March 21 is World Sleep Day
Our country's theme this year is:
Healthy sleep for everyone!
however
The data shows that
There are more than 300 million people in our country
Suffer from varying degrees of sleep disturbance
Did you, uh, really sleep well?

一、Sleep cycle
The sleep cycle is divided into five stages: fall asleep, light sleep, deep sleep, rapid eye movement.

Hypnagogic phase
The beginning of sleep, drowsy feeling belongs to this stage. At this point, brain waves begin to change, slowing down in frequency and decreasing in amplitude.

Light sleep
Officially begin to sleep, at this time the brain waves gradually irregular progress, frequency and amplitude of large and small, which occasionally appear called "sleep spindle" of high frequency, large wave brain waves, and known as "K knot" of low frequency, large wave brain waves.

Deep sleep and deep sleep
Blood pressure, breathing, and heart rate all reach their lowest levels throughout the day, and the length and continuity of this deep sleep phase, called "non-REM sleep," largely determines the quality of our sleep. And at this stage, it is not easy to wake up. At this time, the brain wave changes greatly, the frequency is only 1-2 weeks per second, but the amplitude increases greatly, showing a slow curve of change. These four stages of sleep take about 60 to 90 minutes, and there is no rapid eyemovement phenomenon, so collectively known as non-rapid eyemovement sleep (non-REMs).

Rapid eye movement
Brain waves change rapidly, with high frequency, low amplitude brain waves similar to those seen during wakefulness, but with distinctive zigzag patterns. Sleepers often roll over and wake up easily, appearing to fall back into stage 1 sleep, but actually entering a sleep phase known as rapid eye movement sleep (REMs). Because at this time, in addition to the changes in brain waves, the subject's eyes will show a rapid beating phenomenon. If awakened at this point, most people report dreaming. Therefore, REM has become an important feature of the fifth stage of sleep, and has become an important basis for psychologists to study dreams.

Sleep cycles usually last about 90 minutes. Adequate rest and sleep, are according to the sleep cycle. Transition smoothly from one sleep cycle to the next in a sleep-awaken-sleep-wake pattern. And over time, gradually reduce deep sleep and increase REM sleep until you wake up in the morning.

二、Sleep and health
Boston University's Laura Lewis research team has completely filmed the brain "bathing" process during human sleep, which immediately caused a sensation around the world, and the impact of sleep on health has a new interpretation Angle.

Red is blood and blue is cerebrospinal fluid (CSF). Source: Laura Lewis

When we sleep, a series of amazing things happen in the brain. First, neurons quiet down; After a few seconds, blood flows out of the brain and cerebrospinal fluid (CSF) flows in. After a while, cerebrospinal fluid flows out and blood flows in, and then the process is repeated, "cleaning" our brains in slow, rhythmic waves.

In this process, the cerebrospinal fluid enters the brain and carries away a batch of brain metabolites, including amyloid beta and other harmful substances that cause Alzheimer's disease, the researchers said in the paper. This cleansing can only be done after sleep, when the neurons are firing in sync. When a large number of neurons shut down all together, less blood is needed to carry oxygen to the brain, making room for cerebrospinal fluid to enter. And when we're awake, neurons don't turn on and off at the same time.

So, there's no way to get the blood volume to the brain low enough while awake, and there's no room for cerebrospinal fluid to enter. This important finding tells us that many diseases may be related to sleep problems.

A study in the Annals of Behavioral Medicine found that sleeping for less than six hours is prone to negative emotions such as nervousness, loneliness, irritability and frustration, and even physical symptoms such as back pain, dizziness and gastrointestinal upset. Not only that, but if you sleep less than six hours for three consecutive nights, these bad physical reactions will peak, and not only will the symptoms increase, but their severity will also increase. In addition, the impact of lack of sleep on cardiovascular health is also huge. A joint study by several universities and hospitals found that people who slept less than six hours had a 20 percent increased risk of heart attack compared with those who slept between six and nine hours. In addition, long-term sleep deprivation can also make the immune system more weak, and the probability of cancer will be significantly increased.

三、What kind of sleep is healthy sleep?

1, can fall asleep quickly within 10-20 minutes;
2, will not wake up easily at night, even if wake up can fall asleep quickly;
3, there is no panic dream in sleep, and the dream is soon forgotten after waking up;
4, get up in the morning full of energy, no fatigue.

四、Must sleep 8 hours a day to be normal?

Think back to the people around you, some people feel that they do not sleep enough, and some people can sleep for four or five hours to be full of vitality, it is said that Da Vinci, Edison and other celebrities are such short sleepers. The discovery of a short sleep gene, mutated ADRB1, is reported in the top neuroscience journal Neuron, and people with this gene mutation need only four to six hours of sleep a day. Therefore, the standard to measure the quality of sleep is not only to look at the length of sleep, but to look at the state after waking up.

If you find yourself sleeping 7 hours and feeling energized the next day, then 7 hours is right for you, but if you sleep 10 hours a day and still feel sluggish the next day, this is usually a sign that there is something wrong with your sleep quality. For friends who are always not full of sleep, it is recommended to go to the hospital as soon as possible to assess their sleep status and check whether there are potential health problems.

五、How to improve sleep?

1. Get regular sleep

Try to go to bed and wake up at the same time every day to help adjust your body clock and adjust your body to a regular sleep pattern.

2. Comfortable environment

Ensure that the sleeping environment is quiet, dark, cool and comfortable, and the mattress and pillow should be in line with personal habits to improve the quality of sleep. If you have a habit of napping, don't sleep for more than 45 minutes during the day. Remember to save your bed for sleeping, and don't use it as an office, workspace, or playroom.

3. Avoid stimulants before bed
  
Avoid excessive drinking and smoking 4 hours before bed. Avoid heavy, spicy, or sugary foods.
; Avoid caffeine 6 hours before bed. This includes coffee, tea and lots of soda, as well as chocolate.

4. Exercise properly
  
Regular physical activity can help improve sleep quality, but be careful to avoid strenuous exercise within a few hours of bedtime.

5. Relax

Relaxing activities before bed, such as meditation, deep breathing, yoga, and reading, can help reduce stress and promote sleep.