Recently, people often ask us if Koreans have really evolved out of sleep.

In Korean dramas, the plot always takes place at night. When traveling to South Korea, you'll find cafes everywhere on the streets. Looking at the social media of Koreans, they're still sweating in the gym at 4 a.m. and then sitting in the office full of energy at 9 a.m.

Then I look at myself. I can't eat enough and can't wake up. A Korean's day is longer than my two days. Wait, is this really okay?

First, let's ask if it's true: Do Koreans really sleep so little?

Well, they're not being wronged on this point. A 2022 sleep - tracking survey showed that South Korea is one of the four countries with the least sleep. The average sleep duration of Koreans is only 6 hours and 41 minutes. Another survey found that Korean teenagers are the hardest - hit group for sleep deprivation. On weekdays, 14 - to 19 - year - olds sleep an average of only 5 hours and 42 minutes.

This situation isn't just in South Korea. Look at Nanshan in Shenzhen, Malianwa in Beijing, and Central in Hong Kong. There are quite a lot of people who don't sleep.

Can people really not die suddenly with so little sleep? Can sleep really be evolved out?

Do people who sleep less really die faster?

Not necessarily.

The amount of sleep humans need varies. Due to genetic differences, some people are naturally short - sleepers. Short - sleepers generally need 4 to 6 hours of sleep per day, and their daytime state after waking up is the same as that of normal people, without the various problems caused by sleep deprivation. Most adults who haven't won the "genetic lottery" need 7 to 9 hours of sleep, while teenagers need even more, generally recommended to sleep 8.5 to 9.25 hours per night.

Since sleep needs vary from person to person, a short sleep time can't be directly equated with sleep deprivation. However, we can use a simple way to judge if we've had enough sleep - see if we always want to catch up on sleep. If you often catch up on sleep on weekends and sleep for half a day, you're probably very sleep - deprived on weekdays.

If you're sleep - deprived for a long time, even if it doesn't directly cause death, it will bring a series of health problems.

Research has found that people with long - term sleep deprivation will have a "prematurely aged" heart. Based on their individual cardiovascular risk status, their "heart age" is larger, which also comes with a higher risk of diabetes, high blood pressure, and high cholesterol. Adults who usually sleep more than 7 hours have the youngest heart age.

Sleep deprivation also leads to a decline in immunity and an increase in pro - inflammatory and anti - inflammatory markers in the body. You may have had the direct experience that after staying up late for work or study for several days, you're more likely to get sick, and all kinds of minor ailments will appear.

There's also a relationship between obesity and sleep deprivation. Lack of sleep affects the release of leptin and ghrelin, two hormones that are very important for regulating appetite and metabolism. A 2004 study found that two days of sleep deprivation would reduce leptin levels by 18% and increase ghrelin by 28%, making people crave high - calorie foods and unconsciously eat more. If you want to lose weight, "sleeping more to lose weight" isn't just an empty slogan. Only by ensuring good sleep can you ensure normal appetite and not be easily tempted by delicious food.

Cognitive level and behavior are also affected by sleep deprivation. Sleep deprivation leads to memory decline, makes it harder to concentrate, slows down reactions, and makes people more impulsive. A 2018 study showed that compared with getting 7 to 8 hours of sleep, sleeping only 6 hours increases the probability of a car accident by 33%, and 9% of car accidents are related to the driver's sleep deprivation. Even if the driver doesn't feel sleepy, sleep deprivation will unconsciously affect their reaction while driving.

Less sleep is also associated with a higher risk of suicide, especially among teenagers.

In 2014, a South Korean study surveyed more than 4,000 junior and high school students and found that students who caught up on sleep for a long time on weekends (indicating sleep deprivation on weekdays) often had a higher willingness to commit suicide and self - harm tendencies. People with sleep deprivation are more likely to have depressive emotions and make negative and reckless decisions. For teenagers, who are more impulsive by nature, ensuring sufficient sleep is even more important for a healthy mental state.

Is there a way to stay healthy while sleeping less?

What will happen if you're not a natural short - sleeper but still try to shorten your sleep?

You may have heard of some amazing folk remedies for shortening sleep time. One widely spread method is the "Da Vinci sleep method," which says that people can sleep for 20 minutes every few hours and meet their sleep needs through multiple short naps, leaving a lot of extra time for other things. So, can this method be used?

In short - not recommended! Not recommended! Not recommended!

Before explaining the reasons, let's first understand what a "sleep cycle" is.

A complete sleep cycle lasts about 90 to 120 minutes, and a night's sleep usually consists of 4 to 5 cycles. Imagine using the Da Vinci sleep method. Our sleep cycle is interrupted right at the beginning, and we can't enter deep sleep. Moreover, we have to stay awake for several hours before getting another 20 - minute nap. This completely goes against human sleep patterns.

