Understanding the stages of sleep
What really happens to your brain and body when you sleep?
Sleep. It seems pretty simple: we go to sleep, maybe stir once or twice, have some dreams, and wake up in the morning.
However, there’s actually a lot more to sleep than first meets the (shut)eye.
There are several cycles or stages of sleep – and that’s where it gets interesting.
Ever wondered why we dream when we do? Or maybe you’ve questioned why you don’t feel as rested when you wake up at certain times compared to others?
The stages of sleep play a crucial role in how rested we feel.
Below is an overview of each sleep cycle to help you get a better understanding of what happens to your brain and body when you sleep.
But first, let’s start with some quick definitions.
Sleep cycle: A sleep cycle is what happens when you move through the stages of sleep from point A to point B before starting over again. Most people start a new sleep cycle every 90-120 minutes and experience four to five cycles per night.
REM: Rapid Eye Movement (REM) is when a person’s eyes move quickly beneath their eyelids during sleep, signifying that dreaming is occurring.
NREM: Non-rapid Eye Movement refers to the non-dreaming stages of sleep.
Brain waves: Brain waves are patterns of electrical activity in the brain from neurons (tiny nerve cells) communicating with each other.
Alpha waves: Alpha waves are brain waves at a frequency of 8 to 13 cycles per second associated with a state of wakeful relaxation.
Theta waves: Theta waves are brain waves at a frequency of 3 to 8 cycles per second associated with relaxation, daydreaming and drowsiness, and also learning and memory formation.
Delta waves: Delta waves are slow deep brain waves at a frequency of .5 to 3 cycles per second, associated with deep sleep.
The four stages of sleep
Stage 1
Soon after you fall asleep, your eye movements slow down and your brain starts to produce alpha and theta waves.
This stage is like a light introduction to sleep, lasting only several minutes. This is a light sleep stage, so you can still be somewhat conscious. You might wake up more easily during this stage than in later stages. You can also think of this as the ‘napping’ stage.
Stage 2
This stage is still pretty light and breezy, but it’s also a time for the brain to kick things up a notch.
Your sleeping mind will experience a rapid burst of higher frequency brain waves, known as ‘sleep spindles’, before slowing down and preparing for the next stage. This is a good place to wake up during a nap before you get sucked into true REM sleep.
Stages 3 and 4
At this stage, you’re beginning with deep sleep – shifting from NREM to REM sleep.
In these deep sleep stages, you are much less alert and it becomes more difficult to wake you up.
The brain creates more delta waves and pulls you into the most restorative stage of sleep, where your body can repair itself and do a whole host of other things, including stimulating development, boosting immunity, and building up energy.
All about REM
If you get 7-9 hours of sleep each night, you will generally experience three to five REM (or ‘dreaming’) periods.
These are the periods when, if you’re woken suddenly before completing the cycle, it can leave you feeling disoriented. You might feel like you haven’t had enough sleep, and that makes it harder to get up and tackle the rest of the day.
During your dreaming/REM period, you start to move your eyes around a lot. Breathing increases and becomes more irregular and shallow. Your limbs also become temporarily paralysed to stop you from moving around too much or falling off the bed.
That said, your heart rate, blood pressure, and temperature can rise and fall, making this a very physically active period – even though it may not look like it from the outside.
Age matters
Another key thing to point out is that different age groups will experience their sleep stages in different ways. For example, an infant will have a different sleep pattern than a child, adult or elder.
At the end of the day (or night, as the case may be), the science of sleep is vast and intriguing, and it’s a field that is constantly being examined and reinterpreted.
What most sleep experts tend to agree on is that REM sleep is critical to your wellbeing, as it’s the most restorative cycle of sleep. So, it’s worth creating a comfortable, relaxing sleep environment so you can easily drift through the first three lighter stages and experience as many REM cycles as you can!