Not getting enough sleep can affect not only your mental state the next day, but also your overall health in the long run. In this regard, sleep medicine researchers have identified a number of sleep-related health risks, such as cardiovascular, immune, metabolic and mental health problems, as well as cancer.
Especially for mental health, there has been a lot of scientific evidence that there are specific mental health risks hidden behind sleep time. For example, long-term sleep deprivation may lead to an increased risk of depression. But what exactly is sleep deprivation? Based on the differences in samples, the threshold of sleep deprivation found in different studies is different, basically between 5 and 7 hours. Most people think that sleeping less than 6 hours a day is relatively small.
In 2020, a study published in JAMA Network Open used the sleep data of nearly 20,000 people in China and the UK and found that there is an inverse U-shaped relationship between sleep duration and cognitive decline. Those who slept less than four hours a day or more than 10 hours a day experienced faster cognitive decline than those who slept a relatively healthy amount of seven hours a day. This suggests that sleeping too much, like sleeping too little, may be a risk signal for health.
The three stages of sleep throughout life
However, affected by individual physical differences and living environment, there are many factors that affect people’s sleep duration in real life, and as people grow older, people’s sleep patterns will generally change naturally, so it is difficult to have a one-size-fits-all The precise sleep duration standard applicable to everyone. Uncovering the secrets of sleep from a larger sample could help improve understanding of the health implications of sleep duration.
Recently, a research team composed of researchers from multiple institutions explored the regularity of human sleep duration through sleep data with a larger sample size. Using the self-reported sleep duration data of more than 730,000 people, they found that the sleep status of adults is Life can be roughly divided into three stages, and the two key dividing lines fall around the age of 30 and 50.
Specifically, the data show that people’s sleep time decreases rapidly after adulthood, and it roughly drops to a relatively low level at the age of 33, and then the sleep time continues to decrease slowly, reaching a trough around the age of 50, and then starting after the age of 53. bottomed out. Such an approximately U-shaped three-stage curve makes the age group from 30 to 50 the period with the least sleep time in a person’s life. Relevant research was published in Nature Communications in December 2022. Under the circumstances that sleep differences between people are common, it provides a certain reference for evaluating the overall change of sleep duration in a person’s life.
The distribution of these sleep extremes is of particular interest given that either too much or too little sleep can be a risk factor. Further data analysis shows that if adults under the age of 70 are divided into three age groups, old, middle-aged and young, people who sleep only about 5 hours are reflected in all age groups, but those who sleep less The number clearly increased with age, with the highest proportion of those who slept less in the older age group. In comparison, there are more people who sleep longer in the elderly and young people, especially the young people, and the proportion of people who sleep 9 hours or more per day is higher. In the middle-aged group, this ratio is significantly lower, which is consistent with the social environment where most middle-aged people are busy with career and family at the same time.
For individuals, due to the impact of specific work intensity and daily family affairs in life, the daily sleep duration may be affected and fluctuate. However, judging from these large sample data collected in many places in the world, the characteristics of the three stages of sleep in life are quite stable. Regardless of factors such as gender, education, and culture, people’s sleep duration changes with age. Three distinct stages. According to the analysis of the researchers, behind the three stages divided by age, it reflects the changes in the responsibilities of people in different growth stages.
Different age groups have different sleep standards
For example, on the way to middle age after adulthood, people’s sleep time decreases rapidly, which may be due to the increasing responsibilities of work and child care, and the gradual increase in sleep time after the age of 50 may be related to factors such as parenting pressure. related. Especially after the age of 60, as people retire, work tasks are reduced, and external factors that affect sleep are further reduced, all of which may contribute to the subsequent increase in overall sleep time.
Of course, the latest research only analyzes people between the ages of 19 and 70, and it is impossible to know what will happen after the age of 70. Because the data in this study comes from users of an online game, although more than 3 million people participated, the sample size is relatively large, but considering that it is still relatively small for people over 70 years old to play mobile phones and even play games, it may be possible It will lead to bias in sample selection, which is not enough to represent the elderly in the age group. Therefore, the researchers excluded all survey participants over the age of 70. At the same time, extreme values found in sleep duration, such as those who slept less than 5 hours and those who slept more than 10 hours, were also excluded due to concerns that these individuals might not be able to participate in the survey awake when they self-reported sleep duration outer. This also means that although there are quite a few of the 730,000 people analyzed in the latest study, there are limitations in selection and measurement. It remains to continue to verify this sleep three-stage model with more objective and accurate large-sample sleep measurement data in the future.
