What Is Microsleep? Causes, Signs, How Long It Lasts, and What to Do

Quick answer: Microsleep is a brief, involuntary episode of sleep that happens while you’re normally awake. It often lasts only a few seconds and is more likely when you’re sleep-deprived or extremely sleepy. You may not even realize it happened. Microsleep becomes especially dangerous while driving or doing anything that requires your full attention.

Have you ever been reading, sitting through a meeting, or watching TV when you suddenly realize you missed the last few seconds? Maybe your head dropped for a moment, and you quickly snapped back awake.

Sometimes that brief lapse is microsleep. These short episodes can happen when your brain is struggling to stay awake, and they’re easy to miss because you may not remember falling asleep at all. 

While a few seconds may not sound like much, microsleep can become dangerous when it happens behind the wheel or during another activity where losing awareness can put you or someone else at risk.

What is microsleep?

Microsleep is a very short episode of sleep that happens when you would normally be awake. [1] During the episode, your brain briefly shifts from wakefulness toward sleep, and you may stop responding to what’s happening around you.

Microsleep can be measured in sleep research using tools such as an electroencephalogram (EEG), which records electrical activity in the brain. During a microsleep episode, brain activity briefly shifts toward a sleep-like pattern. [2]

Microsleep itself is not considered a sleep disorder. It can happen because of sleep deprivation, excessive daytime sleepiness, or other sleep problems.

A microsleep can happen so quickly that you don’t notice you fell asleep. You may simply realize that you missed part of a conversation, skipped a few lines while reading, or can’t remember part of what just happened.

What does microsleep feel like?

During or immediately after an episode, you may notice:

• A blank stare

• Your head suddenly dropping

• A brief body jerk as you wake

• Not responding to something someone just said

• Missing part of what you were reading, watching, or listening to

• Trouble processing something you just saw or heard

• Losing track of what you were doing for a few seconds

• Suddenly realizing you don’t remember part of a drive

Before microsleep happens, you may also notice signs that you’re becoming extremely sleepy, including:

• Repeated yawning

• Slow or frequent blinking

• Heavy eyelids

• Difficulty keeping your eyes open

• Trouble focusing

If someone is observing you, they may notice your eyes slowly closing, your head nodding, or a brief period when you stop responding. 

You may not recognize every episode yourself. Microsleep is involuntary, and you can briefly lose awareness before you realize you’re falling asleep.

Also Read: What Are Brain Zaps? Causes, Sleep Connection, and How to Stop Them

What causes microsleep?

Microsleep is closely connected with excessive sleepiness. Anything that leaves you struggling to stay awake can increase the chance of a brief sleep episode.

Microsleep can happen at any time, but it may be more likely during periods when your body naturally becomes sleepier, such as late at night, early in the morning, and sometimes during the afternoon.

Not getting enough sleep

Sleep deprivation is one of the primary causes of microsleep. The longer you stay awake, or the more sleep you lose night after night, the stronger your body’s need for sleep becomes. Eventually, that sleep pressure can become strong enough that your brain briefly slips into sleep even though you’re trying to remain awake.

This can happen after one very short night of sleep, but it can also build gradually when you regularly sleep less than your body needs.

You may think you’re still functioning normally even when you’re sleep-deprived. That can make microsleep especially difficult to recognize because your ability to judge your own alertness may also become less reliable.

Insomnia and disrupted sleep

You don’t have to stay up all night to become sleep-deprived. If insomnia regularly keeps you from falling asleep, wakes you up repeatedly during the night, or causes you to wake up much earlier than planned, you may not get enough restorative sleep.

Over time, that lost sleep can show up during the day as:

• Difficulty concentrating

• Slower reactions

• Irritability

• Heavy eyelids

• Excessive daytime sleepiness

• Unintentional dozing

Microsleep can occur when that daytime sleepiness becomes strong enough. Insomnia itself doesn’t automatically cause microsleep. The concern is the sleep loss and daytime sleepiness that can come with ongoing poor sleep.

Mental health conditions

Mental health conditions can affect both sleep and daytime alertness. 

Depression, anxiety, and bipolar disorder can make it harder to fall asleep, stay asleep, or keep a regular sleep schedule. When those sleep problems lead to ongoing daytime sleepiness, microsleep can become more likely.

Sleep disorders that cause daytime sleepiness

Frequent microsleep can sometimes be related to a sleep disorder.

