Deep Sleep vs REM: How Deep Sleep Is Different From REM Sleep

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Stages of sleep diagram

If you’ve ever wondered what the difference between deep sleep vs. REM sleep is, you have come to the right place. 

Although both deep sleep and REM sleep are necessary parts of a normal sleep cycle, they serve different functions. Deep sleep is important for feeling rested and healing the body, while REM sleep is important for helping you retain new memories and learn new information.

Healthy human adults need between 7 to 9 hours of sleep to function optimally. This amount of sleep is enough to feel refreshed and energized and contributes to productivity levels. Without enough sleep, the body cannot cycle through the different stages of sleep enough times to allow the brain and body to recharge and perform their essential functions. 

A lack of quality sleep is also directly connected to the different sleep stages, including deep sleep and REM sleep. This is why it’s important to understand how both of these stages work and what they do for our minds and bodies.

Keep reading to learn the full differences between deep sleep vs. REM sleep, including the different functions they perform in the brain and body. We’ll also cover which stage is most important and how much of it you should be getting each night. 

Sleep Stages 

Sleep StagesType of SleepAlso Known AsNormal Length
Stage 1NREMN11-5 minutes
Stage 2NREMN210-60 minutes
Stage 3NREMN3, Slow-Wave Sleep (SWS), Delta Sleep, Deep Sleep20-40 minutes
Stage 4REMREM Sleep10-60 minutes
Table showing all four sleep stages

There are four stages of sleep you experience every night, which can be broken up into non-REM and REM sleep. Non-REM sleep makes up the first three stages in the sleep cycle. 

Each night as your body falls asleep, you go through a transition period from being awake to being asleep. These initial stages only take a handful of minutes, and during this time your body relaxes, your temperature cools, and your brain wave activity slows down. 

They are just as important as later stages and are where you’ll spend most of your sleep cycle. You may experience several cycles of the earliest sleep stages in a row before falling into deep or REM sleep. 

What Is Deep Sleep?

Deep sleep is the third stage of non-REM sleep. This stage makes up a maximum of  23 percent of a full night’s sleep in healthy adults. 

But is REM sleep deep sleep? Although it’s common for people to confuse deep sleep with REM sleep, the two cycles couldn’t be more different.  If you’ve ever wondered what is deep sleep called, you may have also seen it referred to as slow-wave sleep of the delta waves the brain puts outs.  

In this stage, your breathing and heartbeat slow down and your body undergoes essential processes, such as growth hormone release, tissue repair, emotional processing, blood sugar and metabolism balance, and memory retention. Harmful waste products can be eliminated from the brain as well. 

Deep sleep is also the time when your body does most of its physical healing from illness and injury. 

Deep sleep is reached between 30 to 45 minutes after falling asleep. Once the body has reached this stage, it is much more difficult to be woken up. If you are woken up from this sleep stage, you will likely experience feeling groggy or disoriented. Carrying on directly from this stage can drastically alter your mood and leave you feeling irritable or grumpy. 

You must spend enough time in the deep sleep stage. When you do, you will experience feeling alert, refreshed, and revitalized. 

If you don’t spend an adequate amount of time in deep sleep, you may end up feeling unrested, fatigued, or sluggish throughout the day. It is also harder to learn new things and remember important information. A lack of deep sleep can affect the body’s ability to fight off infections, cause cravings and increase appetite, and even contributes to the development of insulin resistance. 

Related Reading: 13 Effective Ways to Wake Up a Heavy Sleeper

What Can Cause a Lack of Deep Sleep? 

There is a multitude of reasons why someone may not be getting enough deep sleep. Sleep disorders such as acute or chronic sleep deprivation, insomnia, sleepwalking, sleep apnea, and night terrors can all have a direct impact on the number of quality minutes a person spends in the deep sleep stage. Stress and anxiety also play a role in limiting the number of hours a person sleeps. 

Common, everyday responsibilities are also the main factor in the amount and quality of sleep an individual experiences. Long work hours, family obligations, watching late-night TV, or spending too much time on a smartphone can all affect how well a person sleeps at night.

