Each stage has a different function, and getting enough Stage 3 (also known as slow-wave sleep, deep sleep, and delta sleep), is essential if you want to wake up feeling restored. Here’s what happens while you’re in deep sleep, plus how to make sure you’re spending enough time in this stage nightly. About 20 to 25% of our time asleep is spent in this stage. This is also the stage in which delta brain waves—slow waves that signal relaxation—start to occur. As Hannu Kinnunen, chief science officer at sleep tracker Oura, previously explained to mbg, “Stage 3 sleep falls into the category known as ‘deep sleep,’ which focuses on restoring your body.” He adds that in this stage, your blood pressure drops and your brain flushes out waste1. On top of that, blood flow increases to your muscles, and growth hormone is released, he says. “Deep sleep is really important for growth hormone,” naturopathic sleep doctor Catherine Darley, N.D., explains, adding it’s when roughly 75% (and up to 85%) of our total growth hormone in a day is secreted. In REM, our breath and heart rate goes up, the brain becomes more active, and the human body effectively stops moving. An adequate amount of REM sleep is required for the continuation of sleep cycles3. The older we get, the less time we spend in REM sleep4 each night. In other words, if you don’t get enough deep sleep, you don’t give your body a chance to properly recover from the day—which brings us to our next point. However, Kinnunen adds, one way to tell if you’re getting enough deep sleep is to check in with how you feel. “As you get to know your body, you’ll learn what amount of deep sleep helps you feel your best,” he says, adding, “Getting enough deep sleep helps you awaken alert and ready to face the day.” But as Darley adds, the other sleep stages are at play here, too. “Each of the different stages does a part in making that energized feeling,” she explains, “so we think of it more in terms of total sleep.” The best thing you can do to support deep sleep—and sleep more generally—is set aside plenty of time for it (7.5 to 9 hours) and stay on top of your sleep hygiene routine. The following tips should help and check out these culprits, too. As Kinnunen says, “Keeping your wake-up time consistent ensures that about 16 hours thereafter, you’re sending your body the same, strong signal: ’this is the right time to power down.’” (Check out our guide on how to get your sleep schedule back on track for more tips!) mindbodygreen’s sleep support+ supplement, for example, pairs easily absorbable magnesium with jujube fruit extract and PharmaGABA® to help people fall asleep faster and stay asleep longer.* This is backed by research, she notes, which has shown exercising can promote deep sleep, particularly as we get older. In fact, in one analysis of existing exercise and sleep studies6, researchers write, “Exercise promoted increased sleep efficiency and duration regardless of the mode and intensity of activity” in middle-aged and elderly adults. “Continuing to get exercise will promote deep sleep, which promotes growth hormone, which promotes physical repair,” Darley adds. Knowing this, try to set your alarm for 7.5 or 9 hours after you fall asleep (accounting for the roughly 15 minutes it takes most people to fall asleep). This can help ensure you don’t wake up in the middle of your last deep sleep stage for the night, so you don’t lose out on those all-important minutes. When we don’t get enough, we’ll definitely feel it, but with good sleep hygiene and a consistent sleep schedule, you can clock your 20% of deep sleep every night and wake up ready to go.
