We are often told that 8 hours sleep a night is what we should be aiming for, but why? In this article we explain what happens in the different stages of sleep.
Firstly when you sleep you do so in a number of cycles typically lasting 90 minutes. These cycles are made up of 4 stages:
Stage 1 – First 1-7 minutes – 25% of a total nights sleep
In this first stage you are in-between being awake and falling to sleep or you are in a very light sleep. You are drowsy and may wake easily and this half-asleep, half-awake stage repeats at the start of each cycle.
Stage 2 – Next 10-23 minutes – 45% of a total nights sleep
This is the onset of sleep where you start to become disengaged from your surroundings, your body temperature starts to drop and you have very regular heart rate and breathing. This is still a relatively light sleep and can still be woken easily.
Stage 3 – Next 20-40 minutes – 25% of a total nights sleep
This is the deepest and most restorative sleep when you blood pressure drops and your breathing slows. Your muscles relax, blood supply to them increases stimulating tissue growth and repair which is aided by the release of growth hormones. Finally overall energy is restored. You will be harder to wake in this stage.
Stage 4 – Final 10-60 minutes – 25% of a total nights sleep
This is the rapid eye movement stage which normally starts about 90 minutes into your sleep and gets progressively longer the more cycles you go through. In this stage you brain is very active and receiving energy which in turn causes dreaming and for your eyes to move back and forth. You body is at its most relaxed and you muscles are turned off.
Over the course of a normal night sleep the average number of sleep cycles is 5. It is more than likely that the next time you wake up in the night the length of time you have been asleep is divisible by 1.5 hours!
Your body makes an incredible journey through the night as it progresses through each stage, the graph below shows how the body makes the most of a good night sleep.