In an experiment, scientists recruited 10 volunteers. They were allowed to sleep for 20 minutes every 4 hours, and the experiment lasted for 8 weeks. Most people couldn't last for a month. Only a 25 - year - old man lasted until the 5th week, but the release of his growth hormone decreased by more than 95%, and he couldn't concentrate at all when awake. It was a double blow to his body and mind. Unless you want to challenge your willpower and experience inhumane torture, don't consider this method.

Another popular folk remedy in recent years also comes from Koreans.

It's said that they don't sleep every day, drink iced Americanos at every meal, and rely on the "sudden - death prevention package" - multivitamins, fish oil, and coenzyme Q10 to stay alive. So, can taking supplements make up for the negative effects of sleep deprivation?

No. Currently, there's no supplement that can completely eliminate the impact of sleep deprivation on the body. However, research has found that a healthy diet rich in plant - based foods, low in saturated fat and added sugar, can relieve fatigue and inattention caused by sleep deprivation. In addition, sleep is also closely related to micronutrients. For example, iron, zinc, and magnesium can promote falling asleep and extend sleep time. A 2023 animal experiment also found that supplementing nicotinamide riboside in food can reduce the sleep needs of mice, but there's no definite evidence that it works for humans.

Some people use another method: staying up late at night and taking a nap during the day; or staying up late on weekdays and catching up on sleep on weekends. Can catching up on sleep the next day make up for the damage of staying up late the previous day?

As a country with a high rate of sleep deprivation, South Korea has also done a lot of research in this area. They found that compensatory sleep can't completely make up for the negative effects of previous sleep deprivation, but if staying up late at night is unavoidable, catching up on sleep later is better than not doing it. For example, sleep - deprived students are more likely to be overweight, but catching up on sleep on weekends can reduce their obesity risk. A longitudinal survey in China from 2011 to 2015 also showed that middle - aged and elderly people with short nighttime sleep have an increased risk of high blood pressure, but taking a nap during the day can help them prevent it.

All in all, if you stay up late every day and have short sleep at night, the most reliable way to save your health at present is still to catch up on sleep.

Why do we have to sleep?

Humans spend one - third of their lives sleeping. We've evolved for hundreds of millions of years, evolving bigger brains and more dexterous hands, but we haven't evolved out of sleep. There's a reason for this - sleep isn't just a waste of time; it's much more important than people think.

We can imagine the brain as a computer. When we're awake, it's like the computer is in use. We constantly receive information from the outside world and others and respond to it. When we sleep, the brain isn't in a shutdown state. It's more like the computer is on but the screen is off, reducing information exchange with the outside world and focusing on tasks like memory management and clearing the cache.

Sleep is divided into two different states - non - rapid eye movement sleep (NREM) and rapid eye movement sleep (REM). Non - rapid eye movement sleep takes up most of the sleep time. From stage 1 (N1) to stage 3 (N3), it gets deeper. Stage 3 is generally considered deep sleep. During rapid eye movement sleep, the brain becomes active, but some muscles are paralyzed, and most dreams occur during this time.

During deep sleep, the brain is quietly doing "memory management" - it classifies and filters the memories just acquired during the day, filters out the most important parts, converts them into long - term memories, and deletes the unimportant ones. For example, if we meet a friend or learn interesting new knowledge during the day, this information will be consolidated in the brain, and we can still remember it ten or fifteen days later. However, we meet countless passers - by every day. Most of these people will probably never be seen again in our lives, and we don't need to remember their faces. These redundant memories will be eliminated.

Sleep can also help you solve complex problems. In a study, scientists prepared a series of questions of different difficulties. Volunteers who either slept or stayed awake for a period of time then came back to solve the problems they couldn't solve at first. The results showed that they could solve more difficult problems after sleeping, but for simple problems, it didn't matter whether they slept or not. If you encounter a problem that you can't figure out for a while, "sleeping on it" is really good advice - only when you've had enough sleep can your brain run at full speed and help you make better decisions.

The growth and remodeling of the body also depend on sleep. The release of growth hormone is cyclical, and most of it is released during deep sleep. For children in the growth and development stage, high - quality sleep is the basis for growing up. Sleep can also prevent muscle breakdown and promote fat loss. After a night of staying up all night, the signs of protein breakdown in muscle tissue will increase, and the metabolites related to fat storage will also increase. For young men, sleeping only 5 hours per night for a week will reduce testosterone levels by 10% to 15%, and testosterone is crucial for muscle growth. If you have a plan to build muscle and lose fat, ensuring sufficient sleep will prevent your hard - working workouts from going to waste.

The functions of sleep don't stop there. All aspects of the human physiological system, including cognitive function, growth and development, immune response, psychology and emotions, energy conservation, and most of the body functions you can think of, require regular sleep to function properly.

In the end, why do people try so hard to resist the biological rhythm? Don't envy those natural short - sleepers, and don't be disappointed in yourself if you like to sleep. At every age, enjoying and embracing sleep should be our right.

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