Everything to Know on Sleep Cycles

We go to sleep every night but may never think to wonder what really goes on. Perhaps you’ve wondered for a while but never had your questions answered. Well, that’s about to change.

When we sleep, we fall into a pattern of four sleep cycles, one following the other. Each cycle serves important functions, helping our brain and body to complete important tasks that we can’t do while we’re awake.

REM sleep is one of the most talked-about sleep cycles, as it’s at this stage that we experience vivid dreams. Experts compare REM sleep to being awake due to the activity in our brain and body within this cycle.

But what about the other sleep cycles? And how long do these sleep cycles last? To answer all your questions about sleep cycles, this article will cover:

  • What is core sleep?
  • The four sleep cycles
  • What is REM sleep?
  • How much REM sleep we need.

What Is Core Sleep?

Before we delve into the sleep cycles, we need to discuss one important aspect of sleep: core sleep. Core sleep is the absolute minimum sleep our bodies can handle to be able to continue to function. There are multiple reasons why we need core sleep – to balance our hormones, consolidate our memories, and repair our muscles, among other processes.

Most of us need between 7 and 9 hours of sleep as our core sleep per night. Without this, we may struggle throughout the day. If we consistently don’t get our core sleep, we may struggle to focus, we’ll likely feel groggy and tired, and we might notice mood swings throughout the day.

However, it’s important to bear in mind that our core sleep needs may be fewer than 7 hours, depending on how much time we spend in each of the four sleep cycles. If we spend more time in deep and REM sleep, our bodies may have enough time to rest and recoup, ready for a new day.

The Four Sleep Cycles

When we sleep, we go through four sleep cycles: NREM Stage 1, NREM Stage 2, NREM Stage 3, and REM sleep. NREM refers to non-rapid eye movement, whereas REM means rapid eye movement. Non-rapid eye movement simply means that our eyes are not moving quickly. However, during rapid eye movement, our eyes dart off in different directions. We’ll go into this in a little more detail as we discuss the different sleep stages.

What Is NREM Stage 1?

NREM Stage 1 is the first phase of sleep – the one which involves transitioning from being awake to sleeping. It doesn’t last long, only a few minutes. In NREM Stage 1 sleep, many body processes slow down, including our eye movements, muscle activity, and heartbeat.

What Is NREM Stage 2?

NREM Stage 2 sleep is what takes up most of our night – around 40-60% of it, in fact. During this cycle, our breathing and heart rate continue to drop, and our muscles relax even more. It’s in this sleep cycle that we experience something called “sleep spindles” – this refers to sporadic brain wave activity.

What Is NREM Stage 3?

In our third sleep cycle, NREM Stage 3, our heartbeat and breathing rate are at their very lowest, and our muscles are completely relaxed. We may particularly notice if we haven’t received enough NREM Stage 3 sleep, as this stage is responsible for us feeling refreshed every morning.

Unlike stages 1 and 2, it can be very difficult to wake someone up from NREM Stage 3 sleep.

What Is REM Sleep?

It’s REM sleep where our vivid dreams reside. In this stage, our eyes move quickly beneath our eyelids, our brain activity increases, and our muscles are virtually dormant, in a state of temporary paralysis. REM sleep is the stage that’s most like being awake, as our brain is most awake in this stage.

According to research on REM sleep, this stage has many crucial benefits. It helps our brains consolidate memories, which helps us to learn new information and store it in our long-term memory. It also plays a key role in our emotional health, causing mood disorders or difficulties in coping with everyday life if we don’t get enough of it. Studies also suggest that REM sleep is particularly important for young children and infants, as it aids brain development.

How Long Is a Sleep Cycle?

We tend to go through between 4 and 6 sleep cycles a night. However, the number of cycles, as well as how long we spend in each cycle, differs depending on our age. For example, babies tend to have shorter sleep cycles than adults, with each cycle averaging approximately 50 minutes.

For adults, sleep cycles tend to last between 90 and 110 minutes, but again, this can fluctuate. It may even be different from night to night!

We tend to experience 90 – 120 minutes of REM sleep, and the bulk of this is during the latter half of the night. At this time, our REM period stretches out, getting significantly longer. However, as we age, the amount of deep sleep we get diminishes.

Concluding Remarks on Sleep Cycles

Our sleep is more complex than simply falling asleep and waking up. While we’re unconscious, our brain and body are working away, transitioning through the four sleep cycles. Each sleep cycle is important, as it serves different functions that help us to rest, recover, and build our energy levels for the upcoming day.

Each cycle tends to last between 90 to 110 minutes, but this can change based on our age and even night to night. However, knowing about the different stages of sleep and (if possible) keeping an eye on these can help us to recognise if we’re getting a solid night’s sleep.

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