We’ve all experienced fleeting moments where we’ve completely spaced out, missing what just happened, or had our heads droop and our eyelids close, before we sharply jerk our heads back to reality. Maybe it happened at a movie, or while you were reading a book, listening to a lecture, or (yikes!) while you were driving. In these situations, you may have experienced a strange, but common, phenomenon called a “microsleep,” which is a brief, involuntary lapse in consciousness that typically lasts from a half-second to 15 seconds.
Microsleeps “are common, but it’s hard to know how common because people often don’t realize they’ve had them,” says Jade Wu, Ph.D., a sleep psychologist at Duke University School of Medicine, Sleep.com advisor and author of the book, “Hello Sleep.”
People who are sleep-deprived for any reason, including sleep apnea, shift work, or jet lag, are especially susceptible to microsleeps, Wu notes. A study in a 2019 issue of the Journal of Sleep Research found that microsleeping is a reliable marker of sleepiness in people with obstructive sleep apnea (OSA). More recently, a study in a 2021 issue of the Journal of Clinical Sleep Medicine found that microsleeps also occur frequently in people with idiopathic hypersomnia (oversleeping) or narcolepsy (overwhelming daytime sleepiness).
“Sleep is such a fundamentally strong drive that if you don’t have enough of it, your brain is going to find a way to get more of it,” Wu explains. “The brain is always looking for opportunities to make up for sleep we didn’t get.”
In fact, a study in a 2021 issue of the journal Ergonomics found that 74% of men who performed a supervised driving test after 27 hours of sleep deprivation experienced microsleeps after an average of 52 minutes behind the wheel. Not surprisingly, research has found that driving performance deteriorates during microsleep episodes, especially on curved roads.
Microsleeps can also occur during long periods where you’re engaged in boring or mundane tasks, such as reading a dry or technical textbook or performing a dull tracking task on a computer.
What happens in your brain during microsleeps
Regardless of when they happen, microsleeps cause dramatic changes in brain activity. Often, these alterations in neural activity are limited to certain areas of the brain — such as the thalamus, the posterior cingulate, and the occipital cortex — rather than occurring globally throughout the entire brain, according to research in the journal, Human Brain Mapping. It’s almost as though some parts of the brain go offline for a few seconds during microsleeps, while others stay alert and engaged.
“Periods of microsleeps generally constitute lighter stages of sleep and can occasionally feature dream-like images,” notes Dr. Chris Winter, neurologist, Sleep.com advisor, and host of the Sleep Unplugged podcast. “The features are not well-studied, but probably resemble periods of light sleep, just for shorter periods of time.”
Sometimes, delta waves, the slow brain waves that typically occur during deep sleep — which is alternately called slow-wave sleep — can ripple across parts of your cortex during microsleeps, Wu says. “Other times, it looks like sleep spindles [bursts of neural activity that are visible on an EEG], which occur in stage 2,” or light sleep.
In a nutshell, “the solution is to get more good-quality sleep,” Wu says. If you feel perpetually tired, or like you’re not getting enough good-quality shuteye, or if you regularly experience microsleeps, consider the possibility that you may have a sleep disorder, such as sleep apnea, hypersomnia, or narcolepsy, and get checked out by a sleep specialist. “The signs of sleep apnea often look different for women, so doctors are missing lots of women who have sleep apnea,” Wu notes.
If you feel sleepy before you need to drive, “take a scheduled nap to take some of the sleep pressure off,” Wu advises. If you feel drowsy or struggle to keep your eyes open once you’re behind the wheel, “pull over in a safe place and take a break,” Winter advises. Even a 10-minute nap may help take the edge off. “Caffeine or wakefulness medications can help, but there is no better treatment than sleeping,” he adds.
As an added measure, drinking cold water or splashing it on your face may help you stay alert when you need to.
While essential oils can help you drift off, you can also use scents to decrease drowsiness: After shift-working nurses — who commonly experience sleepiness during the night shift — inhaled a drop of rosemary oil through a mask, their sleepiness levels decreased by 50% and their alertness levels increased, too, according to a study in a 2021 issue of the journal Complementary Therapies in Clinical Practice. Peppermint essential oil has also been found to promote alertness and attention. Consider bringing one of these scents into your car or keeping some at your desk, so you can take a whiff when you need a boost in alertness.
Overall, the best way to stop or prevent microsleeps is to have great sleep habits. This means limiting screen use before bed, keeping your bedroom dark, and sticking to a consistent sleep schedule.