Sleep Stages (Light, Deep, REM)

Sleep helps the body with everything from memory storage to weight loss. When you optimize sleep, you can greatly enhance your physical and mental health. Going through the sleep stages properly 

What Are Sleep Stages?

The 4-5 stages of sleep are different types of sleep, in which our bodies perform certain functions or even sit at different temperatures. The longer we sleep, the more stages we go through. By sleeping for more than two or three hours, we enter these sleep stages multiple times.

sleep cycles

Why Are Sleep Stages Important? 

Sleep is an essential part of our day. We don’t just need it to feel awake – we need it to function. During sleep, our mind processes everything from the previous day. Our muscles relax and reset. We release growth hormones and other hormones that set us up for the next day.

The body needs time to get into the groove of sleeping and perform all of these tasks. It takes up to 90 minutes to enter REM sleep, or the deepest level of sleep where we start dreaming. If we happen to wake up in the middle of one of these cycles, we might feel thrown off our groove. You’ve probably experienced a morning where you woke up and felt extra tired, even though you got a good amount of sleep. The explanation might be that your sleep cycle was interrupted. 

Basics of Sleep Stages

While there are 4-5 stages of sleep, the body goes through two main stages. NREM (non-rapid eye movement) and REM (rapid eye movement.) These names are self-explanatory. During the NREM stages (Stages 1-3 or 4,) the eyes are not rapidly moving underneath your lids. During the REM stage, or the last stage in the cycle, your eyes are rapidly moving underneath your lids. It sounds freaky, but it’s the truth! 

Each sleep cycle lasts between 90 and 120 minutes and goes through each of these four stages. At first, the body is only in the REM stage for a short amount of time. As the night progresses, your body is the REM stage for longer and longer periods. This is one of the reasons that four hours may seem like enough for a night, but seven-nine are ideal. 

In total, the body spends about 25% of its time in REM sleep. During the other 75% of the night, it cycles between deep sleep, the body is in:

  • Deep sleep
  • Light sleep
  • Wakefulness

Let’s go through these cycles. 


We’ll start by talking about wakefulness. The body will take cues from your mind and environment and start to prepare for sleep. At some point during the night, you might find yourself waking up after a sleep cycle. This is completely normal. 

It’s also normal to have some strange sensations as the body is transitioning into sleep. About 10% of the population experiences “hypnagogic hallucinations” as they start to fall asleep. These hallucinations can be quite scary if you don’t know what they are. You might hear someone calling your name or might even smell something. While unsettling, these hallucinations are normal. They might be caused by alcohol or anxiety, so reach out to a sleep specialist if they are starting to disturb your ability to sleep. 

The brain is doing a lot as you transition through the sleep cycle. While you’re awake, the brain is emitting “beta waves” to keep you alert. As you transition to light sleep, these brain waves start to slow down. You start to emit “alpha waves.” 

Light Sleep

Once you enter the “light sleep” stage, your brain starts to emit “theta waves.” These brain waves are even slower.

At this point, the body is starting to slow down. The breathing slows. Blood pressure begins to drop. Body temperature starts to drop. 

Another strange event might occur during this stage. Has anyone ever told you that you twitch while you sleep? It usually happens during this stage of sleep. It’s called a “hypnagogic jerk,” and it’s very common! This “jerk” may make you feel like you’re falling. You may wake yourself up from one of them. Your significant other may make fun of you for them! 

Why do these occur? There’s no real clear explanation. Like hypnagogic hallucinations, anxiety or medication may increase the likelihood of these occurring. Some evolutionary psychologists have theorized that hypnagogic jerks are an evolutionary function – they were a way for primates and early humans to adjust to sleeping in a tree or other location outside. 

Jerk or no jerk, the body spends about half of the night in this stage of light sleep. Then, it moves to deep sleep. 

Deep Sleep 

Deep sleep is the most restorative part of the night. At this point, the respiration slows further and the muscles begin to relax. This reduced tension allows the body to get to work. The blood flows easier to the muscles, hormones are released, and tissues begin to repair. 

Up in the brain area, delta waves are starting to move through the brain. These are the slowest waves that the brain generates. During deep sleep, you don’t experience any dreams. 

At this point, the body may also be going through a “detox.” That’s right. Studies are still looking at how the body detoxes during deep sleep, but the results suggest that this could be what’s happening. Who needs a detox tea when you’ve got a good night’s sleep? 

