Understanding Sleep Cycles
What really happens when you fall asleep
Sleep isn’t just one long, quiet state.
It’s a series of repeating cycles that your brain and body move through each night.
These cycles are essential for:
- Mental recovery
- Physical repair
- Memory processing
- Emotional balance
Understanding how sleep works helps explain why some nights feel refreshing, and others leave you exhausted.
The structure of a sleep cycle
A typical sleep cycle lasts around:
90 to 110 minutes
During this time, your brain moves through different stages of sleep.
Most people experience 4 to 6 cycles per night.
Each cycle includes two main types of sleep:
- Non-REM sleep (NREM)
- REM sleep (Rapid Eye Movement)
The three stages of non-REM sleep
Stage 1: Light sleep
This is the transition between being awake and asleep.
- Lasts only a few minutes
- Muscles begin to relax
- Breathing slows
- Brain activity starts to change
You can wake up easily during this stage.
Stage 2: Deeper light sleep
This is where you spend most of your night.
- Heart rate slows
- Body temperature drops
- Brain activity becomes more rhythmic
Your body is preparing for deeper, restorative sleep.
Stage 3: Deep sleep
This is the most physically restorative stage.
- Also called slow-wave sleep
- The body repairs tissues
- Muscles grow and recover
- The immune system strengthens
- Energy is restored
It’s hardest to wake someone during this stage.
If you’re woken from deep sleep, you may feel:
- Groggy
- Disoriented
- Slow to think
REM sleep: the dreaming stage
After deep sleep, the brain enters REM sleep.
This stage is very different from the others.
During REM sleep:
- Brain activity becomes more active
- Most dreaming occurs
- Eyes move rapidly under the eyelids
- The body becomes temporarily paralysed to prevent movement
REM sleep is important for:
- Memory processing
- Emotional regulation
- Learning
- Creativity
How sleep cycles change through the night
Your sleep cycles aren’t all the same.
Early in the night:
- You spend more time in deep sleep
Later in the night:
- You spend more time in REM sleep
That’s why:
- Early sleep is important for physical recovery
- Late sleep is important for mental and emotional health
What disrupts sleep cycles
Sleep cycles are delicate.
Even small disturbances can break them, such as:
- Noise
- Stress
- Anxiety
- Notifications
- Light
- Irregular schedules
When a cycle is interrupted:
- You may wake up during deep sleep
- The brain has to restart the cycle
- You feel tired even after a full night in bed
Over time, broken sleep cycles can lead to:
- Daytime fatigue
- Poor concentration
- Irritability
- Lower productivity
Why consistent sound helps sleep cycles
The brain is very sensitive to sudden changes.
Random noises during the night can:
- Pull you out of deep sleep
- Interrupt REM sleep
- Reset your sleep cycle
Consistent, natural sounds help by:
- Masking sudden noises
- Creating a steady rhythm
- Giving the brain a predictable environment
This makes it easier for your brain to move smoothly through each sleep stage.
Why ocean waves are so effective
Ocean waves naturally create:
- A repeating rhythm
- Gentle variation
- No harsh or sudden sounds
- A pattern the brain can follow
This type of sound helps the brain:
- Stay relaxed
- Avoid sudden awakenings
- Maintain stable sleep cycles
A simple approach to better sleep
OnlyZZZs was designed around one goal:
Help your brain move smoothly through its natural sleep cycles.
That’s why the app uses:
- One consistent ocean sound
- A carefully tuned loop
- No ads
- No distractions
- No interruptions
Just a steady, calming rhythm that supports natural sleep patterns.
Let your brain follow the rhythm
Sleep isn’t something you force.
It’s something your brain naturally does when the conditions are right.
Give it:
- Calm
- Consistency
- Rhythm
And it will do the rest.
OnlyZZZs
Press play.
Close your eyes.
And let the ocean carry you through the night.
