take away food
Why is sleep important?
Sleep researchers are discovering how important sleep is for learning and memory, and how sleep deprivation affects our health, safety, and longevity.
- Why are we sleeping at all?
take away food
- Our bodies regulate sleep just like we eat, drink and breathe. This suggests that sleep plays a similarly important role in our health and well-being.
- Although it is difficult to answer the question: "Why do we sleep?" Scientists have developed several theories that, taken together, could help explain why we spend a third of our lives sleeping.
- Understanding these theories can help deepen our understanding of the role of sleep in our lives.
Hunger and eating, drowsiness and sleep
While we may not often think about why we sleep, most of us recognize on some level that when we sleep we feel better. After a good night's sleep we feel more alert, more energetic, happier and more productive. However, the fact that sleeping makes us feel better and not sleeping makes us feel worse only partially explains why sleep may be necessary.(Video) The importance of sleep
One way to think about the role of sleep is to compare it to another of our vital activities: eating. Hunger is a protective mechanism that evolved to ensure we get the nutrients our bodies need to grow, repair tissues, and function properly. And while it's relatively easy to understand the role of eating, since it involves the physical intake of the substances our bodies need, eating and sleeping aren't as different as they might seem.
Both eating and sleeping are regulated by strong internal impulses. Refraining from eating creates the uncomfortable feeling of hunger, while without sleep we feel overwhelmingly sleepy. And just like eating reduces hunger and ensures we get the nutrients we need, sleeping reduces drowsiness and ensures we get the sleep we need. Still, the question remains: Why do we need sleep? Is there one main function of sleep or does sleep have many functions?
An unanswered question?
Scientists have studied why we sleep from many different angles. For example, they studied what happens when people or other animals are deprived of sleep. In other studies, they looked at sleep patterns in a variety of organisms to see if the similarities or differences between species might reveal something about sleep functions. But despite decades of research and many discoveries about other aspects of sleep, the question of why we sleep is difficult to answer.
The lack of a clear answer to this challenging question does not mean that this research was a waste of time. In fact, we now know a lot more about how sleep works, and scientists have developed several promising theories to explain why we sleep. Given the evidence gathered, it seems likely that no theory will ever be proven correct. Instead we can find that the dream is explained by two or more of these explanations. The hope is that by better understanding why we sleep, we'll learn to treat sleep's functions with more respect and enjoy the health benefits it provides.
This paper outlines several current theories about why we sleep. To learn more about them, be sure to read the references at the end of this essay. There you will find links to articles by researchers exploring this intriguing question.
Theories about why we sleep
One of the earliest sleep theories, sometimes referred to as adaptive or evolutionary theory, holds that nocturnal inactivity is an adaptation that serves a survival function by keeping organisms out of the way during times when they are particularly vulnerable. The theory suggests that animals that could remain still and still during these times of vulnerability had an advantage over other animals that remained active. For example, these animals suffered no accidents during activities in the dark and were not killed by predators. Through natural selection, this behavioral strategy probably evolved into what we know today as sleep.
A simple argument against this theory is that it's always safer to remain conscious to respond to an emergency (even if you're in the dark at night). So there doesn't seem to be any benefit to being unconscious and asleep when safety is paramount.
theory of conservation of energy
Although it may be less obvious to people living in societies where food sources are plentiful, one of the most powerful factors in natural selection is competition and the efficient use of energy resources. Energy conservation theory suggests that the primary function of sleep is to reduce a person's energy needs and expenditure during part of the day or night, particularly at times when foraging is less efficient.
Research has shown that energy metabolism is significantly reduced during sleep (by as much as 10 percent in humans and even more in other species). For example, both body temperature and calorie requirements decrease during sleep compared to when we are awake. Such evidence supports the thesis that one of the main functions of sleep is to help organisms conserve their energy resources. Many scientists consider this theory to be related and part of the rest theory.
Another explanation for why we sleep is based on the long-held belief that sleep somehow serves to "rebuild" what is lost in the body while we are awake. Sleep provides the body with an opportunity to repair and rejuvenate itself. In recent years, these ideas have received support from empirical evidence accumulated in human and animal studies. The most amazing thing is that animals that are completely deprived of sleep lose all immune function and die within weeks. This is supported by evidence that many of the body's most important restorative functions, such as muscle growth, tissue repair, protein synthesis, andgrowth hormonethe release occurs mainly or in some cases only during sleep.
