Recover from lack of sleep

How to Recover After a Sleepless Night

People at risk for insomnia and sleep deprivation include those with sleep disorders and medical conditions that interfere with sleep as well as caregivers and shift workers who have a tough time regulating their sleep hours.

Effects of Insomnia

“We are all familiar with the short-term effects of sleep deprivation — it makes you feel crummy, grumpy, and sleepy,” Dr. Neumeyer says. “The long-term effects can actually be pretty serious and can include obesity, depression, loss of memory, and serious accidents.”

Sleep deprivation can cause these additional negative consequences:

  • Mood changes from sleep deprivation include irritability, lack of motivation, and anxiety.
  • Performance effects include inattention, inability to concentrate, longer reaction times, and poor decision making.
  • Long-term physical effects may add to your risk for high blood pressure, heart disease, and diabetes.

Short-on-Sleep Tips

“You can’t fight biology,” says Neumeyer. “The only cure for sleep deprivation is sleep.” But for many of us, there are days that we just have to cope with not getting enough sleep. Here are some tips that may help:

  • Eat well and stay hydrated. “When you are sleep deprived, your body tries to conserve energy so you may not have the energy or the appetite to eat and drink normally,” warns Neumeyer. Avoid fast food and empty-calorie snacks that can make you feel even less energetic.
  • Get some exercise. “Some moderate aerobic exercise can give you a temporary boost, but don’t overdue the exercise or you will make your fatigue worse,” he says.
  • Enjoy some fresh air and sunshine. “Getting out in the sunlight helps reset your biological clock,” Neumeyer says. Your body will stop making the hormone melatonin when you are exposed to bright sunlight, and that may make you less sleepy.
  • Drink some coffee. About 80 percent of adults use coffee as a stimulant. You may need to take more than one cup if you are recovering from a night of insomnia. “A couple cups of coffee can help, but avoid the energy jolt from a high-caffeine energy drink,” Neumeyer advises. “The rebound when the caffeine wears off can be much worse if you are sleep deprived.”
  • Try to look better than you feel. If you look sloppy or neglect your personal hygiene, you may start to look and feel even worse. Keeping up appearances can help you hang in there on a sleepy day.
  • Grab a quick nap. You can store up on sleep if you know you are going to have a sleepless night, so restore some energy and alertness by taking a quick nap during the day. Even 15 to 20 minutes can help. In fact, if you nap longer than 30 minutes, it may be too hard for you to wake up again.

“There is no substitute for a good night’s sleep,” Neumeyer says. “If you become sleep deprived, you can eventually make up for lost sleep, but you can’t do it in one night. You can catch up gradually over a few nights.” If you have long-term symptoms of sleep deprivation, or you suffer from frequent insomnia, talk to your doctor. Insomnia can be a sign of a serious medical problem and may need to be treated.

Top 4 reasons why you’re not sleeping through the night

Unhealthy habits and underlying conditions contribute to interrupted sleep.

Published: June, 2019

The world looks sunny after a great night’s rest. But it’s a different story when sleep is frequently interrupted. A lack of Zs makes it harder to think and easier to become irritated and anxious. In the long term, inadequate sleep increases your risk for obesity, high blood pressure, heart disease, diabetes, and even premature death. That makes it important to figure out what’s interrupting your sleep.

1. It could be your age

“We see more interrupted sleep in older adults, although you shouldn’t automatically blame frequent waking on your age,” says Dr. Suzanne Bertisch, an assistant professor of medicine at Harvard Medical School.

Sometimes older adults find they wake early in the morning, when they feel they should be sleeping. But that often reflects your schedule for sleeping and waking, not disrupted sleep.

“Your circadian rhythm, or sleep-wake cycle, may dramatically shift when you’re older, causing you to get sleepy earlier. So if 8 p.m. is the start of your ‘biologic’ night, then your natural wake time may be around 4 a.m.,” Dr. Bertisch says.

2. It could be your lifestyle

One of the common causes of disrupted sleep is lifestyle, including any of the following habits:

Drinking alcohol within four hours of bedtime. A nightcap may help you fall asleep, but it also can interrupt sleep later in the night, and can also cause more trips to the bathroom.

Eating within a few hours of bedtime. Lying down with a full stomach can promote heartburn, which makes it harder to fall asleep and stay asleep.

Napping too much. Long naps in the afternoon or later make it harder to stay asleep at night.

Consuming too much caffeine. Caffeine (in coffee, tea, and sodas) blocks a brain chemical called adenosine that helps you sleep. Go light on caffeine-containing foods and drinks beyond the early afternoon.

Dr. Bertisch says changing these habits can help reduce disrupted sleep, sometimes quickly.