Obstructive sleep apnea repeatedly interrupts breathing and sleep during the night. Someone may spend enough hours in bed but still wake feeling unrefreshed and struggle with sleepiness during the day.

Narcolepsy can cause overwhelming daytime sleepiness and sudden episodes of sleep.

Idiopathic hypersomnia can also cause persistent excessive sleepiness despite getting what appears to be enough, or even more than enough, nighttime sleep.

Excessive daytime sleepiness can have many causes, and doctors may consider these types of sleep disorders when someone repeatedly struggles to stay awake. 

Shift work and an irregular sleep schedule

Working overnight or frequently changing shifts can make it difficult to sleep when your body naturally expects to be awake.

Your circadian rhythm helps control when you feel awake and when you feel sleepy. If your work schedule regularly conflicts with that internal clock, you may have trouble getting enough sleep during the day and become increasingly sleepy during your shift.

The hours between midnight and 6 a.m. are particularly difficult because that’s a period when the body naturally promotes sleep.

Medications and alcohol

Some medications can make you sleepy enough to affect alertness.

Examples can include:

• Some antihistamines

• Sedatives and sleeping medications

• Certain anxiety medications

• Some pain medications

• Some antidepressants and other medicines that cause drowsiness

Alcohol can also make you sleepy and reduce your ability to respond quickly.

If you’ve started unexpectedly nodding off after beginning a new medication, don’t stop a prescription medicine on your own. Talk with your healthcare provider or pharmacist about whether drowsiness could be a side effect.

Long and monotonous activities

A repetitive task can make severe sleepiness harder to fight. Long highway drives are a good example, but the same thing can happen while:

• Watching TV

• Sitting through a lecture or meeting

• Reading

• Studying

• Working at a computer

• Performing repetitive work

The activity itself may not be what’s making you sleepy. But when you’re already tired, a quiet or repetitive task can make it harder to stay awake.

Also Read: This Common Habit Makes Insomnia Worse

How long does microsleep last?

A microsleep usually lasts only a few seconds. Many sleep studies define microsleep episodes as lasting somewhere between 1 and 15 seconds. Other research has used somewhat different definitions, so there isn’t one exact duration that applies to every episode. 

Even a four- or five-second episode can be significant. During that time, you may not respond to something you see or hear, and you may have little or no memory of what happened during those seconds.

If you're sitting on the couch, this might mean missing part of a TV show. At highway speeds, however, the consequences can be much more serious.

Can microsleep happen with your eyes open?

It’s possible to look awake while your attention is failing, but an eyes-open lapse isn’t always classified as microsleep.

Many sleep studies identify microsleep by changes in brain activity together with partial or complete eye closure. [3] Researchers have also recorded sleep-like lapses while people’s eyes remained open. [4]

You may stare ahead, miss what happened for a moment, and only realize afterward that your attention briefly dropped.

Is microsleep dangerous?

Microsleep can be dangerous, especially during activities that require your full attention. Even a few seconds of lost awareness may lead to accidents while:

• Driving

• Operating machinery

• Working at heights

• Using power tools

• Performing safety-sensitive work

Microsleep can also affect performance even when there’s no immediate physical danger. Brief sleep episodes can interfere with concentration, reaction time, and your ability to complete a task accurately. 

Microsleep while driving

Driving is especially dangerous when it comes to microsleep. If you fall asleep for just five seconds while traveling 55 mph, your car can travel more than 100 yards before you are fully alert again. 

During those seconds, you could:

• Drift into another lane

• Miss a traffic light

• Fail to notice a stopped vehicle

• Leave the road

• React too late to a pedestrian or obstacle

In 2024, 644 people were killed in crashes classified as drowsy-driving related in the United States. Drowsiness is also difficult to measure after a crash, so the full impact can be difficult to determine. [5]

If you’re having trouble staying awake while driving, get off the road and stop somewhere safe. Coffee, loud music, opening a window, or turning up the air conditioner shouldn’t be treated as reliable ways to push through severe sleepiness.

Can you control microsleep?

You can’t predict when a microsleep episode will happen. Once you’re extremely sleepy, your brain can briefly slip into sleep even while you’re actively trying to stay awake. You might fight it for a while, but willpower doesn’t remove your body’s need for sleep.

Thinking, I’ll be fine for another 20 minutes, can be dangerous when you’re already nodding off.

Warning signs such as repeated yawning, heavy eyelids, difficulty focusing, head nodding, or forgetting the last few minutes are signals that you’re becoming too sleepy to function safely.

