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Sleep is important for several different reasons including, but not limited to physical healing, recovering from illness, dealing with stress, solving problems, consolidating memories, and improving motor skills. A good night’s sleep isn’t just about how many hours of sleep you get, but also the quality of that sleep.

The two types of sleep:

The first is non-rapid eye movement sleep (Non-REM)- which is often known for helping us recover physically. Non-REM is what allows our bodies to slowly drift off into a deeper sleep and become well-rested for the following day. Non-REM also helps us recover from injuries, stress/anxiety, and recover from illness/ immune system support.

The second type of sleep is rapid eye movement sleep (REM). REM sleep affects your mood, memory, and your learning efficiency. When you achieve quality REM sleep, you improve recall and memory consolidation and help your brain regulate the synapses associated with some types of motor learning. REM sleep is the sleep phase closest to wakefulness, and where most of our dreaming occurs.

>Why Is Non-REM Sleep Important? Non-REM sleep is just as important as the REM stage of sleep but contributes to your health differently. NREM sleep helps your body wind down and fall into a deep sleep, which helps you feel more rested in the morning. However, getting a good night’s sleep is about more than improving daytime sleepiness. NREM sleep can help us physically heal, recover from illness, deal with stress, and solve problems. NREM sleep also plays a role in memory consolidation and can help boost the immune system.

Where Does Non-REM Sleep Fit in the Sleep Cycle?

Our bodies use circadian rhythm and sleep-wake homeostasis to help regulate our sleep. NREM sleep comprises the first three stages of the sleep cycle: dozing off, light sleep, and slow-wave sleep (SWS), also known as deep sleep. These three stages occur as we fall asleep for the first time, but our body will cycle through them another four to six times during the night. Non-REM sleep is heavier earlier in the night but tapers off as the night progresses, with your brain spending more time in REM periods of sleep instead.

What Is the Difference Between Non-REM and REM Sleep?

The main difference between REM and non-REM comes down to brain activity. While REM sleep is characterized by rapid eye movements and high levels of brain activity, non-REM sleep is the opposite.

  • NREM is more restful: NREM sleep is when our brains start to slip into a more restful state. Brain waves are slower, muscles relax, and the body enters a light sleep. NREM sleep also includes a deep sleep stage, where your heart rate and breathing slow, and body temperature drops.
  • REM sleep is closer to wakefulness: While each stage is important to quality sleep, rapid eye movement sleep is more similar to stages of wakefulness, whereas non-REM sleep is when the body and brain are more at rest. Biologically, NREM and REM sleep is regulated by gamma-Aminobutyric acid—also known as GABA, a neurotransmitter. GABAergic neurons are responsible for promoting NREM sleep while suppressing REM sleep. Scientists have observed that people with sleep disorders have significantly lower levels of GABA activity.

Why Is REM Sleep Important?

REM sleep affects your mood, memory, and learning efficiency. Getting enough REM sleep can improve recall and memory consolidation and help your brain regulate the synapses associated with some types of motor learning. The ontogenetic hypothesis claims that neuron activity involved in the REM sleep cycle stimulates the developing brains of newborns, helping them form mature synaptic connections. While scientists are uncertain about the exact reason for dreaming, they speculate that it is how our brains process emotions.

Where Does REM Sleep Fit in the Sleep Cycle?

REM sleep occurs approximately 90 minutes after falling asleep. While it is technically the last stage of the sleep cycle, the body repeats the whole cycle around four to six times per night. REM sleep alternates with the three other stages of non-REM (or NREM) sleep: dozing off, light sleep, and deep sleep, also known as slow-wave sleep (SWS). Though dreaming can occur in different sleep phases, REM sleep is where our most vivid dreams are produced. REM sleep produces brain activity levels similar to those in an awakened state. REM sleep cycles get longer as the night progresses and make up around 25 percent of our total sleep.

What Are the Effects of Diminished REM Sleep?

Sleep deprivation as a whole can affect your body’s wellbeing, but a diminished REM sleep can cause psychological disturbances like anxiety, aggression, irritability, and hallucinations. A reduction in REM sleep can also lead to difficulty concentrating, with those experiencing a restful night sleep having better memory retention and recall. People with REM sleep behavior disorder are at higher risk of developing other neurological disorders like sleep apnea, narcolepsy, and Parkinson’s Disease.

3 Tips for Better REM Sleep

  1. Create a sleep schedule. Creating a schedule for your sleep times can help your body get into the habit of “normal sleep.” Discontinue the use of bright screens or stimulating electronics an hour before bedtime can help your body prepare for sleep. Bright light can confuse your inner clock into thinking it’s daytime, which can cause your body to secrete less melatonin, resulting in less sleepiness at bedtime.
  2. Exercise. Routine exercise can help your body expend its excess energy, which can improve the quality of your sleep at night. The later you go to sleep, the lighter and more REM-heavy your sleep will be. While REM sleep is a necessary part of the sleep cycle, getting too much without a balance of deep sleep can leave you feeling groggy the next day.
  3. Watch when you drink. Drinking a lot of fluids before bed can increase the frequency of late-night bathroom visits. Too many interruptions while sleeping can decrease overall sleep REM sleep, which can affect your cognitive functions. Additionally, drinking alcohol before bed can also be unhelpful. While drinking may cause sleepiness, it can suppress the quality of REM sleep.

Source: Mathew Walker's book: Why We Sleep

Zach Erickson MS, CSCS