3. It could be your medication

Some medications can cause nighttime waking. Examples include

  • some antidepressants

  • beta blockers to treat high blood pressure

  • cold remedies containing alcohol

  • corticosteroids to treat inflammation or asthma

Dr. Bertisch recommends asking your doctor if your medication might be the culprit and if there’s a different time of day to take it or another drug that won’t interfere with your sleep.

4. It could be an underlying condition

Many chronic health problems can throw a monkey wrench into a sound sleep. These are some of the most common in older age:

Anxiety or depression. Worries or a depressed mood may make it hard to fall asleep and stay asleep.

Enlarged prostate gland (benign prostatic hyperplasia, or BPH). The urge to empty the bladder wakes men with BPH throughout the night.

Neuropathy. Tingling, numbness, or pain in the hands and feet can cause frequent waking.

Sleep apnea. Loud snoring and brief awakenings during the night may be signs you have sleep apnea, which causes brief pauses in breathing at night and leads to daytime sleepiness.

How to cope

There’s no need to live with the burden of disrupted sleep. Change your lifestyle if you feel it’s interfering with your sleep, or talk to your doctor about ways to better treat or possibly investigate underlying conditions.

And practice good sleep hygiene:

  • Wake up at the same time each day.

  • Avoid electronic devices (which emit light and stimulate the brain) at least two hours before bed.

  • Sleep in a quiet, dark, cool space.

  • Get regular exercise (but not within an hour of bedtime).

If you are already practicing healthy sleep behaviors but still have trouble sleeping, consider cognitive behavioral therapy for insomnia (CBT-i). CBT-i is a proven way to treat insomnia through relaxation techniques, talk therapy, and adjustment of the amount of time you spend in bed. It works with your body’s natural controllers of sleep to reset the brain to achieve healthier sleep.

The good news: you can boost sleep quality and regain that sunny morning feeling. “When you sleep better,” says Dr. Bertisch, “you’re more likely to see improvements in your day-to-day function, concentration, energy levels, and quality of life.”

Image: © Wavebreakmedia/Getty Images

As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

Repaying your sleep debt

Why sleep is important to your health and how to repair sleep deprivation effects.

Updated: May 9, 2018Published: July, 2007

If sleep were a credit card company, many of us would be in deep trouble.

Medical evidence suggests that for optimum health and function, the average adult should get seven to nine hours of sleep daily. But more than 60% of women regularly fall short of that goal. Although each hour of lost slumber goes into the health debit column, we don’t get any monthly reminders that we’ve fallen in arrears.

In fact, the greater the sleep debt, the less capable we are of recognizing it: Once sleep deprivation — with its fuzzy-headedness, irritability, and fatigue — has us in its sway, we can hardly recall what it’s like to be fully rested. And as the sleep debt mounts, the health consequences increase, putting us at growing risk for weight gain, diabetes, heart disease, stroke, and memory loss.

In some cases, sleep debt results from insomnia or other underlying conditions that may require medical attention. But most sleep debt is due to burning the candle at both ends — consistently failing to get to bed on time and stay there until we’ve slept enough.

Fortunately, sleep doesn’t charge interest on the unpaid balance, or even demand a one-for-one repayment. It may take some work, but you can repay even a chronic, longstanding sleep debt.

How we sleep

We need sleep, and, in a sense, we’re programmed to be sure that we get it. The body summons sleep in two ways: by boosting circulating levels of the neurotransmitter adenosine and by sending signals from the circadian clock, which controls the body’s daily rhythms. Together, these two systems establish an ideal bedtime for each of us.

Adenosine is partly a by-product of the cells’ energy expenditure. As our cells produce power to move us through the day, adenosine is released into the bloodstream and taken up by receptors in the brain region that governs wakefulness (the basal forebrain). There, it acts like a dimmer switch, turning down many of the processes associated with wakefulness, such as attention, memory, and reactions to physical stimuli. As brain levels of adenosine mount, we feel drowsier. (Caffeine keeps us awake by blocking adenosine receptors in the brain.) When we sleep, our energy needs fall, and the level of circulating adenosine drops. After a good night’s sleep, the level is at its lowest, and we are most alert.

The circadian clock regulates all body functions — not just the pattern of sleeping and waking during the 24-hour cycle, but also fluctuations in body temperature, blood pressure, and levels of digestive enzymes and various hormones. Most of us experience a major “sleepiness” peak between 12 a.m. and 6 a.m. and a minor one between 2 p.m. and 4 p.m. Of course, individuals vary. The larks among us might be ready for bed at 9 or 10 p.m. and awake at 5 a.m., while some night owls don’t fall asleep until well after midnight and prefer sleeping until noon.

