How Sleep Affects Your Body, In Both Good And Bad Ways
Getting more sleep can improve your health, but what happens when you are chronically sleep-deprived?
Sleep is weird. Every night you’re supposed to drop everything, lie down in the dark, and just vibe for eight hours with your eyes closed, entering a vulnerable and seemingly unproductive state that will consume a third of your life. It’s no wonder both kids and adults often rebel against sleep — we want to keep playing and working, and sleep can feel like a waste of time.
It isn’t, of course. Most people are at least generally aware that sleep deprivation isn’t great for their health and well-being, aside from well-known effects like grumpiness and grogginess.
But sleep isn’t just about avoiding harm — many people don’t realize how much they could benefit from better sleep. Here are some of the things you may not even realize you enjoy from a good night’s rest, and some ways sleep deprivation may affect you.
How good sleep helps your body
Sleep allows a full-body restoration
Sleep gives the brain — and other systems in the body — an important opportunity for upkeep. Beyond merely making us feel miserable, sleep loss can trigger a surge of problems all over the body.
“It's not a question of comfort,” said Merrill Mitler, a licensed psychologist and expert in sleep disorders as well as former program director for the National Institutes of Health. Laboratory animals will die if deprived of sleep. “The causes of death are complicated, and they involve systemic failures all over the body. This suggests the things that go on in the body during sleep are essential, and they are restorative in all organ systems.”
That certainly includes the brain, where sleep plays a key role in all kinds of cognitive abilities, Mitler said, including the critical task of memory consolidation, a process by which long-term memories are formed.
The nightly restoration also extends to the cardiovascular, gastrointestinal, and immune systems. Sleep gives our bodies a chance to perform restorative tasks like muscle repair and protein synthesis; it’s also a key time for releasing certain hormones.
Sleep improves mental health and alertness
Research shows a correlation between sleep and mental health, but the relationship tends to be bidirectional, which means each factor can affect the other.
While there is still uncertainty about the relationship between the two, a meta-analysis published in Sleep Medicine Reviews in 2021 suggests better sleep really can boost mental health.
Taking steps to improve sleep can reduce anxiety, depression, and rumination, the analysis concluded, and have a “medium-sized effect” on mental health overall. There is evidence to suggest getting enough restorative, continuous sleep can help with emotional regulation and expression, Mitler said.
Sleep also fuels your vigilance, also known as sustained attention or tonic alertness. This helps you maintain focus for longer periods, which is a useful or even vital ability in lots of scenarios, including attending meetings, playing sports, driving a car, or supervising a baby.
If someone isn’t getting a full night’s sleep, short episodes, say three hours here or there, can improve vigilance and help keep you alert, said Marishka K. Brown, director of the National Center on Sleep Disorder Research. However, being alert is not the same thing as being healthy.
“If you're sleeping that way, it doesn't protect your heart, your pancreas, your digestion,” Brown said. “Good sleep is required for those things to function properly.”
Sleep leads to better learning and memory
Learning and memory consist of three basic functions: acquisition (introducing new information to the brain), consolidation (stabilizing a memory), and recall (accessing the information later). Acquisition and recall happen when we’re awake, but consolidation — a key part of learning and memory — seems to shine while we sleep.
When you have a new experience, your conscious memory of that experience at first relies entirely on information stored in both the hippocampus and the neocortex. The term memory consolidation refers to a process in which these fresh, malleable memories in the hippocampus are converted to more stable, long-lasting memories that can reside elsewhere in the brain.
Memory consolidation can unfold for weeks to years after the information was initially acquired, and research suggests sleep is a particularly important time for consolidating memories.
Sleep boosts problem-solving and creativity
Because sleep helps us consolidate memories and learn from them, researchers think it also plays an important role in helping us find creative solutions to problems we encounter while awake. Armed with whatever we learned from our memories as we slept, we often seem to solve problems — especially difficult problems — more easily when well rested.
Research has shown that sleep can boost problem-solving, and slow-wave sleep might be especially important. A study published in Frontiers in Behavioral Neuroscience in 2021, for example, found that people who had a night of sleep after being trained in a problem-solving task were much likelier to later solve the problem when tested than people who had received the same training (and who had waited the same amount of time to be tested) but did not sleep in between.
The researchers reported that 62% of the sleep group solved the problem, compared with 24% of the awake group, and subjects in the sleep group who had gotten more slow-wave sleep also had a higher chance of solving the problem.
Sleep helps immune function
Sleep is a key time for the immune system, which generates protective proteins called cytokines as well as T-cells while we’re asleep. According to a 2021 review article published in Communications Biology, sleep deprivation is associated with a chronic inflammatory state as well as increased risk for both infectious and inflammatory diseases.
Getting enough sleep, on the other hand, can boost your immune system’s ability to protect you from getting sick. When people got enough sleep after receiving an experimental hepatitis A vaccine, for example, their immune systems produced more germ-fighting T helper cells and antibodies, according to a report in the journal Pflügers Archiv European Journal of Physiology.
