Sleep — why it matters for optimal health, performance and anti- ageing

Mirthe Precision Health
8 min readJul 28, 2023


Are you the type that thinks sleep is a time waster, not important, and you can ‘sleep when you are dead’? Do you suffer from ‘revenge bedtime procrastination’ — you put off going to sleep to engage in activities that you haven’t had time for during the day at the expense of sleep? Then you might want to read this.

If you are already ‘sold’ on the concept that sleep is important, but suffer from insomnia, trouble falling asleep or staying asleep, despite trying to, then perhaps don’t read this.. as it might just add to your anxiety. Instead, wait for my soon to come write up on ‘Why can’t I sleep, and what to do about it’ with solutions. Xx I have got you!

But for now, all of you that don’t see the importance in sleeping, let’s look at why you may want to reconsider your sleep habits, and work on extending them where these are too short.

First things first. What is the right amount of sleep? Research suggests anywhere between 7 to 9 hours for adults is the sweet spot. Any less, and one runs into trouble, unless you are one of the very rare individuals with a genetic mutation where that may actually not be of concern.

On the opposite spectrum, regularly sleeping MORE than 7–9 hours has been linked to a range of health issues as well. Scientists found that people that habitually sleep longer than 9 hours, seem to have a higher incidence of inflammation and underlying health issues.

This leaves the question whether longer sleep acts as a coping mechanism of the body to try and heal and repair from an underlying issue, rather than in itself leading to health concerns.

For today, we will look at shorter than optimal sleep, and how that affects us. We live in a sleep-deprived society with about 30% of adults now sleeping for a period less than 6 hours per night!

Let’s first have a little excursion into how sleep works, and why it is so detrimental if we don’t get enough.

Our sleep consists of 4 stages, N1 and N2 are considered light sleep, N3 slow wave or ‘deep sleep’, and REM is the rapid-eye-movement stage where we dream. These 4 stages generally last 90–120 minutes, and we should go through these about 4 to 6 times in one night. While there are many benefits to different stages, some of the most prominent ones include:

Deep Sleep (N3):

  • Did you know that our brain had its very own drainage and cleaning system? It’s called ‘glymphatic system’, and helps clear out toxins and metabolic waste like amyloid plaques!

    The build up of amyloid plaques is considered to be one of the culprits of developing neuroinflammation, with possible long term effect being Alzheimer’s!

    When we are in deep sleep, also called slow wave sleep, our brain shrinks a little, allowing the glymphatic system to flush out any built up debris from the day, thereby being a crucial step towards preventing brain decline. (1, 2)
  • Growth hormone production. plays a role in muscle tone, how our bodies collect fat (especially around the stomach area), the ratio of high density to low density lipoproteins in our cholesterol levels and bone density. In addition, growth hormone is needed for normal brain function (3).

REM Sleep:

  • The most commonly talked about function of REM sleep, the dream stage of sleep, is memory consolidation. It is in this stage that our brain stores information for later recall.
  • Research suggests we make most of our testosterone during the REM (rapid-eye movement, ‘dream’) stage of sleep. If we don’t get enough zzzs it can lead to a drop in testosterone production (4)!

Some of the symptoms of low T for both men and women:
👉🏻 Low libido
👉🏻 Low mood / lack of motivation and ‘zest’
👉🏻 Depression
👉🏻 Low muscle tone & metabolism
👉🏻 Weight gain
👉🏻 Low quality sperm and infertility in men

Other wonderful benefits of sleep are:

  • Proper function of GLP-1, a molecule in our gut that helps us respond to food appropriately, balancing blood sugar, hunger and satiety signals. It has recently gained interest due to the ‘weightloss wonder drug’ Ozempic working along the same pathway by mimicking its function. Sleep helps regulate our own body’s production without any potential side effects!
  • Adequate sleep is vital for tissue repair muscle growth and recovery.
  • It allows our body to rid itself of free radical damage (oxidative stress) (5).

But let’s dive into the baddies.

Some of the detrimental effects of short term lack of sleep include:

  • Lowered mental acuity including word recall, focus and sharpness
  • Reduced immune system function, including increased risk of catching a bug
  • Reduced physical performance in sports and workouts
  • Increased susceptibility to binge eating, cravings and making ‘wrong choices’
  • Low grade inflammation (6).
  • Irritability

Did you know that just one night of insufficient quality sleep will have a direct effect not on one’s productivity, but also resilience to both stress and environmental factors such as bugs and food temptations the next day (7)!