Advice for avoiding sleep deprivation

  • Create a sleep sanctuary. Reserve it for sleep, intimacy, and other restful activities, like pleasure reading and meditation. Keep it on the cool side. Banish the television, computer, Blackberry, and other diversions from that space.
  • Nap only if necessary. Night owls and shift workers are at the greatest risk for sleep debt. Napping an hour or two at the peak of sleepiness in the afternoon can help to supplement hours missed at night. But naps can also interfere with your ability to sleep at night and throw your sleep schedule into disarray.
  • Avoid caffeine after noon, and go light on alcohol.
  • Get regular exercise, but not within three hours of bedtime.
  • If you’re able to get enough sleep but don’t feel refreshed in the morning, discuss the problem with your clinician. Many common medical conditions, from depression to sleep apnea (the condition in which breathing pauses during sleep), could be responsible. If you’re finding it increasingly difficult to get enough sleep but don’t have an underlying medical problem, consider consulting one of the 1,100 sleep centers accredited by the American Academy of Sleep Medicine (

Why we need sleep

Although sleep doesn’t trump food and water in the hierarchy of physical needs, we can’t live without it. Given the ethical limits on research involving human subjects, scientists have no direct evidence on how extended sleeplessness — that is, beyond a few days — affects human beings. Laboratory rats, however, have been deprived of sleep for long periods, and after a week or two, the results include loss of immune function and death from infections.

In a landmark study of human sleep deprivation, University of Chicago researchers followed a group of student volunteers who slept only four hours nightly for six consecutive days. The volunteers developed higher blood pressure and higher levels of the stress hormone cortisol, and they produced only half the usual number of antibodies to a flu vaccine. The sleep-deprived students also showed signs of insulin resistance — a condition that is the precursor of type 2 diabetes and metabolic slowdown. All the changes were reversed when the students made up the hours of sleep they had lost. The Chicago research helps to explain why chronic sleep debt raises the risk of obesity, heart disease, stroke, and diabetes.

Sleep loss exacts a toll on the mind as well as the body, as shown by a study done at the University of Pennsylvania and Harvard Medical School. The researchers studied 48 healthy men and women, ages 21 to 38, who had been averaging seven to eight hours of sleep nightly. They assigned three-quarters of the volunteers at random to three different groups that slept either eight, six, or four hours nightly; a fourth group agreed to go without sleep for three days. Every two hours during their waking periods, all the participants completed sleepiness evaluation questionnaires and took tests of reaction time, memory, and cognitive ability.

Over the course of two weeks, reaction times in the group that slept eight hours a night remained about the same, and their scores on the memory and cognitive tasks rose steadily. In contrast, scores for the four-hour and six-hour sleepers drew closer to those of the fourth group, whose scores had plummeted during their three days without sleep. After two weeks, the four-hour sleepers were cognitively in no better shape than the sleepless group after its first night awake. Their memory scores and reaction times were about on par with those of the sleepless after their second consecutive all-nighter. The six-hour sleepers performed adequately on the cognitive test but lost ground on reaction time and memory, logging scores that approximated those of the sleepless after their first night awake.

Meanwhile, the six-hour and the four-hour sleepers were failing to gauge reliably how sleepy they had become. At the end of the study, their self-rated sleepiness scores were leveling off, even as their performance scores continued to decline.

Selected resources

American Academy of Sleep Medicine

American Sleep Apnea Association

Better Sleep Council

National Sleep Foundation

The architecture of the sleep cycle

Scientists have documented the debilitating effects of sleep deprivation very well, but they still know little about how sleep accomplishes its restorative handiwork. Since the earliest sleep studies, encephalography (EEG) has been used to trace the brain waves of volunteers as they slumber. EEG readings have revealed several distinct phases of sleep characterized by different brain-wave patterns. Information derived from subsequent sleep studies has enabled researchers to correlate brain activity with other physiological processes. Today, sleep laboratories are equipped to evaluate heart rate, blood pressure, oxygen levels, breathing, eye movement, muscle tension, and limb movement.

The studies show that there are two forms of sleep, distinguished by specific brain-wave activity and the presence or absence of rapid eye movement (REM). During non-REM sleep, brain waves become slower and more synchronized, and the eyes are still; during REM sleep, brain waves are faster and less organized, and the eyes scan back and forth under the lids.

We fall into non-REM sleep in four stages that represent a continuum of shallow to deep sleep. In Stage 1, characterized by relatively fast waves, we are perched on the brink of sleep and are readily aroused. By Stage 4, or slow-wave sleep, we are dead to the world; breathing has slowed considerably and blood pressure and heart rate have dropped by as much as 30%. The brain becomes less responsive to external stimuli, making it difficult to awaken. Although most of the body’s systems are in “sleep mode” at this stage, some are at their most productive. Early in Stage 4 sleep, for example, the pituitary releases a pulse of growth hormone that stimulates tissue growth and repair.

REM sleep sets the stage for dreams. Our eyes are scanning back and forth, but our skeletal muscles are paralyzed, perhaps to keep us from acting out our dreams. REM sleep also nurtures cognition and problem solving. Studies have shown that people learning a new physical task will improve their performance overnight, but only as long as they get sufficient REM sleep.

