Less deep sleep and poor sleep quality! How to increase deep sleep time?

With the advancement of technology and the popularization of sleep science, when we discuss sleep now, we no longer simply say "sleep soundly" or "sleep deeply", but use more professional sleep terms and data to measure it.

We will pay attention to the proportion of deep sleep, light sleep, and REM sleep in the total sleep every night, especially deep sleep. Because deep sleep has a restorative effect on the human body, we will pay more attention to it. Today, let’s talk about some knowledge about deep sleep.

01 Deep sleep occurs several times a night

Deep sleep is very important for the human body because growth hormone is secreted during this period. Growth hormone has a repairing effect on the body and can keep us healthy and functioning well. In addition, growth hormone is also beneficial for strengthening muscles and bones, recovering from injuries, and improving immunity.

However, there has always been a misunderstanding about deep sleep. People believe that deep sleep occurs before midnight, so people often say that sleeping before midnight is best for the body. This statement is not comprehensive. What is the correct understanding?

Deep sleep occurs mainly in the first half of sleep

Whether you go to bed at 10 o'clock, 12 o'clock, or 2 o'clock, you will have deep sleep, which mainly occurs in the early stage of your full night of sleep.

(In this sleep stage diagram, the pink part represents deep sleep)

A complete sleep cycle is divided into three stages: light sleep, deep sleep, and REM sleep.

Light sleep is divided into stages N1 and N2, and deep sleep is stage N3.

After a person falls asleep, a normal sleep cycle is:

Sober▼
Light sleep (N1, N2)
▼
Deep sleep (N3)
▼
Light sleep (N1, N2)
▼
REM sleep

Most adults have 4 to 6 such sleep cycles every night, which constitute a complete night of sleep. However, deep sleep may not occur or may be short in the later stages of sleep.

Unfortunately, as we age, the secretion of growth hormone decreases along with the reduction of deep sleep, and insufficient deep sleep often makes people feel very sleepy. Therefore, many people, although they get enough sleep, still feel that they did not sleep well after waking up. They feel sleepy during the day and their mental state is not good. So how can you increase your deep sleep time?

Studies have shown that appropriate and regular exercise during the day can increase deep sleep time; cognitive behavioral therapy for insomnia (CBT-I) can sustainably improve sleep quality by reducing unnecessary time in bed, because even if you sleep longer, you cannot increase deep sleep time. On the contrary, implementing sleep restriction makes sleep motivation sufficient and increases sleep continuity.

In addition, you should also avoid doing things that reduce deep sleep. For example, drinking before bed can help you fall asleep quickly, but it will reduce the time of deep sleep at night. People with sleep apnea will also have reduced deep sleep time, so they should seek treatment early.

Image source: pexels

02 Light sleep and REM sleep are equally important

Deep sleep is important! Light sleep and REM sleep are equally important! They all have their own functions and are indispensable. The more deep sleep, the better. They constitute a complete sleep cycle in a certain proportion.

Taking an adult in his 20s as an example, in a complete sleep cycle, stage N1 accounts for 2% to 5% of the total sleep time, stage N2 accounts for 45% to 55% of the total sleep time, deep sleep accounts for 13% to 23%, and REM accounts for 20% to 25%.

Light sleep is the basis of sleep, which may be between deep sleep, between REM sleep, or between wakefulness.

In the N1 stage, brain waves begin to slow down, muscle activity begins to decrease, and the brain goes from wakefulness to sleep.

These changes will continue until the N2 stage, when the N2 stage has unique brain wave patterns such as sleep spindles and k-complex waves. This stage of sleep accounts for the largest proportion of the entire sleep. After the human body enters N2, other sleep stages will follow.

When entering deep sleep, slow waves (delta waves) begin to appear. This is a wide wave with high amplitude, so it is also called slow wave sleep, delta wave sleep or deep sleep.

REM sleep was discovered in the early 1950s by Eugene Aserski, a graduate student at the University of Chicago, and his mentor Nathaniel Kleitman. The discovery is that children's eyes move rapidly in different directions after falling asleep. They named this stage of sleep REM sleep.

They found that brain activity during REM sleep is very similar to brain activity during wakefulness. This stage is also the stage of a lot of dreaming and is also the basic link in memory processing. REM sleep disorders can cause other cognitive difficulties besides memory difficulties, including inattention, lack of concentration and potential emotional disorders, but REM sleep disorders have no obvious correlation with sleepiness.

Image source: pexels

03 Is it reasonable to sleep according to the sleep cycle?

Our sleep cycle is usually 90 minutes, but this is an average. We must understand that everyone's sleep cycle is different. Mine may be 80 minutes, and yours may be 100 minutes.

There is a misconception that the amount of sleep we need is irrelevant, as long as we make sure it is a multiple of the 90-minute cycle. This means that if people follow a 90-minute cycle and wake up, they will miss out on a lot of sleep.

for example:

Xiao Li is used to going to bed at 11 o'clock every night and getting up at 7:30 in the morning. Following this schedule, he has plenty of energy every day.

Now, in order to meet the 90-minute sleep cycle, he has calculated that, provided his bedtime remains unchanged, he needs to get up at 6:30, so that he will get just enough sleep for five cycles. However, his sleep time is reduced by one hour a day. As a result, he feels exhausted due to lack of sleep.

The most important thing about sleep is "regularity" and "enough sleep". As long as you go to bed and get up on time every day, and sleep for the required amount of time, then it is normal. There is no need to panic if you did not sleep well one day. As long as you don't worry, your sleep will get better and better.