Microsleep and the Mind: What’s Happening and Why

By Rosie Osmun
Last Updated On August 4th, 2020

Ever briefly doze off at your desk, during a Netflix binge, or on a long drive? If so, you’ve probably experienced “microsleep”. It’s a common phenomenon, and often a sign…

Fact checked by
 Dr. Jade Wu Dr. Jade Wu

Dr. Jade Wu

Dr. Jade Wu, Ph.D. is a licensed clinical psychologist specializing in behavioral sleep medicine. She completed her Ph.D. at Boston University, and finished her medical psychology residency and clinical fellowship at Duke University School of Medicine.

Microsleep and the Mind: What’s Happening and Why

Ever briefly doze off at your desk, during a Netflix binge, or on a long drive? If so, you’ve probably experienced “microsleep”. It’s a common phenomenon, and often a sign of not getting enough sleep.

While they can be innocuous, microsleeps also pose some serious risks. For example, zoning in and out of consciousness while driving is clearly dangerous! Sometimes, you might not even realize you’re actually asleep, as it may just seem like a brief loss of focus.

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Read on to learn what’s happening in your body during this phenomenon, when it’s a warning sign, and how to prevent it.

What Exactly is Microsleep?

To put it simply, it’s a sudden, very short period of sleep that occurs when you’re not intending to snooze. You might feel it coming on as your eyelids droop, your head starts nodding, and your thoughts start wandering. Just like during nightly sleep, outside stimuli fade away. You then jolt awake, all of a sudden realizing you have no memory of the last few seconds.

Often, people’s eyes won’t close for a long period of time. You may just see their eyes roll back, or they may just stare blankly or have slower eye movement. Others can snore and even have very brief dreams. Hypnic muscle jerks, that feeling of jolting awake or a sensation of falling, is also common.

“Scientists haven’t come up with a hard-and-fast definition of what is considered “micro” sleep,” explains sleep researcher Dr. Jade Wu, Ph.D. “But sleep researchers generally think of a microsleep episode as any brief ‘blips’ of sleep lasting between 1 and 15 seconds.”

Snapping out of it after a second or two doesn’t mean you’re good as new though. Research suggests impairments to decision-making capabilities during and after awakening from microsleeps.

To learn more about microsleeps, we need to look into what’s actually happening within the brain. The line between asleep and awake isn’t as simple as an on-off switch. Research actually suggests that sleep and wakefulness may exist more on a spectrum.

Here’s What Is Happening Inside Your Brain While You Day-Doze

Essentially, microsleeps appear to be brief, selective shutdowns. They occur as sleep pressure builds. Nitric oxide, adenosine, and other substances build up the longer you’re awake. These substances increase sleep pressure, triggering feelings of sleepiness. Certain areas of the brain like the frontal cortex seem to be more susceptible to fatigue.

Sometimes, even when you feel awake, it’s possible that your entire brain might not be online. This phenomenon is called local sleep, which many animals have and seems to occur in humans too. It appears that some regions of the brain occasionally “go offline,” or rather, goes into what looks like a “blip” of deep sleep, even though the rest of the brain is awake. This seems particularly true for brain regions not actively engaged by current activities.

Researchers speculate that this mechanism might help the brain restore responsiveness. Lasting as short as microseconds, local sleep may partially explain mind-wandering and mind-blanking. Studies suggest local sleep might also play a role in behavioral performance and the way people perceive things.

When tired, the brain switches into some of the patterns associated with light sleep. These episodes show up as identifiable changes to brain activity in sleep research:

  • During wakefulness, your brain shows background alpha waves on an electroencephalography (EEG).
  • However, during a microsleep, the brain briefly displays slower theta waves.

Areas of the brain associated with visual processing slow down. So do those in charge of consciousness/wakefulness. Brain scans of microsleep episodes reveal reduced thalamus activity. This part of the brain serves as a sensory switchboard, relaying incoming data to appropriate cortices for interpretation.

Areas associated with attentional control engage, seemingly as the person tries to stay awake. This attention region also plays a role in imagining movement.

Other research finds that eye closures due to drowsiness trigger increased activity in sensory regions. These same brain regions correspond with dream-like mental states. But, eye closures during sleep deprivation manifest differently than well-rested mind wandering. This may signal that more than daydreaming happens during these episodes.

Why Do Microsleep Episodes Happen?

The most common causes of microsleep episodes are sleepiness, shift work, sleep disorders, medications, and circadian slumps. The exact why behind microsleeps remains a mystery. But, one thing is certain — drowsiness is the most reliable way to cause them.


Sleep deprivation is the most frequent trigger of episodes of microsleep. Getting less sleep than you need at night predisposes you to drowsiness during the day.

