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Book Summary – Why We Sleep: Unlocking The Power Of Sleep And Dreams

Why we sleep - Book summary

All living creatures need sleep. The question is: why? In Why We Sleep, neuroscientist and sleep expert Dr Matthew Walker presents groundbreaking discoveries about sleep and how it affects all aspects of our physical, mental and emotional health, including our creativity and longevity. In this free Why We Sleep summary, we’ll outline what is sleep, why you should sleep, and how you can improve your quantity and quality of sleep.

Why We Sleep: An Introduction

Sleep is absolutely essential to all animals, including humans. Insufficient sleep reduces our learning, memory and cognitive abilities, causes brain impairment and increases the risks of numerous diseases from cancer to diabetes, coronary heart diseases and even death. On the other hand, sleep boosts our mental, emotional and physical health and capabilities in ways that no amount of drugs or medical interventions can provide.

Unfortunately, most people in modern societies are sleep-deprived, and we don’t even realize it because we’re so used to operating at sub-optimal levels. It’s time we understand and unlock the transformative power of sleep. Let’s now take a quick look at some of those ideas in this Why We Sleep summary. For more details, do get a copy of our full 16-page summary.

Why We Sleep summary_introduction

What is Sleep?

REM and NREM Sleep

Every night, your brain switches between 2 types of sleep: REM and NREM sleep.

  1. Non-rapid eye movement (NREM) sleep is characterized by deep, slow brainwaves that’re 10x slower than when you’re awake. During deep NREM sleep, we experience a sensory blackout, and our cortex (the logical center of our brain) is relaxed. Your entire brain is now fully aligned to distill and transfer selected memories from your short-term memory (in your frontal lobes) to your long-term memory (at the back of your brain).
  2. Rapid eye movement (REM) sleep is characterized by faster brainwave activity that’s similar to when you’re awake. You brain’s visual, motor, memory and emotional centers are activated, and pockets of feelings, info, memories, motivations etc. are combined into a giant movie screen, i.e. your dreams. Your eyes may move rapidly as you dream.

When we’re awake, we constantly receive new sensory inputs from the external environment. NREM sleep reinforces and stores those raw data and skills. REM sleep integrates these ingredients by connecting them with one another and with our past experiences and knowledge, to improve our mental model of how the world works, develop new insights and solve problems innovatively.Why We Sleep summary_types of sleep

Basically, NREM and REM serve different but equally-vital functions. When you don’t get full 8 hours of sleep, you lose out on chunks of NREM or REM sleep with serious repercussions.

Wakefulness vs Sleepiness

Your wakefulness and need for sleep are regulated by 2 key factors: your Circadian Rhythm and Adenosine levels.

  1. The Circadian Rhythm is your internal body clock that runs in an approximate 24-hour cycle. It’s regulated by melatonin, which is produced by the suprachiasmatic nucleus in the brain, which calibrates your body clock using the amount of light.
  2. Adenosine is a chemical that makes you sleepy. It builds up progressively when you’re awake and most people will feel “sleep pressure” after being awake for 12-18 hours. It decreases as you sleep and is usually purged fully after 8 hours of sleep.

Get our complete Why We Sleep summary for more details on:

  • Your sleep architecture, including (i) the workings of REM vs NREM sleep, (ii) how different phases of your nightly sleep cycle look like, and (iii) what’s a “sleep spindle”; and
  • Your sleep rhythm, including (i) how Melatonin works, (ii) why we have different internal biological rhythms, (iii) how caffeine dulls Adenosine, and (iv) how the Circadian Rhythm and Adenosine jointly drive your cycles of wakefulness and sleepiness.

Ideal Sleep Patterns

Generally, an adult human needs 8 hours of sleep, and an ideal sleep pattern is a stretch of 7-8 hrs at night with a short mid-afternoon nap (to address the natural dip in alertness). Yet, in most modern societies, people only sleep for 1 stretch of less than 7 hours every night. In short, we’re not sleeping enough nor in the way nature intended.

In our full book summary, you can also get more details on (i) sleep in other animals, (ii) how humans sleep differently, (iii) the difference between monophasic and biphasic sleep patterns, and (iv) how our sleep hours and patterns change across our lifespan (from infants to children, teens, adult & old age).

