Understanding Sleep – The Main Takeaways from Matthew Walker’s Why We Sleep

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Why We Sleep provides an incredibly useful scientific perspective on sleep. It’s written by Matthew Walker, a sleep scientist, researcher and professor. And it’s a comprehensive look into the topic of sleep:

  • The differences in sleep in the animal kingdom
  • The evolution of human sleep
  • The neuroscience and biology of sleep and the functions of the mind and body affected by sleep
  • The differences between Rapid Eye Movement (REM) sleep & n-REM sleep
  • Findings from the latest research
  • Society, Culture and Sleep

The book, whilst providing valuable knowledge, is a little arduous if you’re mainly interested in extracting practical takeaways. In this article, we highlight these main takeaways in a snappy and (hopefully) practical format.

Sleep is NOT a complete brain turning off activity

Activity in certain parts of the brain actually ramp up during REM sleep. In particular, The Limbic System (mainly the hypothalamus, the hippocampus and the amygdala) shows increased acitivity and it’s these areas of the brain that are related to emotional regulation and forming memories.

The prefrontal cortex, the part of the brain responsible for logical reasoning, “turns off” during REM sleep.

Having a regular sleep time naturally fits the biology of our internal biological clocks

Human Beings have a natural biological clock or Circadian rhythm that determines times of sleepiness. It’s why we tend to get sleepy at the same time each day. And why we suffer from jet lag when we travel.

Going to sleep at the same time each day naturally fits the timed release of melatonin: the hormone that signals the body to fall asleep.

Belief or opinion is not an accurate measure of one’s sleep time and quality

Sleep studies show that participants who believe they had an adequate night’s sleep didn’t necessarily display improved performance in completing a task of some sort.

Whereas, sleep time and quality has been shown to positively correlate to performance in the completion of a huge variety of tasks in several studies.

What this reveals is that: opinion and observation is not an accurate determinant of an adequate amount of sleep.

Practically all human functionality is affected by lack of sleep

Lack of sleep has been shown to:

  • Reduce attentional ability in completing tasks
  • Negatively impact working memory function
  • Negatively impact emotional regulation  
  • Correlate to the contraction of Cancer & Alzheimer’s disease

Alcohol, Tobacco and Caffeine all negatively impact the ability to fall asleep and sleep quality

Image for Alcohol, Tobacco and Caffeine all negatively impact the ability to fall asleep and sleep quality
  • Alcohol can sedate but an excessive amount prevents the ability to enter REM sleep: the deep dream sleep.
  • Caffeine affects the release of melatonin: the hormone that regulates sleep (as stated above). IN studies it has been shown to have an effect on quality and quantity of sleep as long as 8 hours before sleep.
  • Smoking before sleep also negatively impacts quality and quantity of sleep.

The majority of REM or deep dreaming sleep occurs in hours 6-8 of sleep

Sleep, as you might be aware, occurs in two recurring cycles of REM and n-REM sleep. The majority of n-REM sleep occurs in the first few hours of sleep. Whereas, the majority of REM sleep occurs in hours 6-8 of sleep.

Both types of sleep are vital. However, it is REM sleep that is linked to forming long-term memory. There are in fact 4 stages of REM sleep. And it’s stages 3 and 4 that are related to memory formation and general emotional well-being. These are stages are vitally missed if you only sleep 6 hours a night.

REM sleep is linked to “creative” insights that “connect the dots” of disparate pieces of information. Not to mention, it is REM sleep that has a real impact on emotional intelligence.

Emotional iQ is vital when dealing with stress and tilt. Your capacity to deal with adversity is greatly impacted by lack of sleep; something which, if you are self-aware, you will have undoubtedly have noticed from your own experience.  

You cannot repay sleep debts by catching up on later days

Repaying sleep debts is a fallacy. Binge sleeping after periods of little sleep does NOT fully restore the damage created by the lack of sleep.

