On the outside, sleep doesn’t exactly appear to be all that productive. You’re sprawled out, eyes closed, pretty much unconscious and totally dead to the outside world.
Unless you consider dreaming to be an efficient use of your time, you probably see sleep as a necessary evil that steals away precious hours of potential when you could be getting stuff done.
Of course, you’re not the only one. Every night, countless Americans trade hours’ worth of quality sleep for working and catching up on emails—not to mention texting, scrolling through Instagram, bingeing on Netflix, and generally falling down the rabbit hole of the Interwebs. After all, what else are the hours between 12:00 and 2:00 A.M. really good for?
Actually, they’re perfect for sleep. Which might seem like an eight-hour dead zone where you’re doing a whole lot of nothing—but in fact, that couldn’t be further from the truth.
While you’re out cold, your brain is hard at work doing all kinds of crazy, good-for-you stuff. Dreaming, yes, but that’s not the only thing. Far from it. Sleep is really the time when your brain is prepping so you can be on your game for the next day—thinking fast without making mistakes, making smart choices, coming up with genius ideas, and more.
Without adequate rest, your brain ends up on the fast track to going haywire. Sort of like a computer that you’ve left running for a month straight and is in desperate need of a reboot.
And you’d never want to be like that computer, right? Of course not. Here’s a look at all of the amazing things your brain does while you sleep—and how you reap the benefits after waking up.
This Is Your Brain On Sleep
Even though you’re lying there all quiet and peaceful, there’s a lot going on inside your head while you snooze. How much? Think of it this way: If slumber was an eight-hour play, your brain would be the director, leading you through the various acts that ensure your body achieves restful sleep worthy of rousing applause. Here’s what the show would look like:
Stage 1. The lights are dim, you’re settled comfortably in bed, and the show is about to get started. At this point, the base of your brain is busy sending signals to the other areas of your brain that it’s time to stop making you feel awake and start powering down. You begin drifting in and out of sleep, and your eye and muscle activity start to slow down. You’re officially in Stage 1 of non-rapid eye movement (NREM) sleep. This is gonna be good!
Stage 2. The show is in session, which means everyone needs to be quiet and still. At this point, your sleep is deep enough that you are no longer aware of the world around you. Your brain has told your eyes to stop moving and allows your body temperature to drop. Your brain waves start to slow down.
Stages 3 and 4. These are the last stages of NREM sleep. By now, you’re fully engrossed in the show and are getting your deepest, most restorative sleep. In this stage, your brain signals your body to let your blood pressure drop, slow down your breathing, and relax your muscles. Now, it can really get to work on the important stuff. While you’re in deep sleep, your brain floods your body with growth hormones that aid in tissue repair and muscle development.
Stage 5. You could call this the best part of the sleep show. During stage 5, you experience rapid eye movement (REM) that gives your brain and body the energy boost you’ll use to get through the day tomorrow. Since your brain is at its most active during REM sleep, this is also when you’ll have dreams (or nightmares, yikes!).
Then, somewhere between 90 and 110 minutes, the show winds down. But it’s not actually ending—instead, it’s just gearing up to start again.
Commenting on how sleep cycles fluctuate throughout the night, Dr. Colleen Ehrnstrom, a clinical psychologist and author of End the Insomnia Struggle: A Step-by-Step Guide to Help You Get to Sleep and Stay Asleep states, “The show changes throughout, with Stages 1-4 dominating the first half and Stage 5 dominating the second half. This is why 7-8 hours of uninterrupted sleep is more restorative than fragmented sleep or naps.”
How Sleep Impacts Your Brain
OK, you get it now. Sleep isn’t exactly the blank, no-man’s land that you might’ve thought—and your brain is actually pretty hard at work the entire time. But aside from moving you from one stage of sleep through to the next, what’s actually going on in there?
Get ready—you’re about to find out.
Sleep Helps Your Brain Work Faster And More Accurately
You might already know this intuitively. When you stay up too late or fall behind on sleep, you end up caught in a dense cloud of brain fog. You know, the one that causes you to make mistakes that you know are dumb but can’t seem to avoid, or that makes it harder than usual to figure simple stuff out.
Adequate quality shut-eyefire on all cylinders when you’re awake, so you can think and respond faster and with fewer mistakes. Likely, that could be because sleep is an opportunity for the neurons that you’ve been using all day to take a break and repair themselves before you start calling on them again tomorrow. Because everything—even tiny neurons—need to rest at some point.
