If you’ve ever wondered about the science of sleep or dreams, then you probably know about the existence of sleep stages. Sleep stages are fascinating to explore and can give us a lot of answers in terms of what our bodies undergo when we sleep. In this article, we will answer two of the most common questions regarding sleep stages: what are the five stages of sleep and what is their order?
On top of providing you with answers to these questions, we’ll also explore which stage includes dreams and what affects our sleep stages, as well as give you more answers in our informative FAQ section.
With that said, let’s start with defining what sleep cycles are.
What Are Sleep Cycles?
First things first, before exploring the five stages of sleep, let’s briefly define them.
Sleep cycles refer to the stages during which your sleep undergoes in a single night. There are five stages of sleep in total, and each one of us repeats the five stages several times in the span of one night. With that said, sleep cycles greatly differ from each other, and in the next section, we’ll look into exactly which processes occur during every stage of our sleep cycle.
Stage 1 of non-REM Sleep
The first stage of non-REM (rapid eye movement) sleep is often referred to as the transitional phase. It occurs when we first start to fall asleep and we’re in a stage between wakefulness and sleep. Our mind also starts to drift off.
During this stage, our sleep is vulnerable to being interrupted and we’re more prone to being woken up. Light sleepers are especially prone to be woken up by someone or a loud noise. Luckily, this sleep stage only lasts for around five minutes, so there aren’t many chances for our dozing off to be interrupted.
In terms of the processes our body goes through during this stage, our muscles are prone to sudden jerky movements and our EEG brain frequency starts to slow down, along with our heartbeat. Additionally, you might also experience a common phenomenon where you feel as if you’re falling. This feeling causes many people to wake up from the first stage, having to repeat the cycle all over again. After a couple of minutes, your body is ready to move onto stage 2.
Stage 2 of non-REM Sleep
Stage 2 follows stage 1 and it’s characterised by some of the same bodily changes that occur in stage 1, such as slowed breathing and heart rate and a drop in our core temperature. During this stage, you’re sleeping more deeply than in stage 1 and you aren’t aware of your surroundings. When it comes to brain activity, our minds aren’t shut down entirely – on the contrary, the brain waves start to speed up. This explains why we might be woken up suddenly. Despite that, we’re in a much deeper sleep than we are in stage 1 and less likely overall to be woken up by external stimuli.
Unlike the first stage, this stage can last anywhere from 10 minutes to half an hour, making it the longest stage of sleeping.
Apart from being the longest sleeping stage, this stage is crucial because it’s when the brain starts to process every information it’s gathered throughout the day. By filtering through this information, it’s able to dump the information it thinks it’s redundant, which is a crucial part of the memory creation process.
In terms of eye movement, our eye movements either completely drop or they’re slowed down as compared to the REM stage. The muscles oscillate between being relaxed and being tense.
Stage 3 of non-REM Sleep
During the third stage of sleep, which is also referred to as delta or slow-wave sleep due to the activity of our delta waves, we experience deeper sleep than in the previous two stages and we’re not likely to be woken up. Our heartbeat and breathing are even slower than during the previous two stages, and our brain waves also slow down.
This stage is one of the most important stages of sleep because this is when cell and muscle repair occurs. If you’ve been putting in hours of work at the gym, this is the stage where your muscles will start to grow, which is one of the many reasons why rest is just as important as exercise if you want to see progress. Additionally, these processes also help repair and boost the immune system, which is crucial for every process in our body. Just like stage two, this stage contributes to the formation of memories and helps detoxify the brain.
What this stage also shares with stage two is the duration, since it can last for up to half an hour.
Stage 4 of non-REM Sleep
Before we move onto what’s called REM sleep, our body goes through the final stage of the so-called non-REM stages of sleep. The fourth stage of this group is the deepest stage and all the processes that occurred previously, such as the decreasing of our core temperature, the slowed breathing, and the brain waves, are even more slowed down. Our body becomes completely paralysed and there are no eye movements.
The body continues to repair itself during the fourth stage – the muscle tissues are restored and our hormones become more regulated.
One main drawback associated with the stage is that, if we happen to wake up while this stage is in progress, we’re extremely tired and even moody, regardless of the total hours of sleep we’ve gotten. This explains the popularity of sleep cycle apps and why so many people prefer to use them instead of setting their alarm at an arbitrary number such as 6 am.
Stage 5 – REM Sleep
The last stage of sleep is the REM stage. Just as its name suggests, it’s characterised by fast movements of our eyes, whereas our body remains completely still.
Apart from our eyes, our brain is extremely active during this stage – the process of compiling memories continues and our brain selects the information it deems worthy of preserving.
In terms of bodily changes, our core temperature and heart rate starts to steadily increase. On average, REM sleep lasts for around 10 minutes, and our bodies undergo this stage every 90 minutes or so.
You know by now how important this stage is for our sleep, but not everyone gets to experience the same quality REM sleep night after night. Those who suffer from sleep disorders are more prone to being woken up during this stage as a result of their disorder, which results in lower sleep quality.
