4 hours of sleep a day is perfect? Lack of sleep makes people ‘selfish’, new study shows

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Don’t be embarrassed and start getting the sleep we need.

Writing |Ling Jun

Source | “Medical Community” Public Account

Recently, Sohu CEO Zhang Chaoyang said in a video program that sleeping too much is a kind of harm to people. It is recommended that everyone sleep less, 6 hours is the best, and 4 hours is perfect.

This topic was on the hot search on August 22. Up to now, the topic #ZHANG Chaoyang advises everyone to sleep less# has caused 1.03 billion reads on Weibo, 66,000 discussions, and some netizens have Jokes, “I fell asleep, I didn’t see a suggestion.”

Interestingly, at the same time, another trending entry was “Those who sleep less than 7 hours have thicker arms and thighs”, which originated from the Tenth People’s Affiliated to Tongji University in Shanghai A study published in the journal Nutrients by a team of hospital experts showed that sleeping less than 7 hours per day was associated with increased fat mass in parts of the body (arms, legs), especially in men and obese people.

Although the above studies only observed the correlation between sleep duration and fat in different parts, and cannot draw conclusions about obesity, it is a consensus that lack of sleep can affect physical and mental health.

And just yesterday (23rd), a research team from the Center for Human Sleep Science at the University of California, Berkeley pointed out in a study in the journal PLOS BIOLOGY that it is not just that it affects personal health, lack of sleep It may make people “selfish and indifferent” and no longer willing to help others.

Lack of sleep makes you “selfish”?

The full title of the study: “Insufficient sleep causes individuals, groups and wider society to stop helping others” and was led by a renowned sleep expert who founded the “Science of Human Sleep” Center,” Matthew Walker, who also wrote a global bestseller: “Why We Sleep”.

On a theoretical basis, the researchers point out, studies have shown that sleep deprivation impairs emotional processing, leading to deficits in expression, which is further associated with antisocial behavior, including increased interpersonal conflict, trust in others degree decreased. At the same time, sleep deprivation reduces activity in numerous regions of the brain’s social cognitive network, disrupting each other’s functional connections.

To further test a series of conclusions, the researchers designed three trials.

Experiment 1 set an extreme scenario. Twenty-four healthy adults were divided into two groups, in the same environment, one group completed 8 hours of sleep at night, and the other group did not sleep a night.

The next day, researchers scanned the participants’ brains with functional magnetic resonance imaging (fMRI) and found that those who stayed up all night, when based on scenarios that required empathy or empathy for others, The corresponding areas of the brain’s mental network were significantly less active. And through questionnaires, the researchers also found that those who stayed up all night showed a significant drop in their desire to help others.

Experiment 2 took the scene out of the lab, and the researchers followed 136 people online to maintain their daily activities. The researchers measured their nighttime sleep quality online, including how long they slept, how many times they woke up halfway through, and then assessed their willingness to help others, such as opening elevator doors for others, helping an injured stranger on the street, and more.

The results showed that the average sleep time of 136 subjects in 4 days was 429±68.8 minutes, and the sleep efficiency was 90.02±9.36%. During this period, once the sleep efficiency decreased, the first The willingness to help others also decreases.

One ​​question is, is feeling tired from not sleeping well enough to impair the motivation for all daily proactive actions the next day? In an additional trial, the researchers balanced this factor and showed that poor sleep alone led to lower empathy.

The third trial involved data on more than 3 million charitable donations in the United States between 2001 and 2016.

Daylight saving time in the United States starts on the 2nd Sunday in March every year. On that night, the hands are moved forward by 1 hour, which means that people are unknowingly deprived of 1 hour. hours of sleep.

Researchers found that donations were 10% lower than average during the week of daylight saving time compared to the weeks before and after. As controls, Arizona and Hawaii, which do not enforce daylight saving time rules—that is, people are not deprived of an hour of sleep—don’t significantly differ from the average in the number and amount of donations.

For this study, Matthew Walker said that when people lose an hour of sleep, our innate kindness and drive to help others take a clear hit.

“We’re starting to see more and more studies showing that sleep deprivation not only affects individuals, but also spreads to the periphery,” said Ben Simon, another researcher. “If you don’t get enough sleep, in addition to your own well-being, it can hurt the well-being of your entire social circle, including strangers.”

Why do we sleep

With a combination of factors such as increasing social pressure and the popularity of electronic products, adequate sleep seems to have become a “luxury” in contemporary society. The “China Sleep Research Report (2022)” shows that in the past 10 years, Chinese people have fallen asleep more than two hours later, and the average sleep time has decreased from 8.5 hours in 2012 to 7.06 hours in 2021. Only 35% of Chinese Get 8 hours of sleep a day.

Although it is affected by many aspects such as sleep efficiency and physical fitness, the amount of sleep required for each person is different, and there are also great differences between individuals. However, from a group perspective, the health hazards caused by insufficient sleep have been widely proven:


People who slept less than 6 hours a night were significantly more likely to be overweight, while those who slept an average of 8 hours a night had the lowest relative body fat rates. In addition, infants with “short sleep” were significantly more likely to develop obesity later in childhood than those with adequate sleep.


Studies report that getting less than 5 hours of sleep per night is associated with a significantly increased risk of developing type 2 diabetes, but improving sleep can positively impact blood sugar control and reduce the risk of type 2 diabetes.

Cardiovascular disease

A study by the American Heart Association found that sleep deprivation was positively associated with the accumulation of calcification in the heart’s arteries. People who slept 1 hour less per night had a 33% increased risk of calcium accumulation in the arteries. Less than 6 hours, the most dangerous changes in the heart’s arteries occur.


Studies show that women who slept less than 5 hours a day had a 36% increased risk of colon cancer and men who slept less than 6.5 hours had a 112% increased risk of lung cancer compared to those who slept 7-7.5 hours.

According to the National Sleep Foundation guidelines, healthy adults need 7 to 9 hours of sleep per night, and people over the age of 65 should also get 7 to 8 hours of sleep per night.

And children and teens need more sleep for growth and development. “Sleep is not only a need for rest for children, but also a catalyst for the development of physical and mental health.” Professor Jiang Fan from the Department of Developmental Behavioral Pediatrics at Shanghai Children’s Medical Center once told the media.

Compared with the suggestion to sleep less, in 1998, Professor Jiang Fan visited more than 30,000 children in 9 provinces and cities across the country under the leadership of his tutor, and found that the main reason for the lack of sleep in Chinese children is “School load too high” and “to school too early”. With the help of a series of scientific data, in 2007, Shanghai issued a notice of “delaying school hours for primary and secondary schools”, which gave children an extra hour of sleep.

“In today’s society people are not getting enough sleep, and the lack of attention to sleep also stems from too many affairs — family, personal affairs, and work.” Director of Behavioral Sleep Medicine, Cleveland Clinic, USA “These are challenges, and once people understand how important it is to get enough sleep, and how to sleep better, can have a huge impact,” Dr. Dreyrup wrote.

Professor Ben Simon also said in the interview that it’s time to give up the idea that sleep is unnecessary or a waste of time, don’t be embarrassed, and start fighting for the sleep we need.

Source: Medicine

Editor in charge: Tian Dongliang

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