People who struggle with mental health and neurological disorders such as Alzheimer’s, Parkinson’s, or schizophrenia tend to experience lower amounts of deep sleep as well. 

Do You Dream in Deep Sleep? 

Most people spend around two hours each night dreaming, and they can show up at any stage of sleep. However, most often, these dreams do not play out during deep sleep. Dreams are more commonly experienced during REM sleep when brain activity is at its highest. 

What Is REM Sleep? 

Rapid eye movement, or REM, sleep is reached approximately 90 minutes after falling asleep. The stage gets its name from the way your eyes move rapidly from side to side behind your closed eyelids. Although your eyes are moving, they aren’t sending any visuals to the brain.

During this stage, your sleeping body goes through periods of REM sleep. The first time you reach REM sleep in a night, you will only be in the stage for 10 minutes or so. As the night goes on, REM sleep stages grow longer. There can be between 3 and 5 REM cycles in a single sleep session, and the last couple of cycles can last up to 60 minutes. 

The body goes through physiological changes during REM sleep as well. Blood pressure and heart rate increase, breathing will speed back up, and brain activity increases. The brain is so active during REM sleep that it needs to send signals to keep your limbs immobilized so you don’t try and act out your dreams as they happen.

Is REM the Deepest Stage of Sleep? 

At this point, you may be asking yourself: what is the deepest stage of sleep? The answer is REM sleep. In this vital stage, your body will remain largely inactive but the brain undergoes intense waves of activity. 

How Much REM Sleep Should I Aim For? 

As we mentioned, there are up to 5 cycles of REM sleep per night in healthy individuals. If you can successfully achieve between 7 to 8 hours of sleep each night, roughly 90 minutes of your night will be spent in REM sleep, which is plenty. 

Age plays a large role in the amount of REM sleep that is needed. For example, babies and young children experience 50% more REM sleep than older adults and the elderly. 

Effects of REM Sleep 

REM sleep is important for helping the body and your brain store new memories and obtain new information. In this sleep phase, the brain works and also strengthens neural connections that have a direct link to mental and physical health. 

People who don’t get enough REM sleep will likely experience negative side effects, including having a harder time remembering things they just learned. Insufficient REM sleep has been suggested as a factor in medical conditions such as obesity, dementia, depression, cancer, cardiovascular disease, and migraines. 

What Is Better: Deep Sleep or REM?

All parts of the sleep cycle are necessary for good quality sleep, and it can’t be said that one is “better” than another. However, when it comes to REM sleep vs. deep sleep, deep sleep is slightly more important for your overall health and well-being.

This is because of the important physiological and mental changes the body goes through during this stage. Deep sleep is directly connected to our body’s ability to improve cognitive function and memory, help us improve our motor skills, and ultimately help our brains develop. 

When people can reach an optimal amount of deep sleep in a night, they are more adaptable, more alert, and prepared for learning new information. 

How to Increase Your Sleep Quality

If you find yourself struggling with any of the side effects that can occur from not getting enough deep or REM sleep, there are a few things you can try to help improve your sleep. Developing good sleep habits are a great way to help enter these stages more regularly. 

  • Remove phones, computers, and TVs from your bedroom 
  • Keep your bedroom dark, quiet, and at a comfortable temperature 
  • Don’t consume caffeine within six hours of your bedtime
  • Eat your last meal at least three hours before going to sleep
  • Go to bed at the same time every day
  • Exercise during the day

The Takeaway

So, what is the difference between deep sleep and REM sleep? While both are important parts of the sleep cycle, they serve different functions. Deep sleep is important for healing and brain development, while REM sleep is where our brains dream and retain new memories. 

It is important adults get enough of both periods of sleep during the night to perform optimally and have the best chance at a long and healthy life. 

Nate Devore
Nate Devore
For over 15 years Nate has been obsessed with solving his own personal and difficult health challenges related to sleep, energy, and fatigue. As one of our sleep experts at sleeping.com, Nate is passionate about helping you get the best night’s sleep possible.

Medical Disclaimer: The content on this page should not be taken as medical advice or used as a recommendation for any specific treatment. Always consult your doctor before making any decisions.

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