Sleep deprivation is what happens when you do not get enough sleep. It is one part of a wider problem the National Heart, Lung, and Blood Institute calls sleep deficiency. That also covers sleeping at the wrong time, sleeping poorly, and having a sleep disorder that cuts into your sleep (NHLBI).
For most adults, regularly sleeping under 7 hours a night is too little (Sleep Foundation). One short night leaves you slower, foggier and more irritable. Months of short nights are linked to heart disease, diabetes, obesity and depression. The fix is more sleep, but recovery takes longer than one lie-in.
This hub gives you the whole picture and points you to the next step. To count the hours you owe, see what sleep debt is and the sleep debt calculator. To check your own habits, use the chronic sleep deprivation risk calculator.
How Much Sleep Is Too Little?
Needs change with age. NHLBI’s chart, based on American Academy of Sleep Medicine (AASM) advice, gives 7 to 8 hours a day for adults and 8 to 10 hours for teens aged 13 to 18. Younger children need more (NHLBI).
The AASM says adults should get at least 7 hours a night to avoid health risks (Sleep Foundation). Our guide to how much sleep you need covers every age group.
Falling short is common. The CDC reports that about 1 in 3 U.S. adults do not get enough rest or sleep every day. Nearly 40 percent say they fall asleep during the day without meaning to at least once a month (NHLBI). Teens are a special case because early school times clash with their body clocks. See teen sleep deprivation.
Acute vs Chronic Sleep Deprivation
- Acute (total) sleep deprivation means going without any sleep, such as an all-nighter. Effects start after one night and usually clear once you sleep again (Sleep Foundation).
- Chronic sleep deprivation means repeatedly sleeping less than you need, often by an hour or two. It is usually diagnosed only after most nights fall short for three months or more. It may then be called insufficient sleep syndrome (Sleep Foundation).
Partial loss adds up fast. After several nights of losing even 1 to 2 hours, your ability to function suffers as if you had not slept at all for a day or two (NHLBI).
Common Causes
Most sleep deprivation comes from not leaving enough time for sleep. NHLBI lists who is more likely to be short on sleep (NHLBI):
- People with limited time, such as caregivers and people who work long hours or more than one job.
- People whose schedules fight their body clock, such as shift workers, first responders and teens with early school starts.
- People who take medicine to stay awake, or who misuse alcohol or drugs.
- People with stress, anxiety, sleep disorders, or other conditions or medicines that interfere with sleep.
Everyday habits play a part too. These include inconsistent sleep times, long daytime naps, devices in bed, a noisy or bright bedroom, and caffeine, alcohol or nicotine (Sleep Foundation).
Signs Of Sleep Deprivation
Short-Term Signs
If you have missed a night or a few hours of sleep, you may notice (Sleep Foundation):
- Physical: fatigue, frequent yawning, headaches, reduced coordination and a bigger appetite.
- Thinking: trouble concentrating, poor decisions, memory problems and slower reaction times.
- Emotional: irritability, anxiety, mood swings and lower tolerance for stress.
You may not wake feeling refreshed. You may often feel you could doze off during quiet, everyday activities (NHLBI). Children can look different. A sleep-deficient child may be overly active, have trouble paying attention, misbehave or slip at school (NHLBI).
Long-Term Signs
With ongoing short sleep, you may take longer to finish tasks and make more mistakes. It gets harder to make decisions, solve problems, manage emotions and cope with change (NHLBI).
Chronic sleep loss has a tricky feature. You may stop feeling very sleepy while your performance keeps slipping, because people can adapt to chronic sleep restriction without noticing the decline (Sleep Foundation). Some people do not realize they are sleep deficient at all and believe they function well (NHLBI).
Not sure whether your routine is wearing you down? The chronic sleep deprivation risk calculator looks at your usual sleep and habits. It gives you a risk level with next steps. It is a self-check, not a diagnosis.
What Happens After 24, 36 And 48 Hours Awake?
There are no universally agreed stages of sleep deprivation. The descriptions below come from studies of total sleep deprivation.
These studies are few and often old, because keeping people awake for long periods raises ethical problems (Sleep Foundation, Sleep Foundation). People differ. Age, health and how much sleep they lose all change the response.
| Time awake | What sources report |
|---|---|
| 18 hours | In one study, reaction time and hand-eye coordination were affected about as much as by a blood alcohol content of 0.05% (Sleep Foundation). |
| 24 hours | Thinking is affected about as much as by a blood alcohol content of 0.10%, which is over the legal driving limit. People may feel anxious or irritable, act disoriented, feel unlike themselves and notice small distortions in how things look, sound or feel, including trouble with depth perception (Sleep Foundation, Sleep Foundation). |
| 36 hours | Symptoms keep worsening and may include anger or aggression, euphoria, difficulty regulating stress and emotions, confusion and hallucinations (Sleep Foundation). |
| 48 hours | Hallucinations become likely, sometimes after blurry or double vision. They can involve several senses, and some people feel detached from themselves (depersonalization) or lose track of time (Sleep Foundation). |
| 72 hours | Based on a small number of studies, speech may slur and walking may become unsteady, and symptoms can come to resemble psychosis (Sleep Foundation, Sleep Foundation). |
Even these severe symptoms usually clear after a person sleeps again (Sleep Foundation). That does not make long stretches without sleep safe. The risk of a crash or other accident rises sharply long before hallucinations appear.
