However, no one realizes that sleeping, a skill we have mastered since birth, seems to be becoming more and more troublesome in recent years. Some people can't sleep all night, some people have difficulty falling asleep, some people struggle between sleeping and waking up every day, or feel that they haven't slept enough after being awakened by the alarm, or they really wake up naturally and feel guilty about the "too long" sleep time.
In July this year, The New Yorker made an in-depth analysis of a series of studies on sleep in recent years, interviewed relevant researchers, and answered public concerns, such as why it is difficult for us to fall asleep, what are the benefits of sleep, and what are the effects of insufficient sleep.
What affects our sleep?
How do people fall asleep? Imagine this process. Your temperature starts to drop, and your hands and feet stay warm. Melatonin secretion increases, the brain gets the message that it needs to rest, your blood pressure drops, your heart rate slows down, and your breathing is gentle. Then, you go to sleep gently.
Perfect! You can't help admiring.
Don't boast yet. In fact, this is just an idealized description. Sleep is not a simple process. It seems to be very troublesome in recent years. Charles Czeisler, director of sleep medicine department of Brigham and Women's Hospital, found that in the past 50 years, people's average sleep time on weekdays has dropped from 8.5 hours to less than 7 hours. More detailed data is that 3 1% people sleep less than 6 hours every night, and 69% people think they don't get enough sleep. However, the phenomenon of reduced sleep does not only occur in the adult world. We humans all sleep less than before. Dr Lisa Matricciani, a sleep expert at the University of South Australia, analyzed the sleep data of children from 1905 to 2008. She found that during this period, children's sleep time was reduced by one minute almost every year.
Basically, the problem of sleep loss is not that we wake up early, but that when and how we choose to sleep has a lot to do with it. Elizabeth Klerman is in charge of data analysis and modeling in the sleep medicine department of Brigham Gynecology Hospital. She studies how individual differences in the environment affect our circadian rhythm and ability to fall asleep. "No matter how tired you are, when you sleep will affect how long you sleep," she said.
How long it takes to fall asleep is influenced by a series of factors. In order to understand the importance of each of these factors, Klerman first evaluated the habits of the subjects, including the time when they usually fall asleep, the time when they get up, the problems they encounter during sleep, and whether they use sleep AIDS. After collecting this information, Klerman and his colleagues took the subjects to the laboratory and monitored their sleep, and evaluated the influence of each factor on sleep.
Genetic factors partly affect our sleep. Many sleep disorders, including insomnia and circadian rhythm disorders, are largely influenced by genetic factors. If you can't rest according to the daily routine because of insomnia in the circadian rhythm, your melatonin level will drop: the hormone that tells you to sleep is insufficient, or the corresponding receptor is missing. However, we can't fully understand how genes affect human sleep.
Dragana Rogulja, a neurobiologist at Jefferson University, has studied the sleep cycle of fruit flies for many years. She pointed out that sleep genes are reserved in many species, and fruit flies have many similarities with humans. For example, the genetic composition of fruit flies is similar to that of humans, and they like to sleep at a fixed time every day. On June 29th, she and her colleagues published a study in Current Biology, which showed that there was a gene mutation called Taranis in Drosophila, which slept less than its peers. "There are still many unsolved mysteries about sleep, especially the protein mechanism that starts this process at the molecular level." Kyunghee Koh, another author of the paper and an assistant professor, said that this study found new molecular pathways and brain regions that can control people's sleep time.
Even so, in the past 100 years, human genes have not changed much. Genetic predisposition cannot explain why so many people have sleep problems. Many researchers find that good sleep hygiene is very necessary. Good sleep hygiene can even overcome the influence of some genetic factors. On the contrary, the effects of poor sleep hygiene may be as bad as the most serious genetic diseases.
The factors of sleep hygiene also include living habits. Nicotine, caffeine and alcohol all have negative effects on sleep, especially before going to bed. Take part in sports and eat on time, and we will fall asleep faster; Eating too late or eating too much makes it difficult to fall asleep. This influence is mutual. Sleep disorders are also associated with weight gain. If you have an empty stomach before going to bed, your sleepiness will escape without a trace.
