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What happens if we don’t get enough sleep? What I learned from a Sleep Expert.

Updated: Mar 1, 2023

For Sleep Month 2023, I caught up with New Zealand Sleep Expert Kim Corley, who answered my question:

What happens if we don’t get enough sleep?


That’s a great question, because when our lives get busy – sleep is often the first thing that gets sacrificed. It’s one of those things that we don’t think about until it’s gone, or until we start having chronic sleep issues.

But not getting enough sleep impacts EVERYTHING.

Indeed, Dr William Dement (the late founder of Stamford University Sleep Research Centre and author of the book “The promise of sleep”) has conducted research that suggests that sleep is the single most important factor in predicting how long people will live. This is over and above things like diet, exercise or hereditary factors. So not getting enough sleep can have significant consequences.

This has been backed up by an Otago University study right here in NZ – Did you know that a good sleep intervention (basically educating parents and prioritising sleep) – was better at preventing obesity than healthy eating or exercise interventions? (1)

But back to not getting enough sleep.

Let’s start with one night of limited sleep. We started talking after the recent storm which had kept us both awake that night (luckily that’s all we had to contend with). How did we feel the next morning?

Slower, with some brain fog. The first thing we talked about was that we weren’t really on our game, right? “Not feeling strong in the brain department”. Just not sharp. Or focused.

Now the truth is, one bad night isn’t the end of the world. Yes, we can feel sluggish and have trouble making decisions, and our day isn’t as rose tinted as it could be. But our standard capabilities are still available to us. Especially if we’re doing something novel or different to usual. We can get by. No issue.

But the thing is – if we don’t catch up on that lost sleep, the issues start compounding. And we start falling into sleep debt.

What sort of issues does sleep debt bring? What can we expect if we don’t catch up on sleep?


It can start quite minimal – let’s say we miss 1 or 2 hours a night, but then life is busy, so the next night, we also lose an hour or two. Maybe we choose to watch TV for longer (or our young children wake too frequently) and we’re running on 6 hours of sleep a night instead of the 7-9 we actually need. This debt starts mounting.

The interesting thing is that when we start receiving less than 7 hours of sleep a night – our bodies start feeling the effects of sleep deprivation. So less than 7 hours of sleep starts impacting our health (BTW, the figure used to be 6 hours a night, now as we learn more about the importance of sleep, we know that 7 hours a night really is the minimum needed to function well).

Here are just some of the impacts of that sleep deprivation:


1. It’s often the effects on our mood we’ll notice first (or, if we don’t notice, other people will notice). When we’re tired we become grumpy and argumentative. And that’s a big bummer for our relationships, as it’s those closest to us that often get the fallout. Lack of sleep really amplifies the negative emotions (particularly anxiety and depression).

2. Then it starts impacting our memory. When we sleep, we strengthen our neural pathways and consolidate learning into memory. Without enough of that, our memory starts failing us. And so does our judgement. It becomes harder to make decisions. Even deciding what to have for dinner becomes a mission. OK, dinner may not be a big deal, but what about when we’re driving? Is there enough time to pull out in front of that car? When we’re sleep deprived, our reactions are slower too. Our overall performance is impaired.

3. Let’s put that impaired performance in context. The US Centres for Disease Control and Prevention (the CDC) state that staying awake for 17 hours is similar to having a blood alcohol concentration (BAC) of 0.05%, which is the legal blood alcohol limit in NZ. Quite simply, it is illegal and dangerous to drive with a BAC over the 0.05% driving limit. (2)

If we increase that to staying awake for 24 hours, our performance is similar to having a BAC of 0.10% (double the limit). I’m not making this up. Driving tired is like driving drunk. It’s dangerous.


4. But it’s not just our brain that is affected. If we are lacking sleep, especially deep sleep, we are much more likely to get sick as our immune system will suffer. It just can’t keep up. Indeed, deep sleep is involved with a number of physical functions like cellular repair along with a multitude of hormones that affect our sleep/wake cycle, but also reproduction, weight and hunger.

Did you know that Human Growth hormone is released in deep sleep? This is what helps our children grow, but also has a role in normal body structure and metabolism in adults. Lack of sleep can be responsible for failure to thrive in babies (it’s not just about eating). Continue missing sleep and we’re encouraging a whole lot of imbalances in our body in terms of our hormones and chemicals.

Another really interesting point is how sleep deprivation affects behaviour, especially in our children. An overtired child is an impulsive hyperactive child.

Sleep deprivation actually mimics the affects of ADHD in children.

Overtired is when we go beyond tired. Our bodies rev back up again - effectively our second wind. It's as if our brain thinks "Uh-oh, for survival we need to stay awake" – and it floods our bodies full of stimulating hormones – typically cortisol. This second wind happens when you’ve passed the optimum window for sleep. You’ll find in these cases a child can’t focus or keep still; if we’re talking babies they will typically cry a lot. When I work with families, I see a lot of overtired children!

(At this point Dionne is thinking - This sounds like me when I ignore my yawns and eye-rubbing because I feel I 'deserve' another half hour of 'me time' to watch TV without the kids. But then the second wind kicks in and, instead of just watching one programme then heading to bed, I now feel too awake and make not such great decisions, like having a cup of tea and a snack, checking emails and other things that delay my sleep by about 2 hours!)

So now I asked:

Ok so overtiredness is interesting – does it affect adults as well as children?


Yes, it is possible for an adult to get overtired – but of course we have a much better tolerance than a child. So it’s harder to see. However, if you’ve ever done a night shift and been exhausted and gotten a bit silly – you’re likely there!

For overtired adults we start seeing more chronic signs of high cortisol. Cortisol has got a bad rep as a stress hormone. But it’s also a natural waking hormone. However, if you’re living on excess cortisol you can start having trouble going to sleep or staying asleep. Cortisol is produced by our adrenals, and if you’re pumping out too much you can start sliding into adrenal fatigue. Having the right cortisol balance is essential for our health, and producing either too much or too little cortisol can cause problems.


That sounds like a whole other topic that my tired brain might have to ask about another time!

Thanks Kim for answering my sleep questions.

If you'd like Kim to offer you some personalized advice based on your unique needs, you can schedule a free consultation with her at

Kim is the founder of Cherished Sleep, Mum to two gorgeous school-age children, and certified Sleep Sense™ consultant. She knows that it’s hard to enjoy your child and really be there for them when you’re exhausted – let alone be your best at work or take care of all your other family and household responsibilities.

Kim’s qualifications include a Bachelor of Science (BSc), majoring in Psychology and Pharmacology, along with post-graduate Health Science papers, and NZQA certificates in adult education and mental health. Prior to becoming a Sleep Consultant, Kim was a trainer for the NZ Police Emergency Communication Centres, so she is well equipped to help you solve your sleep crisis. These days you’ll also find Kim mentoring new Sleep Consultants as they start up around the world.


March is Sleep Month. In recognition of that, for the whole of March 2023, we have two of our most popular Sleep Support products on special.

SO Mg Magnesium Oil with Lavender is the little addition to your evening bedtime routine that can have a BIG impact on your well-being. Normally $23.50, it's only $17.50 during Sleep Month.

You'll also find SO Mg Magnesium Oil in our Tranquil & Thankful Sleep Support Gift Set, along with a pouch of SO:Relaxing bath soak and a mini gratitude diary from Awesome Inc. Normally $48.50, it's only $36.50 in March.


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