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What Are Sleep Cycles, And Why Are They Important?

One of the most important factors in the way sleep helps our bodies regenerate themselves are sleep cycles. We actually have several different cycles of sleep and they have a big impact on almost every aspect of our lives. Here's why.

The first cycle is actually our sleep/wakefulness cycle, known as the circadian rhythm. The circadian rhythm determines when our body should feel tired and when we should feel awake, and not getting enough sleep or going to bed and waking up at different times each day can have very negative consequences on our circadian rhythm which can eventually lead to a sleeping disorder such as insomnia

Nonetheless, to truly understand just what happens when we sleep and why an adequate amount of uninterrupted sleep is so important, we need to look at the actual cycles of sleep (the process that our brain goes through while we're sleeping).

Sleep Cycles Explained

Some people incorrectly believe that sleep is sleep, and that we fall into a good, deep sleep immediately, but this is actually far from the truth. In actuality, we go through many cycles of sleep each night. 

sleep cyclesEach sleep cycle consists of four (or five depending on which expert you ask) different stages of sleep, and we are at different levels of sleep during each stage. 

The first three stages of sleep are known as non-REM sleep and the fourth stage is the REM stage (rapid eye movement). When you put each of these stages of sleep together, they form one full sleep cycle. Typically, each cycle of sleep lasts for around one and a half hours.

Most people will repeat the cycle between four and six times each night. 


While each cycle normally lasts for around the same length of time (90 minutes), the actual amount of time that we spend in each stage changes the longer we sleep. In order to understand why sleeping the correct amount of time each night is so important we need to look at exactly what happens in each stage, and you will soon see that your sleep may not be as restful as you think it is.


In the first stage of sleep, you are just barely on the edge between being asleep and awake. It should be very easy to wake you up during this stage, and you will probably not even think you had been asleep if awoken. While the amount of time you spend in the other stages fluctuates, this stage stays quite constant, and you will spend around five to ten minutes in this stage during each cycle. 

The second stage of sleep is the first one where you are truly asleep. In this stage, your heart rate will slow down and your temperature will decrease. This is also the stage that you spend most of your sleeping time in (approximately 50%), which you will soon see is slightly disconcerting as your body does not do much resting or rejuvenating during this stage of the cycle. 

sleep cyclesThe third stage is considered deep sleep, which is when your body does most of its regenerating. During this stage, your brain activity decreases dramatically as your body directs blood away from the brain and to the muscles. This is extra blood flow to the muscles is actually what is responsible for regenerating energy. 

This stage of sleep is definitely the most important; however we do not actually spend much time in it. We may spend only twenty to thirty percent of our total time sleeping in this rejuvenating phase, and the actual amount of time spend in stage three decreases with each passing sleep cycle during the night.

The final stage of sleep is REM sleep, which is when dreams occur. During this phase, the brain wakes back up and the eyes start to move rapidly, hence the name rapid eye movement. The reason why children have so much more vivid dreams than adults is because they spend up to fifty percent of their sleeping time in this stage, while adults usually only reach around twenty percent.

The Importance of Sleep Cycles

While it may seem strange that we move through these different stages during each cycle of sleep, it is incredibly important that we receive adequate and good quality sleep in order to complete each cycle properly. 

When you suffer from a sleeping disorder or have other sleeping issues, the body is often not able to move into deep sleep (3rd stage) and REM sleep, which are by far the two most important stages. This is why it is so important to ensure that you receive uninterrupted sleep, as any disturbance will reset the sleep cycle and cause you to miss time in the important final two stages. 

This is also why waking up to an alarm clock can also be so detrimental, as it causes you to wake up from the incorrect stage. If you wake up in stage 3, you will be quite disoriented and feel like you barely slept at all. In an ideal situation, the body should be allowed to move back through the stages until reaching stage 1 and then waking up from it. 

sleep cyclesThe reason that the final two stages of the cycle are so important is that they are the ones where the body and mind are refreshed and reenergized. We already stated how the body moves blood to the muscles during stage 3 to give energy and repair damage, but REM sleep is just as important for other reasons. 

It is during the REM stage that the brain processes the images and information that you have seen and learned during the day. This helps in storing information in our memory and to help us remember new things we have learned

It is also during this stage that the brain regenerates its supply chemicals and neurotransmitters which are also of the utmost importance.

So now you can hopefully see why it is so important to sleep for the right amount of time and get uninterrupted sleep, as your body absolutely needs to go through the proper amount of sleep cycles in order to be fully rested.

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