Why We Sleep
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Why we Sleep | Mathew Walker

22 mins read

The Book Review

We all have done all-nighters at some point in our lives. Being a software developer in the early eighties, long coding hours / all night coding was the norm in those days.  Sometimes “couple of nights in a row” too. We felt that sleep was for the lazy bums and not for people who are purpose driven. The same philosophy exists today in most start-ups where highly motivated and driven young people are continuously working and staying awake dependant on caffeine and adrenaline to meet their targets. Little do we realise that long working hours / all-nighters, combined with almost never getting eight hours of sleep, takes a big toll of our health.

Matthew Walker in his fascinatingly readable book explains – how neglecting sleep affects your creativity, problem solving, decision-making, learning, memory, heart health, brain health, mental health, emotional well-being, immune system, and even your life span. “The decimation of sleep throughout industrialized nations is having a catastrophic impact,” he writes.

This book is my first read on subject of sleep and I found it as comprehensive and compelling compendium of nearly all research till date on the subject. It has forced me to believe that our ability to sleep well offers huge health advantage. It addresses in detail all issues surrounding sleep. The author provides an insight on how sleep affects cognitive and physical performance in both the short and long term, and what you can do improve your own sleep including avoiding things causing bad sleep.

The main import of the book is that sleep is vital for many functions of the brain and body, including memory, problem solving, attention, immune function, growth, and the effective and efficient functioning of most of our organs. Hence everyone needs at least seven if not eight hours sleep a night. Sleep deficiency or poor quality of sleep leads to many ailments like dementia, raised blood pressure, heart disease, stroke, cancer, road traffic / other injuries, and makes us prone to infections. In layman terms these are the most common causes of morbidity and mortality.

Walker says that many celebrities boast of less sleep and we admire people like Margaret Thatcher and Ronald Reagan who said they slept only four-five hours. His research proves that people who can sleep so little and not suffer long-term damage are extremely rare. Both Margaret Thatcher and Ronald Reagan succumbed to dementia.

An interesting anecdote from the book was when he refers to a paediatrician talking to the parents of a new born – “From this moment forth, and for the rest of your child’s entire life, he will repeatedly and routinely lapse into a state of apparent coma. It might even resemble death at times. And while his body lies still his mind will often be filled with stunning, bizarre hallucinations. This state will consume one-third of his life and I have absolutely no idea why he’ll do it, or what it is for. Good luck!”

The author severely reprimands the public-school system that forces adolescents to attend school at 7.30am. He says that the educators and education administrators have failed to understand simple sleep biology – an adolescents’ diurnal rhythm runs three hours behind those of adults, implying that getting up at 6am each day to get to school by 7.30am feels like getting up at 3am for an adult.

Sleep is a basic and often neglected activity that humans have evolved for over two million years to sleep eight hours a night and it affects all of us. A strongly recommended read for everyone.

Book Summary

In the next few paragraphs, I will summarise the book and bring about key takeaways for most readers who may not have the time to read the book in full.

The book is organised in four parts, each part addressing a particular aspect of sleep.

  • Part 1: This Thing Called Sleep
  • Part 2 – Why Should You Sleep?
  • Part 3 – How and Why We Dream
  • Part 4 – From Sleeping Pills to Society Transformed

Part 1: This Thing Called Sleep

Comprising five chapters this part is an introduction of sort for sleep. What is it, what affects it etc.? Walker emphasises the need to sleep and says that shorter sleep leads to shorter life spans since sleep resets our brain and body health each day.

There are two factors that determines when a person sleeps or wakes up. Circadian rhythm is one of the factors where melatonin helps regulate the timing of sleep. Sleep pressure caused by build-up of adenosine in your brain is the second factor affecting sleepiness. To identify sleep deficiency, answer these questions: 1) Would you wake up on time without an alarm clock? 2) Do you find yourself re-reading things? 3) Can you function optimally before noon?

An important takeaway from this part of the book is that we cannot sleep back which we have previously lost and its consequences are explained in later chapters.

In the section “How Should We Sleep?” Walker describes how the modern world has taken to “monophasic sleep pattern” – where people take long single bout of sleep at night usually seven-eight hours which is now reduced in most cases to less than seven hours. The author presents the case where tribal and hunter gatherers in Kenya and Kalahari Desert who are untouched by electricity have a “biphasic sleep pattern” – where they take a long sleep of seven to eight hours at night and a thirty – sixty minute nap in the afternoon. The author also points out the improved health of some areas of Greece like Ikaria where afternoon siestas are a norm.

