What is Sleep Cycle and Why Does It Matter?

Sleep Cycle

One of the most common pieces of health advice you get is to get more sleep. As we get older, this becomes easier said than done.

Many of us continue to work in shifts or take work home with us. Others suffer from anxiety, overthinking, and fear of the future. With this, the seemingly easy eight hours of sleep become more elusive.

The impact of sleep problems goes beyond day to day life. Studies have raised concerns about sleep deprivation being a public safety problem. The first step toward getting adequate and more restful sleep is understanding sleep stages.

In this article, we will take a closer look at the various stages you go through during sleep. And the role each stage plays to help your mind and body prepare for the upcoming day.

Sleep Cycle

When reading more about the process of sleep, you will often come across the term “sleep cycle”. This term refers to the progression from stage one to stage R, or REM sleep, that occurs during the night.

Even though there are multiple sleep stages, your brain does not gradually move through each of these stages during the night. Instead, you go through many sleep cycles when you sleep. You may have reached the REM sleep stage within 90 minutes up to 120 minutes

During a full night’s sleep, you will go through about four sleep cycles.

Not every sleep cycle lasts for the same period of time. Your first sleep cycle will last for 70 minutes up to 100 minutes on average. Once you have gone through that first cycle, the next one will be longer in most cases.

You do not spend much time in REM sleep when going through a sleep cycle. During the very first cycle, your brain will only spend a couple of minutes in REM sleep before it starts with a new one. When REM sleep is resumed in the next cycle, you will spend a few more minutes in this phase before the next cycle starts again.

How Many Sleep Stages In A Sleep Cycle?

Sleep might feel like one continuous process that takes place every night. The body actually goes through four different stages in every sleep cycle. Each of these stages consists of different actions that occur in the brain.

Understanding each stage is important, as this helps you realize what happens in your brain and to your body. It can also help to identify particular issues with your sleep patterns.

Below is an overview of the four sleep stages most people go through in every sleep cycle.

Stage 1

The first stage of sleep is a type of Non-REM sleep. This is also the lightest stage of sleep that you will go through and is generally described as a “drowsy” stage. Stage one is the particular sleep phase where you can be brought back to consciousness and become awake easily due to small disruptions.

This is the stage that you enter as you start to fall asleep. You may find that you drift between stage one and wakefulness at times. During this stage, the activity of your brain waves will start to slow down. Your body and muscles also start to relax.

There are some people who experience muscle spasms during sleep stage one. Hypnic jerks are also sometimes experienced. If you do wake up from stage one, you might not even realize that you were already asleep.

Stage 2

Stage two is also a light sleep stage, during which the body takes more steps into the state of ‘sleeping.’ This is considered the main light sleep phase that you will go through. Stage two is important for the brain as memories from the previous day are consolidated during this sleep stage. Synaptic pruning is another activity that occurs during this stage of sleep.

Stage 3

The third stage of sleeping is often called “deep sleep”. When you enter this stage, you will not be as easily woken up as with the previous two stages. During this stage, EEG readings tend to show slow waves. You will cycle through stages one to three of sleep for up to seven hours each night.

REM Stage

REM sleep is the final stage of sleep that occurs after you have gone through a period of deep sleep. This is the last sleep stage that you experience before your brain starts with a new sleep cycle.

Often referred to as Stage R, REM sleep is when brain waves become similar to their activity during wakefulness, but you are still asleep. Your body will not move during the REM stage of sleep.

While dreaming can occur throughout the night, the most vivid dreams are experienced while you are in the REM sleep stage. One study found that a person may have as many as six different dreams in a single night.

You only spend about 90 minutes up to around 120 minutes in REM sleep each night – that is with a full night’s sleep. You are much more likely to remember your dream if you wake up while you are in the REM sleep stage.

While you are in REM sleep, you will start to breathe more rapidly. Your breathing may also be shallow and irregular. Your muscles may become limp and, in some people, even paralyzed temporarily. Your eyes may also “jerk” rapidly.

This stage also comes with an increase in blood pressure and heart rate. The body’s temperature regulation abilities become slightly reduced. In men, an erection may also develop during the REM stage of sleep.

You may have up to five phases of REM sleep during a single night’s sleep. Some people may experience less or more of these stages during their sleep. During the night, the duration of REM sleep will start to increase with every new sleep cycle.

Every time REM sleep occurs, it will last longer. Meanwhile, the periods you spend in stage three of sleep (deep sleep) will start to decrease.

Deep Sleep

Deep sleep is a term used to describe the third stage of sleep. During this stage, brain waves are at their slowest. The brain waves that can be picked up by monitors are called delta waves.

The reason for the naming of these waves is due to the large amplitude, combined with the slow speed, expressed by these waves.

Deep sleep is considered critical as it is a restorative type of sleep. It is this stage that provides the rest you need to wake up feeling refreshed and ready to take on the day. It is also the stage in which you are less likely to be disturbed by external factors.

Deep sleep, or stage three, does not last for an equally significant amount of time as stage two does. Out of the time spent sleeping each night, you will remain in stage three of sleep for 5 – 15 percent of the time. The time spent in deep sleep gradually becomes less as you go through multiple sleep cycles.

In adolescents and children, deep sleep lasts longer compared to adults.

Sleep Patterns When We Get Older?

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One thing that many fail to realize is that your sleep patterns tend to change as you grow older. During the earlier parts of your life, your brain waves will not be as distinctive compared to an adult’s brain waves.

Thus, newborns, up to the age of around four months, will not enter the specific stages of sleep that we have discussed in this post. Instead, they will experience an active, quiet, and indeterminate phases of sleep.

After about four months, sleep patterns, and brain waves during this process tend to become consolidated. This is when a baby starts to develop sleep routines. Several factors will affect a baby’s sleep distribution such as bedwetting, airflow, or softness of mattress pad. We have an in-depth article about this here. A baby may sleep for up to 13 hours each day at this age.

Sleep patterns only become fully developed at the age of one. The body continues to remain in stage three of sleep for a more significant period of time up to the age of 12. At this age, a person experiences a more established set of sleep stages and patterns. However, adolescents still require somewhat more sleep than the average adult, with a recommended nine to nine and a half hours per night.

Once a person becomes an adult, they have a much more established sleeping routine. Sleeping patterns will allow the person to sleep for around six and a half hours to eight hours per night, and feel fully refreshed in the morning. This is because the circadian rhythm shifts into a better balance, allowing for a more “stable” set of sleeping habits to develop. This is when the normal stages of sleeping tend to occur, transitioning from stage one to REM sleep, and then continue repeating in cycles until one would wake up.

Final Thoughts

A good night’s sleep relies on more than just hours spent under the covers. Sleep stages and sleep patterns are very important when it comes to sleep quality. Every night as you sleep, you go through four different stages. The four stages of sleep each have a role to play, ensuring memories can be consolidated, and your mind and body are well-rested, so you feel refreshed when you wake up in the morning. With a better understand of sleep stages and sleep patterns, you will be able to understand the way your body works during the night, and you will be equipped with the knowledge needed to improve your sleep quality.

About author: Chris Nguyen is the Founder & Publisher at SleepStandards.com. He aims to inspire better sleep by providing research-based sleep health advice, actionable sleep tips, and unbiased sleep product reviews.

Find out more at SleepStandards.com  - Research-based Sleep Health Advice & Unbias Sleep Product Review

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