But after they’ve had a chance to chill, you have an easier time concentrating and remembering stuff. You’ll also be less likely to phone it in when it comes time to solving a tough problem, according topublished in the National Library of Medicine.
When City University of New York researchers gave college students a series of math problems after a night of adequate sleep and then again after a night of too-little sleep, the students did equally well after each night. But after not getting enough sleep, students tended to choose less challenging problems.
In other words, they knew that they weren’t as sharp, and tried to avoid failing all together by taking an easier route. Which is fine for an experiment—but probably isn’t the type of behavior that’ll get you the promotion at work.
Sleep Helps You Make Sense Of New Information
Believe it or not, your brain can actually process complex information when you’re sleeping.
Experts have long known that your brain maintains some level of awareness even when your brain is fully engaged in the sleep process. For instance, sleeping people are more likely to respond to their own names or startling sounds like a fire alarm or alarm clock than to other random noises.
But according to mind-blowing research recently published in the journal Current Biology, that’s just the beginning. Researchers asked study participants laying in a dark room to group spoken words into certain categories by pressing a left or right button. Once participants had gotten used to the task so it became automatic, researchers told the participants that they should continue categorizing the words, but that it was okay to fall asleep.
After participants had nodded off, the researchers introduced new words that fell into the same categories as the words that participants heard when they were awake. The crazy thing? Brain monitoring devices showed that even while the participants were snoozing, their brains were using the information they had learned to go through the functions to categorize the words as left or right.
When the participants woke up, they didn’t have any memory of hearing the new words while they were sleeping. In other words, their brains processed all of the new information while the participants were completely unconscious. Which means that, yes, your brain is even learning while you’re sleeping.
Sleep Helps Your Brain Cement Memories
Imagine if every single time you did or experienced something new throughout the day, you had to stop what you were doing to file the experience away in your short- or long-term memory file so you could recall it later when you needed it. Chances are, you’d be spending so much time archiving your life that you’d never actually get anything done.
Thanks to the power of sleep, you don’t have to do that. That’s because snooze time is prime time for your brain to get busy processing memories. As you sleep, your brain works to solidify memories that you formed throughout the day. It also links these new memories to older ones, helping you make connections between different pieces of information to come up with new ideas. (More about that later.)
Remember the stages of sleep we talked about earlier? Stages 1-4, the ones where you aren’t experiencing REM, are key for learning and the memory formation that comes with it. In fact, if you skimp out on non-REM sleep, your ability to learn new information plummets by as much as 40%,at the National Institutes of Health. That’s because sleep deprivation interferes with your hippocampus, the part of your brain that’s responsible for processing memories.
When you’re sleeping, your brain decides what stuff from the day is worth keeping—and what’s worth forgetting about so you can free up space for taking in new information tomorrow.
It makes perfect sense when you think about it. But it’s more than just a theory. More than a century of research shows that sleep improves memory retention—so much so, that the brain can actually be more efficient at consolidating memories while you’re asleep than while you’re awake, wrote German researchers
Unfortunately, the reverse is also true. When your sleep patterns start to change as you get older, so too does your ability to form new memories. Your memory-cementing skills can begin to decline as early as your late thirties, and it only tends to go downhill from there. One study published in the journal Nature Neuroscience found that adults over age 60 had a 70% loss of deep sleep compared to adults ages 18 to 25—and consequently, had a harder time remembering things the next day.
Still, just because you’re getting older doesn’t mean that you’re doomed to a life of total forgetfulness. While some amount of age-related memory decline is unavoidable, getting enough sleep is crucial for making the most of your brain’s memory-consolidating powers. Aim to get seven to eight hours of sleep on most nights—especially on days when you’ve learned important new information.
According to Dr. Josef Parvizi, Associate Professor of Neurology and Neurological Sciences at Stanford University, “the seemingly noisy and disorganized brain activity during sleep has a perfectly unique structure to it,” he added.
During his research he found that populations of cells that were working together during math and memory-related activities, had a coordinated fluctuation of physiological activity during sleep as well, in other words, these cells worked together to complete a task and were paired together during sleep.
“It was almost like they never ceased to be together, almost like a pair of individuals that never depart from each other,” he added. “There is much more going on in sleep than we are able to understand,” said, Parvizi.
Further driving home the point that there is a substantial connection between memory and other activities in your brain while you’re awake and while you’re asleep.
Sleep Helps Your Brain Think More Creatively
On days when you’re running short on sleep, your thoughts probably go on a loop that sounds something like this: “I’m so exhausted. I can’t do this right now. I just want to go home and do nothing.”
