From improving memory to strengthening the immune system, sleep is one of the most essential functions in the body. There have been thousands of studies into the benefits of sleep, and with some of these benefits including building muscle and burning fat, increasing life expectancy and lowering the risk of cancer, there’s really no substitute for a good night’s sleep.

Different stages of sleep

Although we may know most adults require between seven and nine hours a night, with children needing substantially more, the quality of the sleep during these hours is equally as important.

There are four stages of sleep, all of which play an important role in the quality of your sleep. These stages cycle throughout the night, with each cycle lasting between 90-120 minutes. These stages are:

Stage 1 NREM: NREM stands for non-rapid eye movement. This stage is the transition between being awake and sleeping, consisting of very light sleep that typically lasts a few minutes. In this stage muscles start to relax whilst the heart rate, breathing, eye movements and brain waves begin to slow down.

Stage 2 NREM: This stage of sleep usually lasts the longest of the four stages, this is where the heart and breathing rate continue to slow, muscles become more relaxed and eye movement stops completely.

Stage 3 NREM: The third stage is what makes you feel refreshed and alert the next day. It is the deepest form of sleep, where all rates including heart, breathing and brain activity are all at their lowest and muscles are as relaxed as the can be. This stage starts off longer in the first cycle, but will decrease throughout the night.

REM: The final stage is REM sleep. REM (rapid eye movement) usually happens about 90 minutes into the cycle, and is when breathing and heart rate will increase. This stage is when dreaming will typically occur, and many studies link REM to the process of converting recently learned experiences into long-term memories.

What are the benefits of sleep?

Improved athletic performance

Various studies have found that a good night’s sleep can improve athletic performance. In one study of basketball players, more sleep significantly improved speed, accuracy, reaction times and mental well-being. Another study linked poor exercise performance to less sleep duration in women. In the study, it was found that poor sleep led to slower walking, less grip strength and difficulty performing independent activities.

Reduced risk of chronic diseases

The quality and quantity of sleep can have a big effect on many health risk factors which may lead to chronic illnesses such as heart disease and type 2 diabetes. People who sleep for the suggested 7-8 hours a night are at far less risk of developing heart disease compared to those who get less sleep, whilst it has also been found that those who sleep for less than six hours a night have an increased risk of type 2 diabetes.

Improved immune function

Even a small reduction in sleep can have an impact on immune function, according to studies. In a large study that took place across two week period, participants were given nasal drops that contain the cold virus. The results of this study found that those who slept for less than seven hours were 3 times more likely to develop a cold than those who slept 8 hours or more.

Sleep also has the ability to balance some of the most important hormones in the body. Good sleep can lower cortisol levels, the body’s stress hormone. Reducing these levels does not only reduce mental stress, but can also reduce physical stress which intern lowers the risk of chronic illnesses such as heart disease, obesity and cancer. Other research shows that a lack of sleep can desensitise serotonin receptors, making the body more prone to mental illnesses such as depression and anxiety. The last of the important hormones that are affected by sleep is testosterone, with studies showing that men who sleep less than six hours a night showing to have testosterone levels the same as a man ten years their senior.