Sleep Science

Sleep Science


  1. Why is sleep important?
  2. How much sleep do we need?
  3. Stages of Sleep
  4. Sleep Mechanisms
  5. How does the body regulate sleep?
  6. Common reasons for not being able to sleep
  7. Tips for getting a good night's sleep

Why is sleep important?      

The average person will spend about 26 years of their life sleeping, so it’s no surprise that sleep is important to our bodies! When we sleep our body repairs cells and restores energy to support healthy brain function. Not only does our body require sleep, but a good night's sleep also allows our mental health to recharge and relax, allowing us to face the challenges of the day ahead. Sleep is essential to our bodily function and lack of it can have a significant impact on our daily lifestyles by increasing the risk of a variety of physical, emotional, and mental health issues.

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How much sleep do we need?

Your need for sleep and your sleep patterns change with age, so there is no ‘magic’ number of hours that suits everybody the same. Most studies suggest that you should aim to get between seven to nine hours sleep each night, but the more the better! Within a minute of falling asleep, significant changes begin to affect both the brain and the body. Our body temperature drops, our brain activity decreases, and our heart rate and respiration slow down too. 

What happens if you don’t get enough sleep?

Because sleep is so important, a lack of it can put you at risk for a variety of health issues. Lack of sleep is often associated with an increased chance of having high blood pressure, a heart attack and/or a stroke. Sleep deprivation can also lead to a lower immune system. Studies suggest that people that are getting less than seven hours of sleep a night are nearly three times more likely to become infected by a rhinovirus, or common cold![1]

Not only this, lack of sleep can also increase anxiety and is commonly associated with higher rates of depression. In fact, researchers have found that lack of sleep increases the likelihood of suicidal thoughts and, tragically, suicide completion.[2] Less than six hours sleep has also been linked to multiple health conditions like Alzheimer’s disease, diabetes, cancer, and suffering from obesity.

So it’s critical to give yourself a quality amount of time to sleep each night in order to recharge and rest.

Stages of Sleep

While we may only know sleep as one great big stage, there are actually four stages of sleep which are divided into two categories. The first three stages fall into the Non-REM (Rapid Eye Movement) sleep category, while the fourth stage is known as REM Sleep. 

Sleep Stage One

In stage one, you are usually dozing off and making the transition into stage two where your brain and body’s activity starts to slow down. You can easily be awoken during this stage as you’re only lightly sleeping and have not reached you deepest sleep yet. Your body is slowing down here ready to relax properly.

Sleep Stage Two

During stage two, your body enters a more subdued state whereby your body temperature drops, and your muscles begin to relax more. Your heart rate and breathing slows down and eye movement stops. Your body slows down and begins to really relax into sleep mode, before entering stage three.

Sleep Stage Three

In stage three your muscles and body start to relax even more, and your brain waves begin to show a significantly different pattern to your waking brain activity. Stage three is the deepest part of Non-REM sleep. Here, your body is in deep sleep, and it is harder to wake someone up that is in this phase.

Sleep Stage Four (REM Sleep)

Lastly, your body will enter Stage Four known as REM Sleep. This first occurs about 90 minutes after falling asleep and is a deep sleep where the brain waves slow down, your breathing becomes faster and irregular, your heart and blood pressure increase to near waking levels, and you are difficult to wake up. It is believed that tissue repair can occur during this phase of sleep – just another reason as to why sleep is so important to our bodies! While dreams can occur during any sleeping stage, it is most likely that you will have intense and vivid dreams during this stage of sleep. During this phase, your arm and leg muscles become temporarily paralyzed – stopping you from acting out your dreams.

And while all of these stages are important to your wellbeing, it is believed that REM Sleep (Stage Four) is essential to the brain because it enables functions like memory and learning. If you get a good night sleep, you’ll spend most of your sleep in this phase.

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Sleep Mechanisms

And while you probably can’t believe that there is still more to sleep than four stages, there are also sleep mechanisms! The body regulates sleep with two key internal biological mechanisms – Sleep-wake Homeostasis and Circadian Rhythm. Together, these processes determine the sleepiness and alertness of the individual during and after sleep.

What is Sleep-wake Homeostasis?

Sleep-wake Homeostasis essentially keeps track of your ‘need for sleep’, and this is because of the homeostatic sleep drive. Pressure builds up in our body as our time awake increases. This pressure gets stronger the longer we are awake and decreases during sleep – reaching a low even after a full good night sleep.

What is Circadian Rhythm?

Our Circadian Rhythm is part of our natural ‘body clock’. In simple terms, it is the natural cycle of physical, mental and behavioural changes that the body faces throughout a 24-hour period. Circadian rhythms synchronize with environmental cues like  light exposure. Light exposure can have a huge impact on this as light encourages wakefulness, while darkness often makes you feel sleepy – impacting your natural 24-hour cycle.

These two factors play an important role in sleep regulation, and together, they influence how much your body feels the need to sleep, the time of day, your light exposure, and how long you've been awake.

External Factors

There are also a variety of external factors that can affect homeostasis and the circadian alerting system.[3] Stress and hunger are two of these factors. Both of these can have a significant impact on our bodies, as well as disrupt the normal process of sleep regulation. Going on your phone before going to sleep, jet lag, frequent work shift changes and caffeine consumption can also have an impact on your sleep system.