A typical night’s sleep consists of four or five REM/non-REM cycles with occasional, brief episodes of wakefulness. Most Stage 4 sleep occurs during the first two to three hours of sleep. As morning approaches, REM sleep occupies an increasing share of slumber.

Sleep cycles are mapped on what’s known as a hypnogram, a sort of bar graph for sleep stages (see illustration). Because the hypnogram looks like a city skyline, the sleep patterns that it records are dubbed “sleep architecture.” Like the urban landscape, sleep is reshaped over time. At age 20, we spend an average of 7.5 hours a night sleeping — with about 90 minutes each of REM and deep sleep — and we’re awake, intermittently, for about 18 minutes. By the time we’re 60, we’re only sleeping 6.2 hours a night. REM sleep has fallen to about 75 minutes; deep sleep to less than 40; and on a typical night, we’re awake for 44 minutes, on average. However, we don’t outgrow our need for sleep; it’s just harder to come by.

Sleep architecture

When experts chart sleep stages on a hypnogram, the different levels resemble a drawing of a city skyline. This pattern is known as sleep architecture. The hypnogram above shows a typical night’s sleep of a healthy young adult.

Countering the effects of sleep loss

Women often find it difficult to make up sleep lost while caring for infant children, juggling family and career, and weathering the perturbations of menopause. Even those who are fortunate enough to reach midlife fully rested may find themselves gradually slipping into the debit column after age 60.

Too often we regard sleep as an indulgence or luxury. Rather, we should recognize that adequate sleep is just as important for health as diet and exercise are. To that end, he offers the following advice:

  • Settle short-term debt. If you missed 10 hours of sleep over the course of a week, add three to four extra sleep hours on the weekend and an extra hour or two per night the following week until you have repaid the debt fully.
  • Address a long-term debt. If you’ve shorted yourself on sleep for decades, you won’t be required to put in a Rip Van Winkle–like effort to repay the hours of missed slumber. Nonetheless, it could take a few weeks to recoup your losses. Plan a vacation with a light schedule and few obligations — not a whirlwind tour of the museums of Europe or a daughter’s wedding. Then, turn off the alarm clock and just sleep every night until you awake naturally. At the beginning, you may be sleeping 12 hours or more a night; by the end, you’ll be getting about the amount you regularly need to awake refreshed.
  • Avoid backsliding into a new debt cycle. Once you’ve determined how much sleep you really need, factor it into your daily schedule. Try to go to bed and get up at the same time every day — at the very least, on weekdays. If need be, use weekends to make up for lost sleep. And don’t forget to follow the tried and true rules of sleep hygiene described above, in “Advice for avoiding sleep deprivation.”

As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

A missed night of sleep is a fairly common experience for young people, new parents, and all kinds of busy adults. And while sometimes it’s because you’re having fun (New Year’s Eve!) and other times it’s because you must (an infant in the house), the end result of a sleepless night is the same: Your body has been deprived of an essential component for good health and energy.

Most adults do best with between seven and nine hours of sleep a night, but nearly 30 percent get less than six, and some occasionally miss a night entirely, resulting in a slow accumulation of sleep debt that can affect your appearance, your immune system, and even the way your brain functions. Read on to discover a few of the ways a sleepless night affects your body.

Dark Circles

Puffy eyes and a pasty complexion aren’t what you want to see when you wake up in the morning, but your appearance can be affected when you get too little sleep. Missing a night’s sleep can cause fluid to accumulate below your eyes, leading to circles and swelling.

Hunger Pangs

Lack of sleep changes the way your body interprets hunger signals, leaving you with cravings that can be hard to control. In fact, women who sleep five hours or less a night are 15 percent more likely to become obese during the next decade.

Feeling Unfocused

Missing a night of sleep increases the likelihood that you will feel forgetful or experience slow reaction times, which can result in small mistakes (typos on a work presentation) or very big ones (impaired driving).

Common Cold

An itchy, drippy nose is another potential side effect of a missed night of sleep. Your immune system may also be affected, leaving you more susceptible to colds.

Less Sex

Fatigue is a big factor when it comes to being in the mood for sex. In National Sleep Foundation’s Sleep in America poll, about a third of women say they put sexual activity with their partner on the back burner when they are sleep-deprived.

A single night without sleep isn’t usually a big deal, but over time, these occasional lapses can lead to more serious conditions. Longer term, too little sleep may contribute to heart disease, high blood pressure, diabetes, obesity, and stroke. The big takeaway here to a healthy life is to strive to practice good sleep habits, including getting to bed on time.