In fact, any change in plans may affect sleep. Rosalind Picard, director of the Emotional Computing Research Group in the Media Laboratory of MIT, found that the irregularity of sleep is one of the most important factors that affect the quality of individual sleep. Going to bed on time is healthier than staying up all night and catching up on sleep the next day. Regular sleep also helps to get a higher grade point and have a good mood.
Perhaps the most important factor in sleep hygiene is the influence of light. In the past century, lights have become very popular at night. In fact, the special photoreceptor cells in human eyes will respond to the changes of darkness and light, only to regulate our circadian rhythm. These melanopsin receptors are directly related to the part of the brain that regulates the body's biological clock. They even work for the blind: even if the blind are conscious, their bodies still know how to adjust their biological clocks. Light helps the body perceive the future. It tells us how the surrounding environment will change and how our bodies will prepare in the next few hours or days. Steven Lockley, a neuroscientist at Harvard University, said, "Our clock has evolved to predict tomorrow."
However, this natural forecasting system has now become chaotic. Humans are increasingly surrounded by short-wave light or "blue light", and our circadian rhythm system will mistake it for sunlight. Computers, televisions, mobile phones and e-readers all emit blue light; 90% of Americans use electronic devices that emit blue light. When we use a device that emits blue light, we actually send a signal to the brain to postpone sleep. "What did we do to dusk?" Charles Czeisler sighed. When dusk is gradually delayed because of these false sunshine, we feel the spewing energy, not the melatonin that should be secreted.
Chesler found that artificial light can reverse our biological clock by four to six time zones. It depends on what we are in contact with. In a study published in the Proceedings of the National Academy of Sciences (PNAS) earlier this year, Czeisler and his colleagues asked subjects to read paper books or e-books for four hours before going to bed for five consecutive nights. The result is very shocking. Compared with people who read paper books, subjects who read e-books secrete less melatonin and are less likely to feel sleepy. The time to secrete melatonin has also been pushed for an hour and a half, and the biological clock has also changed. It takes them longer to fall asleep. The next morning, they were not alert enough.
However, it is not only long-term exposure to blue light that will happen. Lockley found in the sleep laboratory that the above changes would occur even if the subjects were exposed to short-wave light for less than 12 minutes.
Many people who can't sleep will seek sleep AIDS. Unfortunately, existing drugs may not be enough to change the effects of overstimulation. The sleep we get through medication is different from that of regular sleep, and may not be as effective as we thought. Matt Bianchi, head of the sleep information laboratory and sleep medicine department at Massachusetts General Hospital, said that people who use sleep AIDS only sleep for an average of 30 to 40 minutes more than those who don't use drugs. And there is no drug on the market that can completely imitate the natural path of sleep. On the contrary, many drugs can inhibit REM and slow-wave sleep. Bianchi therefore wrote that this may "damage the healing value of sleep." Using some sleep AIDS can also bring the risk of abnormal sleep. Abnormal sleep means that when a person falls asleep, he will eat or leave the room, but when he wakes up, he doesn't remember doing these things. Generally speaking, it is not recommended to use these drugs continuously for more than one week.
Of course, we also have non-drug methods to promote sleep. Lockley and Czeisler developed a lighting system to help people feel sleepy when they should be sleeping. At first, the wavelength of light emitted by this system keeps us awake, and then it gradually becomes longer and warmer light, telling our bodies to get ready for sleep. The system has also been adopted by NASA and will be installed on the International Space Station in June 20 16. For consumers, most electronic devices can be equipped with blue filters.
There are also some behavioral methods. Susan Redline, a sleep researcher at Harvard Medical School, recommended cognitive behavioral therapy. She believes that other "consciousness-body therapies", such as Tai Chi, yoga and meditation, may also be effective. Redline is developing a yoga intervention therapy for low-income residents with sleep problems in Boston. The related research that yoga can promote sleep provides a theoretical basis for this work. Brazilian therapy, led by Pedro Hallal, a researcher at pelotas University in Brazil, provides free public places in low-income areas, which has a good prospect for improving sleep.
More solutions are needed to improve insomnia. On the one hand, our sleep problem is getting more and more serious, on the other hand, we don't have a good plan to deal with this change.
Why do we need sleep?