At the end of stage 5 REM sleep, we start waking up gradually. When we first wake up, our core temperature is quite low and our heartbeat is slow, and as we start to get progressively more awake, our core temperature starts to rise and our bodies start to get ready for the day.
Each sleep cycle consists of the five stages of sleep which differ in terms of length. The main difference between sleeping in the earlier part of the day and sleeping at the later part of the day is that when we sleep in the later part of the day, we tend to experience more REM sleep than if we sleep earlier.
At What Stage of Sleep Do We Dream?
One of the most common questions that’s asked regarding sleep cycles, apart from what their order is and why they matter, is at what stage of sleep do we dream? Numerous studies have been done to determine this that followed a close moderation of the brain’s activity as we sleep.
Most of our dreams occur during the REM stage of sleep, even though dreams might occur in the other stages as well. As we said earlier, this stage entails the production of memories and filtering through all the information we encountered during the day, so it’s not surprising that it’s this stage that inspires dreams. This explains why your dreams might be related to some of the things you did during the day or the people that you encountered or talked about.
If you notice someone sleeping and their eyes move quite rapidly, chances are they’re dreaming.
How Much REM Sleep Do We Need?
Since we established that REM sleep is the deepest stage of sleep where most of our dreams occur, you might ask yourself how much REM sleep individuals need per night.
REM cycles can last up to ten minutes, so there isn’t a special guidance as to how much REM sleep you should be getting every night. However, since the REM cycle repeats itself every 90 minutes or so, it’s clear that the more hours of sleep we get in total, the higher the chance that we spend more time during the REM stage of sleep.
So, how many hours in total should we sleep at night? The general advice is that adults should get at least seven hours of sleep per night. Oversleeping is also a major issue and can cause many side effects, one of which is, ironically, tiredness, so avoid sleeping for more than nine hours a day.
What Affects Our Sleep Stages?
While our sleep stages have a certain order, there are a few factors that affect them and cause them to vary from individual to individual.
One of the biggest factors that influence our sleep stages is age. Newborns spend a lot more time during the REM stage of sleep since it’s crucial for their growth. And as we get older, our REM sleep stage slowly starts to shorten. That’s the reason why elders spend a lot less time than 10 minutes in the REM stage, and for those who suffer from sleep disorders, this timeframe is even shorter.
Apart from sleep disorders, what also negatively affects our sleep cycles is the consumption of alcohol. Contrary to what it’s believed, large alcohol consumption has a detrimental effect on our sleep hygiene and sleep cycles. The consumption of alcohol, particularly before bed, has been proven to decrease our REM sleep, which results in poor sleep quality overall.
Tips for Improving Your Sleep
To make sure your sleep stages are optimised, your sleep hygiene needs to be pristine. Here are some tips that can significantly improve your overall sleep quality and can have an amazing impact on the duration and flow of your sleep cycle.
Exercise during the day, but not very late at night. One of the easiest ways you can improve your sleep is by introducing exercise to your daily routine. You don’t have to do any strenuous workouts, walking or light stretching will do just fine, as long as you move your body and stay active. If you do decide to incorporate a more rigorous workout routine, make sure you complete it during the earlier part of the day, since exercise has an energising effect on our bodies.
Avoid alcohol and caffeine before bed. Alcohol has a negative impact on our sleep cycle, but so does caffeine. If you drink caffeinated beverages prior to going to sleep, your sleep might get interrupted and you might end up tossing and turning at night without being able to fall asleep.
Create a relaxing evening routine. Another easy change you can implement is creating a relaxing evening routine. Your routine could include activities like journaling, doing yoga, reading, or cleaning your room. It’s a great way to slowly start signaling to your body that it’s time for bed, but make sure you stick to it for long enough in order for it to become a habit.
How Long Is Each Sleep Stage?
One of the most commonly asked questions about sleep stages is regarding their duration. The non-REM stages of sleep (stages 1, 2, 3, and 4) vary in terms of length. The first stage is around 10 minutes, the second can last anywhere from 10 minutes to half an hour, and the third is usually 20 minutes long. The REM stage of sleep typically lasts for ten minutes in healthy adults, whereas babies spend more time at the REM stage.
How many Stages of Sleep Are There?
There are a total of five stages of sleep: non-REM stages (stages 1, 2, 3, and 4) and a REM stage.
How Long Is REM sleep?
REM sleep usually lasts for 10 minutes, although its length can vary from infants and adults to elderly people.
There are a total of five stages of sleep that comprise the sleep cycle: four non-REM stages and a REM stage. The duration of these stages, as well as the way our bodies respond to them, differs from stage to stage.
We experience our deepest sleep during the third, fourth, and REM stage of sleep. During the REM stage of sleep, the filtering of information occurs, and it’s also the stage during which we dream.
The flow and quality of our sleeping stages depend on the quality of our sleep hygiene, which is why it’s important to take steps in preserving our sleep quality like exercising, limiting our alcohol intake, and relaxing before bed.