When we sleep we actually progress through several cycles of sleep. There are two types of sleep cycle: REM (Rapid Eye Movement) sleep and NREM (Non Rapid Eye Movement) sleep.
REM is concerned with deep sleep primarily when we dream and takes up 20-25% of total sleep in adults. During this stage our eyes dart around under our eyelids giving this cycle its name. Contrary to our perception of sleep being when we completely switch off, our brains are in fact most active during this cycle. REM is extremely important in maintaining our overall health.
NREM sleep makes up around 75-80% of an adult’s total sleep and is divided into 3 stages:
Stage 1 - Wake To Sleep
This stage is when we transfer from being awake to gradually falling asleep and lasts about 5-10 minutes.
Stage 2 - Light Sleep
This stage is just before we enter deep sleep and accounts for 50% of an adult’s sleep. Muscles begin to relax and brain waves slow down.
Stage 3 - Slow Wave Sleep
Our brain waves and heartbeat have slowed; the body starts healing itself including flushing toxins from our brain. This stage can last around 40 minutes.
NREM sleep is responsible for the first cycle and this is then taken over by REM sleep. Each cycle lasts around 90 minutes as we go from NREM to REM sleep and circle back again. A good night’s sleep normally has 5 or 6 cycles and a total duration of 7.5 to 9 hours in adults.
Whilst both stages are critical to our brain and body resetting ready for the next day, REM sleep is crucial to retaining a sharp mind, memory function, reducing anxiety and depression and decreasing our blood pressure. Disturbing our REM sleep can be very detrimental and can lead to degradation of our cells, a weakened immune system and mental health issues.
In 2010 an eye-opening study called ‘Effects of earplugs and eye masks on nocturnal sleep, melatonin and cortisol in a simulated intensive care unit environment’ showed how serious having disturbed sleep cycles was on some ICU patients. It concluded that the light and noise from the ICU environment increased sleep disturbance which could lead to ‘patient morbidity’ and ‘degenerate quality of life’. They then gave the patients sleep masks and earplugs to combat the stressors and this led to a notable increase in REM sleep time, less waking up and increased melatonin production.
So getting good quality sleep is important not only to allow us to rebalance and refresh our bodies and minds but also it is key in ensuring that our mental health is taken care of. We all know that feeling when you have had an amazing deep, undisturbed sleep that you can take on absolutely anything the next day - we should aim for that feeling every day!