucial.
If you can't switch over smoothly, you won't be able to fall into a deep sleep.
In that case, you won't be able to fully utilize the golden 90 minutes, when non-REM sleep is deepest.
Let's ensure your brain and body are well-rested to improve sleep quality.
3-2. Memory organization and consolidation: Cramming before a test is counterproductive.
It's sometimes said that memories are consolidated during specific sleep stages, but in fact, various research groups have different opinions, and there's no complete consensus.
Also, memory processes are complex and often cannot be easily simplified.
However, there is extensive evidence that memory consolidation progresses after sleep following learning.
It is believed that different types of memories are organized and consolidated during REM and non-REM sleep, which can be categorized as follows:
- REM sleep consolidates episodic memories (what, where, and when something happened)
- Shallow non-REM sleep consolidates procedural memories (body memories like sports or playing an instrument)
- Unpleasant memories are erased during non-REM and REM sleep
REM and non-REM sleep cycles switch 4-5 times while you sleep, meaning memories are gradually organized and consolidated.
As mentioned above, sleep can be considered indispensable for memory consolidation.
Recently, reports have also indicated that during the golden 90 minutes, information moves from the hippocampus to the cerebral cortex, playing a role in memory consolidation.
3-3. Balancing hormones: Sleep is the best beauty treatment.
Have you ever felt your skin condition worsen when you're sleep-deprived? This might be because you're not producing enough hormones that are secreted during sleep.
During sleep, a hormone called growth hormone is secreted. This hormone is vital for the growth and repair of muscles, bones, and skin, and it ensures that metabolism functions normally.
Growth hormone is known to be secreted most abundantly during the golden 90 minutes.
Similarly, it's worth remembering that prolactin, which is related to reproductive behavior, is also secreted in large amounts during the golden 90 minutes.
That's not all. There are other hormone balances that sleep affects.
These are leptin, which suppresses appetite, and ghrelin, which stimulates appetite. It's known that when sleep-deprived, leptin decreases and ghrelin increases.
This means you can't control your appetite, and naturally, you're more likely to gain weight. I've written more about leptin and ghrelin in another article, so please check it out! As mentioned above, sleep and hormone balance are closely related, and sleep can be considered the ultimate beauty treatment.
3-4. Boosting immunity: Sleep prevents colds.
Sleep also plays a role in boosting immunity.
It's long been said that "if you catch a cold, sleep it off," and this makes sense in terms of boosting immunity and providing rest.
The reason you're more prone to illness when sleep-deprived is that hormonal imbalances disrupt immune function. Sleep deprivation also increases the incidence of colds and flu.
Indeed, there are reports indicating that even if you get a flu shot, it might not be effective if you don't get enough sleep.
While it's important to sleep when you have a cold, sleep is also essential to prevent catching one in the first place. Of course, immunity is crucial not only for colds but also for allergies and other diseases, so it's important to prioritize getting enough sleep every day.
3-5. Brain waste removal: A thorough cleansing during sleep.
An often-overlooked function of sleep is the removal of brain waste products.
Brain waste? Many people might be curious. The brain is protected by a fluid called "cerebrospinal fluid."
This cerebrospinal fluid prevents the brain from directly hitting the skull, even with vibrations.
And the cerebrospinal fluid is not static; it's replaced about four times a day. During this replacement, brain waste products are also removed.
It's known that brain waste typically accumulates during wakefulness when the brain is actively used. While cerebrospinal fluid is also replaced during the day, it's not enough to keep up with the amount of waste that accumulates.
Therefore, a major maintenance session to remove waste products is conducted primarily during sleep, when the brain is less active. In other words, it's the brain's deep cleaning time. If this deep cleaning doesn't happen properly, waste products will accumulate and can contribute to Alzheimer's disease.
While not a direct cause, it is certainly a risk factor. From this perspective, it's clear that the removal of brain waste during sleep is important.
4. Sleep isn't just about resting your body! Brain sleep means resting your brain too.
We've explored the five roles of sleep, and it's clear that it's connected not only to the body but also to the brain. Brain sleep means both the body and the brain are thoroughly rested.
The ease with which we perceive physical fatigue makes it easy to focus solely on that aspect.
However, numerous studies have shown that sleep also benefits memory consolidation and waste removal.
While these effects aren't immediately visible, if you pay attention, you might realize, "My mind truly feels clear and sharp!"
It's helpful to consciously compare days when you've slept well with those when you haven't.
People in today's busy world tend to overwork their brains and bodies if left unchecked. Overworking or studying endlessly can lead to sacrificing sleep, which is a common bad habit among Japanese people. To avoid this, it's essential to consciously rest.
Let's improve daily performance by resting both our brains and bodies!
5. What happens in the brain during sleep? The workings of brain sleep.
Sleep is important for both the brain and body, but what exactly happens in the brain when we're asleep?
What happens in the brain during sleep includes the organization of synapses and the removal of waste products within the brain.
Since it's not something as visibly apparent as physical growth or wound healing, it might be harder to perceive, but understanding what's happening is important.
Let's take a look.
5-1. Synaptic organization occurs in the brain during sleep.
During sleep, the brain organizes its synapses.
Synapses are contact structures for information transmission that develop between the output side and the input side of neural information.
The number of synapses varies depending on each individual's environment and experiences, leading to differences in memory capacity.