Why We Sleep & Why You Should Sleep

Sleep is the ultimate therapy and enhancer to provide a range of benefits that medicine and other interventions cannot. In our complete version of Why We Sleep summary, we break down exactly how sleep impacts all aspects of your mental, emotional and physical health. In a nutshell:

  • Sleep benefits the brain with 3 main cognitive benefits: (i) improved memory, (ii) improved motor task proficiency or “muscle memory”, and (iii) improved creativity. REM sleep connects your different memories, experiences and skills to create new ideas and insights.
  • Dreams deliver real benefits. REM-sleep and dreams (i) reduce the pain from traumatic events, (ii) helps us decode facial expressions accurately, and (iii) improve problem-solving and creativity.
  • Sleep-deprivation harms the brain to (i) impair memory, (ii) worsen focus/concentration, (iii) worsen emotional control, and (iv) play a role in mental illnesses from psychiatric conditions to Alzheimer’s Disease.
  • Sleep-deprivation harms the body—it damages every aspect of our physiology and is linked to a shorter lifespan and a host of diseases like cancer and heart diseases. That’s because it severely impacts your cardiovascular system, metabolism, reproductive system, immunity system, cancer growth and inflammation, and even genetic activity and makeup.
  • Sleep disorders can disrupt our lifestyle and well-being. Such disorders include somnambulism, insomnia and narcolepsy. At the extreme, sleep deprivation can even cause death.

Improving Sleep Quality & Quantity

On average, half of all adults in developed countries aren’t getting the recommended hours of sleep. We can systematically improve our sleep quality and quantity at individual, educational, organizational, public and societal levels. Get our complete summary to learn about:

  • Various sleep barriers and how to overcome them;
  • How to improve business returns with sleep;
  • Why our school schedules are damaging our kids’ health
  • Why alcohol and sleeping pills hurt rather than aid sleep;
  • Ways to address sleep-deprivation at organizational, educational and public levels; and
  • Tips for improve your sleep hygiene and quality immediately.

Meanwhile, here are 3 simple tips that you can apply straight away to start improving your sleep quality and quantity:

  • Use blackout curtains to keep your bedroom completely dark
  • Take a hot bath (or warm your hands/feet) before bed, to draw heat to the skin surface and reduce your core body temperature
  • Do not consume alcohol close to bedtime: it’s actually a sedative that disrupts REM sleep and causes you to wake up throughout the night.

Getting the Most from Why We Sleep

In this article, we’ve briefly outlined some of the key insights and strategies you can use to achieve desired change. For more examples, details, and actionable tips to apply these strategies, do get our complete book summary bundle which includes an infographic, 16-page text summary, and a 26-minute audio summary.Why We Sleep summary - book summary bundle

This book is packed with useful background, theories, examples and discussions on sleep and its implications, including:

  • Evolutionary and scientific information about sleep;
  • How NREM/REM sleep relate to various biological functions and lifestyle factors; and
  • Detailed insights, tips and ideas on how we can improve our quality and quantity of sleep.

You can purchase the book here for the full details, or check out more resources/details at

About the Author of Why We Sleep

Why We Sleep: Unlocking The Power Of Sleep And Dreams is written by Dr Matthew Walker –an English scientist and professor of neuroscience and psychology at the University of California. His research focuses on the impact of sleep on human health and disease. Previously, he was a professor of psychiatry at Harvard Medical School. He is also the founder and director of the Center for Human Sleep Science. He has received numerous funding awards from the National Science Foundation and the National Institutes of Health, and is a Kavli Fellow of the National Academy of Sciences. He has published more than 100 scientific research studies and has been featured on numerous television and radio programs.

Why We Sleep Quotes

“Sleep is the single most effective thing we can do to reset our brain and body health each day—Mother Nature’s best effort yet at contra-death.”

“There is much that sleep can do that we in medicine currently cannot.”

“Sleep is not like the bank. You cannot accumulate a debt and hope to pay it off at a later point in time.”

“The shorter your sleep, the shorter your life span…The elastic band of sleep deprivation can stretch only so far before it snaps.”

“Ounces of sleep offer pounds of business in return.”

“We as a society must work toward dismantling our negative and counterproductive attitude toward sleep.”

Click here to download the Why We Sleep summary & infographic

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