Say Goodbye to Sleep Debt

Getting enough sleep is central to living your best life—from staying safe on the road to being productive on the job. Adults typically need seven to nine hours a night, but for about 40 percent of Americans, that much shuteye is an elusive goal. The average is more like 6.8 hours—12 minutes shy of the minimum recommendation. A difference of just 12 minutes a night may not seem like a lot, but over time those minutes can add up to a huge sleep debt (especially if you really need eight or nine hours).

Over time those deficits can take a toll on your health, too, raising your risk of weight gain, diabetes, heart disease, and memory loss. And when you’re in the grips of sleep debt, you often don’t even remember what it’s like to feel well rested, so you may not realize just how tired you are.

So what do you do if you’ve spent weeks or even years of your life logging fewer hours of sleep than you need? You might think that closing the blinds and turning off your alarm on Saturday morning would do the trick, but sleeping in too much on weekends can actually do more harm than good, throwing off your circadian rhythm and making it harder to fall asleep on Sunday night. And that could mean starting your Monday with an even bigger sleep deficit than before.

Luckily, with some persistence, you can chip away at your sleep debt. These are some simple ways to do it.

Start with bedtime.

Rather than sleeping in later, which can make it harder to fall asleep the next night, go to bed earlier and wake up at your normal time. If it feels like there isn’t enough time in the day to get everything done, tracking exactly how you spend your time each day for a week may help you uncover extra minutes—or even hours.

Go slow and steady.

To avoid tossing and turning, try backing up your bedtime by 15 minutes per night to gradually shift your body’s clock. On the weekends and vacations, avoid sleeping in more than a couple of extra hours or it could interfere with nighttime sleep.

Be careful with naps.

Like sleeping in on the weekends, napping can be a quick way to lop a few hours off your sleep debt. But also like sleeping in, if you nap too long in the afternoon, you might have trouble falling asleep at night. And that can mean two steps forward, three steps back. For the best rejuvenation, go for either a 20-minute power nap or a longer 60- to 90-minute snooze.

Commit to healthier sleep habits.

Once you figure out how much sleep you need to feel well rested during the day, think about what changes you need to make in your life to reach that goal. Would making dinner ahead of time with a slow cooker or ordering healthy takeout more often help you get to bed earlier? Would exercising in the morning instead of after work help you to wind down in the evenings? With a few small tweaks, you’ll be back in business.

It might take time to adjust your lifestyle, but the payoff of attacking each day with the sleep you need is worth it.

Let’s do some sleep math. You lost two hours of sleep every night last week because of a big project due on Friday. On Saturday and Sunday, you slept in, getting four extra hours. Come Monday morning, you were feeling so bright-eyed, you only had one cup of coffee, instead of your usual two. But don’t be duped by your apparent vim and vigor: You’re still carrying around a heavy load of sleepiness, or what experts call “sleep debt”—in this case something like six hours, almost a full nights’ sleep.
Sleep debt is the difference between the amount of sleep you should be getting and the amount you actually get. It’s a deficit that grows every time we skim some extra minutes off our nightly slumber. “People accumulate sleep debt surreptitiously,” says psychiatrist William C. Dement, founder of the Stanford University Sleep Clinic. Studies show that such short-term sleep deprivation leads to a foggy brain, worsened vision, impaired driving, and trouble remembering. Long-term effects include obesity, insulin resistance, and heart disease. And most Americans suffer from chronic deprivation.
A 2005 survey by the National Sleep Foundation reports that, on average, Americans sleep 6.9 hours per night—6.8 hours during the week and 7.4 hours on the weekends. Generally, experts recommend eight hours of sleep per night, although some people may require only six hours of sleep while others need ten. That means on average, we’re losing one hour of sleep each night—more than two full weeks of slumber every year.
The good news is that, like all debt, with some work, sleep debt can be repaid—though it won’t happen in one extended snooze marathon. Tacking on an extra hour or two of sleep a night is the way to catch up. For the chronically sleep deprived, take it easy for a few months to get back into a natural sleep pattern, says Lawrence J. Epstein, medical director of the Harvard-affiliated Sleep HealthCenters.
Go to bed when you are tired, and allow your body to wake you in the morning (no alarm clock allowed). You may find yourself catatonic in the beginning of the recovery cycle: Expect to bank upward of ten hours shut-eye per night. As the days pass, however, the amount of time sleeping will gradually decrease.
For recovery sleep, both the hours slept and the intensity of the sleep are important. Some of your most refreshing sleep occurs during deep sleep. Although such sleep’s true effects are still being studied, it is generally considered a restorative period for the brain. And when you sleep more hours, you allow your brain to spend more time in this rejuvenating period.
As you erase sleep debt, your body will come to rest at a sleep pattern that is specifically right for you. Sleep researchers believe that genes—although the precise ones have yet to be discovered—determine our individual sleeping patterns. That more than likely means you can’t train yourself to be a “short sleeper”—and you’re fooling yourself if you think you’ve done it. A 2003 study in the journal Sleep found that the more tired we get, the less tired we feel.
So earn back that lost sleep—and follow the dictates of your innate sleep needs. You’ll feel better. “When you put away sleep debt, you become superhuman,” says Stanford’s Dement, talking about the improved mental and physical capabilities that come with being well rested. Finally, a scientific reason to sleep in on Saturday.

