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The most important thing you can do for your body—right up there with working out and eating right—is getting enough sleep. The benefits of sleep are as plentiful as the sheep most Americans stay up late counting: It improves your memory, curbs inflammation, aids weight loss, makes you more likely to stick to your workout plans, and even helps you live longer.
But it's not just about getting the seven or more hours of sleep recommended by the American Academy of Sleep Medicine (which a third of Americans aren't clocking, BTW). It's about getting quality sleep—and that means spending enough of your sleep hours in rapid-eye-movement (REM) sleep, the phase when dreaming occurs. Here's what you need to know about your sleep cycle, the benefits of REM sleep, and how you can bank more of it next time you're in bed.
What Is REM Sleep?
REM is one of the four stages of sleep, explains W. Chris Winter, M.D., author of The Sleep Solution: Why Your Sleep Is Broken and How to Fix It. "There's N1, a transitory stage of sleep where you go from wakefulness into sleep; N2, or what we consider light sleep; N3, or deep sleep; and then REM sleep," he says.
REM gets its name from the rapid eye movements that occur throughout it. The scientists Eugene Aserinsky, Nathaniel Kleitman, and William C. Dement were the first to observe REM sleep in the early 1950s, says Dr. Winter. And it was especially interesting because they also noted that there was almost no movement from the rest of the body during that sleep stage. "From a physiological point of view, it's almost as if your brain is awake but your body is paralyzed—perhaps to keep you from acting out your dreams," says Conor Heneghan, Ph.D., lead sleep research scientist at Fitbit.
During the beginning of the night, you're going to experience a longer period of deep sleep—when your body repairs and regrows tissues, builds bone and muscle and strengthens the immune system—says Heneghan. Most people generally experience their first cycle of REM sleep 90 minutes after falling asleep. "Initially, you get shorter bursts of REM, and as the night progresses and the body satisfies its need for deep sleep, you take in longer periods of REM sleep," he says.
Over the course of a night, you typically spend about 20 to 25 percent of your sleep time in REM, and you'll likely go through four or five sleep cycles overall if you're getting adequate sleep. (Related: 5 Health Benefits You Get from Sleeping Naked)
What Are the Benefits of REM Sleep?
Scientists are still exploring the importance of REM, and it's not entirely clear what's going on in our brains during that time, says Dr. Winter. The rapid eye movement that is representative of REM sleep may occur as our brain cycles through new mental images, which, according to a study published in the journal Nature Communications, could be a part of processing new memories. Researchers also found REM to be associated with learning new information and maintaining important neural pathways.
"During sleep, your brain is sort of replaying certain things you've experienced and trying to figure out if it should put that experience into your short-term or long-term memory—or to just forget about it," says Dr. Winter. "Unlike deep sleep, which is really concerned with rest and recovery, REM sleep has lots more to do with concentration, focus, memory consolidation, and pain perception."
Studies have shown that a lack of REM sleep can affect your memory, mess with your mood, impact your cognitive performance, and screw with cell regeneration. Obviously, that could impact your workday, but it could also eff up your athletic performance, making it hard to perform more complicated activities, Dr. Winter says. Not to mention, if your mood is in the toilet, that could put a serious damper on your workout motivation.
Pain perception has also been linked to REM sleep. "Imagine two people with [an] identical knee injury, but one person is getting good REM sleep and the other person isn't," says Dr. Winter. "The person who isn't sleeping well is going to perceive that pain as being a lot worse. It has to do with the way our brain gates stimuli." (Related: Is Muscle Pain a Good or Bad Sign?)
How Can You Get More REM Sleep?
The first thing you can do: Get more total sleep. The average American sleeps 6.8 hours a night, according to a Gallup poll—and 40 percent log less than six hours. "If you only have a four-, five-, or six-hour time window to sleep, just by natural physiology you'll get a higher percentage of deep sleep and a lower percentage of REM sleep," says Heneghan.
But your sleep habits are also important. "People who go to bed more irregularly tend to actually sleep less than average, and they also tend to see less of the REM [cycle] than those who are more regular [with] their sleep hygiene," says Heneghan. (That's why sleep docs generally advise against trying to "make up for lost sleep" on the weekends.)
In a 2017 study using data from over 6 million Fitbit trackers, researchers found that while sleeping longer can lead to getting more deep and REM sleep, sleeping seven to eight hours gives you the highest combined percentage of time in these stages. (The Fitbit tracks your heart rate, which tends to spike during REM as your body actually responds to the situations in your mind, says Heneghan.) Waking up earlier than usual was also shown to impact the percentage of REM sleep you get.
Lastly, don't use a glass of wine or a couple beers as a crutch to fall (or stay) asleep. "Alcohol is extremely suppressive of REM sleep," says Dr. Winter. "Other medications can suppress it, too, like some of the common medications we use for depression. (Related: Did You Know There Are 4 Different Types of Depression?) So talk to your doctor about any prescriptions you're taking if you're concerned about your sleep."
The best thing you can do? Stick to a schedule, and make time for those seven to eight hours so your brain can really go through all the proper cycles of sleep. Not only will you enjoy a better night's sleep, but it'll help make your days go smoother as well.