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Sleep 101: How Sleep Works

16 August 2022

Sleep is a vital part of maintaining a healthy lifestyle. While we sleep, our body restores and repairs itself, processing information from the day and releasing inflammation-fighting molecules. If we are deprived of sleep, we suffer both mentally and physically. A poor night’s sleep can affect your energy levels, concentration, motivation, and mood and leave your immune system weakened and vulnerable. Despite sleep being crucial for our general wellbeing, many of us are unsure how sleep works. In fact, it is quite a complicated process, made up of various stages. In this article, we will help you to find out more about the science of sleep.

What Are The Different Stages Of Sleep?

There are four different stages of sleep:

1. Awake

While being awake may seem like an unlikely stage of the sleep cycle, waking signals the beginning and end of your sleeping journey. Did you know that you experience brief periods of awakeness throughout the night? These occur during the transition between each stage of the sleep cycle.

2. Light

The following sleep cycle stage occurs as your body starts to drift off to sleep. It is a period of very light sleep, where your body temperature drops, your heart rate slows, and your brain's electrical activity begins to slow down. As your muscles start to relax, you may experience muscle twitches where you fall like you are falling and wake up with a start. This stage of the sleep cycle generally lasts under 10 minutes. If somebody wakes you up during this stage, you may not even realise that you were asleep!

3. Deep

Deep sleep is when your body begins to repair itself. Your body increases blood flow to your muscles and releases growth hormones to support cellular repair and tissue growth. When you are in deep sleep, your heart rate, muscle activity, and breathing drop to their lowest. Your brain remains active as it consolidates memories and forms new connections. It eliminates useless information you no longer need to provide space for your important long-term memories. You will likely feel disorientated and groggy if awoken from a deep sleep. Others will probably find it harder to rouse you from a deep sleep.

4. Rapid Eye Movement (REM)

Around an hour to an hour and a half, after you fall asleep, you will cycle through the REM stage. You experience your most vivid dreams during the REM stage of sleep due to increased brain activity. In addition, your blood pressure, heart rate and breathing will increase. Temporary muscle paralysis prevents you from acting out your dreams during this time. During REM sleep, your eyes move rapidly beneath your eyelids, hence the name! Interestingly, we experience increased REM sleep during the second half of the night.

During a typical night’s sleep, your body will cycle through all the sleep stages between 4 and 5 times. Each sleep cycle lasts for around 90 to 120 minutes. The amount of time that we spend in each stage of the sleep cycle changes throughout our lifetimes; for example, newborn babies spend between 70% and 80% of their cycle in REM sleep. By age 5, children spend around 20% to 25%  of their sleep in the REM stage. Chronic medical conditions and sleep disorders can also influence the dynamics of the sleep cycle.

How Do We Regulate Sleep?

Sleep is a very tightly regulated process, with parts of our brain working harmoniously to control our sleep-wake cycle. Sleep is regulated via sleep homeostasis (the balance between sleep and wakefulness) and the body’s circadian rhythm. Several external factors can influence your sleep-wake cycle, including sleep environment, stress and worries, medication and medical conditions. Disruption of the natural circadian rhythm, for example, in those that work night shifts, can lead to sleep difficulties and other health problems.

How Much Sleep Do We Need?

According to the National Sleep Foundation guidelines, healthy adults should aim to get around 7 to 9 hours of sleep every night. The exact amount of sleep required varies with age, with babies, infants, children and teens needing extra sleep to support continued growth and development. Obviously, there is no one-size-fits-all approach and your exact sleep requirement will depend on your individual health and daily activity level. Still, you should stick to these guidelines as closely as possible. Some people may naturally survive on less sleep, while others need an uninterrupted 10 hours to feel refreshed. Try not to compare your needs to others.

The Bottom Line

Sleep helps us live a happy and healthy life, providing our bodies and minds with a chance to relax and refresh. Sleep deprivation may lead to unpleasant side effects, such as low mood, weakened immunity, poor motivation and daytime fatigue. If you struggle to achieve a good night’s sleep, get advice from your doctor or another medical professional.