Health experts agree: Not getting enough sleep is bad for you. It can mess with your heart health, immune system and even your weight-loss efforts. And while getting enough sleep overall is important, it’s also key to spend enough time in each phase of the sleep cycle — especially deep sleep.
We sleep in cycles, and most people go through 4–6 sleep cycles per night. Before you reach REM sleep, the phase where you dream, there are two main sleep stages:
- Light sleep (non-REM): During this phase, which is two distinct phases, N1 and N2, you fall asleep, but you can more easily wake up.
- Deep sleep (non-REM): This is the type of sleep, also called N3, that your body needs to feel rested in the morning. If you wake up during deep sleep, you are likely to feel groggy at first.
“We spend about 25% of our night in deep sleep, the majority of which comes in cycles during the first half of the night,” explains Dr. W. Christopher Winter, president of Charlottesville Neurology and Sleep Medicine. Deep sleep is also sometimes called slow-wave sleep because, when looking at brain waves on an EEG, deep sleep creates a large, slow, wave pattern that indicates minimal brain activity.
All the sleep phases are important for our health, but deep sleep is crucial. “During deep sleep, your body is in repair mode, releasing growth hormone, repairing damaged tissue and consolidating memory,” says Dan Ford, a behavioral sleep psychologist at The Better Sleep Clinic.
Most people need 1 1/2–2 hours of deep sleep per night, Winter notes. It’s also somewhat dependent on how much we’ve slept in the previous nights, according to Frida Rångtell, PhD, sleep expert at Sleep Cycle. “The longer we stay awake at night, the more deep sleep we will have during the next night’s sleep recovery.”
The amount of deep sleep we get also changes throughout our lifespan, typically decreasing as we get older. “This decrease of deep sleep with age is larger for men than for women,” Rångtell says. “However, it’s not known if it’s the need for deep sleep or the ability to maintain deep sleep that changes with age.”
It can be tricky to tell if you’re skimping on deep sleep, but here are signs experts suggest looking out for. These could signal you’re not getting enough deep sleep, in particular, or that you’re just not getting enough sleep overall.
1. YOU’RE NOT SEEING FITNESS GAINS, AND YOU’RE NOT RECOVERING FROM WORKOUTS
“Deep sleep is essential for athletic recovery,” Winter says. “We typically make growth hormones during deep sleep, so if you are not getting enough deep sleep, you are not making growth hormone. If you don’t get enough, you might find it more difficult to recover from athletics.”
Consolidation of motor memory (Think: better coordination) also happens during deep sleep, Ford says. So, if you don’t seem to be making progress in your workouts despite training hard, it could be a sign you’re not recovering enough at night. “If you exercise hard, your body will respond with more deep sleep. Basically, no sleep, no gains.” Lastly, if you notice more muscle pain and soreness than usual, this could be a sign your body isn’t adequately repairing overnight during your deep sleep phases.
2. YOU FEEL SLEEPY AND GRUMPY DURING THE DAY
This is a sign of not getting enough sleep overall, but it can be indicative of problems with deep sleep specifically. “You will feel sleepy during the day and be at risk of accidents and other sleep deprivation-related health issues: high-blood pressure, cardiovascular problems, metabolic syndrome and so on,” Ford says.
3. YOU WAKE UP A LOT
“If you wake up multiple times throughout the night, you will ‘short’ your deep sleep, because you’ll have to go to the ‘front of the line’ and go through stage N1 and N2 before you get back to deep sleep (N3),” explains Max Kerr, DDS, a dental sleep expert with Sleep Better Austin.
This is probably the most important thing you can do to boost your deep sleep time. “Reduction of total sleep usually impacts total deep sleep, particularly going to bed later than normal,” Dr. Winter says. Most people need 7–9 hours per night, though individual sleep needs vary.
Experts agree stimulants and depressants like caffeine, nicotine, alcohol and cannabis have a negative impact on sleep overall and reaching adequate deep sleep levels. You might think anything with a sedative effect would help with deep sleep, but Winter points out that quality sleep and sedation are not the same.
“Keeping the body and mind active with exercise and complex, engaging work and social engagements has been shown to result in deeper sleep at night,” Ford says.
“Since so many of us are working from home, it’s really easy to snuggle up in bed during the day, but this can create sleep difficulties,” says Ginger Houghton, a licensed social worker. “Likewise, leave your bed if you’re awake for more than 20 minutes. Find a low-key activity to do until you feel the signs of sleepiness, and then return to bed.”
Sleep pressure refers to how much need your body feels to sleep. “A lower sleep pressure can decrease deep sleep and make it more difficult to fall asleep at a regular bedtime,” Rångtell says. “Taking a nap close to bedtime lowers our pressure to sleep, making it more difficult to fall asleep. Consider the timing and schedule naps earlier in the day,” she advises.
You may get more deep sleep by increasing your sleep hours before midnight. “If you’re a normal sleeper without trouble falling or staying asleep, and you tend to go to bed late (10:30 p.m. or later), you may wish to experiment with going to bed earlier to see what difference it makes in recovery, inflammation and pain,” Ford says.
“Listening to discouraging reports about the virus on the evening news before bed may not be a good idea, and could keep your mind racing throughout the night,” Kerr says. “Opt for shows that are lighter and more entertaining later in the day, and reduce screen exposure one hour prior to bedtime.”
“Just as we can have a bad day, all of us have bad nights every now and then,” Rångtell notes. “Of course, we may feel more tired during the day after a bad night, but shorter periods of bad sleep are usually recovered after one or a few nights of recovery sleep.”
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