I spend nearly one third of my life sleeping. Why should we sleep?
When we sleep, our body consciousness is very fragile. Besides, when we sleep, we do nothing. On the surface, we can't generate any benefits. 17 19, Cotton Mather said in a sermon that too much sleep was "sinful" and lamented that we often slept when we should be working. Benjamin Franklin famously said, "People will sleep well in the grave."
For a long time, sleep was considered useless, and even scientists who studied it thought it was interesting. Robert Stickgold, a sleep researcher at Harvard University, remembers his former collaborator J. Allan Hobson joking that the only function of sleep is to treat drowsiness. In 2006, neuroscientist Marcos Frank concluded in a paper on sleep function that the influence of sleep on human cognition is "weak or vague".
In the past ten years, especially last year, the mystery of sleep is gradually being revealed. In fact, sleep is an important part of our life. We need to close our eyes, do nothing and go to sleep.
Observing the abnormal phenomena in sleep can help us understand why human beings need sleep. Patients with sleep behavior disorder during rapid eye movement (REM) will engage in sports activities consistent with their dreams when they enter REM sleep state. REM sleep behavior disorder is a precursor of neurodegenerative diseases. A sleep research center in Montreal found that more than half of patients with REM sleep behavior disorder had clinical manifestations of neurodegenerative diseases, such as apnea for several seconds or even minutes during sleep, after onset 12 years. Experiments show that REM sleep behavior disorder is related to diabetes and cardiovascular diseases, which will lead to cognitive dysfunction. About 10% of the dysfunction in awake state is the result of chronic insomnia. Chronic insomnia can lead to low quality of life, depression and the increase of cardiovascular diseases, hypertension, cognitive dysfunction and motor dysfunction.
Sleep is the need for the body to repair and maintain cognitive function. At the same time, sleep may be beneficial to relieve vascular tension. The fact that insomnia is related to depression shows that sleep may help to cope with emotional stress or other chaotic situations.
In 2000, a study published by Stickgold in Nature showed that sleep and dreaming played an important role in memory consolidation. The subjects were asked to play games for seven hours every day for three days. Some people have never played this game, while others are familiar with it. The third group of subjects were amnesiacs, whose medial temporal lobe and hippocampus were seriously damaged. In this case, they cannot form a new memento mori. Every night, when the subjects sleep, they are constantly woken up and asked to recall what they dreamed. It turns out that this game is what they dream of. Surprisingly, even amnesiacs dream about this game. When they woke up the next day, the subjects couldn't remember the game or the person who woke them up in the middle of the night, but the shape of their memory was very consistent with the pattern structure observed in the game before.
Since then, evidence about memory and memory function has appeared continuously.
20 13, Stickgold published a review, summarizing the progress of other researchers in this field. He believes that sleep is not only important for memory consolidation, but also an unusual selection mechanism. Sometimes, we remember something just because it is exciting or sad. Sometimes, in order to understand why something is important, we try to recall every trivial detail. Stickgold said that sleep and dreaming help us filter materials and store important content, whether it is the gist of a lot of information or a specific detail. "In the dream, all we got was fragments. After waking up, we know everything. "
Jane Born, a neurobiologist at the University of Tubingen, and Ullrich Wagner, a neuroscientist at the University of Mü nster, once asked subjects to solve a relatively complicated mathematical problem. There is a simple solution to this problem, and an abstract concept can quickly get the answer. Of course, the subjects did not know this. A few people found the answer from the beginning. Eight hours later, each subject did the problem again. In the meantime, some people can sleep, while others can't. The results show that only a quarter of people who didn't sleep quickly got the answer, and 60% of those who slept in these eight hours found a shortcut to solve the problem. In fact, when we sleep, the brain will play back the experience of the day and process, learn and filter this information. In a sense, the brain thinks while sleeping.
Our physical health also seems to be closely related to sleep. In order to test the interaction between heart and sleep, physiologists put a group of healthy male subjects with no history of heart disease into sleep deprivation. At different time points, scientists measured the vascular health of these subjects, and checked their heartbeat, blood pressure and protein level related to heart disease. Within two days, almost all the subjects' indexes went up. On the contrary, a study on sleep apnea found that the treatment of respiratory asphyxia improved vascular function. Once the patient can sleep well, the pressure in his heart will be relieved.