Sleep improves athletic performance
We need sleep to help our bodies recover and adapt after physical exercise, but there is evidence from research that sleep supports our athletic endeavors in other ways, too. Sleep duration and improved sleep quality are both associated with improved performance and competitive success of athletes, according to a 2017 study published in Current Sports Medicine Reports, and they may also help reduce athletes’ risk of injury or illness, both by boosting their immune systems and by helping increase their participation in training.
Other research supports this, such as a 2021 study published in Frontiers in Sports and Active Living, which found that athletes who get at least eight hours of sleep, or who had higher levels of sleep quality, were less likely to suffer from illness or injury. And aside from just getting hurt less, research has found many athletes enjoy better performance following sleep improvements. That includes better reaction times, according to a 2019 study published in the International Journal of Sports Medicine, along with sprint times, tennis serve accuracy, swim turns, kick stroke efficiency, and accuracy with both free throws and 3-point shots in basketball.
How sleep deprivation may affect your body
Lack of sleep can increase anxiety
Like mental health in general, anxiety has a bidirectional relationship with sleep, said Jonathan Jun, a pulmonary, critical care, and sleep medicine physician as well as assistant professor of medicine at Johns Hopkins Medicine.
Jun pointed to research by the late William C. Dement, a renowned sleep researcher who found that if you interrupt people while they’re dreaming, they wake up irritable and anxious the next day. Since then, more studies have also found that totally depriving people of sleep for short periods can make them more anxious, Jun added, although it may depend at least partly on the duration and severity of sleep deprivation.
“Acute, really severe deprivation of sleep is going to make you more anxious, but it’s not clear that just being a short sleeper, like chronically not sleeping as long, is going to have the same effect,” Jun said.
Lack of sleep can impair cognition
Don't count on smooth cognitive functioning if you aren't getting enough sleep. Losing even a few hours of sleep can wreak havoc with a wide variety of cognitive processes such as attention, language, reasoning, decision-making, learning, and memory.
Research shows that even a single night of mild sleep restriction can hinder your vigilance, for example, as reflected in subjects’ reduced processing capacity for decision making.
“When you don't get enough sleep, one of the first things to happen is you start to not be able to focus, you start to lose your attention span, and you can't react as quickly to things coming your way,” Jun said. “There’s a part of your brain that filters what’s coming in and decides what's important, and your ability to do that gets compromised.”
Lack of sleep can affect coordination
Sleep deprivation tends to sap your cognitive abilities fairly quickly, but it can also sneakily disrupt your coordination. The effects on coordination may be less severe than the cognitive effects, Mitler said, but they can still cause big problems — partly because they're often so hard to notice in yourself.
"Frequently the impairment process can reach dangerous levels before the subject is aware of the adverse effects," he said.
Reaction time is also delayed. “It is not an overwhelming difference, fractions of a second usually,” Mitler said. However, that’s enough to affect your ability to drive a car or truck or pilot a ship at sea.
Studies have shown that staying awake for 24 hours is similar to having a blood alcohol content of about 0.1% percent, Jun said, which is over the legal limit for driving while impaired.
Most of the time sleep-deprived people are not aware of their altered performance; they think they are doing just fine, Jun said. Even in studies where people are told to sleep six hours a night for two weeks, it’s the equivalent of being awake for two nights straight.
“If you ask people if they're falling asleep at the wheel they’ll say no, but their reaction time is slow, and they're not going to be able to react in time to what's happening,” Jun said. “Even before they fall asleep, they're already impaired.”
Lack of sleep is linked to heart disease and diabetes risk
Cardiovascular disease is the leading cause of death globally and in the United States, and there’s evidence that inadequate sleep does result in heightened risk for heart disease, according to a research review published in Sleep Medicine Clinics.
More research is still needed to shed light on how exactly sleep deprivation might contribute to heart disease, but there are clues about how it might work. Some research suggests sleep loss can lead to changes in particular hormones, for example, which trigger the chronic inflammation that sets the stage for atherosclerosis.
There is also evidence to suggest inadequate sleep is related to a higher risk of Type 2 diabetes, the most common form of the disease, according to a 2017 research review published in Current Diabetes Reports. Other analyses have reached similar conclusions, including a 2021 literature review in Diabetologia, which reported that sleep disorders like insomnia, sleep apnea, and restless legs syndrome are linked to the development of Type 2 diabetes, and diabetes complications.
Lack of sleep is linked to hormonal changes and inflammation as well as increased food intake and impaired decision making. Many of these are also risk factors for obesity, which is itself a risk factor for diabetes.
Sleep deprivation can lead to changes in certain hormones, Jun said, including leptin and ghrelin, which are involved with hunger. Loss of sleep is associated with decreases of leptin, a hormone that tells us we’re full, and increases of ghrelin, a hormone that tells us we need to eat.
“So if you don't sleep, and your leptin levels are low and your ghrelin levels are high, you are going to wake up hungry,” he said. Along with other hormonal changes, this might cause sleep-deprived people to overeat, resulting in weight gain.
“I think we as a society should destigmatize sleep,” Jun said. “It's kind of worn as a badge of honor that you don't sleep long, you don't need to sleep, sleep is for the weak, that kind of thing. I think that's number one: Don't stigmatize sleep. Recognize it's important to get enough of it.”