In addition to people over the age of 70, data for people under the age of 19 were also missing from the latest study. However, in 2021, researchers from institutions such as Erasmus University used data from more than 1 million people in the Netherlands, the United Kingdom, and the United States to summarize the sleep characteristics of local people. The time does not meet the recommended sleep duration of 8 to 10 hours, and 18% of people report daytime sleepiness.
In 2015, the National Sleep Foundation of the United States organized experts to give advice on healthy sleep duration based on a large amount of scientific evidence. Among them, for adults aged 18 to 64, it is recommended to sleep 7 to 9 hours a day; for the elderly over 65 years old, it is recommended to sleep 7 to 8 hours a day.
Adults aren’t faring particularly well either, with one in four not getting the recommended amount of sleep for their age group, but most are not unacceptably sleep deprived. In 2015, the National Sleep Foundation of the United States organized experts to give advice on healthy sleep duration based on a large amount of scientific evidence. Among them, for adults aged 18 to 64, it is recommended to sleep 7 to 9 hours a day; for the elderly over 65 years old, it is recommended to sleep 7 to 8 hours a day. The growth of minors changes rapidly, and the overall required sleep time decreases significantly with age. In addition to the amount of 8 to 10 hours for adolescents, school-age children and preschool children need 9 to 11 hours and 10 to 13 hours respectively.
Sleeping too much or too little may not be good
Combined with the sleep pattern characteristics found in the latest research, 7 hours of sleep is an important reference index for the health of adults. Because the latest study not only investigated the sleep situation with a large number of game players, but also indirectly measured the cognition of the respondents through their game performance such as their spatial navigation ability in the game. It turned out that there is a certain relationship between sleep and cognitive performance.
Taking the elderly group aged 54 to 70 as an example, although the sleep duration of people in this stage will generally increase with age, the cognitive ability measurement shows that the more sleep the better. Similar to previous studies, the relationship between spatial perception ability and sleep time of the elderly is also an inverse U-shaped relationship. People who sleep about 7 hours a day have the best cognitive performance, and other people who sleep too much or too little have better cognitive performance. Difference. In addition to the elderly group, although such an obvious reverse U-shaped relationship has not been found in other age groups, the data shows that if you sleep about 7 hours a day, your cognitive performance is relatively better. This is yet another confirmation that sleeping too much or too little may not be a good thing.
Although people know that too little sleep will lead to poor mental condition the next day, so they must maintain enough sleep, but for scientists, why do people and even animals have enough sleep, and what role does sleep play in the maintenance of life? There are still many unsolved mysteries surrounding the phenomenon of sleep. For now, scientists have found that sleep has a positive effect on the consolidation of memory. If people do not sleep or sleep too little, the brain cannot make full use of processes such as neural replay during sleep to consolidate long-term memories.
In 2013, a key study in the journal Science also found that in the sleep state, the interstitial space will expand by 60%, and the brain can clear the metabolic waste of neural activity significantly faster than in the awake state, showing that sleep may It also has a protective effect on the brain by this mechanism. In 2021, researchers at the University of Paris also found through a long-term follow-up study that lasted nearly 25 years that people in their fifties and sixties who sleep too short, less than 6 hours, have an increased risk of subsequent dementia 30%, the risk of getting too little sleep is further revealed by long-term research data.
As for why too much sleep is not good, the relevant scientific evidence is even scarcer, making it more difficult to establish a causal relationship between too much sleep and cognitive decline.
As far as the current scientific evidence is concerned, there is a possibility that sleeping too much may not be the cause of impaired health, but the result and sign of impaired health, such as depression, fatigue, and cognitive decline. It will increase, even if you don’t sleep well at night, if you are always disturbed, your sleep time may also become longer. On the other hand, this emphasizes that sleep should not only focus on the duration, but also the quality of sleep and the time to fall asleep.
seven hours of sleep
In addition, the latest research, using data across multiple regions, also found two common factors that affect the overall sleep patterns of people in a place, one is cultural norms and the other is latitude. Cultural norms are mainly reflected in lunch break culture and overtime culture. Lunch break can reduce the pressure of going to bed at night, and too much overtime will obviously occupy sleep time. In terms of latitude, the difference in sunrise and sunset times in various places will affect the time when people fall asleep, which in turn will affect the overall sleep duration.
As far as China is concerned, on March 17, 2023, the Institute of Sociology of the Chinese Academy of Social Sciences and other institutions released the “China Sleep Research Report 2023”. The latest data shows that in 2022, the average sleep duration of residents is about 7.4 hours, nearly half of people sleep less than 8 hours a day. These data have once again sounded the alarm for people with obvious sleep deprivation. Combined with current scientific understanding, for most adults without special circumstances, even if they don’t get enough sleep for 8 hours a day, they should have at least 7 hours of sleep. In this way, we can lay a solid foundation for maintaining physical and mental health.