Other rejuvenating aspects of sleep are specific to the brain andcognitive function. For example, while we are awake, neurons in the brain produceAdenosine, a by-product of the activities of cells. The accumulation of adenosine in the brain is believed to be a factor that leads to our perception of tiredness. (By the way, this feeling is counteracted by usingCaffeine, which blocks the effects of adenosine in the brain and keeps us awake). Scientists believe that this accumulation of adenosine during waking hours can promote the "urge to sleep." While we are awake, adenosine builds up and stays high. During sleep, the body has a chance to clear adenosine from the system, which makes us feel more awake when we wake up. Consistent with the need to remove chemical deposits in the brain, recent studies in experimental animals reveal a previously unknown brain drainage pathway now known as the glymphatic system. This network of "tunnels" surrounding existing blood vessels promotes the removal of substances from the brain. Its efficiency increases during sleep; Studies have shown that removing toxins via this route, such as B. amyloid beta, a protein associated with Alzheimer's disease, is reduced by sleep deprivation.
Synaptic homeostasis theory
A recent theory states that sleep is necessary to reduce neural connections, or synapses, in the brain. He suggests that the number of synapses increases throughout the day as a result of daily activity. If it were allowed to build up continuously, the brain would become overloaded, much like a hard drive in a computer nearing capacity. Therefore, it is necessary to trim unnecessary synapses and strengthen essential ones. Studies supporting this theory show that synapses contract and expand with sleep and wakefulness in experimental animals.
Theory of brain plasticity
One of the newest and most compelling explanations for why we sleep is based on discoveries that sleep is related to changes in the structure and organization of the brain. This phenomenon, known as brain plasticity, is not fully understood, but its connection to sleep has several critical implications. For example, it is becoming increasingly clear that sleep plays a crucial role in the brain development of infants and young children. Babies spend about 13 to 14 hours a day sleeping, and about half of that time is spent in REM sleep, the stage when most dreams occur. A connection between sleep and brain plasticity is also becoming clear in adults. This is reflected in the effect that sleep and sleep deprivation have on people's ability to learn and complete a variety of tasks.
While these theories remain unproven, science has made great strides in discovering what happens during sleep and the mechanisms in the body that control the sleep-wake cycles that help determine our lives. While this research addresses the question "Why do we sleep?" not answered directly. creates the conditions to put this question in a new context and to gain new insights into this essential part of life.(Video) Sleep Benefits & Importance - Why You Need Sleep | Anthem
- frank mg The mystery of the sleep function: current perspectives and future directions. Rev. Neurosci. 2006;17(4):375-92. doi: 10.1515/revneuro.2006.17.4.375.
- Jessen NA, Munk AS, Lundgaard I, Nedergaard M. El sistema glinfático: una guía para principiantes. Resolution Neurochemie 2015;40(12):2583-99. doi: 10.1007/s11064-015-1581-6.
- Porkka-Heiskanen T. Adenosine in sleep and wakefulness. Ana Med. 1999;31(2):125-9. doi: 10.3109/07853899908998788.
- seal JM 2005. Evidence of mammalian sleep functions. Nature. 437:1264-1271.
- Tononi G, Cirelli C. Sleep function and synaptic homeostasis. Sleep Med Rev. 2006;10(1):49-62. doi: 10.1016/j.smrv.2005.05.002.
- sleep, learning and memory
take away food
- Research suggests that sleep plays an important role in memory, both before and after learning a new task.
- Lack of adequate sleep affects mood, motivation, judgment, and our perception of events.
- Although there are some unanswered questions about sleep's specific role in memory formation and storage, there is general consensus that sound sleep during the night is optimal for learning and memory.
The learning process and sleep
Sleep, learning and memory are complex phenomena that are not yet fully understood. However, animal and human studies suggest that the quantity and quality of sleep has a profound impact on learning and memory. Research suggests that sleep supports learning and memory in two different ways. First, a sleep-deprived person cannot optimally focus attention and therefore cannot study efficiently. Second, sleep itself plays a role in memory consolidation, which is essential for learning new information.
Although the exact mechanisms are not known, learning and memory are often described in terms of three functions.acquisitionIt refers to the introduction of new information into the brain.consolidationrepresents the processes by which a memory becomes stable.Rememberrefers to the ability to access information (either consciously or unconsciously) after it has been stored.
Each of these steps is required for the memory to function properly. Acquisition and retrieval only occur while we are awake, but research suggests that memory consolidation occurs during sleep by strengthening the neural connections that form our memories. Although there is no consensus on how sleep enables this process, many researchers believe that the specific properties ofbrainwavesduring different stages of sleep are associated with the formation of certain types of memory.
dr Robert Stickgold discusses how sleep plays a role in memory, both before and after a new learning situation.