Microsleeps: Falling Asleep Without Knowing It
A microsleep is a very brief episode of sleep, usually 15 seconds or less. Your brain stops processing what is going on around you. Your eyes may droop or close, or your head may nod. You may also keep your eyes open and still look awake (Sleep Foundation).
You cannot control a microsleep and may not notice it. If you have ever driven somewhere and could not remember part of the trip, you may have had one (NHLBI).
Sleepiness and sleep deprivation are the main causes. Microsleeps can also happen to rested people during dull, repetitive tasks. A microsleep itself probably does no physical harm. The danger is what you are doing when it hits, such as driving or operating machinery (Sleep Foundation).
How Sleep Deprivation Affects Your Body And Mind
Damage from sleep deficiency can happen in an instant, such as a car crash. It can also build up over time (NHLBI). Here are the headline effects. The linked guides go deeper.
Mood And Mental Health
Short sleep can make you feel frustrated, cranky or worried. It can make it harder to read other people’s emotions (NHLBI). Sleep deficiency changes activity in the parts of the brain that handle decisions and emotional control. It has been linked to depression, suicide and risk-taking behavior (NHLBI).
Memory, Learning And Focus
While you sleep, your brain forms the pathways that help you learn and remember. A good night’s sleep improves learning, problem solving, attention and creativity. Too little sleep works against all of them (NHLBI).
Immunity
Ongoing sleep deficiency can change how your body’s defenses respond, so you may have trouble fighting common infections (NHLBI). For the research, see can good sleep improve your immune system and does poor sleep cause inflammation.
Appetite, Weight And Blood Sugar
When you do not get enough sleep, the hunger hormone ghrelin goes up and the fullness hormone leptin goes down. So you feel hungrier. Sleep deficiency also leads to higher-than-normal blood sugar, which may raise the risk of diabetes (NHLBI). NHLBI-funded research found that adults who regularly sleep 7 to 8 hours have a lower risk of obesity and high blood pressure (NHLBI).
Heart And Long-Term Health
Sleep helps heal and repair your heart and blood vessels. Sleep deficiency is linked to heart disease, kidney disease, high blood pressure, diabetes, stroke, obesity and depression (NHLBI, NHLBI). There is also some evidence that a single night without sleep can raise blood pressure (Sleep Foundation).
Injuries And Accidents
Sleep deficiency raises the chance of injury at every age. In older adults it may be linked to more falls and broken bones. It has played a role in human errors behind serious accidents involving ships, planes and nuclear reactors (NHLBI).
Drowsy Driving: The Most Immediate Danger
Sleep deficiency can harm your driving as much as, or more than, being drunk. Driver sleepiness is estimated to be a factor in about 100,000 crashes and about 1,500 deaths a year in the U.S. (NHLBI). Crashes from drowsy driving happen most often between midnight and 6 a.m. and in the mid-afternoon, when sleepiness peaks (Sleep Foundation).
Pull over and rest if you notice (Sleep Foundation):
- frequent yawning, heavy or droopy eyes, or blinking more;
- drifting out of your lane or hitting rumble strips;
- not remembering the last few miles, or missing a sign or exit;
- following too closely or struggling to keep a steady speed.
Opening the window or turning up the radio does not fix sleepiness. It can pull your attention from the road. Caffeine can help for a few hours but wears off. The safe choice is to stop somewhere secure and rest, or to share the driving (Sleep Foundation). After a sleepless night, it is safer to take a bus, train or taxi than to drive (Sleep Foundation).
How To Recover From Sleep Deprivation
After One All-Nighter
- Do not drive drowsy. Arrange another way to get around for the day (Sleep Foundation).
- Take a short nap if you can. A power nap of about 10 to 20 minutes can reduce sleepiness. Five minutes is too short to help much, and 30 minutes may leave you groggy (Sleep Foundation).
- Get daylight and move. Sunlight tells your body clock it is time to be awake. Exercise can improve attention and memory (Sleep Foundation).
- Use caffeine carefully. It can give a temporary boost but is not a substitute for sleep. It can trigger anxiety in some people. Late in the day, it can steal the sleep you need tonight (Sleep Foundation, Sleep Foundation).
