The Causes, Dangers, and Prevention of Microsleep

On a cross-country trip, it is common to spend some of the time driving at night. Without adequate rest, this may raise the risk of experiencing sudden, brief lapses into sleep. The car may swerve a little, or you might hear the sound of the tires running along the rumble strip at the road's edge. It may be time for someone else to drive. What explains these episodes of microsleep? Learn about the signs, causes, dangers, and prevention.

A driver who is tired while behind the wheel
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What Is Microsleep?

Microsleep is a fleeting, uncontrollable, brief episode of sleep which can last anywhere from a single fraction of a second up to 10 full seconds. These episodes of microsleep occur most frequently when a sleepy person is trying to fight sleep and remain awake. They may occur while driving and increase the risk of a serious car accident.

There are two main stages of sleep that a person goes through. The two stages of sleep are rapid eye movement sleep (REM) sleep and non-rapid eye movement sleep (NREM). Microsleep does not fall directly into either category of sleep, as it is a fleeting and uncontrollable episode that does not last long enough for the characteristics of either state of sleep to emerge.

For reference, REM sleep is characterized by vivid dreams, rapid eye movements, paralysis of most muscles of the body, and changes in blood pressure, heart rate, and overall breathing rate. Also during REM sleep, blood flow becomes increased to the brain, as well as the penis and clitoris, which results in engorgement (leading to the incidence of morning wood).

Non-rapid eye movement (NREM) sleep is typically characterized by a decreased amount of blood flow to the brain and the skeletal muscle. Other characteristics of non-rapid eye movement sleep include decreased heart rate, blood pressure, and total volume of air cycling in and out of the lungs. Microsleep does not occur for long enough for any of these characteristics to fully occur.


What are some of the potential signs of experiencing microsleep?

  • Inattentiveness
  • Brief memory lapses
  • Missing an exit while driving
  • Hitting the highway's rumble strip
  • Car accidents or near misses
  • Head bobbing
  • Brief loss of muscle control
  • Falling down or slumping over
  • Dropping something held

There may be an awareness of these symptoms right after waking. It is also possible that the microsleep episodes could be so brief that they may not be fully recognized.


Microsleep often occurs more often when an individual is sleep deprived. Nighttime is when a vast majority of microsleep incidents happen, in terms of driving. Drivers driving at night often become tired. However, they often have places to get to or deadlines to meet, and thus force themselves to push on.

Sleep disorders may also increase the risk of experiencing microsleep episodes. Potential contributors include:

Many of these conditions lead to fragmentation of the states of sleep and wakefulness, making an unexpected transition from one to the other more likely.


While it can be harmless if it occurs on your couch while you’re trying to stay awake for a movie, instances of microsleep can also be extremely dangerous. If it occurs at the wrong time, when you’re driving, for instance, microsleep can lead to accidents involving cars or heavy machinery as well as other dangerous situations. Falling asleep behind the wheel, even briefly, is a gravely dangerous situation that can lead to the potential injury or even death of you and others on the road.


Microsleep is often the direct result of sleep deprivation. Thus, the elimination of sleep deprivation can help to reduce the chance of microsleep. It is important to get enough sleep to meet your sleep needs. For adults, this means getting at least 7 to 9 hours of sleep on a nightly basis. A great way to eliminate sleep deprivation, other than simply sleeping more, is to improve overall sleep efficiency.

Luckily, there are many ways to improve sleep efficiency. One great way to improve sleep efficiency is to eliminate all potential distractions when sleeping. There should be no television on and no music playing. If you are accustomed to having the television or music on, you should work to break those habits and go to sleep in a quiet, dark, and peaceful atmosphere. All lights should be off, especially flashing, blinking, or especially bright lights. Cell phones should not be looked at in bed, as the lights of the screen can work the stimulate the brain and keep it awake.

There may be some other ways to sleep better. Taking such steps can help to improve sleep efficiency, and thus work to eliminate microsleep.

A Word From Verywell

If you experience excessive daytime sleepiness with frequent episodes of microsleep, it is important to seek evaluation by a board-certified sleep physician. A sleep study may help to identify the cause of your condition and treatment may prevent you from facing serious consequences, including a potentially fatal car accident.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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Additional Reading
  • Arnal PJ, et al. "Benefits of Sleep Extension on Sustained Attention and Sleep Pressure Before and During Total Sleep Deprivation and Recovery." Sleep. 2015 Dec 1;38(12):1935-43. doi: 10.5665/sleep.5244.

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  • Lian Y, et al. "Prediction of drowsiness events in night shift workers during morning driving." Accid Anal Prev. 2017 Nov 7. pii: S0001-4575(17)30391-3. doi: 10.1016/j.aap.2017.11.004.

  • Poudel GR, et al. "Temporal evolution of neural activity and connectivity during microsleeps when rested and following sleep restriction." Neuroimage. 2018 Jul 1;174:263-273. doi: 10.1016/j.neuroimage.2018.03.031.

By Brandon Peters, MD
Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist.