We may receive financial compensation for products purchased through links or codes on this website. is owned by Healthy Sleep, LLC and includes Amerisleep, LLC advertising. Learn more

The Science Behind Sleep Cycles

Tyler Joseph (TJ) Thomas


What is REM Sleep?

During the sleep cycle, your brain will complete five different stages of sleep. The stages begin with lighter sleep, then progress into deeper patterns, then this process repeats itself throughout the night. Rapid eye movement, or REM sleep, is one of the most productive stages of sleep, where much of your body’s recovery occurs. This stage got its name from the fact that your eyes will move rapidly in various directions.

How Long Until You Hit REM Sleep?

Your body will typically enter REM within the first 90 minutes of falling asleep. It is one of the various sleep cycles that will repeat throughout the night. You should hit your REM cycles several times. On average, an adult should have about 20 to 25% of their sleep throughout the night consisting of a REM cycle. In infants, it is crucial to helping them grow and develop and should make up about 50% of their sleep.

Stages of Sleep

There are four primary stages of sleep in a sleep cycle.

Stage One

The first stage of your sleep cycle occurs within a few minutes of falling asleep. During this stage, your body will begin processing alpha and theta waves. Physically, your eye movements will begin to slow, and your body will fall into a more relaxed state. This stage is relatively brief, only lasting about five to ten minutes in most cases.

This stage is referred to as a light stage of sleep. Even small noises, movements, or changes in light can wake you. If woken, you will probably still be alert. If you enjoy a little catnap every now and then, this is the stage you are enjoying during those brief nod-offs.

Stage Two

The second stage of sleep is also considered a lighter stage of sleep. While you may still be woken up by loud sounds or changes around you, it will take a little more to rouse you. You will also be less alert when woken up at the stage.

This is the stage in which the activity and waves in your brain begin to slow down. If you are fond of power naps, this is the stage you will want to wake up to provide yourself with the necessary amount of brief, yet refreshing sleep.

Stage Three

These stages mark the beginnings of deep sleep. Physically, you will no longer have the eye movement from the previous stages, and your muscles will be inactive as well. As your body becomes less responsive to stimuli in the room, it will be harder for you to wake. In addition, this is often when you will get the most restful sleep.

Stage Four

Your brain is now producing more delta waves, drawing you into a restorative sleep. At this stage of restorative sleep, you will be extremely difficult to wake. Even though your muscles and eyes do not move at this stage, your body is working hard as the tissues and muscles begin to repair themselves.

These are the other things that happen to your body during this stage:

  • Your body will stimulate any necessary growth and development
  • Immune function is being restored
  • Begin building the energy that the body will need to take on the next day

REM Stage of Sleep

You will go through multiple stages of sleep cycles during your sleep period. The beginning of your first REM cycle is usually about an hour and a half after you have fallen asleep. Each stage of REM will average up to an hour in length, with the first and final round being around 10 to 20 minutes. You can experience up to five cycles of REM per night. As you age, you may start getting less REM cycles. Those under the age of 30 experience up to two hours and those older can get as little as 30 minutes.

Physical Signs of a REM Sleep Cycle

Physical Signs That Someone is in Their REM Sleep Cycle

Your brain is very active during the REM stage. This is the time of sleep when you are likely to experience dreams. The body physically responds to this cycle by becoming more active as well.

  • The eyes can jerk wildly in all directions and at a very rapid pace
  • Heart rate and blood pressure will increase as well
  • A person in REM will begin taking more rapid and shallow breaths that seem irregular
  • Fluctuations in body temperatures, increased oxygen to the brain, twitching in the face and limbs of the body, and even sexual arousal

Role of REM Sleep in a Person’s Memory and Cognitive Functions

This time of sleep is remembered for the sometimes-vivid dreams it can produce. However, this cycle actually plays a major role in your memory and brain functions. During this period, your brain will be functioning at the same activity level, it does while it is awake. At this time, your brain is consolidating and processing all of the information it had received from your previous wake cycle. This information will then be stored in your long-term memory for future use.

Even though your brain is extremely active during the REM stage, and you may experience jerky movements, the body is actually immobilized. This is the reason why REM is also referred to as paradoxical sleep.

Some people may even experience a state of temporary paralysis. This is caused by the brain sending signals down the spinal column to stop the movement in the limbs. When this occurs, it is referred to as atonia and can be a defense mechanism built in the body to prevent the body from moving in accordance with its dreams.

Your Body is Equipped With Built-in Sleep Controls

Your body craves sleep in the same way that it craves food. As you go about your day, your desire to sleep will continue to build. Although your body cannot force you to eat when it is hungry, it can force you to sleep. This makes having a normal sleep cycle so vital to avoid such issues as falling asleep while working or even while driving. When deprived of adequate sleep your body can even force you into microsleep episodes, which last a few seconds and do not even involve the closing of your eyes.

What is REM Behavior Disorder?

