The science of sleep

What's going on in your mind and body while you sleep?

An average person will spend 26 years of their lifetime asleep. Seven additional years are spent trying to get to sleep 😴

Sleep is something that gets weirder the more you think about it. Night after night, we will ourselves into unconsciousness, hallucinate, and then get up the next day and start all over again 🤷‍♀️

But what actually happens when we lie in bed at night? How can we sleep better and for longer? And why do researchers like Matt Walker keep going on about how important sleep is for our health?

To get to the bottom of these questions, we’ve broken down some of the key pillars of sleep science. Let’s get into it 🤓

Different kinds of sleep

Do you ever find you can sleep the same amount on two different nights, but feel much more well rested on one day than the other?

All sleep is not equal. How rested we feel after a night’s sleep has as much to do with the kind of sleep we’re getting as how long we’re getting it for.

There are two kinds of sleep: REM (rapid-eye-movement) sleep and non-REM sleep.

Non-REM sleep is the kind of sleep we get when we first drift off. It can be broken down into three stages, moving from light sleep to a much deeper sleep state. This kind of sleep plays an important role in learning and memory.

In REM sleep, our eyes move rapidly (hence the name ‘rapid eye movement’ sleep), and our brain waves look similar to when we’re awake. Our breath rate increases, and the body becomes temporarily paralysed as we dream. This can last for anything from 10 to 60 minutes.

MindLabs Tip: Drinking alcohol can mean we get less REM sleep, which is why you may get a great night’s sleep after a night out but still wake up feeling tired (the hangover probably doesn’t help either!)

The sleep cycle

Every night, we go through four or five cycles of sleep. Each cycle lasts between 70 to 120 minutes, and looks a little like this:

Brown Beige Abstract UI Selfcare Cycle Instagram Post (1920 × 1080px)

The cycle repeats itself, but with each cycle you spend less time in stages three and four and more time in REM.

Circadian rhythms

We can’t talk about the science of sleep without talking about circadian rhythms.

Essentially, our bodies are cyclical: they follow 24-hour cycles that help to regulate sleep and wakefulness (i.e. a circadian rhythm). These cycles are responsive to environmental cues like light, as well as internal factors like stress, hunger and caffeine.

Circadian rhythms exist across all lifeforms. Plants use light cues to know when to open and close; nocturnal animals wait until it’s dark to leave their place of shelter.

Back when our routines relied on the rising and setting of the sun, our circadian rhythms helped us too. We got up for work when the light came into our windows at dawn, and went to bed at sunset.

Nowadays, things are a bit more complicated. And as a result, our sleep routines have got more complicated too. Our bodies are designed to release melatonin (a hormone that makes us sleepy) when it gets dark, and wake us up when we’re exposed to light. But in a world where we’re often watching TV or scrolling on our phones until late at night, or staying inside for most of the day, these signals get pretty confused.

We can work with our circadian rhythms to help us sleep better by:

  • Going to bed and waking up at the same time each day
  • Minimising artificial light at night and exposing ourselves to more sunlight in the day

How else does the body regulate sleep?

As well as our circadian rhythms, our sleep is regulated by something called a sleep drive (also known as the ‘homeostatic sleep drive’. This is our biological drive for sleep (much like we have a biological drive to eat). Essentially, it’s a measure of how much you need to sleep, and is caused by a build-up of a neurotransmitter called adenosine, which accumulates when you’re awake.

Did you know? 

Caffeine temporarily blocks adenosine receptors, which is how it makes you feel energising. However, it doesn’t actually stop the brain from producing adenosine, which is why you can feel extra tired once the caffeine has worn off.

Essentially, the longer you’re awake, the more you feel the need to go to sleep. This is a self-regulating system within the body, that will take over if you haven’t had enough sleep.

MindLabs tip: Chasing sleep by e.g. by taking naps or waking up later, can actually diminish our sleep drive, which makes it harder to sleep at night.

science of sleep MindLabs

Why do we need sleep?

Sleep is about so much more than replenishing our energy levels. When you’re sleeping, your body is hard at work repairing cells, releasing hormones and boosting your immune system. It’s thought that we haven’t yet discovered all the bodily processes that go on while we’re sleeping 🤯

Sleep is also vitally important for our minds. When we switch off, our brain keeps going: working on important processes like consolidating memories and making sense of new information. Sleep is also essential for neuroplasticity (i.e. the neural flexibility that helps us to learn new skills and build new habits).

Not sleeping can have several adverse effects on our health. Over a long period of time, it can result in a weakened immune system, impaired memory, cardiovascular problems, and has also been linked to obesity and type II diabetes. A lack of sleep is also thought to be implicated in mental health problems like depression and anxiety (although it’s a bit of a chicken and egg situation, as these conditions can also make it more difficult to fall asleep).


Sleep is super important, keeping your mind happy and healthy, and letting your body do all the things it doesn’t have time to do when you’re awake. It’s thought that eight hours of quality sleep a night is optimal for our health - but we all have slightly different needs (sleep is less important as you get older, for example). It’s also important that we’re getting the right kind of sleep. Having a good sleep routine can help with this.

Sleep with us 😉

Sleep with MindLabs app

We know that many of you come to MindLabs wanting to improve your sleep habits, so we’re doubling down on our efforts to create top-quality sleep content.

Most excitingly, we’ve just launched our new 30-day sleep series: a comprehensive, month-long series helping you build healthy bedtime habits and learn tools for a restful sleep.

30-day sleep series MindLabs

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