How Sleep Works

One way to understand why we sleep is to look at what happens when we don’t get enough:

  • As you know if you have ever pulled an all-nighter, missing one night of sleep is not fatal. A person will generally be irritable during the next day and will either slow down (become tired easily) or will be totally wired because of adrenalin.
  • If a person misses two nights of sleep, it gets worse. Concentration is difficult, and attention span falls by the wayside. Mistakes increase.
  • After three days, a person will start to hallucinate and clear thinking is impossible. With continued wakefulness a person can lose grasp of reality. Rats forced to stay awake continuously will eventually die, proving that sleep is essential.

A person who gets just a few hours of sleep per night can experience many of the same problems over time.


Two other things are known to happen during sleep. Growth hormone in children is secreted during sleep, and chemicals important to the immune system are secreted during sleep. You can become more prone to disease if you don’t get enough sleep, and a child’s growth can be stunted by sleep deprivation.

But the question remains — why do we need to sleep? No one really knows, but there are all kinds of theories, including these:

  • Sleep gives the body a chance to repair muscles and other tissues, replace aging or dead cells, etc.
  • Sleep gives the brain a chance to organize and archive memories. Dreams are thought by some to be part of this process.
  • Sleep lowers our energy consumption, so we need three meals a day rather than four or five. Since we can’t do anything in the dark anyway, we might as well “turn off” and save the energy.
  • According to ScienceNewsOnline: Napless cats awaken interest in adenosine, sleep may be a way of recharging the brain, using adenosine as a signal that the brain needs to rest: “Since adenosine secretion reflects brain cell activity, rising concentrations of this chemical may be how the organ gauges that it has been burning up its energy reserves and needs to shut down for a while.” Adenosine levels in the brain rise during wakefulness and decline during sleep.

­What we all know is that, with a good night’s sleep, everything looks and feels better in the morning. Both the brain and the body are refreshed and ready for a new day.

Dreams are another important part of sleep. We’ll take a closer look at how dreams work in the next section.

After a restless night people think they can make up for the lost sleep by going to bed early and sleeping in the next day. This certainly helps people feel rested, but a new study finds that just one night of sleep deprivation negatively impacts metabolism and cellular biological clocks.

“When had been sleep deprived and it was only one night … their glucose levels were at the level where you would say there is an increased risk of diabetes,” says Dr. Jonathan Cedernaes, a neuroscientist from Uppsala University in Sweden and an author of the paper in the Journal of Clinical Endocrinology & Metabolism.

While the study shows one night of bad sleep can impact people in significant ways, the experts advise people not to panic after a bad night’s rest.

Previous research indicates poor sleep increases people’s risk of being overweight or developing diabetes. Many thought metabolic changes occur after prolonged periods of sleep loss, but this study shows the body changes after just one night.

“We don’t know how long lasting these changes are,” Cedernaes says.

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What’s more, one sleepless night throws the molecular clocks that regulate the cells out of whack. Much like the circadian clock controls the sleep/wake cycle for the entire body, clocks in the cells control their sleep/wake cycles.

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“Everything going on in our body is regulated by our circadian rhythm even down to the cellular level. A disrupted night of sleep is altering the genetic foundation of the time keepers,” says W. Christopher Winter, a sleep medicine expert at Charlottesville Neurology & Sleep Medicine in Virginia, who wasn’t involved in the study.

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To understand how sleep loss impacts the body, Cedernaes asked 15 healthy men, with an average age of 22, to visit the lab on two different occasions. On the first, the researchers took tissue samples from their stomachs and thighs as well as blood and allowed the men to sleep as they would normally. These samples provided the baseline measurements. When the men returned, the researchers took the same samples. Instead of allowing the men to sleep, the researchers kept them awake in bed for an entire night.

And that’s all it takes for cellular and metabolic changes to occur.

“The most important thing was that there are some physical repercussions from missing a night of sleep … mental, physical. Something is changing that is not supposed to,” says Dr. Shalini Paruthi, a fellow of the American Academy of Sleep Medicine and director of the Pediatric Sleep and Research Center at Saint Louis University and SSM Cardinal Glennon Children’s Medical Center, who wasn’t involved in the study.

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While the study shows one night of bad sleep can impact people in significant ways, the experts advise people not to panic after a bad night’s rest. The best thing to do to recover is to nap and go to bed early the next night. Eating protein might increase wakefulness, says Winter, but getting sleep works best.

This study adds to the growing body of evidence showing poor sleep presents risks to overall health.