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The Brain and Sleep

Several parts of the brain are involved with sleep including the “hypothalamus, the thalamus, the pineal gland, the basal forebrain, the midbrain, the brain stem, the amygdala, and the cerebral cortex”.[4]

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Here’s a little bit about their roles:

  • The hypothalamus – consists of groups of nerve cells that act as control centres for sleep and arousal.
  • The brain stem – controls the transitions between wake and sleep by communicating with the hypothalamus.
  • The thalamus – serves as a relay for sensory information to the cerebral cortex. The thalamus becomes quiet during most stages of sleep, allowing you to tune out the outside world.
  • The pineal gland – when it gets dark, the pineal gland receives signals from the SCN and increases production of the hormone melatonin, which aids in sleep.
  • The basal forebrain – promotes sleep and wakefulness.
  • The amygdala – REM sleep causes the amygdala to become increasingly more active.

This presents the biological complexity of sleep since so many parts of the brain are involved in wakefulness and sleep itself!

How does the body regulate sleep?


So it's clear that the biological process of sleep is far more complex than we imagined when we doze off after a long day. Neurotransmitters are chemicals in the nervous system that transfer signals to activate or deactivate certain cells. The transition from wakefulness to sleep causes changes in thousands of neurons in the brain. GABA, the main inhibitory neurotransmitter, is often associated with sleep, muscle relaxation and sedation. It reduces the activity of nerve cells throughout the nervous system helping your mind transition from its wakeful state into a sleeping state.

What chemicals and hormones regulate sleep?

Our sleep is often regulated by numerous chemicals and hormones that are involved in the mechanics of sleep-wake homeostasis and the circadian alerting system. A chemical called adenosine is believed to play a central role in sleep-wake homeostasis. When we’re awake, adenosine builds up and increases sleep pressure – making us feel tired. Unlike caffeine that supresses adenosine and makes you feel more awake and alert.

Hormones also play an important role in regulating sleep. Melatonin is one of the best known hormones associated to sleep. It promotes sleep and is naturally produced as light exposure decreases. Another hormone linked with sleep is adrenaline, cortisol and norepinephrine. The function of these chemicals and hormones may differ depending on the individual based on their genetics which is why some sleep disorders run in families.

Genes and sleep

While environment and lifestyle changes play a role in your sleep pattern, your genes may also affect how much sleep you need. Several chromosomes have been identified in genome-wide association studies as having increased susceptibility to sleep disorders.[5] Sleep disorders such as familial advanced sleep-phase disorder, narcolepsy, and restless legs syndrome have all been linked to specific genes.

Common reasons for not being able to sleep

But, as you probably know already, falling asleep isn't always easy. This can be down to many potential things like: 

  • Anxiety and Depression
  • Stress
  • Too hot or too cold room
  • Jet lag
  • Work shift changes
  • Uncomfortable environment
  • Noise
  • Alcohol and Caffeine
  • Recreational Drugs

All of these factors can contribute to a lack of sleep, and because sleep is so important to our health, it is critical that you recognise the issue to get a good night sleep to support your mental and physical wellbeing.

Lack of Sleep

Symptoms of insufficient sleep include:

  • Lack of energy
  • Worsened memory
  • Mood changes – including stress, anxiety, irritability
  • Reduced attention span
  • Lack of concentration
  • Slow thinking

Potential Health Risks

Chronic sleep deprivation can also lead to some potentially serious health problems including: 

  • High blood pressure
  • Diabetes
  • Heart attacks
  • Heart failures
  • Strokes 

It’s important to seek medical advice and support if you feel like your sleep deprivation is affecting your lifestyle and health.

Tips for getting a good night sleep

If you feel like you’ve already tried everything and nothing is helping, give these tips a go! Sometimes all we need is a little direction and a change in our lifestyle to get a good night's sleep.

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Set a sleep schedule

Set yourself a time to wake up and go to sleep each day to get your body into a ‘sleep routine’. It’s important to try and maintain a regular sleep schedule for your body’s internal clock to help you fall asleep and wake up more easily. You don’t have to put pressure on this schedule but setting yourself mini goals can support your wellbeing too.


Exercise can help stabilise your mood and decompress your mind allowing you to disengage with wakefulness and doze off into a deep sleep. Try doing just 20 minutes of exercise a day to release some serotonin and relieve your mind and body of any built up tension!

Avoid Caffeine, Nicotine and Alcohol

If you're having trouble sleeping, try avoiding caffeine, nicotine, and alcohol throughout the day, especially in the late afternoon and evening. Alcohol, nicotine and caffeine are believed to increase ‘sleep fragmentation’ which has a negative effect on sleep duration and efficiency.

Relax before bed

Try taking a nice warm bath before bed and letting yourself wind down. Listen to some calm music or pick up a good book and immerse yourself in the story. Maybe even try some meditation and yoga to allow your entire body to zone out of the busy woke mind before getting into bed.

Sleep is vital to our bodies. It enables us to recharge, reset, and feel refreshed and alert, ready for the next day. Try and get a good night sleep and you’ll feel better for it in the morning! 


  1. Brain Basics: Understanding Sleep | National Institute of Neurological Disorders and Stroke.
  2. Circadian Neurobiology and the Physiologic Regulation of Sleep and Wakefulness, National Library of Medicine.
  3. How Sleep Works: Understanding the Science of Sleep | Sleep Foundation,
  4. Suicide and sleep: Is it a bad thing to be awake when reason sleeps?, Sleep Medicine Reviews, Science Direct.
  5. Sleep habits and susceptibility to the common cold, National Library of Medicine,
  6. Sleep State Switching, National Library of Medicine.
  7. The Body, The new science of sleep: Everything we know about how it affects your health and brain, BBC Science Focus Magazine. 
  8. The Effects of Sleep Deprivation,