Disruptions to your sleeping cycle can impact on your quality of life  

When it comes to getting restorative sleep, quality is just as important as quantity.   

This means that even though you may sleep seven to nine hours every night, if you are not progressing smoothly through each stage of the sleep cycle, you may still feel tired.   

By learning about the stages of the sleep cycle, coupled with the issues and disorders that can disrupt them, you will have a better chance of getting the complete, quality sleep you need.  

What is the sleep cycle? 

The sleep cycle comprises four separate stages, with each stage playing a vital role in allowing your mind and body to properly recover so you wake up refreshed. On average you will go through four to six rounds of the sleep cycle with each one lasting around 90 minutes.¹  

However, it is normal for the duration of each sleep cycle to change in adults throughout the night. The first one is typically the shortest and the later cycles tend to be slightly longer.¹  

The four stages of the sleep cycle 

Brain activity during the sleep cycle determines which stage you are in. There is one cycle for rapid eye movement (REM) and three for non-REM (NREM) sleep.² 

REM sleep

This stage gets its name, rapid eye movement, because even though your eyes are closed, they can be seen moving very quickly. However, during REM there is a temporary paralysis of all your other muscles apart from the ones that control your breathing – this is called atonia.^1,3 

Around a quarter of adult sleeping time is spent in the REM stage, and this cycle is essential to cognitive functions such as learning, creativity and memory. The first REM stage may only last for 10 minutes while later in the night this stage may last up to an hour.⁴ 

During this sleep stage you will experience your most vivid of dreams. The significant amount of brain activity present during REM is close to levels experienced when you are awake. Dreams can occur during NREM sleep as well but they tend to be less intense.^1,4 

NREM sleep 
NREM sleep is broken up into three stages. The higher your stage of NREM, the harder it is to wake you up.  

Stage 1 
This normally lasts just one to five minutes and is regarded as the dozing-off stage. At this point, you can still be easily woken up. During this stage your body and brain slow down as you relax, a period punctuated by quick movements or twitches. As you progress through the sleep cycles you may spend less and less time in this stage.^1,5  

Stage 2 
Overall, you will spend almost half of your sleep time in this stage. The first time you experience NREM stage 2 during your sleep, it will last 10 to 25 minutes and then it usually spreads to lasting longer later in the cycle. In this stage, your body is relaxed with slower breathing, your heart rate slows and your temperature drops. During this stage, brain activity decelerates.^1,5  

Stage 3
Here you are in a deep sleep, and it is much harder to wake up. It is also called delta sleep or slow-wave sleep because of the slow pattern of delta brainwaves present. This stage lasts 20 to 40 minutes at the beginning of the sleep cycle and gets shorter as the night goes on, giving way to more REM sleep.  

During this stage, your body continues to relax and your heart rate and breathing slow down even more. NREM stage 3 is regarded as the most critical stage for restorative sleep, allowing the body to recover and grow. It may also help the immune system.^1,6,7 

The importance of the sleep stages 

Each of the four stages is essential for restorative rest, which lets your brain and body recuperate and continue to develop. When you fail to get a good sleep, this process is severely compromised.  

If you are not getting enough REM sleep as well as deep sleep, it cannot be overstated how seriously this can impact your health – it can negatively affect everything from your thinking and physical well-being to your emotions.¹  

The impact of sleep apnea 

Sleep apnea can be especially disruptive to your sleep cycle as this repeatedly stops your breathing throughout the night causing you to wake before you can progress into the deeper sleep stages.  This can contribute to insomnia.¹   

There are two main types of sleep apnea  – obstructive sleep apnea (OSA) and central sleep apnea (CSA). Both disrupt your sleep cycle and can have an adverse effect on your health.² 

If you feel tired all the time, wake up gasping for air or have a dry mouth in the morning, talk with your doctor about the possibility you could have sleep apnea. Your healthcare provider will be able to advise you on the best treatment options available so you can get the restorative sleep you need.  

The content is for educational purposes only. It should not be used as a substitute for the medical advice of one’s healthcare provider.