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Why is sleep important and what are the benefits?

Why is sleep important and why do we do it.jpg
Updated 29 October 2021

The birds do it. The bees do it. We all need to do it. But why DO we all need sleep? 

Key points:

  • A lack of sleep can cause health problems
  • On average, Australian adults get 7 hours of sleep each night 
  • A lack of sleep can lead to poor concentration, mood changes and irritability 
  • Sleep is part of the restorative process, but it’s not the only thing that restores us, resting is just as important

 If there’s ever been a period in your life when you haven’t got enough sleep – work, kids, stress, – you might have wondered why we need it so much. Or why it doesn’t happen when you want it to.

So, what happens if we don’t sleep enough? And what is ‘enough’, anyway? Do we all need a perfect eight hours of uninterrupted sleep each night? Why does a lack of sleep make us so cranky? 

We asked sleep specialist Dr David Cunnington to explain it all.

Sleep is a biological process driven by what's happening in our bodies and minds, which is affected by how we live our days and how we live our lives.

- David Cunnington, Sleep Specialist

Why do we sleep?

“We know that we need sleep to maintain our physical and mental health,” Dr David says. “It’s an important restorative process that all humans need.”

As well as resting your body, sleep is really important for your brain. Far from being a period of doing nothing, sleep is a time when your brain actively organises itself and processes the events of the day.

But beyond that, the evidence for why we need it is, “a bit light on the detail”, Dr David acknowledges. What we do know, however, is that a lack of sleep can cause health problems.

“If we work and play hard but choose not to sleep as much as we need, that lack of sleep may be linked to a host of physical and mental health problems. These include elevated blood pressure, weight gain and low mood, among others.”

Recommended reading: How to sleep better naturally - 7 ingredients for sleep  

What happens during sleep?

If you sometimes have trouble falling asleep, sleep can seem like a mysterious process that just happens when it wants to, thank you very much.

“Sleep is a biological process,” Dr David says. “It’s driven by what's happening in our bodies and minds, which is affected by how we live our days and how we live our lives.”

Neurons in our brain send out signals to switch off the neurotransmitters (brain chemicals) that keep us awake, including serotonin and norepinephrine.

Then, after we fall asleep, our deepest sleep happens during the first few hours. After this, we usually have a light stage of sleep when we’re more likely to dream.

“If you wake in the early hours of the morning and can’t go back to sleep,” Dr David adds, “it’s probably during that lighter sleep stage."

How much sleep do we need?

On average, Australian adults report getting seven hours of sleep at night. But is this enough? How many hours of sleep should an adult get?

The idea of needing eight hours of sleep a night is so ingrained that you might think it’s a biological fact. But culturally, we didn’t always have the ideal of eight hours of sleep a night, Dr David says.

In fact, the eight-hour ideal is a construct of the labour movement in the 19th century: eight hours each for work, rest and sleep. 

Before then, when there was no artificial lighting, people in Europe (and some other cultures) would sleep for about four hours when it got dark. Then they’d have periods of waking in the middle of the night – known as the witching hour. “That’s just what sleep was like for millennia until industrialisation,” Dr David adds.

So don’t stress about whether eight hours of sleep a night is enough. How much sleep each person needs depends totally on that person.  

Instead, he recommends, “putting aside an eight-hour window of time for sleep, without worrying too much about sleeping for that whole eight hours.” He also recommends aiming to sleep for about 85% of the time you’re in bed. 

Why we need sleep (and signs that we’re not getting enough)

Obviously, feeling tired is a sign that you didn’t get enough sleep the previous night. But sometimes, sleep deprivation can have less obvious symptoms.

“Lack of sleep can affect our social relationships, our working relationships and our performance at work,” Dr David says.

So, what happens when you don’t sleep enough? You might experience:

  • poor concentration
  • mood changes
  • irritability
  • poor memory
  • lack of energy
  • reduced sex drive

On a physical level, a lack of sleep can also decrease your reaction times. Combined with poor concentration, that’s a recipe for accidents. It’s also why driving (or operating heavy machinery) when you’re tired is considered as dangerous as driving over the limit.

What’s good sleep hygiene?

Talking about ‘sleep hygiene’, meaning the habits and routines you establish to help you sleep better, has become more common. But Dr David says that there’s no need to get caught up in having exactly the right conditions for sleep. 

“You don’t need a certain lamp or essential oil burner,” he adds. “If you’ve looked after yourself mentally and physically during the day, and you’re prepared for sleep, your body will do its job. It’ll take the sleep it needs during that eight-hour window.”

So what does ‘looking after yourself’ look like? Here are Dr David’s top tips for good sleep habits:

  1. Develop a sleep schedule that works for you.
    Get up at the same time each day, and then let your body’s cues tell you when to go to bed.

    “Start getting ready for bed when you notice your eyelids getting heavy and your head starting to nod - Netflix will still be there tomorrow night!” Dr David recommends.
  2. Take naps if you need to catch up on sleep during the day.
    “Naps are a great way for most people to rest,” Dr David says.
  3. Watch your light levels and screen time.
    Avoid looking at screens or having bright lights in the house in the hour or two before bed.

    The blue light from screens can keep you awake, and bright lights can keep you from producing melatonin, your body’s sleep hormone.

We need rest as well as sleep

Sleep is a part of the restorative process, but it’s not the only thing that restores us physically and mentally. Resting is just as important as sleep, Dr David says.

“Far too often in the modern world, the only time we down tools is when we’re asleep.” But if you only stop when you sleep, he says, there’s a risk of placing too much importance on getting a perfect night’s sleep.

 Instead, add periods of rest into your day. Just a few ten-minute breaks during the day can help you feel restored. And it doesn’t have to be a nap – just switching off for a short time gives your brain a vital break.

If you struggle with not being productive when you rest, remember that resting IS productive for your mental wellbeing. Here are some easy ways of adding rest into your day:

  • Make rest a priority: don’t just focus on night-time sleep – instead, set aside time each day for rest.
  • Prioritise your needs: it’s all-too-easy for women to put their own needs last, but remind yourself that it’s important to look after yourself. 
  • Ignore your to-do list for ten minutes: try to simply close your eyes and do nothing.
  • Try meditation: apps are an easy way of helping you focus, or simply pay attention to your breath for a few minutes.
  • Do something that brings you joy: walk outside, talk to a friend or listen to music.

Your stress levels also affect your ability to rest and sleep, so improving your mental wellbeing, managing stress and practising mindfulness can all help.


Dr David Cunnington is a specialist sleep physician who helps his clients to treat their complex sleep problems while also promoting sleep health through education, research and advocacy.

Reviewed by the healthylife Advisory Board June 2021