Regulation of sleep

When we sleep, our bodies go into a pattern that we call “sleep architecture” – our own personal blueprint that navigates our way through the sleeping world. We alternate between REM (rapid eye movement) and NREM (non-rapid eye movement) sleep throughout the night in a cycle that repeats roughly every 90 minutes. 1 2 3 This architecture, which is regulated by melatonin, determines when we will fall asleep, how long we’ll sleep and when we’ll wake up. 2

The sleep-wake cycle

As adults, our sleep cycle is an ever-changing pattern. The sleep-wake cycle is regulated by two things – how tired you are and your circadian (biological) clock. 2 4

Sleep isn’t always at the top of our list of things to do as other waking priorities seem to take precedence, but it’s important to get the best out of the hours you have to sleep, and understanding your sleep cycle is a good start. As you shuffle, every 90 – 110 minutes or so, between non-REM sleep and REM sleep, your body goes through phases of rest and recovery. This process may be repeated up to 5 times over the course of a single night and comprises the following stages: 1 2 3

The stages of sleep

Stages 1 and 2: Light sleep

When you first fall asleep, your body prepares to shut itself down. During this first stage, it’s easy to be woken up by noises, a busy mind or those jarring moments when you’re woken up because you feel like you’re falling. This first stage is essentially the bridge between being awake and being asleep. 1 2 3
After a few minutes of this, you will pass into another form of light sleep, known as stage 2 Non-REM sleep. During this second phase, your breathing and heart rate slows down and you become less aware of the world around you. This stage forms nearly half of your sleep cycle and is referred to as true sleep. However, it is also considered light sleep and if you are woken up during this phase, you won’t even know you were asleep at all! 2 3

Stages 3 and 4: Deep sleep

The next two stages of non-REM sleep are grouped together. During these phases you are passing into slow wave sleep or deep sleep. Your breathing and heart rate are at their lowest levels, and muscle activity decreases. Deep sleep is a very refreshing type of sleep, and it is particularly important in helping the brain process information. 1 2 3

Stage 5: Dream sleep

Eventually, this will lead into rapid eye movements (REM) sleep. This takes its name from the movement your eyes make behind closed lids. During the REM stage, your breathing rate and blood pressure rise, your brainwaves are similar to what it was in light sleep but all your voluntary muscles become paralyzed so that you cannot move your limbs. 1 2 3

On average, a person will have around three to five episodes of REM sleep per night, starting about 70 – 90 minutes after falling asleep. It is during this stage of sleep that we experience dreams. 1 2