What is a Sleep Cycle?

What is a Sleep Cycle? How Much Sleep Do We Need?
This will vary from person to person. Most healthy adults need between 7½ – 9 hours of sleep a night so that we can function at our best.
Children and teenagers need more. Between 12 – 18 hours. The quantity of sleep that teenagers and pre-teens actually get has decreased because of the impact of technology.
What is a Sleep Cycle?
A sleep cycle lasts approximately 90 – 110 minutes.
Each stage may last between 5 to 15 minutes.
During your night’s sleep, your body will move through 4 different stages of sleep:
• NREM (Non-Rapid Eye Movement) sleep.
• REM (Rapid Eye Movement) sleep.
The first 3 stages make up our NREM sleep.
The 4th stage is when REM occurs.
Once you have finished REM, you will then return for another cycle of sleep and repeat the 4 stages.
Most of us need 4 – 5 Sleep Cycles in a 24 hour period.
What is a Sleep Cycle? : The 4 Stages
The Sleep Cycle is divided into the following stages, with each becoming progressively deeper.
• Stage 1 – NREM 1 (Light phase of sleep)
• Stage 2 – NREM 2 (Light phase of sleep)
• Stage 3 – NREM 3 (Deeper phase of sleep)
• Stage 4 – REM (Intense dream and brain activity)

What is a Sleep Cycle? The 4 Stages Explained
Stage 1 – NREM 1 (light phase of sleep)
• This is the stage when you are first falling asleep. You are on the border between being awake and being asleep.
• You will feel like you’re floating in and out of consciousness. We are partially awake while your mind begins to drift.
• This may cause your muscles to jerk suddenly. A falling sensation may follow.
• Your eyes are closed during this stage and they will move slowly.
• It’s easy for you to wake you up during this stage.
• This stage is also known as the transitional phase.
• This phase may last for 5 to 10 minutes.
• It is called ‘hypnic myoclonic’.
• After winding down in stage 1 you will slip into stage 2.
Stage 2 – NREM 2 (light phase of sleep)
• This is when you will start to fall asleep and disconnect with the outside world.
• Almost 50% of the time spent asleep is in Stage 2.
• Breathing and heart rhythm will take on regular patterns.
• Heart rate will slow down.
• Your body temperature will drop. Your body is getting ready to enter deep sleep.
• During Stage 2 your eye movement stops.
• Your brain waves will slow down. Except occasionally it will produce sudden increase in brain wave frequency known as sleep spindles.
Stage 3 – NREM 3 (deeper phase of sleep)
• This is the deep stage of sleep.
• You will find it hardest to wake during Stage 3.
• If you try and wake someone during this stage, they will most likely be disoriented and groggy for a few minutes.
• Slow wave sleep is a NREM phase of sleep.
• It is the deepest sleep that your body enters throughout the night.
• Your blood pressure will drop even further.
• Your breathing will become deeper and slower, and more rhythmic.
• During slow wave sleep there is no eye movement, and the body becomes immobile. However, even though there is no muscle movement, the muscles still have the ability to function.
• Sleep walking, and nightmares are experienced during these stages.
• Bedwetting for children may occur during these stages.
• During Stage 3, body will repair, regrow tissue, build bones and muscle tissue. Also, your immune system will strengthen.
• Your hormones will also help to control your appetite and help limit feelings of excessive hunger the following day.
• As you get older, you sleep more lightly and get less deep sleep.
• Ageing is also linked to shorter time spans of sleep, although studies show you still need as much sleep as when you were younger.
Stage 4 – REM (intense dream and brain activity)
• Stage 4 (Rem) of sleep kicks in around 90 minutes after falling asleep.
• The first time you go into REM sleep, it will last around 10mines. For each additional cycle, you will see an increase in REM sleep.
• Most dreaming takes place in Stage 4 as a result of heightened, desynchronized brain waves.
• This stage of sleep revitalizes the brain, supporting sharp and alert daytime function.
• Stage 4 is the only stage of rapid eye movement (REM).
• Most adults spend about 20% of sleep in REM, while infants spend almost 50%.
• During non-REM sleep, the mind rests while the body heals, but in REM sleep the mind energizes itself while the body is immobile.
• During this stage of REM sleep the eyes dart in various directions while the limbs and muscles are temporarily paralyzed.
• Your breathing will become faster.
• You heart rate and blood pressure will rise from the levels they were in previous stages.
• During REM sleep, your body loses the ability to regulate its temperature. Therefore, if your body is hot or cold you may wake during this REM stage.
• REM sleep is very important for learning. It stimulates areas of the brain used in learning.
• Individuals begin waking up at the end of stage 4.