Sleep researchers study the role of sleep in learning and memory formation in two ways. The first approach analyzes the different stages of sleep (and changes in their duration) in response to learning a variety of new tasks. The second approach examines how sleep deprivation affects learning. Sleep deprivation can be total (no sleep allowed), partial (early or late sleep deprivation), or selective (deprivation of certain sleep stages).
sleep stages and memory types
Different types of memories are formed in new learning situations. Scientists are investigating whether there is a link between the consolidation of different types of memories and the different stages of sleep.
Early research on sleep and memory focused ondeclarative memory, that is knowledge of factual information or "what" we know (e.g. the capital of France or what you had dinner last night). A research study found that people who took an intensive language course experienced an increase ofRapid eye movement sleep or REM sleep. This is a stage of sleep when dreams are most common. The scientists hypothesized that REM sleep plays an essential role in the acquisition of learning material. Other studies have shown that REM sleep appears to be involved in declarative memory processes when the information is complex and emotionally charged, but probably not when the information is simple and emotionally neutral.
That's what the researchers are now assumingSlow Wave Sleep (SWS)Deep, restful sleep also plays an important role in declarative memory, processing and consolidating newly acquired information. Studies on the link between sleep and declarative memory have produced mixed results, and this is an area of ongoing research.
Research has also focused on sleep and its role in bedtimeprocedure memory– Remembering “how” to do something (e.g. riding a bike or playing the piano). REM sleep appears to play a crucial role in consolidating procedural memory. Other aspects of sleep also play a role: motor learning appears to depend on the number of light sleep stages, while certain types of visual learning appear to depend on the amount and timing of deep sleep (SWS) and REM sleep.
The effects of sleep deprivation on learning and performance
Another area researchers are studying is the impact that a lack of adequate sleep has on learning and memory. When we are sleep deprived, our focus, attention, and alertness drift, making it difficult to receive information. Without adequate sleep and rest, overworked neurons can no longer function to coordinate information properly, and we lose our ability to access previously learned information.
dr Robert Stickgold describes studies showing the importance of sleep in memory consolidation after learning a new task.(Video) 🔴 Heavy Rain on Road to Sleep Faster, Beat Insomnia, Block Noises, Study, Relax | Heavy Rain Sounds
Our interpretation of events can also be affected. We lose our ability to make informed decisions because we can no longer properly assess the situation, plan accordingly, and choose the right behavior. The verdict worsens.
Chronic fatigue to the point of exhaustion or exhaustion means we are less likely to perform well. Neurons aren't working optimally, muscles aren't resting, and organ systems in the body aren't in sync. Lack of concentration due to sleep deprivation can even lead to accidents or injuries.
For more information on how sleep deprivation affects performance, seeSleep, performance and public safety.
Poor sleep quality and sleep deprivation also negatively impact mood, which affects learning. Mood swings affect our ability to acquire new information and then retain that information. Although chronic sleep deprivation affects different people in different ways (and the effects are not fully understood), it is clear that a good night's sleep has a powerful impact on learning and memory.
Although current research suggests that sleep is essential for proper memory function, as in any area of active scientific research, there are unanswered questions. For example, certain medications significantly, if not completely, suppress REM sleep. However, patients taking these drugs do not report memory impairment. Likewise, injuries or illnesses that lead to injuriesbrainstem(and subsequent removal of a person's REM sleep) have not resulted in any apparent loss of the ability to form new memories. The exploration and debate continues.
Not all researchers are convinced that sleep plays such a prominent role in memory consolidation as others believe. In experiments in which animals completed a course through a complicated maze, the animals' amount of REM sleep increased after completing the task. Some researchers believe that the increase in REM sleep reflects an increased demand on the brain processes involved in learning a new task. However, other researchers have suggested that any change in REM sleep duration is due to the stress of the task itself, rather than a functional relationship to learning.
Researchers also disagree about the effects of sleep deprivation on learning and memory. For example, rats often perform much worse on learning tasks after being selectively deprived of REM sleep. This suggests that REM sleep is necessary for the animals to consolidate memory of performing the task. Some scientists have argued that the observed differences in learning are not actually due to a lack of REM sleep, but may be due to the animals not getting as good a rest because they were deprived of some of their sleep.
