We’ve all experienced brief episodes where we’ve completely zoned out, losing attention and focus, or had our heads bob and our eyelids close for a moment (or two or three) … until a sudden head jolt brought us back to reality. There’s a name for this bizarre, but common, phenomenon: It’s called a microsleep, and it’s a brief, involuntary episode of unconsciousness that typically lasts from a fraction of a second up to 15 seconds.
“It’s a real episode of sleep — if you were to record it on EEG [an electroencephalogram, which measures electrical activity in the brain], there’s a slowing of neural activity, and muscle tone drops, just as it does during real sleep — but a microsleep is only a few seconds long,” explains Dr. Chiara Cirelli, a neuroscientist and professor in the department of psychiatry at the University of Wisconsin–Madison. “It’s not very deep sleep; it’s a superficial sleep [like] stage 1 or 2.” To put this in context, there are five stages of sleep: Stages 1 and 2 are light, stages 3 and 4 are deep sleep, and rapid eye movement, or REM, sleep is the final stage, in which most dreaming occurs.
In most cases, microsleeps are caused by extreme fatigue. When you don’t get enough shut-eye, parts of your brain can shut down for a few seconds while you’re awake, essentially so they can take a forced nap and become rejuvenated. “Basically the brain is so sleep deprived and tired, it is trying to force the person to get some sleep — this is due to a build up of a substance called adenosine in the brain,” says Michael Breus, a board-certified clinical sleep specialist in Manhattan Beach, California, and author of “The Power of When.” (Levels of adenosine decline during any sleep period.) During microsleeps, faster beta waves that normally occur during engaged wakefulness are replaced by slower theta waves, and spindles — which are sudden bursts of oscillatory brain activity that occur during stage 2 of light sleep — also occur.
[Read: Are Sleep Problems Affecting Your Mental Health?]
It doesn’t take much to set yourself up for microsleeps. If you normally get plenty of good quality shut-eye, a single night of insufficient sleep (as in: four hours) can result in an increased number of microsleeps, according to research to be published in the July 2018 issue of the journal NeuroImage. Shiftworkers are particularly susceptible because they’re working against their bodies’ natural rhythms, as they try to stay alert and functional at night when the biologic urge to sleep is high, experts note. What’s more, research has found that microsleeps also can happen if you spend an extended period of time performing a monotonous task (such as a visual tracking exercise).
Your Brain in Sleep Mode
To appreciate the physiology behind microsleeps, it helps to understand what happens in your brain when you normally sleep. Simply put, “we all have a sleep switch in our brains,” explains Dr. Ilene Rosen, president of the American Academy of Sleep Medicine and a professor of clinical medicine for the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. After multiple nights of enough quality sleep, the sleep switch stays in the “off” position as you go through your day; then, when night comes and your internal circadian clock becomes less active, “the sleep switch turns to ‘on’ and the brain waves begin to slow and cycle through the various stages of sleep,” Rosen explains. After a full night’s sleep, the sleep switch goes back into the “off” position and you enter into a state of wakefulness.
Here’s where things get tricky: If you’re sleep-deprived or you’re having poor quality sleep, “the sleep switch is never fully stable in the ‘off’ position in the morning or throughout the day,” Rosen notes. “A microsleep can be thought of as the brain going temporarily ‘offline’ when the sleep switch flops into the ‘on’ position,” she explains.
[See: Trouble Sleeping? Ask Yourself Why.]
Not surprisingly, microsleeps can be dangerous, even fatal. For one thing, driving performance (with cars, motorcycles, trains or airplanes) deteriorates during microsleep episodes — often without the person realizing it, research has found. “Essentially, a microsleep causes a brief failure to respond to external stimuli,” Rosen says. “A microsleep can be incredibly dangerous if it occurs when a person is driving, operating a train or using heavy machinery.” But performance on completing tasks such as those you might do at work is also compromised, setting you up to make mistakes at a desk job, too.
Protecting Yourself From Microsleeps
Not surprisingly, the best way to prevent microsleeps is to get plenty of good-quality slumber — at least seven hours per night — on a regular basis. “The only way to recover from the need for sleep is to sleep,” Cirelli says. “There is no substitute.”
If you can’t get enough sleep at night, “a brief nap of 20 to 30 minutes can refresh you without causing you to wake up feeling sluggish and groggy,” Rosen says. If you know that you’re going to be skimping on sleep for a couple of nights — due to upcoming social events or work demands, for instance — you can try to “bank sleep” by extending your usual sleep for a few nights ahead of time, Rosen adds.
[See: 8 Steps to Fall Asleep Fast.]
Alternatively, if you feel drowsy during the day, exercising or doing another form of physical activity can help stave off the natural inclination to drift into microsleep, Cirelli says. (Just don’t exercise too close to bedtime or it might interfere with your nighttime slumber.) Exposing yourself to bright light at work also can promote alertness and reset your sleep switch to “off,” Rosen says. “Periodic use of a stimulant, such as caffeine, can provide a short-term boost to alertness; however, the more frequently you consume caffeine, the less effective it is as a stimulant.”
The take-home message: If you make an effort to stay alert to these soporific episodes, you can take action to either prevent them from occurring or to quickly regain a state of full wakefulness when they happen. Otherwise, if you microsnooze, you may lose control of your faculties and impair your performance in dangerous ways.
More from U.S. News
Are Sleep Problems Affecting Your Mental Health?
Trouble Sleeping? Ask Yourself Why
The Bizarre Phenomenon of Microsleep originally appeared on usnews.com
