When it comes to getting the sleep we need, most of us think about deep sleep. It just sounds like the most beneficial part of sleep. And it is beneficial: Experts believe it helps with everything from recovery to memory to strengthening our immune system — not to mention helping us feel rested the next day. However, we argue, there’s just no point worrying about getting enough deep sleep each night.
That’s in part because we cycle through different stages of sleep and each one helps us feel and perform our best the next day. But it’s also because we can’t control how long we spend in the deep sleep stage. What we can control, however, is how long we spend sleeping overall. And when you get enough sleep in general, without otherwise getting in the way (more on that later), your brain will get enough deep sleep by itself.
Below, we’ll dive into why deep sleep is important, but why you’re much better off focusing on getting enough sleep overall.
Even though we talk about sleep in terms of hours a night, those hours look very different. We sleep in cycles that last from 70 to 120 minutes, and, depending on the number of hours of sleep we each uniquely need, we get four to six of these sleep cycles a night.
Within each sleep cycle, we move through different stages of sleep. These include three stages of non-rapid eye movement (NREM) sleep, which make up about 75% to 80% of the night, and one stage of rapid eye movement (REM) sleep, which makes up the remaining 20% to 25%.
Here’s how a night of sleep should go:
Once you’ve moved through all the stages of non-REM and REM sleep, you’ll start another cycle in stage 1 again. As the night goes on, your sleep cycles will consist of more time in stage 2 and REM. The deep sleep stage is longest in the first cycle of sleep, and gets shorter and shorter with each cycle — it’s common to not go into deep sleep after the second cycle at all.
Deep sleep is vital for rest and recovery. In this stage, your immune system is strengthened, your brain detoxified, and your pituitary gland secretes growth hormone, which helps cells in the body regenerate and repair. This is also the sleep stage where your brain works on creating and storing memories and consolidating new information you’ve learned during the day.
Not getting enough deep sleep can affect metabolic function, glucose regulation, and even your ability to retain information properly. Not to mention you simply won’t be feeling or performing your best. Plus, a lack of deep sleep has been linked to serious health problems such as heart disease, stroke, and Alzheimer’s disease.
After a night of total sleep deprivation, the next time you go to sleep, you’ll spend less time in stages 1, 2, and REM sleep, and more time in deep sleep, which experts say shows just how vital this phase of sleep is.
After a night of partial sleep deprivation — think six hours or fewer — you’ll spend less time in stages 1, 2, and REM, but deep sleep may be less affected as this mainly happens in the first few cycles of sleep. But that doesn’t mean this kind of sleep deprivation is okay. You’ll be throwing off the balance between the sleep stages, your daytime performance will keep getting worse and worse until you get enough sleep, and sleep studies show you’ll be increasing your risk of developing everything from type 2 diabetes to cancer.
However, what this does show is that your brain is very good at self-optimizing. It prioritizes deep sleep, trying its best to get enough of it even if you're sleep deprived. Therefore, the best way to make sure you’re getting enough deep sleep is to get enough sleep, period.
Deep sleep should be about 10% to 15% of your overall sleep, but as everyone needs a different amount of sleep each night, the ideal amount of deep sleep can vary wildly from person to person.
Plus, we can’t control how we move through the phases of sleep and how long we spend in each one. But we can control how much sleep we get overall each night. And by getting the right amount of sleep, you’re giving yourself the best chance of cycling through all of the stages of sleep, naturally spending the ideal amount of time in each. So if you’re trying to work out how much deep sleep you need, you should instead work out how much sleep you need in total, and focus on getting that.
This is called your sleep need, the genetically determined amount of sleep you should be getting each night. Just like height or eye color, you have no control over it. The average sleep need is 8 hours 10 minutes, plus or minus 44 minutes or so. But 13.5% may need 9 hours or more sleep a night.
RISE takes the guesswork out of calculating your sleep need. The app uses historical sleep data on your phone to see how much sleep you’ve been getting. It then uses proprietary sleep-science-based models to calculate your exact sleep need in hours and minutes. All you need to do now to get the right amount of deep sleep, is to get this amount of sleep each night. That, of course, is easier said than done, so that’s where sleep hygiene comes in.
Sleep hygiene is a set of behaviors you can do each day to get a good night's sleep. They’ll help you fall asleep faster, stay asleep all night, and ultimately get the right amount of sleep, and therefore the right amount of deep sleep.
Here’s what you should focus on:
RISE can tell you the right time to do these sleep hygiene behaviors based on your circadian rhythm (more on that later) and remind you to do them each day.
Sleep hygiene also extends to what your sleep environment is like. For the ideal night’s rest, your bedroom should be cool, dark, and quiet. To achieve that, aim to keep your bedroom at 65 to 68 degrees Fahrenheit, and consider wearing ear plugs, an eye mask, and using blackout curtains.
Perhaps the reason you’re wondering how many hours of deep sleep you need is because you want to improve your productivity, energy, or overall wellness. But what if we told you there are two things that make the biggest difference to how you feel and perform each day, and deep sleep isn’t one of them? Instead of worrying about deep sleep, you should instead turn your attention to sleep debt and your circadian rhythm.
Sleep debt is the amount of sleep you owe your body compared to how much you’ve had over the last 14 nights. So if you need 8 hours 10 minutes of sleep a night, but you’ve only been getting 7 hours, you’ll have built up quite a bit of sleep debt.
Your circadian rhythm is your internal body clock that governs when you feel awake and tired over a roughly 24-hour cycle. Everyone’s circadian rhythm is slightly different as it is affected by your chronotype. This is our natural tendency to be an early bird, night owl, or somewhere in between. You can learn more about chronotypes in our in-depth guide.
RISE calculates sleep debt and helps you keep track of it as you pay it down. The app also predicts your circadian rhythm each day, so you can align your schedule as best you can to match it. By keeping your sleep debt low — we recommend under five hours — and living in sync with your circadian rhythm — which includes waking up, sleeping, and doing high and low-energy tasks at the right times, you’ll notice a huge difference in your days.
Deep sleep is important, of course, but you shouldn’t worry about how much of it you need and whether you’re getting that amount each night. Instead, calculate the total sleep time you need and focus on getting that.
If you’re practicing good sleep hygiene, you’ll be much more likely to get the right amount of sleep each night. Then your brain will simply do its thing and get more deep sleep if it needs it. And if you really want to feel your best, keep your sleep debt low and align your schedule with your circadian rhythm for maximum productivity, energy, and well-being.
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