If you worked out the day before, you might find yourself in the deep sleep stage more often. Otherwise, we only spend about 15% of our night in deep sleep. 

different things that affect sleep

REM Sleep 

Wakefulness, light sleep, and deep sleep are all stages in NREM sleep. This final stage, REM sleep, is when the eyes begin to rapidly move underneath the eyelids. 

The muscles are completely relaxed during this stage of sleep, but the brain is moving a lot faster. This is the stage of sleep when you typically experience dreams. The respiration also increases during REM sleep. 

REM sleep is also known as “active sleep” or “paradoxical sleep.” It’s paradoxical because while the body seems to be “paralyzed,” the mind is certainly not. 

If you’ve ever experienced sleep paralysis, you know just how “paralyzed” the body is at this time. Sleep paralysis occurs when the mind becomes conscious, but the body is still in REM sleep mode. Try as hard as you might, you cannot move your limbs or yell out. You may also project your dreams onto what you are seeing, which is why some people claim to see demons or other figures in their room while in sleep paralysis. Needless to say, it’s pretty freaky. 

REM sleep may last for up to an hour at a time, but progresses as the night progresses. We spend about 25% of our time in REM sleep, dreaming away. 

Can You Skip Sleep Stages?

If you want to get a good night’s sleep and wake up on the right side of the bed, moving through these stages is crucial. The body has a natural instinct to sleep and move through these cycles, and cues outside of the body can easily disrupt any of these stages. Prepare yourself accordingly for sleep and you’ll get the most out of your 7-9 hours. 

Understand Circadian Rhythms 

The four stages of sleep are not the only cycle our body goes through. Bodies naturally develop a 24-hour Circadian Rhythm that moves through different stages of wakefulness and fatigue. Have you ever noticed that you feel more tired than normal in the afternoon? Or that the sun gets you up in the morning? You can thank your Circadian Rhythm.

Your body uses external cues to move through these stages. And this has happened for centuries. Before electricity, our Circadian Rhythms relied mostly on the sunrise and sunset to prepare the body for sleep and wakefulness.

Nowadays, we spend our nights looking at bright blue lights, even when we are about to go to sleep. I’m talking about your phone, the television, or your laptop. This light stops your body from producing melatonin, which helps you go to sleep. 

If you want to get better sleep, you’re going to have to get rid of some bad habits. Limit your blue light intake before bed. Turn off your laptop and stop scrolling at least one hour before bed. Wear blue light blocking glasses. Switch out your Kindle for a paperback book. 

You’ll fall asleep faster without the blue light and the distractions. By falling asleep faster, you spend more time in each sleep cycle and more time preparing the body for the next day. 

factors that affect sleep cycles


You can also log into an app (but don’t scroll!) to help you get to sleep and wake up during the right part of your sleep cycle. 

Sleep Cycle App

The Sleep Cycle App, for example, is an app that works a little differently than most alarm clocks. It asks for a 10-to-45-minute window rather than one time to wake up. As you sleep, the app tracks which cycle you’re in and wakes you up when it’s easiest for you to transition to wakefulness. You can also look at your chart the next morning and see how long you spent in deep sleep. 

Insight Timer 

While Insight Timer doesn’t track your sleep cycles, it can help you transition from wakefulness to sleep. This app provides guided meditations, binaural beats, and other resources to help you sleep. Some of the tracks on Insight Timer are intended to encourage the production of theta or delta brainwaves. 

Medical Professional 

Disorders like insomnia or fibromyalgia may also impact your ability to enter REM sleep. If you are having trouble sleeping, it may be time to talk to a doctor. Blue light is far from the only thing affecting a person’s ability to sleep. Anxiety, medications, diet, and routine may also be contributing factors. If you are having trouble sleeping, start to keep track of how much sleep you are getting a night and bring this information to your doctor. They may suggest lifestyle changes, medications, or further testing to help you get more sleep at night.


Practical Psychology

Practical Psychology began as a collection of study material for psychology students in 2016, created by a student in the field. It has since evolved into an online blog and YouTube channel providing mental health advice, tools, and academic support to individuals from all backgrounds. With over 2 million YouTube subscribers, over 500 articles, and an annual reach of almost 12 million students, it has become one of the most popular sources of psychological information.

Leave a Comment