“We are seeing these changes to the whole body after one night of sleep deprivation,” says Paruthi. “We know there are physical things that are changing in your body when you miss a night of sleep and that leads to long-term problems.”

Sleep is for the weak, right? Wrong, according to science.

A new study has found that missing just one night of sleep can really screw with your body. Time to ditch the caffeine for a kip?

Swedish researchers discovered that one sleepless night can change actual genes which control what your body’s cellular biological clocks, reports MailOnline. Changes to these ‘clocks’ can affect everything from appetite to body temperature.

Scientists took fifteen ‘normal-weight’ men and let them snooze one night and made them stay awake on another.

The men were kept under strict lab conditions with light levels, food intake and movement all being monitored. Even when the men were kept awake, they still had to stay in bed. Cruel.

After testing tissue samples from the men, researchers were surprised at how quickly lack of sleep could impact on genes.

“It was interesting that the methylation of these genes could be altered so quickly, and that it could occur for these metabolically important clock genes,” said Dr. Jonathan Cedernaes.

Scientists were left unsure whether the changes could be easily reset by a few good nights sleep, or whether they were more permanent.

Dr. Cedernaes said: “At least some types of sleep loss or extended wakefulness, as in shift work, could lead to changes in the genome of your tissues that can affect your metabolism for longer periods.” Eek.

We may not be scientists, but we reckon y’all deserve a good snooze.

Natasha Preskey Cosmo’s Digital Intern.

Not getting enough sleep can be detrimental to your health; many studies even link the lack of Z’s to higher odds of dying during a certain time period. But a new study from Sweden suggests that if you can’t sleep as much as you need during the week, you may be able to make up for it on the weekends.

The researchers found that people ages 65 and under who slept 5 hours or less a night had a 65 percent higher risk of death during the 13-year study period than those who got 6 or 7 hours of sleep a night. But individuals who balanced their short weekday sleep with longer weekend sleep did not appear to have any increased mortality risk.

The findings suggest, in other words, that you may be able to make up for the damaging effects of lost sleep.

“We can’t really say 100 percent we have proven this, but it’s a reasonable assumption that this is what’s happening,” said lead study author Torbjörn Åkerstedt, a professor of behavioral medicine at Stockholm University in Sweden.

The study was published today (May 23) in the Journal of Sleep Research. Previous studies looking at sleep deprivation and mortality risk often asked participants about their “usual” sleep duration, which is often interpreted as one’s weekday sleep schedule. But “we suspected that might not be the whole story,” Åkerstedt told Live Science.

In the study, Åkerstedt and his colleagues gathered the data of more than 38,000 adults, collected in a medical survey in Sweden in 1997. In the survey, the participants answered two questions about their sleep duration, on weeknights and on days off.

The team then tracked the participants for up to 13 years, using the country’s national death register, and controlled for factors that can contribute to health or mortality risk, such as gender, body mass index and smoking.

Just as previous studies have shown, sleep duration had a U-shape relationship with mortality risk. In other words, both too much and too little sleep were linked to risk of death during the study period. Like people who slept less than 5 hours a night, people who consistently slept 8 or more hours fared worse than those who slept 6 or 7 hours a night.

Short sleep duration has been linked to numerous health problems, including stroke, heart disease, metabolic syndrome, hypertension and obesity, all of which increase the risk of death. But the link between long sleep duration and mortality risk is more mysterious, and may be driven by a third factor, such as an underlying health problem that is not measurable, Åkerstedt said.

“With long sleep we don’t have a good explanation. We think there has to be something going that has to do with higher need for sleep and is not healthy,” he said. In other words, an underlying health problem may be the reason a person is sleeping too much.

The study also found that the link between sleep patterns and mortality disappeared for those ages 65 or older. “At that age, people get the sleep they need, whereas for a 30- or 40-year-old, there’s often a huge discrepancy between the sleep they need and what they actually get,” Åkerstedt said.

Although the consequences of this discrepancy can be mitigated with a weekend sleep-in, there may be a limit. Studies have found that sleep deprivation induces physiological changes, such as loss of neurons and alterations in brain connectivity, that could be potentially long term.

In addition, losing just 1 hour of sleep may have different effects on the body than losing several hours. “You are much more hit by an all-nighter than a half-nighter,” Åkerstedt said.

Original article on Live Science.

Sleeping In On the Weekend Doesn’t Make Up for Lost Sleep During Week

“Sleep hygiene is the practices that we have before we go to bed and how we set up our sleep environment,” says Amy Korn-Reavis, MBA, a clinical sleep educator. “The best way to make up for sleep loss is to have a strong sleep routine and plan to make your sleep an important part of your day.”

Put a routine in place. Establish a set of practices that you can repeat nightly. This may include drinking a cup of tea and reading a book for 30 minutes before getting dressed for bed. As you do your nightly ritual, your body will learn this is the signal to wind down and prepare for sleep.