Don’t wait for a microsleep episode to convince you that you need rest.

Also Read: Sleep Quantity vs Sleep Quality: Which One Do You Actually Need?

How do you stop microsleep?

There isn’t a trick that permanently stops microsleep while allowing you to remain severely sleep-deprived. The most important step is to identify the cause of your excessive sleepiness.

If you’re struggling to stay awake right now

Stop anything that could become dangerous if you lose awareness.

If you’re driving:

1. Pull over somewhere safe.

2. Stop driving.

3. Rest before getting back on the road.

A short nap can temporarily improve alertness. Caffeine can also help for a limited time, but it doesn’t replace sleep. If you’re seriously sleep-deprived, caffeine alone may not prevent microsleep. 

Get enough sleep regularly

If lack of sleep is the cause, the most reliable prevention is getting enough sleep consistently.

Try to:

• Give yourself enough time for sleep each night

• Keep your bedtime and wake time reasonably consistent

• As much as possible, avoid repeatedly cutting sleep short for work, entertainment, or other activities

• Make your bedroom dark, quiet, and comfortable

• Limit things that regularly interfere with your sleep

One night of recovery sleep may make you feel better, but regularly losing sleep and trying to catch up later can leave you sleepy during the week.

Address ongoing sleep problems

If you frequently have difficulty falling asleep or staying asleep, it’s more effective to address the underlying cause of your sleep problems rather than just trying to combat daytime sleepiness.

For example, ongoing insomnia may require a different treatment approach than obstructive sleep apnea or a circadian rhythm sleep disorder.

If a medication is causing your drowsiness, your healthcare provider may be able to adjust the dose, timing, or type of medication. Any changes to prescription medications should be made under the guidance of a medical professional.

When should you see a healthcare provider?

An occasional episode of falling asleep after a severely sleep-deprived night may be understandable. However, frequent microsleep episodes are different. You should talk with a healthcare provider if you experience any of the following: 

• Keep nodding off during the day

• Have microsleep episodes despite getting enough sleep

• Fall asleep unexpectedly at work, while talking, or during other activities

• Regularly struggle to stay awake while driving

• Sleep for long periods but still feel excessively sleepy

• Snore loudly or wake gasping or choking

• Have frequent insomnia or poor-quality sleep

• Develop severe daytime sleepiness after starting a medication

Persistent daytime sleepiness can sometimes signal an underlying sleep disorder or another health condition. Seek evaluation if your sleepiness affects your driving, work, school, or ability to function safely.

About the author

Dr. Ruchir P. Patel, MD, FACP, is the Medical Director of the Insomnia and Sleep Institute of Arizona and the founder of Sip2Sleep. He is triple board-certified in sleep medicine, obesity medicine, and internal medicine. Dr. Patel is a multi-year Phoenix Magazine Top Doctor and holds the Inspire Excellence designation.

References

1. Malafeev, A., Hertig-Godeschalk, A., Schreier, D. R., Skorucak, J., Mathis, J., & Achermann, P. (2021). Automatic Detection of Microsleep Episodes With Deep Learning. Frontiers in neuroscience, 15, 564098. https://doi.org/10.3389/fnins.2021.564098

2. Zaky, M. H., Shoorangiz, R., Poudel, G. R., Yang, L., Innes, C. R. H., & Jones, R. D. (2023). Increased cerebral activity during microsleeps reflects an unconscious drive to re-establish consciousness. International journal of psychophysiology : official journal of the International Organization of Psychophysiology, 189, 57–65. https://doi.org/10.1016/j.ijpsycho.2023.05.349

3. Davin, A., Tamisier, R., Barateau, L., Peter-Derex, L., Dauvilliers, Y., Pépin, J. L., & Baillieul, S. (2025). Shedding light on microsleep episodes for comprehensive sleepiness assessment: a narrative review. Sleep medicine reviews, 82, 102113. https://doi.org/10.1016/j.smrv.2025.102113

4. Zaky, M. H., Shoorangiz, R., Poudel, G. R., Yang, L., Innes, C. R. H., & Jones, R. D. (2024). Conscious but not thinking-Mind-blanks during visuomotor tracking: An fMRI study of endogenous attention lapses. Human brain mapping, 45(11), e26781. https://doi.org/10.1002/hbm.26781

5. National Highway Traffic Safety Administration. (n.d.). Drowsy driving. https://www.nhtsa.gov/risky-driving/drowsy-driving