It has been discovered that the dendritic spines of these synapses are pruned during REM sleep. This pruning reduces their number, thereby organizing and strengthening the connections.
In other words, what you've learned becomes easier to remember.
While such organization and strengthening are particularly crucial for children in their developmental stages, similar changes also occur in adults.
5-2. Brain cleansing during sleep! The glymphatic system.
As previously mentioned, sleep is a time for the brain to undergo maintenance and remove waste products.
This function is called the "glymphatic system."
Normally, waste products in the body collect in the lymphatic system, circulate throughout the body, and are excreted as urine.
It is popularly said that massage of the lymph nodes might remove lumps from the skin, implying that these peripheral lumps contain waste products.
However, the brain does not have a lymphatic system.
Instead, it has cerebrospinal fluid, which washes away waste products. This mechanism is the glymphatic system.
While waste removal also occurs during waking hours, this function increases 4 to 10 times during sleep.
If you don't get enough sleep, you miss out on this powerful function, and waste products will continue to accumulate.
Therefore, sleep is crucial for effectively removing waste products.
6. Sleep is essential for brain development!
So, we've learned that sleep is intimately connected to both the body and the brain.
While important in adulthood, it is especially crucial during the rapid brain development of childhood.
However, although children are often told "go to bed early," few adults explain why.
This is primarily because many adults simply lack that knowledge.<
As a result, education aimed at raising awareness about sleep has recently begun.
It's called "sleep education" (眠育) and is gradually spreading. Let me introduce what sleep education is all about.
6-1. Focus on "sleep education" spreading throughout Japan!
Sleep education has been conducted in various regions, with the example in Sakai City, Osaka Prefecture, being particularly prominent.
Sleep education was initiated because irregular sleep patterns and late-night tendencies often lead to difficulty waking up in the morning and, in many cases, truancy. A "Sleep Education Handbook" was distributed, categorized for lower, middle, and upper elementary grades, summarizing the importance and issues of sleep appropriate for each age group.
After implementing sleep education, problems like truancy decreased by 30% in three years.
Thus, sleep education is gaining traction due to its proven effectiveness.
It's easier to integrate into education at elementary and junior high schools, but such opportunities are surely important for adults too.
Overseas, many companies provide nap rooms in offices or allocate separate time for naps in addition to breaks.
This is evidence that the importance of sleep is gradually spreading to the general public. In Japan, too, such companies are slowly increasing.
If sleep education can raise awareness about sleep, more people will be able to manage sleep effectively in the future.
6-2. Gaining the right sleep knowledge can change your life.
If you consider sleeping for 8 hours a day, that means one-third of your life is spent sleeping.
Despite dedicating so much time to it, few people actually learn about sleep.
However, if you deepen your understanding of sleep, that one-third of your life will significantly change. Considering the performance improvement that follows, not just the sleeping hours themselves, you'll likely gain even more benefits.
If you understood the relationship between sleep and memory, you might not have had to cram all night.
Some might think, "It's too late now that I'm an adult," but that's not true at all.
Improved immunity through sleep might mean fewer sick days, and getting proper sleep could boost your work performance.
Because sleep is something you do every day, it's never too late to start learning about it.
Gain the right knowledge about sleep and live a better life than ever before.
There's also an article summarizing the benefits of getting enough sleep, so please read it!
7. Discretion is key! Much information about sleep is ambiguous.
With the recent focus on sleep, opportunities to encounter information about it have increased.
However, the reality is that some information lacks strong evidence and makes you scratch your head.
Since knowledge about sleep is not common, it's easy to blindly accept information found online, but that can be dangerous.
Things you do thinking they're correct might actually be wrong.
For example, "wearing socks during sleep." Many people actually do this.
However, from the perspective of radiating heat from the feet to lower core body temperature, it's better not to wear socks while sleeping.
So, be careful, as some things you do routinely might actually hinder your sleep.
It's important not to blindly accept information but to carefully select and discard it.
Consider the stance from which the information was written, whether evidence supports it, and how you want to utilize that information.
By doing so, you can discover accurate information about sleep and avoid going down the wrong path!
Summary: Utilize the new common sense of "brain sleep" for the best sleep habits.
We've learned that sleep is connected to both the brain and the body.
In addition to thinking, "I'm tired, so I'll sleep," it would be ideal to think, "My brain is tired, so I'll sleep."
Consciously getting "brain sleep," which rests both your body and brain, will likely change your life.
Here's a summary of this article:
- Brain sleep means getting deep sleep where both the body and brain are thoroughly rested.
- Sleep has five main roles.
- Synaptic organization occurs in the brain during sleep.
- The glymphatic system removes waste products from the brain during sleep.
- Gaining correct sleep knowledge through sleep education can change your life.
Sleep has an unbreakable connection to human beings.
Even if you don't intend to sleep, you'll eventually get sleepy, and many people love to sleep.
However, if you don't manage it well, it will affect your daily performance.
Conversely, once you know how to manage it, you can effectively use it to improve your life.
While personal awareness is important, it's also crucial to avoid disturbing the sleep of partners, family members, or anyone sharing the same room or bed to ensure proper brain sleep. If someone is already asleep, try to be quiet and avoid bright lights! By being considerate of each other, you can enjoy a better sleep life.
Take this opportunity to review your sleep habits so you can get optimal brain sleep.