Plan for adequate sleep.The American Academy of Sleep Medicine recommends adults get seven or more hours of sleep nightly. If you have a specific time you must be up every day, work your bedtime back from that point to establish the hour at which you turn in.

Create a sleep-inducing space. Make your bedroom dark, cool, and quiet. A white noise machine or fan can help drown out sounds or create a comforting level of noise that may help you sleep.

Make your bed welcoming. If your bed is not comforting or your pillows and sheets are irritating, you may struggle to relax enough for adequate sleep. An investment in a quality mattress, good sheets, and supportive pillows is an investment in your health.

Leave your phone outside. The bright lights of smartphones, tablets, and laptops may stimulate your brain. That can make sleep allusive. “We should not have electronic devices next to the bed, and we should not use them at least 30 to 45 minutes before bed,” Korn-Reavis says.

Be consistent with your bedtime, even on weekends. With the data from this study, it’s clear the harms of weekend sleep may outweigh the benefits. “This practice of keeping the same wake time throughout the week and into the weekend is linked to feeling sharper and having an improved mood during the day,” says Conor Heneghan, who leads sleep research at Fitbit. “By waking up at the same time every day, our bodies can have a more regulated sleep cycle, which can lead to overall improved nighttime sleep.”

Talk with your doctor. “If you are suffering with a sleep timing issue, such as a mismatched internal body clock with a shift-work position, you may need to incorporate clinical grade sleep and wake treatments to help you alter the activation and deactivation of your sleep and wake systems to better correspond with your ‘off-shift’ environment,” Durmer says. Likewise, your doctor may diagnose an underlying medical condition that makes getting adequate sleep difficult.

“The key take-home message from this study is that ad libitum weekend recovery or catchup sleep does not appear to be an effective countermeasure strategy to reverse sleep-loss-induced disruptions of metabolism,” Kenneth Wright, PhD, a professor of integrative physiology at the University of Colorado Boulder and one of the study researchers, said in the press release.

Make sleep during the week a priority. Resist the temptation to sleep less every night in favor of sleeping in on the weekends.

You won’t make up as much sleep as you believe and you can’t recover from the damage a loss of sleep does to your body in that brief period of time.

Here’s a polite reminder that you can’t “catch up” on sleep. That is, if you didn’t sleep well several nights this week — because you were out late partying; had some long nights at the office; tried to get a full night’s sleep, but tossed and turned instead; or some combination thereof — you can’t “make up” that lost sleep by snoozing until the early afternoon on Saturday.

Nope, that’s not how sleep works.

Two nights of 10 hours of sleep will not erase the damage of sleeping only six hours every other night of the week. And the false perception that you can make up sleep is counterproductive — basically helping people justify their erratic sleep habits and preventing them from adopting better ones.

“But I always feel better when I sleep for 13 hours on Saturday night!” you say in defiance.

Well, yeah.

Lots of sleep feels better than too little sleep.

Even then, though, you’re still not offsetting the cumulative effect of your many sleepless nights, since your ability to focus is still impaired.

Sleep scientist Matthew Walker explained why on a recent episode of NPR’s Fresh Air:

“Sleep is not like the bank. You can’t accumulate a debt and pay it off at a later point in time. If I were to deprive you of sleep an entire night, and then in a subsequent night give you all the sleep you want, you never get back all that you’ve lost. You will sleep longer, but you will never achieve that full eight-hour repayment. The brain has no capacity to get back that lost sleep…”

Instead, you need to adhere to a strict sleep schedule, sometimes sleeping up to 10 hours a night for several months straight if you’re chronically sleep-deprived. Only then will your sleep debt be fully paid off. And you’ll have to maintain an eight-hour-a-night sleep schedule afterward to prevent racking up another debt.

I, too, used to operate under the delusion that sleep was a luxury, especially during the workweek, and that any sleep deficiency I accumulated Monday through Thursday could be made up by sleeping until noon on Saturday and Sunday. Sleeping a full eight hours each night was unrealistic — an impediment to the important work I had to do. It was an act for the un-busy, the unserious and insufficiently caffeinated.

Sleep was for the weak.

But what I’ve since come to learn is that all of these supposedly time-consuming self-help behaviors we hear about — such as getting enough sleep, exercising regularly, eating a healthy diet, meditating, stretching and taking frequent walking breaks throughout the work day — are actually time-saving behaviors.

It’s a quality vs. quantity calculation. Self-care activities might cut into your work time, but practicing them ensures you’ll be sharper and more productive during the hours you do spend working.

So don’t tell yourself, “Ah, I’ll just make up for it by sleeping in on the weekend.” Because you’re not making up for shit. Go to bed at the same time every day, sleep eight hours and spend your waking moments at 100 percent.

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