Your sleep environment has a direct impact on the quality of your sleep

  • Using LED devices like iPads and smartphones even two hours before sleep can have a significant impact on the quality of sleep. It’s the shorter wavelength, blue light that is damaging. As it delays the release of melatonin. There was a study conducted on iPad readers vs book readers. And those that read on an iPad in the hour before sleep had a 3-hour delay of melatonin release.
  • Core body temperature has to reduce before you fall asleep. And so sleeping in a cool room at 18 degrees. Having a warm wash before sleep also aids sleep as it reduces core body temperature.
  • A dark room helps to induce the release of melatonin as it is intrinsically linked to sunlight and light in general. Black-out curtains provide the best solution in this regard.

Mid-afternoon naps of 30-60 minutes provide useful benefits

They have been shown to have:

  • Measurable benefits to cardiovascular health
  • Correlate to improved performance on memory-based tasks: improving alertness, concentration and learning.

Naps, however, cannot be used to make up for a short night’s sleep as sleep debt cannot be fully repaid as noted above.

However, taking naps after 3pm can affect night time sleeping so avoid those.

Diet and Meal Timing does have an affect on sleep

The general advice from Matthew Walker is to neither sleep too full or too hungry. Sleeping directing after eating doesn’t allow the body to shut off as the digestive process is in full motion. Whereas, sleeping on an empty stomach can cause you to wake up too early disrupting the cycles of sleep.

All in all, this likely means to eat 2-3 hours before falling asleep.

When it comes to specific diets, scientific studies haven’t as yet rigorously looked at the effects on sleep quality and time due to specific diets like the ketogenic or paleo diets.

However, what is known is that diets high in sugar and low in fibre are poor for sleep. They are linked to more fragmented and less deep sleep.

Emotional distress is one of the main causes for poor sleep

Image for Emotional distress is one of the main causes for poor sleep

If you regularly struggle to get to sleep it likely is due to an overactive
sympathetic nervous system (SNS), emotional distress and/or ruminative thinking.

The SNS is also known as the fight or flight system. The SNS releases cortisol, adrenaline and neuro-adrenaline. All three increase metabolic rate and core body temperature.

For good sleepers, activity in the hippocampus and the amygdala ramps down before sleep. This isn’t the case for insomnia patients. Insomnia patients struggle with a patterned ruminative worrying activity.

NOTE insomnia is actually very rare and to self-diagnose yourself can be false and detrimental. If you are experiencing sleep problems then it is always best to see a sleep specialist. It’s also good to be aware of the fact that there is a sleep course, Cognitive Behavioural Therapy for Insomnia (CBTI) that has shown real results in rigorous scientific studies.

With all of this combined, one can infer it is highly beneficial to release the experience of what happened in the day and to allow yourself to effectively ‘switch off” and “relax” before you fall sleep. Guided meditations and yoga likely provide real switching off benefits. Although these are not touched upon in Why We Sleep.

Another VERY IMPORTANT NOTE is that sleeping pills most likely do not put you in a natural state of sleep i.e. they do not allow you experience the natural n-REM and REM sleep cycles.

The field of sport understands the value of sleep

Image for the field of sport understands the value of sleep

If sleep were a legal drug in sport, every athlete would be popping it. Matthew Walker reveals in the book how he has consulted NBA teams on the benefits of sleep.

The time spent asleep, as an independent factor, has been shown to improve performance in movement-based sport by 20-30%.

And in a recent podcast interview, LeBron James and his trainer revealed how seriously they take sleep; always ensuring 8 hours of sleep in the sleep environment described above.

General society and culture does not have a well-informed perspective on sleep

We tend to value those people who sleep only a few hours a night; associating this information to success and high achievement.

If you take an objective view at the statistics however, they reveal how sleeping more is positively correlated to higher incomes. Not to mention better health. 

The Main Takeaway – Sleep 7-9 hours every night

These are the main practical takeaways from a great resource for clearing up any ignorance you may have surrounding this vital aspect of human existence. If you have the time, then please do read Why We Sleep as it provides an invaluable knowledge on this vital aspect of human existence.

Or if you have two hours, then Joe Rogan’s podcast with Matthew Walker provides the main insights from the book from the man himself in a shorter audio format.

As a final note, Lions sleep 16 hours/a day. LeBron James sleeps 8-9 hours a night.

If you work long hours, “hustle hard” or believe, “sleep is for the weak”, hopefully (and for the benefit of your health and performance), this summary or a full reading of Why We Sleep stops you in your tracks.