The Stages of Sleep

It will come as no surprise to hear that we at Dormeo HQ are fascinated by all things sleep-related and if you’re reading this, you probably love sleep almost as much as we do.

But how much do you really understand about what happens when you’re asleep? Did you know that the average person takes 7 minutes to fall asleep? Do you know your REM from your non-REM?

It may feel as though sleep is the only time that you completely switch off and shut down but our brains are working super hard. It’s this brain activity that defines the four different Sleep Stages which make up one Sleep Cycle, lasting anywhere from 90-110 minutes.

Stage 1

Have you ever gently drifted off to sleep only to suddenly jerk awake, convinced you’ve just had a fall or crashed into something? This happens in the first sleep stage during which muscle activity and eye movement really begin to slow down.

If you want to be a bit of a smarty-pants, the next time someone tells you they’ve experienced this phenomenon you can tell them that they were startled awake by a ‘myoclonic jerk’.

This first stage only lasts about five to ten minutes and if you’re woken up during this stage you’re unlikely to even feel you’ve been asleep. During this phase our brains produce small, fast brain waves called ‘beta waves’ before slowing down to produce ‘alpha waves’ and then finally ‘theta waves’.

Stage 2

This stage lasts for about twenty minutes.  Eye movement stops altogether, our heart rate slows and our body temperature drops. Our brain waves slow down further but are interspersed with bursts of rapid brain waves called ‘Sleep Spindles’.

Stage 3

Stage 3 lasts for about half an hour and is also sometimes called ‘Delta Sleep’ after the extremely slow brain waves that define this Stage. This is the Stage during which children wet the bed or experience night terrors and adults or children may sleepwalk. During this stage, there is still no eye or muscle movement and it’s extremely hard to wake someone.

Stage 4

The Stage of many names, Stage 4 is also known as the REM (Rapid Eye Movement) Stage, the Dream Stage or the Paradoxical Sleep Stage. Why?

Dream Stage

This is the main phase of dreaming which occurs due to the increase in brain activity. On average, we experience three to five phases of REM sleep each night and if you wake up during one of your REM sleep intervals, you are likely to remember your dreams.

Paradoxical Sleep Stage

During this phase our brain waves are comparable to when we are awake. Our heart rate and blood pressure go up, respiration quickens and we take quick, shallow breaths but although our brain and other systems become more active, our voluntary muscles become paralyzed. Our involuntary ones (our heart for example), thankfully keep on moving. Quite some paradox.

The paralyzing of voluntary muscles is a safety thing. If our legs and arms can’t move, we can’t get up and run away screaming from the zombie we just met in our dream. Pretty cool, eh?

REM Stage

As the name would suggest, this stage is also characterised by our eyes moving and jerking about rapidly.

These days, most people have heard of REM – and not just in relation to the 80’s American rock band – but it wasn’t actually until 1953 that the sleep-related REM was ‘discovered’ by a graduate student of the University of Chicago called Eugene Aserinsky.

He went on to prove a correlation between eye movements, dreaming and increased brain activity (up until then, believed to stop completely during sleep).

He is now recognised as one of the founders of modern sleep research. More recent research is being carried out into the link between REM sleep and memory.

Interestingly, children spend nearly half their sleeping time in REM sleep whereas adults spend half of their sleeping time in Stage 2 and only 20% in REM.

It would be nice and neat and tidy if we just cycled through Stages 1-4 in sequence throughout the night but of course, it doesn’t quite happen that way. The actual sequence is slightly more complicated with Cycle 1 looking something like this: 1, 2, 3, 2, and 4 and then Cycles 2-5 looking something like this: 2,3,2,4.

Of course it isn’t even that straightforward, because the length of time each Stage lasts also changes as the night goes on.  During the first Sleep Cycle, we will enter Stage 4 approximately 90 minutes after falling asleep. The first REM sleep, however, may well last only a short time with later REM sleeps lasting up to an hour.