Sleep quality is as important to your physical and mental wellbeing as sleep duration.
There are four individual and important stages of sleep, one classed as rapid eye movement (REM) sleep and three that form non-rapid eye movement (NREM) sleep. The classification of sleep stages was updated in 2007 by the American Academy of Sleep Medicine (AASM).
Stage 1 – Dozing off, lasts between 1-5 minutes. Body and brain activities begin to slow. It is easy to wake a person up at this stage and throughout the night an uninterrupted sleeper will move very quickly into the next stage.
Stage 2 – Lasting for 10-25 minutes, a temperature drop, slowed heart rate and breathing, relaxed muscles and slowed brain activity occur in stage 2 and eye movements stop. You tend to spend on average half of your night’s sleep in Stage 2.
Stage 3 – Deep sleep, it is hard to wake a person up in this further relaxed state where pulse, muscle tone and breathing rates further decrease. Brain activity enters an identifiable pattern called delta-waves or slow-waves. Experts believe that stage 3 sleep is vital for bodily recovery, growth, immune system repair and even contributes beneficially to creativity and memory. The first sleep cycle of the night is where you typically spend the longest time in stage 3.
Stage 4 – REM sleep. Brain activity increases to a level comparable to a person who is awake. Apart from the eyes and muscles used to breathe, in this 4th stage the body experiences a temporary paralysis of the muscles (atonia). The eyes move rapidly although shut and this is the time where you may experience vivid dreams. Total REM Stage 4 sleep makes up on average 25% of sleep in adults. Typically, you spend more time in this stage in the later part of the night.
Each sleep stage individually ensures that your body and mind awake refreshed and all are vital to ensure high-quality, restorative rest and development. Without spending enough time asleep in stages 3 and 4 you may suffer the consequences of insufficient sleep which can affect your mental and physical health, emotions and wellbeing.
In a typical night, a person smoothly progresses multiple times (between 4-6) through sleep cycles, each composed of the four separate sleep stages above.
The first sleep cycle is normally shortest (between 70-100 minutes), later cycles tend to be longer (between 90-120 minutes) and the amount of time in each sleep stage also changes throughout the night.
Sleep cycles can vary from person to person and from night to night based on factors including age, weight, levels of physical activity, caffeine and alcohol consumption and recent sleep patterns.
To ensure the best possible quality sleep you should focus on creating a good bedroom environment, try to enjoy natural light and exercise during the daytime, eat as healthily as possible and avoid stimulants, all of which can affect your natural sleep cycles and your circadian rhythm.