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Does sleep deprivation matter?

Dr Carmel Harrington
A mum comforts her yawning baby

What happens to your body when you don't get enough sleep?

A mum comforts her yawning baby

If you find you’re often tired all day, constantly yawning, feeling cranky and struggling to concentrate, you might be one of the 33-45% of adults who regularly experience poor sleep quality.

How much sleep should I be getting each night?

While everyone’s needs are different, most of us need somewhere between seven and nine hours of sleep a night, says sleep physician Dr Carmel Harrington, author of The Complete Guide to a Good Night’s Sleep.

“If you need eight hours and you’re getting one hour less than that on a regular basis, you would be deemed sleep deprived.”

After as few as three or four nights of reduced sleep, you can start to feel so tired that you can’t think straight, says Carmel – and there are significant health impacts.

What happens to your body when you don’t get enough sleep?

Here are some of the most common effects of sleep deprivation:

1. Fatigue

When we’re not getting our recommended hours of sleep on a regular basis, it shows, explains Carmel.

“Your behaviour, your mood and your cognitive ability changes. You’re not a good decision-maker, you’re more of a risk-taker, you’re foggy headed, you can’t join the dots and you’re not as rational.”

2. Moodiness

You may also find that your emotional responses are out of proportion, she says.

“You’re much more likely to react from the emotional centre. You get more annoyed, you’re grumpy or you’re less tolerant.”

3. Inability to concentrate

Other sleep-deprivation effects might include reduced alertness, shorter attention span, slower reaction times, poorer judgement, memory and concentration as well as reduced motivation and productivity at work and making more mistakes.

A man sitting on the side of his bed stretches his arms out as he yawns

4. Increased appetite

Research has shown significant links between skipping your recommended hours of sleep and weight gain.

“The relationship between sleep and good metabolic function is really, really fundamental,” says Carmel.

The Nurses’ Health Study – which followed around 70,000 women for 16 years – showed that women who slept for five hours a night were 32 per cent more likely to gain 15kg or more than those who slept for seven hours or more a night, and were 15 per cent more likely to become obese.

The exact reasons aren’t known, but there could be several factors at play. Lack of sleep causes changes in the hormones that tell us when we’re hungry (ghrelin) and full (leptin). So, if you’re tired, you’re more likely to feel hungry and eat more, and tiredness can also lower our metabolic rate and affect insulin production.

Excessively tired people might also find that they simply don’t have the energy to exercise, so they’re not burning as many kilojoules and if they’re awake longer, they may also eat more.

5. Mental health issues

There are also links between mental illness and lack of sleep.

“If you have sleep issues, you’re more likely to have depression – and if you have depression, you’re more likely to have sleep issues,” says Carmel of the relationship between the two.

“And there’s a good reason mental health is tied in with our sleep. When we sleep, we reset our emotional balance and if we’re not resetting that emotional balance, or other things are happening at the same time, this can send us into a negative-mood state and then it spirals.”

6. Microsleeps

Tiredness can also cause ‘microsleeps’ – unintended periods of sleep that can last from a few seconds to a few minutes.

It’s easy to imagine the consequences of a microsleep while driving. Fatigue-related crashes are twice as likely to be fatal, as drivers who are asleep can’t brake – and in New South Wales alone, more people died in fatigue-related crashes from 2013 to 2017 than drink-driving crashes.

“We know from research that 18 hours of maintained wakefulness is equivalent to being legally drunk, because your prefrontal cortex starts to shut down,” says Carmel. “So, let’s say you’re awake from 6am to midnight – if you got an early start and you’re driving home after a late-night dinner on the same day, your performance in the absence of any alcohol consumption is equivalent to being legally drunk.”

We know from research that 18 hours of maintained wakefulness is equivalent to being legally drunk

What can you do to sleep better?

If you’re not getting the recommended hours of shut-eye, it’s time to make sleep a real priority in your life.

“One of the simplest things I talk about is our 24 hours in a day,” says Carmel. “We can roughly divide the day between eight hours’ work, eight hours’ play and eight hours’ sleep. Now, lots of us work for longer than eight hours – let’s say we work 10 hours.”

Many people take two hours from their sleep rather than from ‘play’, she says – and that’s where we need to start prioritising the eight hours of sleep.

“If I have to, or choose to, work for 10 hours, then I only have six hours of play. I might have to forego my one-and-a-half-hour exercise and just do 15 minutes of star jumps,” she advises.

For some of us, however, no matter how hard we try, we still can’t sleep. If you’ve tried making sleep your priority, including creating the right conditions for a good night’s sleep, and it’s not working, it’s time to visit your GP, says Carmel.

“People think, ‘Oh, it’s only sleep.’ But ‘only sleep’ is really important – it underpins our health.”

For more tips and advice on how you can increase your odds of a good night’s sleep, check out our article How to sleep better.

Please note: The tips throughout this article serve as broad information and should not replace any advice you have been given by your medical practitioner.

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Dr Carmel Harrington

Dr Carmel Harrington is a sleep scientist who, over the past 25 years, has extensively researched the processes and functions of sleep. Good sleep is a fundamental need that underpins physical and mental health, without it we suffer significant consequences. She believes it is time to wake up to the wonders of sleep.