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Microsleep – The Unintended, Potentially Dangerous Sleep

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If you’ve ever been extremely tired, trying hard to focus on what the professor is saying when your head suddenly falls down and you quickly jerk to an upright position, having no idea what just happened – you’ve experienced microsleep.

Falling asleep for a short time, usually from exhaustion, is called microsleep. This tiny amount of sleep is not to be ignored – it can embarrass you in front of others, but more importantly, it can cost you your life and health (or lives and health of other people). This goes for people who drive while excessively sleepy or work nightshifts on demanding positions, such as operating heavy machinery or performing surgery.

What is microsleep?

Microsleep is a very short episode of sleep. It can last anywhere from a millisecond to thirty seconds. During this time, some parts of our brain fall asleep while other stay awake. Microsleep means that, for a very short period of time, a person becomes unconscious. They usually become aware of this when they wake up, or, in some cases, they are not aware microsleep ever happened.

Things that usually precede microsleep are sleep deprivation, doing a repetitive type of work, frequent yawning, difficulty concentrating. Just moments before an episode of microsleep, a person is having trouble staying awake with the eyelids closing slowly, nodding head and droopy eyes.

Is microsleep dangerous?

Although not always dangerous, it surely can be. If we fall asleep during a lecture, at our desk, or while putting the baby to sleep – it bears no serious consequences. However, if microsleep happens to a commercial driver, airline pilot, shift workers working with dangerous machines or nuclear reactors, even to a doctor after performing 10-15-hour surgery, microsleep is very dangerous.

According to the Centers for Disease Control and Prevention, drowsy driving causes at least 72,000 crashes per year. It is estimated that among 25 people, one has fallen asleep in the previous month. A study showed that those who return home from a night shift are at the highest risk of having a near-crash or an accident.

What causes microsleep?

Sleep deprivation is one of the main reasons for microsleep. If someone has been awake for far too long, the brain functions impair significantly. We make more mistakes and are unable to focus. Sometimes it is caused by sleep disorders and sometimes by behavior – working in shifts, or working long hours, drinking too much alcohol and coffee at night, frequently going out late and pulling all-nighters. If you want to be healthy and safe, try to arrange your schedule in such a way that you always have time for rest.

Certain medication causes sleepiness, so it’s always a good idea to read the instructions before taking any type of medicine. If there is a warning that a particular drug causes sleepiness, either try to consume it in the evening or avoid driving and doing things that require decision making and physical response.

Sleep disorders, especially when untreated, can cause excessive daytime sleepiness which impairs cognitive ability throughout the day and may lead to sleep onset in inappropriate situations. Hypersomnias like narcolepsy, obstructive sleep apnea, circadian rhythm disorders, insomnia, restless leg syndrome all play a role in the poor abilities of motor skills and thinking. Depression and excessive stress also lead to poor sleep.

How does microsleep happen?

If we observe brain activity, during microsleep the brain regions which are associated with wakefulness become less active, whereas ‘sleep’ regions are more active. A study on rats showed that after a long time of sleep restriction, some parts of their brains turn off as if they were asleep. This suggests that their brains partially sleep, while the animal is still awake.

Similar findings were published in the Human Brain Mapping. Researchers tested 20 healthy, well-rested people, whose task was to perform a boring, repetitive task for 50 minutes. They found that 70% of people experienced a microsleep (while actively performing the task) in the sense that their brains weren’t fully deactivated, but only certain parts. This is how microsleep can happen even with the eyes open.

However, there are cases in which people completely lose consciousness and abruptly regain it. This ‘real’ microsleep is sometimes explained as a problem in the flip-flop switch of our brain, whose task is to make us fall asleep by ‘switching off’ and wake us up by ‘switching on’. People who suffer from poor sleep due to behavior, medical state, or sleep-fragmenting disorders run the risk of having damaged the nerve cells which make up this switch.

It makes the switch less stable, so these people may experience microsleep on one hand or sleep paralysis (the brain wakes up but the body doesn’t, maintaining the REM – rapid eye movement – muscle paralysis) on the other.

Microsleep symptoms and causes – recognize it on time

We’ve mentioned some of the ways to recognize a person who is in danger of having an episode of microsleep and the groups at the highest risk. To summarize, you should pay attention if you (or a person you know) have done one or more of these things:

  • been drinking,
  • finished a night shift,
  • not slept all night or has slept too little (partial sleep deprivation),
  • just woken up and isn’t fully awake yet (sleep inertia),
  • accumulated sleep debt,
  • driven for many hours without proper rest,
  • suffering from sleep disorders,
  • taken medication known to cause drowsiness.

A person who is about to or has just experienced microsleep:

  • is not responsive to given information, fails to recognize danger,
  • doesn’t react to their surroundings/expresses slow reaction time,
  • has a blank stare with eyelids closing slowly,
  • yawns excessively,
  • is dropping their head,
  • suddenly jerks their body,
  • is unable to remember what happened just a moment ago,
  • keeps blinking, while trying hard to keep the eyes open.

How to avoid microsleep?

Microsleep is linked to our health, obligations, way of life, and sleep habits. Not every person who experiences microsleep does so for the same reason. Here is a checklist that might help you avoid this potentially dangerous problem.

  • If you are tired, take a nap. This can be a 20-minute power nap or a long, 90-minute nap. These two nap time lengths are recommended if you don’t want to wake up groggy. Grogginess (sleep inertia) is associated with waking up from the deep sleep stage.
  • If you’ve worked a night shift, take a ride-share or a taxi. Spending some money on this is definitely worth it. Also, if possible, avoid doing physically and mentally demanding tasks at the end of your night shift.
  • Keep talking to people around you – this is very helpful in staying awake. Move around if possible.
  • Avoid carbs and alcohol, because they make you sleepy.

And, maybe most importantly:

  • Get proper treatment for any sleep problems you might have.
  • Stick to healthy sleep habits, such as respecting your sleep-wake cycle and get a sufficient amount of sleep (7-8 hours for most people), avoid alcohol and caffeine before bed, and sleep in a dark and cool room.
  • It’s always a good idea to take someone with you if you’re about to drive a long way. Many people don’t recognize they are in danger of falling asleep behind the wheel and having someone who can drive instead of us can save our lives.

Additional resources

  1. Vyazovskiy V. V, Olcese U, et al. Local sleep in awake rats. Nature. April 28, 2011. https://www.nature.com/articles/nature10009 Accessed January 25, 2019.
  2. High drowsy driving crash risk on daytime commute after night work. EurekAlert! December 21, 2015. https://www.eurekalert.org/pub_releases/2015-12/bawh-hdd121715.php   Accessed January 25, 2019.
  3. Poudel G,  Innes C, et al. Losing the struggle to stay awake: Divergent thalamic and cortical activity during microsleeps. Human Brain Mapping. September 24, 2012. https://onlinelibrary.wiley.com/doi/abs/10.1002/hbm.22178 Accessed January 25, 2019.
  4. Morbidity and Mortality Weekly Report. Centers for Disease Control and Prevention. January 4, 2013. https://www.cdc.gov/mmwr/pdf/wk/mm6151.pdf Accessed January 25, 2019.
  5. Drowsy Driving: Asleep at the Wheel. Centers for Disease Control and Prevention. https://www.cdc.gov/features/dsDrowsyDriving/index.html Accessed January 25, 2019.

The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. Read our full medical disclaimer.

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