Some people find themselves affected by a REM behavior disorder (RBD). It is a condition where someone does not experience the muscle paralysis that should occur during REM. Thus, when they have their most vivid dreams during their body may respond as if the dream was occurring. This could mean screaming, flailing about, kicking, climbing, or other movements similar to what their body is doing in the dream. This disorder can result in injury either by striking objects or rapid body contortion.

When someone suffers from REM behavior disorder, the symptoms usually develop at a gradual rate. These symptoms increase in severity over time. The cause of RBD is linked to a malfunction of the nerve pathways in the brain. While the disorder can affect anyone, there are factors that increase your risk of developing the disorder. You are at higher risk for developing RBD if you are:

  • Male
  • Over the age of 50
  • Certain prescribed medications including certain types of antidepressants
  • Have other neurological conditions or neurodegenerative disorders Lewy body dementia or Parkinson’s
  • Have been diagnosed with narcolepsy

REM behavior disorder is a treatable condition with certain medications. Alterations should also be made to the sleep environment. Even when the disorder is controlled with medication, it is advised that the sleep environment is modified. This will ensure the safety of the person who has the disorder as well as anyone sleeping in the same room with them.

The Benefits of REM

The Benefits of REM SleepREM cycles are a vital component of learning, memory, and mood. This is particularly true to the development of the infant brain.

The Development of the Central Nervous System

REM cycles have been the subject of much research in regards to the development of the infant brain. Some studies have shown that this is the stage when infants further develop their central nervous system. It is believed that the need for REM to improve development is why you will require less REM as you grow older and your need for sleep changes.

The Removal of Waste Products From Brain Cells

REM is also the time when your brain will be able to remove waste products that are no longer necessary. This waste removal occurs while you are awake as well, as your brain is taking in new information. However, it is believed that this process runs more efficiently during the REM cycle.

What Happens without Enough REM?

The REM cycle is an essential component of the body’s restorative and mental process. When the body is deprived of the REM cycles, it could lead to mental and physical consequences. Some of the consequences that can occur when you fail to or have too little REM includes:

A Reduction in the Ability to Cope

In sleep studies where animals were subjected to sleep deprivation, some abnormalities occurred. Some examples include reduced defensive responses and coping mechanisms to threatening stimuli.

An Increase in Migraines

One group was subjected to three nights of sleep deprivation while the control group got proper rest. Researchers discovered that the sleep-deprived rats had an increased expression of both the proteins p38 and PKA. These proteins regulate the response in your facial nerves. These facial nerves also referred to as trigeminal nerves, play a role in the onset and severity of migraines.

People who suffer from migraines, or any other type of chronic headaches, will often have difficulty getting a good night’s rest. This can lead to a cycle of headaches.

Chronic Pain

In the same study, the rats that were suffering from sleep deprivation began secreting high levels of the protein that both stimulates and arouses the nervous system. In contrast, they had lower levels of the proteins needed to shut it down. The arousal proteins can sometimes spark high enough to begin triggering chronic pain in the body.


In a study, the University of Pittsburgh looked into the connection between a lack of REM sleep and weight increase. The study found that due to the functions that sleep performs, lack of sleep, especially lack of healthy REM cycles, can lead to excessive weight retention.

During sleep, the body will modulate several body functions that can affect how your body stores excess fat. This includes both neuroscience function and glucose metabolism. When sleep deprivation occurs, the body’s metabolic and endocrine systems become altered. Your body will experience such things as:

  • Increased concentrations of cortisol, which is linked to the storage of body fat
  • Decreased glucose tolerance, which inhibits your body to regulate and break down sugar
  • Decreased insulin sensitivity, which can affect the regulation of blood sugar
  • Increased levels of ghrelin, which will trigger your appetite, increase food intake and promote the storage of fat
  • Decreased levels of leptin in the body, which is the chemical that lets you know you have enough fat stored.

Overall, the study showed that you are at higher risk of being overweight if you suffer from lack of sleep.


There has also been research conducted that explored the links between a lack of REM sleep and depression. The link is the fact that sleep abnormalities produce similar symptoms as major psychological concerns such as major depressive disorder.

In his clinical practice, psychiatrist, Dr. Brian Wu sees, “Many elderly patients with signs and symptoms of clinical depression. They indicate that they have difficulty falling asleep and maintaining uninterrupted deep sleep. Research is showing that over time this pattern can lead to changes in the brain’s neural pathways.”

The studies included neuroimaging and the study of brain lesions. These are their findings when they analyzed brain activity:

  • Major depressive disorder (MDD) involves high levels of activity in the brain’s ventromedial prefrontal cortex
  • They also showed high activity in the paralimbic structures
  • Findings also showed extremely low levels of brain activity occurring in the dorsolateral prefrontal cortex

There were symptoms found in the neuroimaging of people who suffer from MDD, though they do not directly link with known causes of MDD. They do relate to problems that can occur with REM dis-inhibition. It is the REM cycle that activates these key brain structures, helping to regulate the systems.

The regulation of these patterns helps the brain process and consolidate negative emotional memories. This shows how intimately REM and depression are tied.

