What Happens During Deep Sleep?

What Happens During Deep Sleep?

On average over a 7-9 hour night of sleep, we go through 4-6 cycles of sleep.

During these cycles there are two different kinds of sleep, NREM (non-REM) and REM (Rapid Eye Movement). Deep sleep consists of both NREM sleep and REM sleep, taking place in stages 3 and 4 of the sleep cycle.

Deep sleep is important because these are the stages where your mind and body recharge from the day. Stage 3 of the sleep cycle allows your body to recharge while stage 4 helps with your cognitive functions too. Without these stages of sleep, our thinking would suffer along with our mental and physical health.

So what happens during deep sleep? First you’ll need to understand a little more about the stages of sleep.

Stages of Sleep

During stage 1 your body is relaxing and your brain is slowing down. You might twitch a little. It’s the stage you hit just after you lose consciousness.

During stage 2 your body continues to slow down further. While your brain waves have mostly slowed down by this point, there are short bursts of electrical activity that allow you to stay asleep. Without them, you’d be more likely to wake up.

During stages 3 and 4 you’re in deep sleep. These are the stages of sleep that rejuvenate your body and brain and allow you to feel rested the next day. This is the point of sleep where your bodily functions, like heart beat, breathing, and muscle tension relax or slow the most.

What is REM sleep?

REM stands for Rapid Eye Movement and is the 4th stage of sleep. During this stage your body often goes into sleep paralysis, except for your breathing and eyes, and your brain activity increases greatly.

This stage gets its name due to the eye activity that happens in this cycle. If you’ve ever seen someone deeply asleep with their eyelids fluttering, this is the stage they’re in. The eyes dart back and forth quickly and your heart beat, breathing and muscles become faster again. This is also when you’re most likely to dream in even though you can dream at any stage.

Why is deep sleep so important?

As mentioned above, this is the time when the body and mind are restored. According to Healthline, this is the time that your brain is recharging your memory and your ability to take in new information.

Your body is also busy strengthening your immune system, replenishing energy stores, and repairing itself.

Without enough deep sleep you’re at risk of higher levels of stress, a weak immune system, impaired cognitive functions like thinking and memory, and higher risk of infections and disease.

What can I do to improve my deep sleep?

The same tips that will help you fall asleep faster, will help you have quality deep sleep.

This includes keeping a regular sleep schedule, doing a guided sleep meditation before bed, or trying a BioActivate deep sleep patch. Avoiding alcohol, caffeine, and nicotine close to bedtime, avoiding blue-light for an hour before bed, and creating a clean and tranquil sanctuary in your bedroom will all help promote deep sleep as well.


1.Ashley Marcin, “What Is Deep Sleep and Why Is It Important?,” Healthline, June 12, 2020. Accessed July 18, 2021. https://www.healthline.com/health/deep-sleep

2.Eric Suni, “Stages of Sleep,” Sleep Foundation, Accessed July 18, 2021. https://www.sleepfoundation.org/how-sleep-works/s...

3.“Brain Basics: Understanding Sleep,” NIH Publication No. 17-3440c, Accessed July 18, 2021. https://www.ninds.nih.gov/Disorders/Patient-Careg...