Consider just how essential quality sleep is for cognitive and physiological functioning, and it’s no surprise that there’s an upper limit for how much deprivation we can handle. That precise amount varies by person, but once you’ve reached the point of max-tiredness, your body’s drive to sleep can outweigh even your mind’s best intentions to remain awake. That’s when you might experience microsleep, or tiny periods of sleep that can happen involuntarily and, in some cases, without the person even noticing until after the fact.
Experts in This Article
Carlos M. Nunez, MD is the Chief Medical Officer at ResMed, the world’s leading provider of solutions for sleep, respiratory care, digital health, and out-of-hospital clinical software. He leads the Medical Affairs, Market Access, Healthcare Economics, Government Affairs, Clinical Safety and Compliance, and Clinical Science and Innovation functions.
board-certified in pulmonologist, sleep medicine specialist
Regarding what microsleep is, exactly, it’s important to know there’s not a unified clinical definition, but sleep doctors typically clock it as a momentary lapse in wakefulness (that is, around 30 seconds or less). “Often, these episodes are associated with cognitive or psychomotor lapses, as a result,” says sleep specialist Peter Polos, MD, PhD, sleep expert for Sleep Number. “You might be performing a task, and then for a few seconds, do that task without fully realizing you’re doing it,” he says. Or, in some cases, you might briefly nod off only to be jolted back awake, or your eyes seem to linger in a blink for just a few seconds longer than usual.
Feeling chronically fatigued or tired throughout the day often precedes one of these episodes of microsleep, says Carlos M. Nunez, MD, chief medical officer at sleep-technology brand ResMed. But, specifically, they tend to happen when you’re doing a repetitive activity or something that doesn’t require much mental or physical effort, says Dr. Polos. Case in point: You’re reading a book or watching a movie and suddenly forget what happened in the last few paragraphs or scenes. That happens when a microsleep episode is so very brief, your brain barely has the time to register it as the intrusion of sleep into wakefulness that it is.
“The inherent danger of any high-risk activity will only be amplified if someone is trying to do it within a microsleep episode.” —sleep expert Peter Polos, MD, PhD
That said, occasionally microsleep can occur while you’re in the midst of something that requires your full attention, like, most notably, driving a car. “The inherent danger of any high-risk activity will only be amplified if someone is trying to do it within a microsleep episode,” says Dr. Polos. “For example, a microsleep episode lasting three seconds for a person who’s traveling in a vehicle at 60 miles per hour can lead to them having traveled almost 300 feet while in that state of sleep.” And, of course, that’s more than enough distance to cause an accident.
The most common causes of microsleep
While an insufficient quantity of sleep—that is, clocking less than the recommended seven to eight hours of sleep per night—is the top trigger of microsleep, poor quality of sleep can also play a role. In general, that happens when sleep is disrupted throughout the night, whether by episodes of wakefulness that may be triggered by insomnia, or a medical condition, like sleep apnea that prevents you from cycling through all the stages of sleep.
“Because up to 80 percent of people with sleep apnea don’t know they have the condition, it’s important to speak to a doctor if you find yourself nodding off during the day, despite getting enough sleep,” says Dr. Nunez.
Folks who work overnight or late-night shifts will also be more at risk for microsleep, says Dr. Polos. That’s mostly because these schedules don’t align with our circadian rhythm, or 24-hour body clock that naturally leads us to fall asleep when it gets dark and rise when it gets light again. In that vein, anyone who’s following a schedule that bumps up against their sleep chronotype—or natural variation within that circadian rhythm that makes you more alert or more sleepy at different times throughout the day—may also be more likely to experience microsleep.
How to ward off episodes of microsleep
Any good sleep situation thrives on routine: You’ll want to not only get enough sleep each night—though, again the importance of that can’t be overstated—but aim to do so around the same time of the night, if you can. That also helps ensure you’re going to bed when your environment is dark and waking up when it’s light, which aligns your body with that good, old circadian rhythm.
Practicing good sleep hygiene can also help you fall asleep more efficiently at night, which can, in turn, leave you more well-rested and less likely to experience microsleep come morning. “Try to avoid alcohol and exercise within three hours of going to bed and caffeine within eight hours of going to bed, and limit blue light for about an hour beforehand, too,” sleep doctor Shelby Harris, PsyD, previously told Well+Good.
Because medications and medical conditions (like the aforementioned sleep apnea) can sometimes cause microsleep, it’s worth checking in with your doctor if the episodes persist after you’ve taken care of your sleep routine and hygiene. You can also get ahead of microsleep by actively listening to your body, says Dr. Polos, and fitting in a power nap during the day, if you can, before you get so tired that you blink yourself asleep.
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