The importance of sleep to brain function may be even more critical. In addition to affecting memory and problem-solving functions, sleep can also help the brain to stay alert, young and healthy.
Two years ago, McCann Nedgard, a neuroscientist at the University of Rochester, published the results of years of research on the effects of sleep. She analyzed the awake and sleeping brains of mice and found that sleep is the maintenance system of the brain. When awake, our activities build up rubble in the brain, and toxins are formed in the brain, such as β -amyloid peptide (Aβ) which leads to Alzheimer's disease, and some normally harmless protein are misfolded. Abnormality of Aβ is a biomarker of early Alzheimer's disease. A large number of studies have shown that Aβ accumulation plays an important role in brain lesions and cognitive impairment of Alzheimer's disease. When we sleep, the lymphatic system of the brain will expand and cerebrospinal fluid will be pumped back to the brain through brain tissue to clean up the waste in the brain. Lymphatic system is a purification system to deal with brain cell waste. This is a tribute to the lymphatic system, which is responsible for cleaning up waste in the body. If the brain does not get enough rest, endotoxin will accumulate in the brain and neurodegenerative diseases will occur. One of the earliest signs of dementia is sleep disorder, and some genes that control the duration are also related to Alzheimer's disease. Sleep disintegration and neurodegeneration have the same biological mechanism.
All studies show that when we sleep, our bodies are doing important work. However, few people get enough sleep. Some people will never even know what it feels like to be fully awake. What is the state of not having a good rest at night? More and more researchers are beginning to study how long-term lack of sleep affects our lives.
What are the consequences of insufficient sleep?
Did you sleep well last night? You think you are completely awake, and now you are the smartest, smartest and most capable?
Unfortunately, this can only be a daydream of most Americans. Josna Adusumilli, a neuroscientist and sleep medicine expert at Harvard University, told The New Yorker: Most people are not at their best. She said that 50 million to 70 million Americans suffer from chronic sleep disorders.
Lack of sleep can have serious consequences. Sleep inertia is a groggy and not awake state after waking up. In fact, everyone has sleep inertia. The duration of sleep inertia largely depends on the quantity and quality of our sleep. If you have enough rest, your sleep inertia will soon dissipate. However, if you don't have a good rest, it may last all day, making you unhappy and even dangerous.
Many people have experienced the consequences of lack of sleep. Judith Owens, director of the Children's Sleep Center of Boston Children's Hospital, studied the impact of school hours on the health of school-age children. Her conclusion is not very optimistic. For most adults, 8 hours of sleep every day is enough, but children need about 13 hours of sleep, including daytime naps. Teenagers need about nine and a half hours; Besides, they are often night owls. According to the ideal physiological rhythm, they should go to bed late and get up late. Since1960s, the school timetable has been advanced, which has seriously affected students' health. "This will not only lead to lack of sleep, but also disturb the circadian rhythm," Owens said. "When their brains are still in a deep sleep state, they have to wake up. Waking a child at 6 am is like waking an adult at 3 pm. "
This result is similar to persistent jet lag, which will be aggravated by excessive sleep on weekends. Decision-making function and emotional response become worse. The ability to make correct decisions is affected, and children may become prone to depression. In fact, the increase in the diagnosis of attention deficit hyperactivity disorder (A.D.H.D) may be the result of children's lack of sleep to some extent. Symptoms of sleep deprivation in children include ADHD and impaired understanding of external stimuli. Owens encountered many such misdiagnosis in her clinical practice. Lack of sleep can also affect physical development. Children who sleep less than the standard sleep time are more likely to be obese. Even the sleep time of a 6-month-old baby can predict his weight gain after three years. On the other hand, schools with healthier class hours have better attendance, test scores, GPA and health status.