According to many researchers, the evidence suggests that different sleep stages are involved in the consolidation of different types of memories and that sleep deprivation decreases the ability to learn. Although open questions (and debates) remain, the general evidence suggests that getting enough sleep every day is very important for learning and memory.
- Ellenbogen JM, Payne JD, Stickgold R. The role of sleep in declarative memory consolidation: passive, permissive, active, or neither? Current Opinion Neurobiol. December 2006; 16(6):716-22. doi: 10.1016/j.conb.2006.
return to Sleep Healthy Home
This content was last revised on October 1, 2021.
A resource from the Department of Sleep Medicine at Harvard Medical School
About this site|sitemap|glossary|Videoindex|technical help|Comment|credits|disclosure|Disclaimers|understand the dream
- public education
- Sleep and Health Education Program
- HEALTHY SLEEP
- Why Sleep Matters: Benefits of Sleep
- Why Sleep Matters: Consequences of Sleep Deprivation
- Why Sleep Matters: Historical and Cultural Perspectives on Sleep
- Sleep Science: What is Sleep?
- Sleep Science: How is sleep regulated?
- Genetics, Aging and Sleep: Sleep and Aging
- Genetics, aging and sleep: profiles of changes with age
- Genetics, Aging, and Sleep: The Genetics of Sleep
- Getting the Sleep You Need: Overcoming Factors Disrupting Sleep
- Get the sleep you need: you and your biological clock
- Get the sleep you need: jet lag and shift work
- Getting the sleep you need: when to seek treatment
- HEALTHY SLEEP
- Sleep and Health Education Program
- public education
© 2023 by the President and Fellows of Harvard College
Why is sleep important for sleep? ›
During sleep, your body is working to support healthy brain function and maintain your physical health. In children and teens, sleep also helps support growth and development. Getting inadequate sleep over time can raise your risk for chronic (long-term) health problems.Why is sleep important 4 reasons? ›
Sleep is important because it enables the body to repair and be fit and ready for another day. Getting adequate rest may also help prevent excess weight gain, heart disease, and increased illness duration.What is the most important function of sleep? ›
Sleep is important to a number of brain functions, including how nerve cells (neurons) communicate with each other. In fact, your brain and body stay remarkably active while you sleep. Recent findings suggest that sleep plays a housekeeping role that removes toxins in your brain that build up while you are awake.How does sleep impact your life? ›
“Sleep affects almost every tissue in our bodies,” says Dr. Michael Twery, a sleep expert at NIH. “It affects growth and stress hormones, our immune system, appetite, breathing, blood pressure and cardiovascular health.” Research shows that lack of sleep increases the risk for obesity, heart disease and infections.What are 3 emotional benefits of sleep? ›
The mental benefits of sleep are thought to include the capacity to improve creativity and problem solving; lower the likelihood of depression and other mental disorders; and even increase life expectancy.What happens if we don t sleep? ›
What happens if you don't sleep? Not getting enough sleep can lower your sex drive, weaken your immune system, cause thinking issues, and lead to weight gain. When you don't get enough sleep, you may also increase your risk of certain cancers, diabetes, and even car accidents.How much sleep is necessary? ›
|Age group||Recommended amount of sleep|
|3 to 5 years||10 to 13 hours per 24 hours, including naps|
|6 to 12 years||9 to 12 hours per 24 hours|
|13 to 18 years||8 to 10 hours per 24 hours|
|Adults||7 or more hours a night|
Experts recommend that adults sleep between 7 and 9 hours a night. Adults who sleep less than 7 hours a night may have more health issues than those who sleep 7 or more hours a night.How does sleep affect human behavior? ›
Studies show people who are sleep deprived report increases in negative moods (anger, frustration, irritability, sadness) and decreases in positive moods. And sleeplessness is often a symptom of mood disorders, such as depression and anxiety.What are 5 effects of lack of sleep? ›
An ongoing lack of sleep has been closely associated with hypertension, heart attacks and strokes, obesity, diabetes, depression and anxiety, decreased brain function, memory loss, weakened immune system, lower fertility rates and psychiatric disorders.