- Eat sensibly. Even one night of sleep loss pushes you toward less healthy, higher-calorie food. Sugary snacks can leave you flatter later (Sleep Foundation).
- Get back to your normal schedule. Keep your bedtime and wake time steady to resync your body clock. Expect to feel below par for a few days. One estimate is that it can take up to 4 days to recover from 1 hour of lost sleep (Sleep Foundation).
After Weeks Or Months Of Short Sleep
The cure for insufficient sleep is sleeping longer each night, once other sleep disorders have been ruled out (AASM Sleep Education). In practice:
- Make time in bed the priority. Add sleep gradually, 15 to 30 minutes at a time, until you reach the amount that leaves you rested (Sleep Foundation). If your schedule has drifted, the sleep schedule reset calculator plans the steps.
- Do not rely on weekends. Catching up at weekends is usually not enough to make up for a week of short nights (AASM). Sleeping in did not reverse the metabolic effects of regular sleep loss in one study (Sleep Foundation).
- Watch long lie-ins. Sleeping much more on days off may itself be a sign you are not getting enough sleep. It can also upset your sleep-wake rhythm (NHLBI).
- Treat naps as a stopgap. Naps can boost alertness for a while, but they do not supply all the benefits of nighttime sleep (NHLBI).
- Give it time. In one study, a full week of free sleep after 10 nights of restricted sleep was not enough to restore cognitive performance to baseline (Sleep Foundation).
- Fix the basics. Keep regular sleep and wake times. Wind down for an hour or two before bed. Keep devices out of the bedroom and the room dark, cool and quiet. Avoid caffeine, alcohol and nicotine in the evening (Sleep Foundation).
To see how many hours you are behind and how long catching up might take, try the sleep debt calculator.
When Sleep Deprivation Is Really A Sleep Disorder
Ordinary sleep deprivation has a simple test. Give yourself more time in bed, and you sleep it off and feel better. With insufficient sleep syndrome, symptoms improve when you sleep longer (AASM). If extra time in bed does not help, something else may be going on.
- Insomnia. With sleep deprivation you can fall and stay asleep when you have the chance. With insomnia you have the chance but struggle to fall asleep, stay asleep or both (Sleep Foundation). Chronic insomnia occurs 3 or more nights a week for more than 3 months (NHLBI). Read our insomnia guide and about CBT-I, the usual first treatment.
- Sleep apnea. Breathing stops and restarts many times during sleep. Snoring, gasping and daytime sleepiness are clues. Untreated sleep apnea raises the risk of stroke and heart attack (NHLBI). See the health risks of sleep apnea.
- Narcolepsy. This lifelong neurologic disorder brings overwhelming daytime sleepiness even after a full night’s sleep. A nap helps briefly, but sleepiness returns within an hour or two. Some people also have sudden muscle weakness triggered by strong emotions (AASM). See narcolepsy explained.
Talk with your doctor if you sleep more than 8 hours a night but still do not feel rested (NHLBI). Your doctor may ask you to keep a sleep diary for a few weeks. You may also need a sleep study (NHLBI). Our guide to the signs of a sleep disorder lists the warning signs disorder by disorder.
When To See A Doctor
- You often feel sleepy during the day, do not wake up refreshed, or struggle to adapt to shift work (NHLBI).
- You snore loudly or wake up gasping or out of breath (NHLBI).
- You doze off or struggle to stay awake during routine tasks, especially driving (NHLBI).
- You have trouble falling or staying asleep most nights, or notice changes in your mental health (Sleep Foundation).
Doctors may not spot sleep problems during routine visits because you are awake, so raise it yourself (NHLBI). If you have hallucinations, confusion or thoughts of harming yourself, seek urgent medical help.
Sleep Deprivation FAQs
How Many Hours Of Sleep Counts As Sleep Deprived?
For most adults, regularly sleeping under 7 hours a night. Teens and children need more.
What Is The Difference Between Sleep Deprivation And Sleep Debt?
Sleep deprivation is the state of not getting enough sleep. Sleep debt is the running total of hours you have missed. For example, losing 2 hours a night for a week adds up to 14 hours.
Can You Die From Sleep Deprivation?
Dying directly from lack of sleep is uncommon. Long-term sleep loss contributes to serious illness, though. Drowsiness also causes fatal crashes, falls and workplace accidents.
How Long Does It Take To Recover From An All-Nighter?
Most acute effects fade after a good night’s sleep. Full recovery can take several days. Keep a normal schedule and avoid driving while drowsy.
Can You Get Used To Less Sleep?
No. You may feel less sleepy over time, but your performance and health still suffer. Feeling fine is not proof that you are rested.
Is Sleep Deprivation The Same As Insomnia?
No. Sleep deprivation is usually about not having enough time to sleep. Insomnia is trouble sleeping even when you have the time and a good setting.