A study shows that delaying class time through intervention can not only improve academic performance, but also reduce the number of car accidents and the reporting rate of depression by 70%. Owens found that even if he was delayed for half an hour, his grades still improved. She said, "Students' health and state should be considered in class time, not for the convenience of adults. "
As we get older, our sleep quality will only get worse and worse. Adusumilli said that if a person sleeps six hours every night for 65,438+02 consecutive days-which is also the time that many Americans sleep every year-his cognitive and physical performance becomes almost as indistinguishable as a person who can't sleep for 24 hours. Sleeping for four hours every night for six days is the same result. A person stays awake for 24 hours, and his performance is similar to that of a person with a blood alcohol concentration of 0. 1%. In other words, the "normal" level of sleep deprivation makes our performance achieve the effect of drunkenness.
In the short term, lack of sleep has a profound impact on our performance. The first is the influence on sensory and motor skills. In a study of college basketball players, well-rested players perform better than those who work and rest as usual. Emotional control will also be affected, and the connection between prefrontal cortex and amygdala will be weakened, making us impulsive and prone to depression.
Our thinking and decision-making ability will also decline sharply, and we will not perform well in learning, memory, simple calculation and analytical reasoning. The ratio of accidents and mistakes has increased. In a study of interns in Brigham Gynecology Hospital, compared with those interns who worked for 65,438+06 hours in shifts and got rest, interns who worked normally made twice as many mistakes every night because of inattention, and this result has been repeated many times.
Lack of sleep has a longer-term impact on health. We are more prone to metabolic and endocrine problems, such as weight gain, which leads to an increased risk of diabetes and cardiovascular disease; Decreased immune function increases the risk of cancer; Cognitive decline is accelerated, and the risk of dementia is increased.
Even if you increase your sleep from now on, it may be too late, because children's brains grow and change too fast, and they are more prone to lack of sleep than adults; Those influences may be with them all their lives, regardless of their later habits.
For adults, we can recover from short-term lack of sleep. David Dinges, a sleep researcher at the University of Pennsylvania, found that after five nights of sleep deprivation, a good night's sleep can rejuvenate you. If it is really a long-term lack of sleep, it depends on the quality of sleep if you want to recover. Physical recovery may take weeks, sometimes even longer. We often can't enjoy ten hours' sleep every night, even for a week, which is too extravagant.
Ironically, many people don't want to get some sleep, even if they can. We didn't realize that we deprived ourselves of sleep. Many people think that we can sleep for five to six hours every day. We sincerely believe that we are fully awake, which is also our best state. However, we know very little about how much sleep we need.
In one study, Elizabeth Klerman, a sleep scientist at Brigham Gynecology Hospital, asked people to follow their sleep plan for two weeks. They can choose how long they wake up and sleep every day. Then, they enter the sleep lab. Klerman is interested in two things: preparation time and sleep duration. The next day, she found that the average sleep time of the subjects was 1.2 and a half hours, and they could even sleep 1.6 hours, which indicated that they all had the problem of insufficient sleep. On the first day in the laboratory, when testing the preparation time for falling asleep, some people fell asleep before the technicians left the laboratory. In other words, they are very sleepy.
However, they think they are sober and in good shape. Kellermann said that each of us has our own "degree of discomfort", but that doesn't mean that we really perform well.
Charles Czeisler found that we realized the influence of lack of sleep on our performance a day or two ago. Then, we didn't play our best, and we never realized it again. "This is another you," Chesler said.
In another experiment, Kalerman studied what factors limited the subjects' sleep time. She was impressed by a subject because he came back after sleeping normally. He said that he hoped to fill in the form again and reassess the sensitivity and performance of his brain. He said that he didn't realize how bad he used to be until he slept for a while, hoping to lower his previous scores. "He has forgotten the feeling of being warned," Clemen said. At that time, he thought he was sober and capable.
"Why should the brain monitor itself?" Clemen asked.
The current research on sleep has given us a deeper understanding of sleep. Each of us wants to be efficient, but when we try to improve our performance by extending working hours, there is actually no benefit. The less rest we have, the more we lose and the less efficient we are. Your original keen observation will be reduced, even your happiness will be reduced, and you will even get sick more easily. No one knows how much ability and health we have sacrificed in this process. People will only tell you that it doesn't matter if you sleep for five or six hours every day, you will still perform well. In fact, we completely underestimate the value of sleep, although it may have a fundamental impact on present and future performance.
Unlike most things, sleep needs to be done by yourself. No one in this world can sleep instead of you.