What happens if you don't get no sleep? ›
Some of the most serious potential problems associated with chronic sleep deprivation are high blood pressure, diabetes, heart attack, heart failure or stroke. Other potential problems include obesity, depression, reduced immune system function and lower sex drive.How long can a human survive without sleep? ›
The longest recorded time without sleep is approximately 264 hours, or just over 11 consecutive days. Although it's unclear exactly how long humans can survive without sleep, it isn't long before the effects of sleep deprivation start to show. After only three or four nights without sleep, you can start to hallucinate.How much sleep does a 100 year old need? ›
Older adults need about the same amount of sleep as all adults—7 to 9 hours each night. But, older people tend to go to sleep earlier and get up earlier than they did when they were younger.How many hours sleep by age? ›
|Age Group||Recommended Hours of Sleep Per Day|
|Newborn||0–3 months||14–17 hours (National Sleep Foundation)1 No recommendation (American Academy of Sleep Medicine)2|
|School Age||6–12 years||9–12 hours per 24 hours2|
|Teen||13–18 years||8–10 hours per 24 hours2|
|Adult||18–60 years||7 or more hours per night3|
When it comes to bedtime, he says there's a window of several hours—roughly between 8 PM and 12 AM—during which your brain and body have the opportunity to get all the non-REM and REM shuteye they need to function optimally.What affects sleep quality? ›
External factors, such as what we eat and drink, the medications we take, and the environment in which we sleep can also greatly affect the quantity and quality of our sleep. In general, all of these factors tend to increase the number of awakenings and limit the depth of sleep.What happens if you sleep too much? ›
Too much sleep on a regular basis can increase the risk of diabetes, heart disease, stroke, and death according to several studies done over the years. Too much is defined as greater than nine hours. The most common cause is not getting enough sleep the night before, or cumulatively during the week.Can too much sleep make you tired? ›
Research bears out the connection between too much sleep and too little energy. It appears that any significant deviation from normal sleep patterns can upset the body's rhythms and increase daytime fatigue.Why do we sleep 3 reasons? ›
Sleep is an essential function. View Source that allows your body and mind to recharge, leaving you refreshed and alert when you wake up. Healthy sleep also helps the body remain healthy and stave off diseases. Without enough sleep, the brain cannot function properly.What are 3 reasons sleep is important for learning? ›
Sleep research from the last 20 years indicates that sleep does more than simply give students the energy they need to study and perform well on tests. Sleep actually helps students learn, memorize, retain, recall, and use their new knowledge to come up with creative and innovative solutions.
What happens if you don t sleep? ›
You increase your risk of serious health issues.
A number of chronic health conditions may be affected by not getting enough sleep on a regular basis. These include high blood pressure, diabetes, heart failure, coronary heart disease and some cancers. You may also be more likely to have a stroke.
Sleep occurs in five stages: wake, N1, N2, N3, and REM.How much sleep is important? ›
For adults, getting less than seven hours of sleep a night on a regular basis has been linked with poor health, including weight gain, having a body mass index of 30 or higher, diabetes, high blood pressure, heart disease, stroke, and depression.Why do humans love to sleep? ›
It recharges us with new energy. After a hard day's work you certainly deserve a good rest. Your tired eyes need to close for a few hours while your brain “cleans itself up” and your body produces many new cells!How does lack of sleep affect your brain? ›
Sleep deprivation makes us moody and irritable, and impairs brain functions such as memory and decision-making. It also negatively impacts the rest of the body – it impairs the functioning of the immune system, for example, making us more susceptible to infection.Do you age if you don't sleep? ›
Beneath the surface, your body is aging too, and sleep loss can speed up the process. A study done by UCLA researchers discovered that just a single night of insufficient sleep can make an older adults' cells age quicker. This might not seem like a big deal, but it has the potential to bring on a lot of other diseases.Is it OK to sleep without sleep? ›
All-nighters have extensive and potentially serious negative effects. Sleep is vital to the proper functioning of the body, and completely skipping a night of sleep can harm your thinking and cognition, your mood and emotions, and your physical well-being.Why do we wake up at 3am? ›
You wake up at 3am because this is the time you shift from a deep sleep into a lighter sleep. If you turn in at 11pm, by three in the morning you're mostly out of deep sleep and shifting into longer periods of lighter sleep, known as REM.What is the best sleep cycle? ›
An average sleep cycle lasts about 90 minutes. Ideally, you need four to six cycles of sleep every 24 hours to feel fresh and rested. Each cycle contains four individual stages: three that form non-rapid eye movement (NREM) sleep and one rapid eye movement (REM) sleep.What is the deepest part of sleep? ›
Stage 4 - REM Sleep
The first round of REM in a night lasts about 10 minutes, with the stage getting longer and longer each time you enter REM in one night1. It's also the deepest stage of sleep, where you'll experience1: Quickened breathing. Faster heart rate and blood pressure.