REM sleep as per Walker, fine-tunes the emotional circuits of the human brain and fuels creativity. Alcohol is one of the most powerful suppressors of REM sleep.

This part also explains in detail as to how sleep changes across a person’s life span. Importance of sleep in brain development of a child / adolescent is clearly established. It is a myth that older adults need less sleep. Discussion on sleep of middle aged and seniors aged person is illuminating to read.

Part 2 – Why Should You Sleep?

This part of the book focusses on benefits of sleep for the brain, affect of sleep on memory and creativity and affect of sleep derivation on the overall heath with special reference to its effect on cardiovascular health, obesity, reproductive health and immune system.

It has been clearly established that sleep aids memory: both before learning, to prepare your brain for initially making new memories, and after learning, to cement those memories and prevent forgetting. Sleep is most essential for creativity.

Research also points to some devastating effects of sleep loss on human health. Like Walker says, “No facet of the human body is spared the crippling, noxious harm of sleep loss.” Sleep loss is linked to numerous neurological and psychiatric conditions (e.g., Alzheimer’s disease, anxiety, depression, bipolar disorder, suicide, stroke, and chronic pain), and on every physiological system of the body. Diseases like cancer, diabetes, heart attacks, infertility, weight gain, obesity, and immune deficiency have proven linkages to sleep loss.

Concentration is one of the brain functions that gets impacted with the smallest dose of sleep deprivation and is one of the leading causes of drowsy driving which has fatal consequences across the globe. Some illuminating facts strongly highlighted in the book are:

  • Humans need more than seven hours of sleep each night to maintain cognitive performance.
  • After ten days of just seven hours of sleep, the brain is as dysfunctional as it would be after going without sleep for twenty-four hours.
  • Three full nights of recovery sleep are insufficient to restore performance back to normal levels after a week of short sleeping.
  • The human mind cannot accurately sense how sleep-deprived it is when sleep-deprived.

Part 3 – How and Why We Dream

Emotional concerns are what have been found to correlate most with our dreams. In the chapter, Dreaming – The Soothing Balm Walker states that “REM sleep is the only time during the twenty-four-hour period when your brain is completely devoid of this anxiety-triggering molecule. Noradrenaline, also known as norepinephrine, is the brain equivalent to a body chemical you already know and have felt the effects of adrenaline (epinephrine).” He goes on to state that, deep NREM sleep strengthens individual memories, but it is REM sleep that offers the complementary benefit of fusing and blending those elemental ingredients together, in abstract and highly novel ways. Key takeaway from this part is that dreaming is essential, and it is the Creative Incubator for human beings.

Part 4 – From Sleeping Pills to Society Transformed

This is one of the most practical and informative part of the book. Insomnia, as per the author, is one of the most pressing medical issues facing modern society, yet few speak of it this way, recognize the burden, or feel there is a need to act. In addition to longer commute times and sleep procrastination caused by late-evening television and digital entertainment, Walker brings out the following factors which are preventing us from sleeping – 1) constant electric light as well as LED light 2) regularized temperature 3) caffeine 4) alcohol 5) a legacy of punching time cards.

Sleep and Electric / LED Light. Compared to reading a printed book, reading on an iPad suppressed melatonin release by over 50% at night. iPad reading delayed the rise of melatonin by up to three hours, relative to the natural rise in these same individuals when reading a printed book.

Due to its omnipresence, solutions for limiting exposure to artificial evening light are challenging. A good start is to create lowered, dim light in the rooms where you spend your evening hours. Avoid powerful overhead lights. Mood lighting is the order of the night. Some committed individuals will even wear yellow-tinted glasses indoors in the afternoon and evening to help filter out the most harmful blue light that suppresses melatonin.

Maintaining complete darkness throughout the night is equally critical, the easiest fix for which comes from blackout curtains. Finally, you can install software on your computers, phones, and tablet devices that gradually de-saturate the harmful blue LED light as evening progresses.

Sleep and Alcohol. In addition to its artificial sedating influence, alcohol dismantles an individual’s sleep in an additional two ways. First, alcohol fragments sleep, littering the night with brief awakenings. Alcohol-infused sleep is therefore not continuous and, as a result, not restorative. Most of these night-time awakenings go unnoticed by the sleeper since they do not remember them. Second, alcohol is one of the most powerful suppressors of REM sleep that we know of.