When you’ve got a one-track mind for crawling into your bed and getting some much-needed rest and relaxation, you probably aren’t all that concerned about coming up with cool new ideas. Which is one of the reasons why sleep deprivation zaps your ability to be creative.
Of course, there’s way more to it than that. While your brain is busy consolidating memories as you sleep, it’s also forming connections between new ideas and old ones—setting the stage for that all-important light bulb moment.
Research published in the Proceedings of the National Academy of Sciences of the United States of America backs this up. After a night of restful sleep, study participants were 33% more successful at completing tasks that required them to make unusual (read: creative) connections in their brain compared to people who hadn’t slept yet.
Perhaps unsurprisingly, Stage 5 (or REM sleep)—the part of the sleep cycle that involves dreaming—is key to boosting creativity.
One recent study presented at the American Psychological Association’s annual convention found that people who took 90-minute naps featuring REM sleep performed 40% better on word problems that required them to see connections between seemingly unrelated words than people whose naps didn’t feature REM sleep or people who didn’t nap at all. That could be because REM sleep helps your brain “detach” your memory of a word’s meaning and apply the word in another context, say researchers.
Sleep Helps Your Brain Clear Out Harmful Toxins
The word “toxin” gets thrown around a lot these days. And in health-oriented circles, you can find endless solutions that are touted as effective for clearing out toxins in your body. (Juice fasts, activated charcoal, and apple cider vinegar, we’re looking at you.)
For now, it’s up for debate whether any of those things are actually effective. But when it comes to clearing out toxins, one thing that actually has been shown to work is sleep. At the same time that your brain is busy sending out growth hormones, consolidating memories, and forming creativity-boosting connections, it’s also busting out the vacuum to suck up any unwanted dirt and clear it away.
“There is evidence the brain clears out toxic wastes accumulated during the day at night, through convective motion of the fluid that bathes the brain,” according to Dr. John Medina, a developmental molecular biologist and author of the New York Times bestseller Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School. “If you don’t sleep, you won’t get the molecular waste removed,” he added.
Studies conducted on mice back in 2013 found that during sleep, the space between rodents’ brain cells actually expanded, allowing for the brain to sweep away harmful molecules that had built up throughout the day. And not just any harmful molecules—we’re talking about ones that are associated with neurodegenerative diseases like Alzheimer’s and Parkinson’s.
Fast forward to 2015, and we’re learning that the same seems to apply to humans. When University of California-Berkeley researchers used imaging tools to look at the brains of 26 older adults who had not been diagnosed with dementia or sleep problems, they found that people with the highest levels of beta-amyloid—a toxic protein associated with the development of Alzheimer’s and dementia—tended to have the poorest quality sleep. They also performed worse on simple memory tests compared to those who slept better and had lower beta-amyloid levels.
Of course, it’s only one study, and experts still have a lot to learn about how exactly beta-amyloid buildup affects memory. But when it comes to keeping your brain as clean as possible, sleep just might be key.
Sleep Helps Your Brain Regulate Your Appetite
By now, you’ve probably heard that regularly skimping on sleep can lead to weight gain. And while it’s true that most of us are more likely to snack on junk at night, and that being tired could make you more likely to skip your workout, those aren’t the only factors at play.
Just like how sleep prompts the release of growth hormone, snooze time also plays a major role in regulating the hormones that determine whether you feel like eating. Countless studies have shown that lack of sleep prompts your brain to release more ghrelin, the hormone that causes you to feel hungry. At the same time, too little sleep causes your brain to pump out less leptin, the hormone that makes you feel full.
Translation? When you’re zonked, you’re more likely to scarf down everything in sight. In fact, people who are sleep deprived tend to take in about 300 more calories per day compared to their well-rested counterparts.
That adds up to a pound gained in less than two weeks—but some research suggests that the effects could be even more dramatic. One University of Colorado-Boulder study found that just five days of sleep deprivation prompted people to load up on more comforting carbohydrates (hello, mac and cheese!)—and pack on two pounds in the process. (The good news? When subjects got back to healthier sleep patterns, they started making healthier food choices, too.)
To make matters worse, the whole thing ends up turning into a vicious cycle. When you gain weight, you up your risk for running into sleep-stealers like chronic pain, sleep apnea, and even type 2 diabetes. The sleep deprivation makes you feel even more tired, which makes you more likely to make poor food choices and less likely to have enough energy to exercise.
Sleep Helps Your Brain Keep Your Body Looking Good
Seriously, they call it beauty rest for a reason. Sleep is the time that your brain gives the green light for releasing the growth hormone that your body uses to grow new cells and repair damaged tissue.
