What Are the Stages of Sleep?


Sleep is one of the most vital processes your body undergoes. During sleep, your body rests and repairs all of the processes that were active during the day. Most people need 6-8 hours of sleep a night, however, quality sleep doesn't just consist of the number of hours but also the stages of sleep your body goes through.

What Are the 4 Stages of Sleep?

When asleep, people usually experience 3 stages of sleep followed by REM which is Rapid Eye Movement. These stages repeat over and over, and some can last anywhere from 90 to 110 minutes. During sleep, the stages cycle and REM sleep gets longer and longer as the other stages shorten. Below are the 3 sleep cycle stages including REM:

Stage 1 

This is the initial stage between wakefulness and sleep where you begin to drift off. Your eyes may move slowly, and your muscles begin to relax. Many people even experience the sensation of falling- where their muscles contract. This stage only usually lasts for a few minutes. 

Stage 2

The second phase of sleep is the longest stage of sleep. About half the time is spent in Stage 2 as eye movement decreases. Your heart rate and temperature slightly drop as your brain waves succumb to a rhythm with sudden bursts of movement. 

Stage 3

Delta waves are introduced in the brain as activity becomes very slow. Smaller, faster waves also appear sporadically. Before 2008, there used to be 4 stages of sleep, but it has since become eliminated, and stage 4 is combined with stage 3. During the end of stage 3, only delta waves are present. This is usually when people experience night terrors, sleepwalking, or bedwetting. Adults spend about 10% of their sleep time in this state. 


Rapid Eye Movement Sleep is where the remaining 50% of the sleep period is spent. During REM your eyes move rapidly, and the heart rate increases. Blood pressure rises, and brain waves increase to levels equivalent to being awake. Dreams occur most often during this time. This is also the stage where most males may develop erections. You may feel as though your hands and legs are paralyzed. REM sleep usually occurs 3-5 times per night. 

What Is the Most Important Stage of Sleep?

Deep sleep is the most important of all the sleep stages. This usually occurs during Stage three when the Non-Rem or Delta waves begin to slow down. Your body can fall into a deep sleep, which is when you body does most of the repair work. This restorative sleep stage helps your body regrow tissue, build muscle, strengthen bones, and the immune system. Your mind is able to rest while your body heals itself. Your heart rate slows as well as your breathing so your body's focus is on repair. Our brain repairs memories and enhances the knowledge databases within our minds known as Semantic memory. 

What Is Light Sleep Stage?

Light sleep occurs when you first start to drift off. You are easy to wake up during this stage. During the initial stage of sleep your eyes may roll to the back of your head or even side to side. Your muscles begin to relax, and you may even experience a jolt. Many people feel like they are falling during light sleep. Your body also begins to process emotions and memories you've experienced throughout the day. In addition, your metabolism regulates during this time while your breathing and heart rate start to decrease. 

What Is Rem Sleep?

REM sleep definition is known as Rapid Eye Movement Sleep. This sleep stage occurs after Non-Rem or stage 3 sleep and where your eyes may begin to move rapidly from side to side. Your heart rate and breathing may also accelerate. Dreams often occur during this stage as your brain waves increase along with your blood pressure.

Babies spend half their sleep time during REM sleep. If you have ever watched a newborn sleep you may have seen their eyes moving rapidly as they make all kinds of faces, smiling, and even laughing. Adults spend only about 20% of their sleep time in REM and it decreases as they age. 

What Stage Is Rem Sleep?

REM sleep cycle is the 4th stage of sleep. It usually occurs within the first 90 minutes of sleep. You may experience dreams while your eyes move about rapidly. After about 10 minutes of REM sleep your sleep recycles back to the beginning. The last cycle of REM before your body wakes up is usually the longest, lasting about an hour or so. 

Is REM or Deep Sleep Better?

Contrary to popular belief the majority of deep sleep occurs in stage 3. REM sleep soon follows as your heart rate and eye movement speed up. Below is a comparison of the events that take place in these two phases that are often confused with one another. 

REM includes:

  • Rapid eye movement 
  • Increased blood pressure
  • Higher heart rate
  • Delta waves increase
  • Dreams
  • Feelings of limb paralyze 
  • 50% of sleep is spent
  • Cycle lasts about 10 minutes 

Deep Sleep/Stage 3:

  • Lower heart rate
  • Decreased blood pressure
  • Recovery takes place
  • Delta waves slow
  • 10% of sleep is spent
  • Night terrors and bedwetting may occur

What Is Deep Sleep?

Deep sleep is when your body surpasses the first 3 stages and begins to deeply fall into a state of rest and recover. This stage is also known as slow wave sleep. Your body relaxes even more as your temperature decreases and eye movements slow. Your brain waves also decrease but are not without short bursts of elevated activity. In deep sleep you do not wake easily even through loud noises. Your respiratory rate slows, and heartbeat lowers. 

Because your body is operating so slowly the body is able to do much needed repairs. Deep sleep is the most important stage out of all the sleep stages because of this main reason. Without deep sleep and repair the body would operate in a more stressed out state. If you have ever had to go without sleep for many days, you know the toll it takes on your overall mood.  

How Long Should You Be in Each Stage of Sleep?

Sleep cycle length fluctuates during various cycles. Normally your sleep cycles lengthen the longer you are asleep. Sleep cycles usually are between 90-120 minutes long. Depending on your age, sleep patterns, lifestyle habits, and medications your sleep cycles can vary. 

Stage 1 usually lasts 1-5 minutes while stage 2 can range from 10-60 minutes long. Stage 3, which is deep sleep, lasts for about 20-40 minutes. Stage 4, also known as REM Sleep is usually 10-60 minutes. The last REM sleep for the night may be longer than previous REM cycles. 

Supplements Can Help

Using supplements to aid in a restful night's sleep is a helpful addition to your regiment. While your body is resting and repairing, adding something like Spermidine can undoubtedly increase the body's healing abilities. SpermidineLife developed Spermidine which mimics autophagy in the body. Autophagy is the body's cell recycle and repair process. You can get a more effective night's sleep by activating this process while supporting your body to make the repairs it needs to achieve optimal wellness. 


  • Don Moxley - Director of Applied Science

    Don Moxley is the Director of Applied Science at Longevity Labs. Moxley draws upon his career as an athlete, a sports scientist, and an instructor to lead and educate on the science of autophagy and longevity.