The intriguing science behind why we sleep

Sleep might be something you don’t give much thought to, but a good night’s sleep is vital for your wellbeing.

If sleep is something you struggle with, you’re not alone.

According to a YouGov poll, 1 in 8 Brits says they have trouble falling asleep every night. And around a quarter of people say they take sleeping tablets to help them drift off. What’s more, 68% said they often still feel tired in the morning.

So, what does science tell us about sleep?

Your internal “body clock” regulates your sleep cycle

The 24-hour cycle of your body clock – known as the “circadian rhythm” – regulates when you feel tired.

Scientists believe feeling tired could be linked to adenosine, an organic compound that’s produced in the brain. Your levels of adenosine gradually increase throughout the day. Your brain then breaks down this compound while you sleep.

Light also plays a role in your body clock by affecting the hormones your body releases. In the evening, your body will release melatonin, which can cause drowsiness. In the morning, by contrast, your body releases the hormone cortisol, which can help you feel more alert.

REM sleep is linked to memory consolidation

There are four stages of sleep that you will repeat cyclically throughout the night. The final stage is called “REM”, or rapid eye movement sleep.

As the name suggests, your eyes move rapidly back and forth during REM sleep. It’s during this stage that you’ll often dream and your arms and legs will become paralysed – it’s thought this is to prevent you from physically acting out your dreams.

What’s important about REM sleep is that it’s linked to memory consolidation. This means that your recently learned experiences become long-term memories.

REM can explain why remembering can become more difficult as you age. As you get older, the duration of REM decreases.

Research from Stanford University in 2011 found a link between interrupted sleep and impaired memory in mice. The researchers noted that uninterrupted sleep, even if it’s just a small amount, is crucial for memory consolidation.

Sleep is vital for brain plasticity

Brain plasticity, or neuroplasticity, refers to the brain’s ability to change and adapt as a result of experience. It’s thought that sleep is vital for this process by providing a restorative period.

Without brain plasticity, you may not be able to pick up new skills or use your experiences to make informed choices in the future.

Sleep during adolescence can affect social interactions

Parents of teenagers will be well aware that they need more sleep than adults.

Interestingly, research reported by the Human Frontier Science Program suggests uninterrupted sleep in adolescence is vital for healthy social interactions.

The researchers carried out the study on mice. The results indicate that for generally healthy people, good sleep during adolescence may affect the quality of their social life in the long term.

So, next time you’re trying to encourage a teenager to get up early, leaving them to sleep in might not be such a bad idea.

But there’s still a lot that scientists don’t know

Despite the research, there’s still a lot that scientists don’t know about sleep. It’s something all animals do. Yet, if you ask scientists why we sleep, they aren’t exactly sure.

One hypothesis is that sleep serves as a type of cleaning process. Some researchers believe your body removes waste products from brain cells when you sleep, which can improve your health.

Whatever the reason for sleep, studies have consistently shown that not getting enough can affect many aspects of your physical and mental health.

3 excellent books about sleep

If you’re keen to learn more about the science of sleep and the crucial role it plays in your life, there are plenty of books on the topic to delve into, including these three:

1. Why We Sleep by Matthew Walker

This book answers some of the most asked questions about sleep, such as what happens during REM? Or how does caffeine affect sleep? The book does an excellent job of making complex scientific evidence accessible to everyone.

2. The Promise of Sleep by William Dement

If you want more reasons why you should make sure you get a good night’s sleep, Dement has plenty. He explores the consequences of not getting enough sleep, from fatigue-related accidents to the psychological disadvantages.

3. Snooze by Michael McGirr

As well as looking at why we sleep, Snooze explores the sleep patterns of some of the greatest minds in history, from Aristotle to Thomas Edison.

More stories

26 Jul 2022 News

5 unexpected lessons you can learn about finances from Roald Dahl

26 Jul 2022 News

5 ways you can donate tax-efficiently to mark the UN’s International Day of Charity

How can we help?

We’re very happy to answer your questions. Complete the form below and one of our team will respond with an answer.

    You voluntarily choose to provide personal details to us via this website. Personal information will be treated as confidential and held in accordance with the Data Protection Act 1998. You agree that such personal information may be used to provide you with details of services and products in writing, by email or by telephone. Please read our Privacy Statement before completing any enquiry form or before sending an email to us.

    Important information

    AKFP Group is the trading name of AKFP Ltd which is authorised and regulated by the Financial Conduct Authority ( Financial Services Register No: 176477.

    The Financial Ombudsman Service (FOS) is an agency for arbitrating on unresolved complaints between regulated firms and their clients. Full details of the FOS can be found on its website at

    AKFP Ltd, Registered Address: Building 2, The Sidings, Antrim Road, Lisburn, BT28 3AJ. Registered in Northern Ireland, No. NI29631.

    The information contained within this site is subject to the UK regulatory regime and is therefore targeted primarily at consumers based in the UK.