Of course, your body needs growth hormone to do things like heal wounds or build stronger muscle tissue after a tough workout. But it also uses growth hormone to fight stress and damage caused by the sun and the oxidizing environmental pollutants that we’re all exposed to on a daily basis.
Over time, those things can cause your skin to get dull and wrinkly. And while you can’t keep your skin looking like the way it did when you were 20 forever, logging adequate shuteye can help stave off premature aging by fostering the growth of fresh, healthy cells that keep your skin looking younger, smoother, and more radiant.
And research suggests that you won’t be the only one who can actually tell the difference. In one Journal of Clinical Sleep Medicine study, University of Michigan researchers looked at adults with untreated obstructive sleep apnea who experienced excessive sleepiness.
After just two months of CPAP treatment, the subjects boasted improvements in their facial volume (read: more suppleness and fewer wrinkles) and less redness, while independent raters said that the subjects appeared more youthful and attractive.
Frequently Asked Questions
What does sleep do to the brain?
Sleep helps the brain re-organize itself, essentially. Brain tasks that occur during sleep include disposing of toxins that build up in the brain during the day and stabilizing memories of the day’s events. Getting enough sleep is also linked to higher levels of cognitive performance, creativity, and improved moods.
How much sleep do I need?
According to the CDC, adults aged 18 to 60 need 7 or more hours of sleep a night. Every person has different sleep needs, though, so the exact amount needed varies from sleeper to sleeper.
Our sleep calculator can help readers determine when they should be going to bed to wake up refreshed and well-rested.
How can I improve my sleep health?
To improve your sleep health or sleep hygiene and get enough rest, consistency is key. When you fall asleep and wake up at roughly the same time every day, your internal clock has an easier time staying on track and keeping you on a good sleep schedule.
To make it easier to fall asleep at night, you’ll want to disengage from electronic screens. Instead, spend the last hour or so before bed doing something relaxing, like reading a chapter in a favorite book, taking a warm bath, or doing some light stretches.
What are the health benefits of sleep?
Sleep doesn’t just benefit the brain but the whole body. Getting an adequate amount of sleep means you are also taking care of your immune system, regulating your mood, and keeping your cognition sharp.
Sleepers also find it easier to watch their weight when they’re well-rested. This is one reason that sleep apnea and weight gain are so interconnected, as the former tends to worsen the latter due to sleep loss.
Does sleep clean your brain?
Essentially, yes, research suggests that the brain accomplishes “housekeeping” tasks while you sleep, which includes flushing toxins out of your brain. These toxins build up in your brain during the day and it’s important to get enough sleep to cleanse them all out of your system.
How is this cleaning accomplished? While you sleep, cerebrospinal fluid (the fluid inside the brain and spinal cord) flows in and out to get rid of the brain’s “trash.”
How To Get The Sleep That Your Brain Needs
Imagine being at work and trying to get an important project done. You’re clacking away on your keyboard and you’re totally in the zone–when all of the sudden a coworker walks into your cubicle and stands in front of your computer screen. Suddenly, you can’t get your stuff done because somebody is literally blocking your path.
Similarly, sleep is the time that your brain uses to get all of its important projects done—allowing you to function like a healthy, productive human instead of a zombie during the day. But when you stay up late or do other stuff that makes it harder to fall asleep (like load up on caffeine before bed or spend tons of time in front of electronic devices), you become the coworker standing in front of the computer screen. With your bad habits in the way, your brain can’t get its stuff done.
So how much sleep do you actually need? Everyone’s a little different. While some people aren’t at the top of their game with anything less than nine hours, others do just fine on seven.
And anything within that range is considered healthy—so it’s really a matter of experimenting to see how you feel. If you’re tired or fuzzy during the day, you aren’t getting enough sleep, so tack on some more time and bed to see if that leaves you more alert.
If your problem is trouble falling asleep, though, the answer might not be so obvious. If you’re already sleeping for eight and a half or nine hours, it could be a sign that you need to push your bedtime back by a little bit.
More likely, you’re having trouble falling asleep because you’re stressed or are exposed to too much energizing stimuli at night, or are just plain uncomfortable. If that’s the case, try finding a calming bedtime routine to help you wind down, or take steps to make your bedroom more comfortable.
Don’t overlook what you sleep on either. You can practice the best sleep health tips but if you’re going to bed on a rock, good quality sleep will be hard to find. Finding a comfortable mattress that supports you will go a long way in helping you sleep better.