While it is important to make sure you get enough sleep, it is not just about the quantity of sleep but the quality. There is no point in being in bed for 8 hours a night if you are getting poor quality sleep. In order to feel fully rested in the morning your brain needs to go through a cycle of sleep during the night which takes you through various levels of sleep depth.

Sleep as we currently understand it comes in two forms, REM sleep and non-REM sleep. REM stands for Rapid Eye Movement, and it is these two types of sleep our brain cycles through during the night. REM sleep is best described as active sleeping, meaning your physiological systems are actively changing as you sleep. Your breathing alternates between slow and heavy and short and fast, your body temperature increases and the blood circulation to your brain also increases. It is during REM sleep that your main body muscles such as arms and legs become paralyzed, however your eye muscles become very active and your eyes move back and forth as if watching a tennis match – hence the name REM sleep. It is during REM sleep that your most vivid and emotional dreams occur, it is thought this may be due to our brains trying to process the emotions of our waking lives. It is unknown why we need REM sleep but our bodies seem programmed to make sure we experience it every night.

Non-REM sleep is a lighter, stiller sleep. Your breathing is slow and regular as is you brain activity, your body is relaxed and calm. Dreams experienced during non-REM sleep tend to be more like thoughts than emotional experiences.

A typical nights sleep starts with non-REM sleep, of which there are four stages from light to heavy. Non-REM sleep will last for about 80 minutes, then suddenly your sleep switches from the deepest level of non-REM sleep to the first of your REM sleep periods for the night. This first REM phase lasts about 10 minutes, ending when you switch back to the lighter non-REM sleep phase which gradually deepens and the cycle starts again, with the next REM phase lasing a little longer. Each cycle takes around 90 minutes to complete and with each cycle the REM phase increases to the point where anything up to 60 minutes of the cycle is REM sleep. The total amount of REM sleep varies with age, with babies having up to half their sleep at REM and adults only having around a quarter.