The evidence of harmful effects of alcohol is extraordinarily strong. Many people enjoy a glass of wine with dinner, even an aperitif thereafter. But it takes your liver and kidneys many hours to degrade and excrete that alcohol, even if you are an individual with fast-acting enzymes for ethanol decomposition. Nightly alcohol will disrupt your sleep, and the annoying advice of abstinence is the best, and most honest, I can offer – says Walker.

Sleep and Temperature. Thermal environment, specifically the proximal temperature around your body and brain, is the most underappreciated factor determining the ease with which you will fall asleep, and the quality of sleep you will obtain. Ambient room temperature, bedding, and nightclothes dictate the thermal envelope that wraps around your body at night. A bedroom temperature of around 65 degrees Fahrenheit (18.3°C) is ideal for the sleep of most people, assuming standard bedding and clothing. A hot bath before bedtime helps us fall asleep quickly because after hot bath, the blood vessels on the surface of the skin dilated and quickly help radiate out inner heat dropping your core body temperature. Hence you fall asleep faster because your core is colder. Hot baths prior to bed can also induce 10 to 15% more deep NREM sleep in healthy adults.

In the chapter “Hurting and Helping Your Sleep”, Walker discusses sleeping pills and their harmful effects and offers Cognitive Behavioural Therapy for Insomnia (CBT-I) as an alternative to sleeping pills for people suffering from insomnia.

Key Takeaway: Twelve Tips for Healthy Sleep

For people not suffering from insomnia or another sleep disorder, using good sleep hygiene practices will help securing a good sleep. A list of twelve key tips, given below can be found at the National Institutes of Health website:

  1. Stick to a sleep schedule
  2. Exercise is great, but not too late in the day. Try to exercise at least thirty minutes on most days but not later than two to three hours before your bedtime.
  3. Avoid caffeine and nicotine.
  4. Avoid alcoholic drinks before bed.
  5. Avoid large meals and beverages late at night.
  6. If possible, avoid medicines that delay or disrupt your sleep.
  7. Don’t take naps after 3 p.m.
  8. Relax before bed. Don’t overschedule your day so that no time is left for unwinding. A relaxing activity, such as reading or listening to music, should be part of your bedtime ritual.
  9. Take a hot bath before bed.
  10. Dark bedroom, cool bedroom, gadget-free bedroom.
  11. Have the right sunlight exposure. Daylight is key to regulating daily sleep patterns. Try to get outside in natural sunlight for at least thirty minutes each day. If possible, wake up with the sun or use very bright lights in the morning.
  12. Don’t lie in bed awake.

Quotes from the Book

 “The best bridge between despair and hope is a good night’s sleep.”

“Inadequate sleep – even moderate reductions for just one week—disrupts blood sugar levels so profoundly that you would be classified as pre-diabetic.”

“Humans are not sleeping the way nature intended. The number of sleep bouts, the duration of sleep, and when sleep occurs has all been comprehensively distorted by modernity.”

“Practice does not make perfect. It is practice, followed by a night of sleep, that leads to perfection.”

“After thirty years of intensive research, we can now answer many of the questions posed earlier. The recycle rate of a human being is around sixteen hours. After sixteen hours of being awake, the brain begins to fail. Humans need more than seven hours of sleep each night to maintain cognitive performance. After ten days of just seven hours of sleep, the brain is as dysfunctional as it would be after going without sleep for twenty-four hours. Three full nights of recovery sleep (i.e., more nights than a weekend) are insufficient to restore performance back to normal levels after a week of short sleeping. Finally, the human mind cannot accurately sense how sleep-deprived it is when sleep-deprived.”

“the shorter your sleep, the shorter your life. The leading causes of disease and death in developed nations—diseases that are crippling health-care systems, such as heart disease, obesity, dementia, diabetes, and cancer—all have recognized causal links to a lack of sleep.”

“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.”

“…our lack of sleep is a slow form of self-euthanasia…”

About the Author

Mathew Walker, PhD

Dr Matthew Walker is a British scientist and professor of neuroscience and psychology at the University of California, Berkeley. Prior to this he was a professor of psychiatry at Harvard Medical School. He is one of the most well-known public intellectuals in the world on the subject of sleep hygiene and its impact on human health. Funded by National Science Foundation and the National Institutes of Health for his studies, he has to his credit, published over a hundred scientific research papers / studies. He has shared his research on the importance of sleep on television and radio outlets including CBS’s “60 Minutes,” National Geographic, NOVA Science, NRP and the BBC. He is also host of the TED original series Sleeping with Science. His popular science work “Why we Sleep” published in 2017 became an international best seller.

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