The stages of sleep are by far the most important part to comprehend when it comes to understanding how sleep works. While most of us focus on how many hours of sleep we get, it’s not the only part of the equation.
What’s truly important is the quality of sleep. There are 4 stages of Sleep that make up the Sleep Cycle, moving through this cycle is a vital part of getting high-quality rest.
Each sleep stage plays a part in making your mind and body wake up refreshed, ready to face the challenges of the day or an upcoming match. Understanding this cycle has helped clarify how sleep can do more than solve tiredness, it can reduce injury, consolidate memory & new skills & build immunity against attack.
So! what exactly is this Sleep Cycle? Throughout the night, your entire sleep is made up of multiple rotations of the sleep cycle, which as we’ve said, has four individual stages. A typical night will consist of a person going through four to six cycles. They won’t all be the same length, but roughly last about 90 mins. The shortest of the cycles will be the first one, & later ones increase steadily up to 120 minutes. Of course, there are so many circumstantial elements that can change or disrupt this cycle.
Now for the science bit! The 4 stages of Sleep are simple;
A stage for rapid eye movement (REM) sleep, and three that comprise non-REM (NREM) sleep. Analysis of brain activity during sleep shows distinct patterns that characterize each stage.
Stage 1 is an NREM called N1 & lasts 1-5 minutes.
Stage 2 is an NREM called N2, this stage can last 10-60 minutes.
Up next we have Stage 3, another NREM stage called N3, Slow-Wave Sleep (SWS), Delta Sleep, or Deep Sleep. This is 20-40 minutes in duration & finally, Stage 4, is the one & only REM stage known as REM Sleep lasting 10-60 minutes.
NREM Sleep Patterns
The three NREM sleep stages are like steps. The higher the step or stage, the harder it is to wake a person up.
Stage 1 / N1
Effectively the “dozing off” stage, the body starts to relax, and brain activities start to slow, there will still be periods of brief movements. The changes in brain activity are associated with falling asleep in this stage, although they are very small changes. Stage 2 can be moved into rather quickly from here.
Stage 2 / N2
During stage 2, the body enters a more subdued state including a drop in temperature, muscle relaxation, and slowed breathing and heart rate. Brain activity slows & starts to show a new pattern while eye movement stops. There are short bursts of activity that help resist being woken up.
You can typically spend about half your sleep time in N2 sleep.
Stage 3 / N3
Stage 3 is understood as deep sleep. The body relaxes even further, & brain activity during this period has an identifiable pattern of delta waves. Hence, it is known as delta sleep or slow-wave sleep (SWS).
Experts believe that this stage is crucial to restorative sleep, allowing the body to recover and grow, vital for athletes. It also strengthens the immune system. Despite brain activity being reduced, there is evidence that deep sleep contributes to memory recall, insightfulness and creativity.
REM Sleep Patterns
Stage 4 / N4
Brain activity picks up within REM sleep, similar to the levels seen when you’re awake. Simultaneously, the body enters a temporary paralysis of the muscles, except for the eyes and the muscles that control breathing. This stage is named due to the eyes moving quickly, underneath the eyelids.
REM sleep is considered to be paramount to the cognitive functions of memory and learning. While dreams can occur at any stage, this stage is the one where you have the most intense, vivid dreams, due to the increased brain activity.
The REM sleep stage will happen after you’ve been asleep for about 90 minutes. This stage will also get longer in each cycle until it makes up around 25% of sleep in adults.
Why Do the Sleep Stages Matter?
Sleep stages are important as they allow the brain and body to recover and develop. A lack of sleep may explain some of the effects on thinking, emotions, and fitness.
Sleep Apnea disrupts the process & can prevent properly cycling into the deeper sleep stages. Insomniacs may not get enough total sleep to benefit from the needed time in each stage.
Athletes who don’t sleep fully will see a decline in performance & fitness.
What Affects Sleep Stages?
As mentioned there can be several circumstantial elements that affect the Stages of Sleep:
- Sleep disorders: Sleep apnea, Insomnia and Restless Leg Syndrome (RLS), are some conditions that cause numerous awakenings and interrupt a beneficial sleep cycle.
- Age: Newborns spend around 50% of their sleep in REM sleep and may enter a REM stage as soon as they fall asleep. It is not until the age of 5 that their sleep becomes similar to that of adults. On the flip side, elderly people tend to spend less time in REM sleep.
- Alcohol: The theory of alcohol making you sleepy may be true but it doesn’t mean beneficial sleep. Alcohol is known to decrease REM sleep. As you sober up, you fall into a deeper than normal REM sleep, while that sounds like a good thing, it’s rather disruptive to the sleep cycle as a whole.
- Recent sleep patterns: If a person gets irregular or insufficient sleep over a few days or more, there is a substantial & damaging effect on sleep.
How Can You Have a Healthier Sleep Cycle?
You may not have full control of your sleep cycle, but you can make efforts to improve each sleep stage.
Sleep Hygiene is the first port of call to look at. Sleep hygiene is your sleep environment AKA the bedroom (the best mattress, best pillows, etc.) and sleep-related habits. A consistent sleep schedule, natural daylight exposure during the day, avoiding alcohol before bed, and stopping noise and light disruptions can all help achieve uninterrupted sleep, it will also stabilise your circadian rhythm.
Excessive daytime sleepiness or lethargy could indicate a sleep disorder, it’s important to talk with a doctor if you suffer from this.