Lowered Immune Functions

There has also been a link between the lack of REM and lower immune function and response. Your body’s immune system is controlled and regulated by cytokines. These will signal the molecules in both your brain and immune system that it is time for them to act.

When your body experiences an illness, the levels of the pro-inflammatory cytokines will increase. This can trigger the fatigue you will feel when you are sick. This is the body’s way of prompting you to get more sleep so that the other levels in the immune system will increase. This will help you better recover from your illness. However, during this time, your cytokines will also increase, which can cause your deep and REM cycles to become more fragmented. This will often result in restless sleep and possible waking throughout your illness.

If you suffer from a chronic condition, this natural cycle of increasing and decreasing levels in your immune system can occur. For autoimmune diseases, higher levels of inflammation that stay in the body can cause you to feel constantly fatigued. This is because the body is pushing you to sleep to recover. In these cases, the resulting fatigue can be debilitating.

When the body’s protective cytokines decrease, so does your body’s ability to respond to infection or other diseases. This will make you more vulnerable to illness.

Related: 8 Cold-Weather Tips for Better Sleep

Ways You Can Improve Your REM Sleep

Ways You Can Improve Your REM

Enhancing both your nighttime REM and non-REM sleep can do the following:

  • Help you improve your health
  • Provide you with the energy you will need to begin your day
  • Allow your body to restore itself

If you struggle with sleep or are just looking for ways to improve the quality of your REM cycle, you can try the following.

Establish a Solid Bedtime Routine

Having the same bedtime routine every night can help the body and mind begin a cycle to prepare themselves for sleep. Eventually, your body will regulate itself and create a sleep clock. This will allow you to maximize the amount of time that you are asleep, which will give you the best chance for more REM cycles.

Reduce the Causes of Night Time Waking

While not all stimuli that can wake you during the night is avoidable, you can do your best to minimize them. Be sure to avoid the sudden brightness caused by lights. If you have a floodlight or other light outside, make sure you have blinds or drapes that can keep the light out. When it comes to temperature, an ideal room temperature that is conducive to a good night’s rest is between 60 and 68 degrees.

Make Sure You Get the Required Amount of Sleep

There are many times when you may shorten your sleep cycle due to the need to accomplish other things in the morning or evening. You may think that getting an hour or two of less sleep a night is not a big deal. However, it can eliminate some of your REM cycles and disturb the restorative process. For an adult, you will need to get at least 7-9 hours of sleep each night, with the amount of time going down as you age.

Take Care of Any Medical Conditions That Can Cause Sleep Problems

If you suffer from conditions that can affect your sleep, it is essential to get them treated. This will ensure they do not begin to deprive you of much-needed REM. Sleep apnea is a common sleep disorder that can severely affect the REM stages of sleep and cause symptoms of sleep deprivation.

Avoid Caffeine Before Bedtime

Avoid Caffeine Before Bedtime

Caffeine and other substances that can stimulate your body can decrease the number of REM phases you experience. For this reason, it is best to avoid caffeinated beverages four to six hours before you go to sleep, or completely if possible. It may take your body a couple of days to get used to the change. However, once you are getting more REM cycles, you will eventually experience less fatigue. This will also lessen the need for caffeinated drinks.

Practice Bedtime Relaxation Techniques

Getting your body into a relaxed state before you go to sleep can help aid you in falling asleep. This can also provide you with sleep that is more restful. If you are tense during the day, make sure you allow yourself to unwind about an hour before your scheduled sleep time. You can do this by soaking in the tub or even through progressive relaxation techniques.

Avoid Screen Time

You will not only need to relax your body as you prepare it for sleep but also your mind. Avoid using your phone or watching TV as these cause increased stimulus to your brain. This can make it harder to turn off your mind and make obtaining deep sleep take longer.

Invest in a High-Quality Mattress

Invest in a High-Quality Mattress

Finding the best mattress can be difficult, you may be looking for the best mattress for side sleepers or the best memory foam mattress or something else completely. Mattresses have come a long way in allowing the body to stay in a comfortable position during sleep. Still, with so many options it can get confusing. Please feel free to read our guides on multiple mattress companies and sleeping styles. However, no matter what kind of mattress you end up wanting, do not forget to consider purchasing a mattress a long-term investment. A consumer can expect to sleep on a mattress for 10+ years, from 6-8 hours each day. That is significantly more use than our cars or phones or other electronic devices receive.

As you can see, REM sleep is a vital part of maintaining and healing your body systems. Unfortunately, there are many lifestyles and medical issues that can disrupt this sleep. This can lead to long-term health issues and other physical difficulties while sleeping. However, following a few lifestyle changes, creating the right sleep environment, and avoiding things that can stimulate your nervous system will help you improve your REM sleep. This will also help you reap the benefits of having healthy and frequent REM cycles.

Is there anything else you’d like to know about REM? Let us know in the comments section below.

Was this article helpful?

Leave a comment

Your email address will not be published. Required fields are marked *