If you didn’t sleep well the night before, it’s important to be aware of potential effects to alertness. People who generally have normal, healthy sleep patterns actually may be more vulnerable to microsleep when they have an occasional single night of poor sleep.


Working night shifts or irregular shifts puts people at a higher risk of insufficient sleep. Since these patterns aren’t in sync with most people’s circadian rhythms, shift work throws off snoozing patterns. For many people, it makes it harder to get a sufficient amount of high-quality sleep.

Large bodies of research found that people working evening and night shifts have higher risks of accidents, injuries, and mistakes on the job. This is generally attributed to cognitive declines and microsleeps caused by sleep deprivation. When tired, it becomes harder to concentrate and remember things. Coordination suffers, as do response times and decision-making abilities.

One study looked at 16 night-shift workers. All drove on a closed-course for two hours after a good night of sleep. Then, they drove two hours after a night of work (after being awake an average of 12.8 hours). No participants had accidents the day after a night of sleep.

But, the day after their night of work, 37% had near-crashes requiring emergency braking by observers. After 15-30 minutes of driving, participants showed difficulty keeping their eyes open and lane drifting.

Another study of female hospital workers examined alertness at the end of night shifts versus day shifts. At the end of night shifts, participants showed a much slower reaction time. They also noted more attention lapses compared to after day shifts.

Sleep Disorders and Medications

Frequent microsleep episodes may also signal certain sleep disorders. Several sleep disorders exhibit excessive daytime sleepiness as a primary symptom. These include narcolepsy, hypersomnia, restless legs syndrome, parasomnias, circadian rhythm disorders, sleep apnea, and insomnia.

All of these disorders impact both nighttime rest and daytime alertness, either by impeding sleep or affecting the brain’s ability to maintain wakefulness. Thus, making people more prone to symptoms like microsleep.

Medications that induce drowsiness also increase microsleeping risks. Antihistamines, benzodiazepines, epilepsy drugs, heart medications, and other prescriptions can trigger daytime sleepiness.

If you experience microsleeps often or recently noticed changes to your alertness unrelated to nighttime sleep, it’s a good idea to discuss it with your physician.

Boredom and Normal Circadian Slumps

Doing repetitive, boring, or monotonous tasks can also bring on drowsiness. Common times to experience a microsleep include:

  • Long drives on open roads
  • Riding in an airplane or train
  • Stationary work
  • Prolonged sitting
  • Repetitive, simple tasks

Sometimes, boredom can trigger it, even if you’re well-rested. This is especially the case during dawn and dusk, during the mid-afternoon time, or late at night. These are the times when our circadian rhythms naturally dip into the drowsy territory. In fact, most car accidents occur between 1 PM and 4 PM, and also 1 AM to 4 AM.

Take note of your normal patterns of sleepiness and try to avoid tasks requiring high alertness at these times.

Worrisome Side Effects of Sleep Deprivation & Drowsiness

A head dip here and there while reading emails likely isn’t going to be a big deal for most people. But, when your job requires constant attention (think pilot, driver, surgeon, etc) or you’re behind the wheel, microsleep becomes quite dangerous. Constant drowsiness also impairs cognition.

Drowsy Driving

Falling asleep while driving is one of the most common causes of car accidents. And, microsleeps dramatically impair people’s driving abilities.

One study found that under sleep deprivation, driving in a realistic car simulator led to an accident probability of 35% during microsleeps. When the microsleep occurrence exceeded 50% of a 4-minute period, that probability rose to near 100%.

Studies of real driving patterns of sleep-deprived people show that tiredness impairs visual abilities. Sleepy people blink more and blink longer. They also show more scattered gaze and fixation patterns. All of these changes reduce the visual attention necessary for driving safely. Indeed, sleep-deprived people veered out of lane three times more often, increasing the longer they drove.

Teens and younger adults should be particularly aware of drowsy driving. Young adult drivers experience a greater proportion of sleep-related crashes than older adults.

  • Research suggests people 18 to 24 are involved in 20% of fatal crashes in developed countries.
  • Younger drivers exhibit more sleepiness when driving at night.
  • Lifestyle factors predispose younger people to higher risks of sleep deprivation.
  • They also are more vulnerable to the effects of sleep deprivation compared to older adults. Until mid-twenties, the decision-making parts of the brain are still maturing which may play a role here.

People with sleep disorders that increase the risk of daytime sleepiness also have higher risks of accidents while driving. For example, obstructive sleep apnea increases risks of car accidents by two to three times. One study of drivers with OSA found impairments to vehicle control ability and overall performance during EEG-recorded microsleeps.

Workplace Accidents

During drowsiness, your brain isn’t operating at its best. Once microsleeps start occurring, performance tends to drop significantly.