After a night of insufficient sleep our body goes into survival and ‘fight-or-flight’ mode. When we are in that state, our brain functions primarily from its ‘survival’ centre in the amygdala in the back of our brain, rather than from the rational, forward-thinking prefrontal cortex. We tend towards ‘decision fatigue’ and can be more prone to make choices that might feel rewarding in the moment, but have negative lasting effects. Be that emotional, cognitive (ie work decisions, the way we handle social interactions, etc) or regarding healthy living efforts and food choices. All of the sudden that burger with fries, or breakfast bagel, or snickers bar look all so tempting — and it becomes that much harder to resist, even if we had previously made the decision to look after ourselves (8)!

Throwing gasoline onto that fire is the fact that after just one night of insufficient quality sleep, our cells turn slightly insulin resistant. I have written in more detail about blood sugar control and insulin in other posts (check them out here if you missed them), but in a nutshell, even if we manage to eat the same healthy-ish meals that day, our body’s response is different to it, making us more prone to blood sugar swings and accumulation of fat around the waist, rather than the energy consumed being utilised properly for fuel.

Not sleeping enough has also been shown to mess with our immune system, both making us slightly inflamed (ie an overreactive immune system via something called IL6 and NLRP3 inflammasome (9)), but also less able to fight of infections, get rid of senescent cells (old, mutated, sick ‘Zombie’ cells that should be cleared), and allowing for ‘immune escape’.

Luckily science suggests that we can indeed catch up on some sleep debt by making sure we go to bed and get those extra zzzs the night after. However, lack of quality sleep messes with our circadian rhythm, changing our internal clock and hormones necessary for alertness during the day and sleepiness at night by lowering morning cortisol (when we want a nice rise) and increasing evening cortisol (when we want it to drop to allow for melatonin production and a restful dozing off to lala land), so it might be harder to get back into a good routine and fall asleep as we should.

In addition, research also proposes that we do actually accumulate our ‘sleep debt’. Meaning that if you consistently only have 6 hours of sleep during the work week (let’s say for this example 5 nights), this would leave you with a sleep debt of at least 5 hours. Trying to get some more sleep over the weekend will help lower that debt. However, realistically it is difficult to get these extra 5 hours back in, as we are usually habituated to waking up at a certain time even without an alarm clock. And even if you do manage to get those added 5 hours over the weekend, then unfortunately these may still not be of the best quality and the right amounts in stage 3 (deep sleep) and REM, and hence not getting all the wonderful benefits that we missed during the week. Plus this may mess with our circadian rhythm even more, and make it that much harder to get back to a good routine on a sunday night! There even is a thing called ‘social jetlag’, where shifting our habits over the weekend messes with our inner clocks like a jetlag would! Meh.

Have you already read enough and are convinced you should try to not only get your beauty, but also your ‘health and performance’ sleep? Fab! But you may want to read on, as what starts of with a snowball of annoying short term symptoms, can turn into a whole avalanche of ill health effects if continued too long.

Research suggests some of the many long term risks associated with low quality and quantity sleep are:

  • Insulin resistance and metabolic syndrome, which are associated with type 2 diabetes, PCOS, cardiovascular disease and more
  • Hypertension/ High blood pressure (10)
  • Stroke (10)
  • Obesity (10)
  • Alzheimer’s (11, 12)
  • Other forms of neurodegeneration
  • Cancers
  • Autoimmune diseases
  • Mood disorders
  • Low testosterone
  • A reduced desire in love making (13)
  • Estrogen dominance in women, with symptoms of estrogen dominance including a higher risk of PMS, painful periods, cysts, fibroids, endometriosis, anxiety and even breast cancer (14).
  • Reduced sperm count and infertility in both men and women, including a higher risk of early pregnancy loss, failed embryo implantation, and missing a period all together (15).
  • And an increased risk of all cause mortality! Ouch!

And if you are yet to have enough reasons as to why sleep is indeed crucial to optimal health, wellbeing and anti-ageing, reduced sleep duration has further been associated with biomarkers of disease (16).

Sold? Wonderful! Enjoy your sleep, and until next time my friend!


PS: As mentioned in the first section, if you struggle sleeping, then stay tuned, as I will shortly publish a post on sleep supporting strategies to help you get your zzzs and stop tossing and turning. Xx

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Mirthe Precision Health

Functional Medicine Practitioner. Hormones, epigenetics, health optimisation. IG/ TikTok/ Youtube/ Fb: @mirthe_precisionhealth,,