“NEWS JUST IN… There has been an amazing breakthrough. 

Scientists have discovered a revolutionary new treatment that helps you live longer, enhances your memory and makes you more creative. It keeps you slim, improves your skin and reduces food cravings, and wards off dementia, colds and flu.  It lowers your risk of heart attack and stroke, wards off diabetes and makes you feel happier, less anxious and depressed… 

These are not the outcomes of a proven wonder drug but simply the scientifically backed up benefits of getting enough sleep”.

(From the book “why we sleep” by Matthew Walker)

How Much Sleep Do we Need?

7-9 hours in bed – less and your body, mind and soul are all impacted:

  • Sleep is a fundamental part of better health
  • Consistently less than 7-9 hours and you will increase risk factors
  • Even if you feel you function on 6 – I’m sorry you are wrong, email me at chris@habitual.hk and I’m happy to “discuss”

Why do we sleep?

Biological processes creating a ‘drive’ to want to sleep.

  1. Our bodies internal clock* (circadian rhythm), directed by the SCN (suprachiasmatic nucleus) in the hypothalamus (Brain), in response to
  2. Increased melatonin secretion (from the pineal gland) spiking at night time (due to the dark) increasing the drive to sleep – It is not know exactly how this works.
  3. Increased adenosine levels from daily activity (it is a side product of energy production) increase the drive to sleep through inhibiting arousal levels (yes why we feel tired after a work out).
  4. Decreased body temperature due to hormonal responses and typical external temperature over 24 hours. (also linked to melatonin)

*Note the actual cycle is different for all, some get sleepy early, some late – the key is knowing what works for you.

How do we sleep?

We sleep in cycles of around 90 minutes, working between

  1. NREM/deep sleep (Not Rapid Eye Movement sleep)
  2. REM sleep (Rapid eye movement sleep)

Fig 1

What happens when we sleep


  • The body recovers from the days stresses: 
    • Hormones are released e.g., testosterone for growth**
    • We clear waste built up
    • We resupply energy stores
  • We physically get ready for the next day or part of the day (napping post workout is a great way to increase the training benefit – Usain Bolt broke the 100m world record after a nap).
  • We mentally recover and store new learnings from the day.


  • We process emotions, this is why all things feel better after a good night’s sleep; (interestingly this is missing for those who suffer from PTSD – Post Traumatic Stress Disorder)
  • We make sense of facts; (during NREM we file the facts (crystallized intelligence), during REM we make connections between them (fluid intelligence).

**Note here for those who want to take sport seriously or simply get big muscles – if you fail to sleep well you will NOT get the full benefit of your work out!

What happens when we get less sleep?

A lack of sleep will alter recovery.

If you do not get enough hours in bed, the body will concentrate on physical recovery (NREM sleep) at the expense of mental recovery (REM sleep).

This means if you stay up late to do work – you will not efficiently remember, recall or be able to make links to your knowledge; your  creativity will be reduced and you will be less emotionally stable.

  • A lack of sleep is compounding, tiredness leads to poor habits and practices that lead to more poor sleep 
  • You are less efficient throughout the day as your prefrontal cortex shuts down (the human part of the brain) leading to an increase in  emotional direction, leading to poorer decisions which leads to poorer sleep
  • This is a vicious cycle.

What impacts sleep?

There are 5 main impacts on sleep.

  1. Light/screens:
    1. Delay your body’s internal clock (your circadian rhythm)
    2. Suppression of melatonin
    3. Delays in the onset of REM sleep 
    4. Reduction of the total amount of REM sleep
    5. Increases your alertness when you should be getting sleepy
    6. A lack of alertness the next morning 
  2. Alcohol:
    1. It is a sedative – you pass out not sleep
    2. It fragments sleep – you wake up numerous times in the night (you are sedated so don’t notice) 
    3. Which impacts sleep cycles preventing mental and physical recovery
    4. It impacts REM sleep heavily (mental recovery and learning)
    5. Takes many hours to leave your bloodstream 
  3. Caffeine
    1. Not everyone drinks coffee but add dark chocolate, teas, energy drinks, soda’s and you can see caffeine is a widely used drug.
    2. Caffeine mutes the signal of adenosine decreasing our drive to want to sleep.
    3. After 5-7 hours about 50% of the Caffeine is still in the system (we call this a half life)
    4. After 11-13 hours about 25% of the Caffeine is still in the system (we call this a quarter life)
    5. Some of us are more sensitive to caffeine than others, this is genetic.
  4. Travel/shift work/weekends
    1. Disrupt your circadian rhythm
    2. International travel is pretty obvious
    3. Depending on your habits weekends can put you out by 2-3 hours from late nights and lie ins.
  5. Stress
    1. Stress raises cortisol (fight or flight) .
    2. Cortisol impacts hormonal response and brain activity
    3. You can not get into deep sleep and wake frequently

How do I know if I get enough sleep?

The following is a self assessment tool for you to measure and track sleep health.

  • Read each statement and choose the response that fits you best right now – rarely (0), sometimes (1) or usually/always (2) 
  • Add up your total score based on your responses out of 10
  • The higher the score the better your sleep health
  • It is subjective (i.e., your opinion) but when you compare yourself with yourself it provides useful data on sleep progress

What do I do with that information?

It depends.

  1. What do you want to do with it?
  2. Do you want to make any changes?
  3. Are you ready to make a change?
  4. Are you willing to do something different?*
  5. Are you able to make space for some change?

*for many the answer is no, as change means accepting what you are doing, is not working.

What can I do to embrace change?

Work with what you have, no matter how small that space is.

To accept what you are doing is not working brings about judgement from yourself. Are you willing to be vulnerable and open yourself for that judgement?

Put another way – are you able to accept you have not got everything figured out ‘yet’ but are willing to allow yourself to grow lean and adapt using the resources, strengths and time available to you? Are you willing to let go of the fixed views of why you can not change and allow in the why you can?

Next Week, Sleep, Part 2 – Practice.


Buysse D. J. (2014). Sleep health: can we define it? Does it matter?. Sleep37(1), 9–17.

Walker, M. P. (2017). Why we sleep: Unlocking the power of sleep and dreams.

Spread the love
  • 37
  • 3

2 Responses

Leave a Reply

Your email address will not be published. Required fields are marked *