Sleep deprivation is implicated in some of the most shocking accidents in recent history. The Chernobyl nuclear disaster, Challenger Space Shuttle explosion, Exxon Valdez oil spill, and Air France Flight 447 crash all involved impairments of over-tired people. One study estimates that fatigue-related losses cost the US around $18 billion annually.

Sleepiness remains a particularly important topic in the medical field. Hospitals and other care facilities tend to operate on shift schedules. People in these fields also need to maintain alertness and excellent decision-making capabilities.

Research finds that long hours and shift work weariness creates documentable detriments to patient safety. For example, one sleep-deprived anesthesiologist was observed experiencing microsleep episodes for 30% of a 4-hour procedure. In one survey, one-third of nurses working night shifts reported falling asleep at work in the prior week. In the healthcare setting, increased risk of errors represents dangerous risks for both patients and staff.

Regardless of where you work, microsleeps and exhaustion won’t do you any favors. When tired, it’s harder to focus, harder to keep your attention on a task, and harder to avoid mistakes. You’re likely missing important information, forgetting things, acting more irritably, and making less rational decisions.

Cognitive Side Effects

Even when you’re not driving or working, frequent microsleeps take away from your day-to-day experiences.

Sleep deprivation affects our alertness, memory, and accuracy. It’s harder to stay on task, and more difficult to make accurate judgment calls. Being in a state of daytime sleepiness with frequent microsleeps may also cause amnesia-like symptoms.

Even without obvious microsleeps, it’s likely you’ll experience more attention lapses even during complex tasks when tired.

If you experience microsleep, here’s what you can do:

Researchers are working on ways to detect signs of microsleep to prevent accidents, but there’s still a way to go. Tracking these lapses currently involves monitoring brainwaves and eye muscle movements. Eventually, it’s likely your car, heavy machinery, and planes will recognize sleepiness and alert you!

Until then, minimizing the side effects of microsleeps remains a manual task. The best way to stay alert is to stay aware of the signs of microsleep, seek help for potential sleep disorders, and practice healthy sleep habits.

Be Aware of the Warning Signs of Microsleeps

The best way to avoid the side effects of drowsiness is to be aware of the symptoms. Watch out for:

  • Feelings of sleepiness
  • Struggling to keep your eyes open
  • Excessive blinking or heavy eyelids
  • Yawning
  • Difficulty focusing on what you’re doing
  • Increased moodiness or irritability
  • Mentally drifting off or losing focus
  • Inattention while driving, such as drifting out of the lane, missing lights, or not remembering portions of the drive.

Episodes of microsleep brought on by not getting enough rest require one thing — more sleep. Healthy people generally recover from sleep deprivation symptoms by returning to normal sleep patterns.

If you think you’re getting a normal amount of rest but still feel tired during the day, bring it up to your physician.

Microsleep Prevention and Safety Tips

There is no guaranteed way to stave off sleep once your internal sleep pressure and biological clock decide it’s time to snooze!  The best way to avoid the dangers of microsleep episodes is simply awareness.

  1. Get enough sleep! Prioritize rest, and listen to your body. If you’re not feeling well-rested in the morning or are falling asleep very quickly at night, you may not be getting sufficient sleep. Most adults need 7 to 9 hours nightly, as well as exercise and daily sunlight during the day.
  2. When you feel tired, don’t push yourself into continuing to drive or do potentially dangerous work. Take a break.
  3. Sleep well before road trips. If possible, drive with a passenger. Avoid driving at times when you naturally feel tired, such as times you’re normally asleep, near dusk, or during your post-lunch lull.
  4. If you have a long day at work or a long drive, schedule in regular naps. NASA research on pilots found that those taking planned naps during long haul flights showed fewer microsleep events during times of active work.
  5. Talk to other people. Multiple studies find support for conversation reducing sleepiness. One study also found that hearing your own name was more effective than beeps at preventing attention lapses during a vigilance test.
  6. Don’t rely on loud music. Contrary to popular belief, music won’t do much to keep you awake while driving. Some research suggests that the brain isn’t registering auditory inputs during periods of microsleep.
  7. Caffeine helps—a little bit. One of the few heavily studied ways to boost alertness is caffeine. But, it’s not a miracle cure-all for being sleepy and it will not prevent microsleeps. It takes a while to kick in and only provides a moderate effect for a couple of hours.
  8. Take movement breaks. Fidgeting, stretching, and moving keeps the mind more engaged. Take regular breaks and stretch if you are sitting for long periods of time.

This article is for informational purposes and should not replace advice from your doctor or other medical professional.

About the author

Rosie Osmun regularly contributes to the Amerisleep blog writing about topics including, reducing back pain while sleeping, the best dinners for better sleep, and improving productivity to make the most of your mornings. She finds the science of sleep fascinating and loves researching and writing about beds. Rosie is also passionate about traveling, languages, and history.

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