Why We Sleep by Matthew Walker: Summary & Notes


Only book I ever read which talks about importance of sleep. Definitely worth a read for better understanding why we sleep and for those who have hard time sleeping.

After reading this book you will be convinced how sleep plays major role in our day to day life and body function, also in depth analysis of what sleep is made and what happens if we don't sleep.

In the end author summarize how we can improve the sleep and why we need more awareness regarding such important part of life which hardly anyone talks about.

My rating: 4.5/5


Following are few key points from individual chapter which I find useful. Obviously cannot summarize all the important and complex subject. Will recommend to read book for better understanding

Chapter 2: Caffeine, Jet Lag, and Melatonin

  • Circadian rhythm -> Internal body clock somewhat about 24 hrs and 15 minutes.
  • Scientific experiment -> In 1700s on plant (scientific name:mimosa pudica) to prove plants also have internal clock.
  • In 1936, two scientists from uni of Chicago went to Kentucky mammoth caves for 32 days to prove this.
  • Every person have different clock, some are morning, some are night owls and few lies in between.
  • Melatonin is like a time keeper not actually participating in sleep
  • adenosine is chemical in brain which accumulates when we are up and deprives when sleeping.
  • If level of adenosine is high you are more likely to sleep, factors like coffee  push adenosine level and makes it difficult to sleep.

Chapter 3: Defining and Generating Sleep

  • REM and NREM sleep.
  • 90 min cycle where first half is more of NREM and other of REM, NREM is where the brain storage is dump, and in REM it will process and make connection to store in the brain

Chapter 4: Ape Beds, Dinosaurs, and Napping with Half a Brain

  • Do animals sleep? Yes all the animals ever existed sleep.
  • REM and NREM sleep differ in animals.
  • Which sleep is important? Both REM and NREM are important.
  • When should we sleep? Hunter-gatherer tribes, such as the Gabra in northern Kenya or the San people in the Kalahari Desert, whose way of life has changed little over the past thousands of years, sleep in a biphasic pattern. Both these groups take a similarly longer sleep period at night (seven to eight hours of time in bed, achieving about seven hours of sleep), followed by a thirty- to sixty-minute nap in the afternoon.
  • Studied done in Greece says biphasic sleep help reduce cardiovascular disease.
  • Because of fire humans sleep on ground compared to apes sleeping on trees.

Chapter 5: Changes in Sleep across Life Span

  • That older adults simply need less sleep is a myth. Older adults appear to need just as much sleep as they do in midlife, but are simply less able to generate that (still necessary) sleep.
  • The second hallmark of altered sleep as we age, and one that older adults are more conscious of, is fragmentation. The older we get, the more frequently we wake up throughout the night.

Chapter 6: Your Mother and Shakespeare Knew

  • Sleep and memory benefits, those who sleep early have more memory retention in NREM sleep
  • Sleep also plays role in forgetting and improving skills which we call muscle memory
  • Post-performance sleep accelerates physical recovery from common inflammation, stimulates muscle repair, and helps restock cellular energy in the form of glucose and glycogen. Example of Andre Iguodala's performance when he's been sleeping more than eight hours a night, relative to less than eight hours a night.

Chapter 7: Too Extreme for the Guinness Book of World Records

  • Sleep deprivation causes lack of concentration, example of drowsy driving and road accidents
  • 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.

Chapter 12 - Things That Go Bump in the Night

  • Talks about insomnia and type of sleep related issues.
  • Narcoleptic is something where person loses body control suddenly. Sleep paralysis
  • Cataplexy for eg-  if someone have some emotional trigger like laughing or surprise then their muscle loses control like string toy.
  • One of the reason is lack of chemical called Orexin in brain and receptor

Chapter 13 - iPads, Factory Whistles, and Nightcaps

  • Five key factors have powerfully changed how much and how well we sleep: (1) constant electric light as well as LED light, (2) regularized temperature, (3) caffeine (discussed in chapter 2), (4) alcohol, and (5) a legacy of punching time cards.
  • Effect of blue light on sleep.
  • Room temperature and sleep. Ideal temp is 65 degree for sleep.

Chapter 14 - Hurting and Helping Your Sleep

  • Sleeping pills target the same area which alcohol does sedating your brain.
  • Sleeping pills increased death rates according to study, also great association with developing cancer
  • The obvious methods involve reducing caffeine and alcohol intake, removing screen technology from the bedroom, and having a cool bedroom. In addition, patients must (1) establish a regular bedtime and wake-up time, even on weekends, (2) go to bed only when sleepy and avoid sleeping on the couch early/mid-evenings, (3) never lie awake in bed for a significant time period; rather, get out of bed and do something quiet and relaxing until the urge to sleep returns, (4) avoid daytime napping if you are having difficulty sleeping at night, (5) reduce anxiety-provoking thoughts and worries by learning to mentally decelerate before bed, and (6) remove visible clock faces from view in the bedroom, preventing clock-watching anxiety at night.

Chapter 15 - Sleep and Society: What Medicine and Education Are Doing Wrong; What Google and NASA Are Doing Right

  • REM sleep is what stands between rationality and insanity.
  • Studies on changing school start times to an hour later have shown higher GPAs following the change, increased life expectancy due to lower traffic accidents, increased attendance, and more.
  • Many medical schools used to require residents to work thirty hours. Medical errors are the third leading cause of death among Americans after heart attacks and cancer

Chapter 16 - A New Vision for Sleep in the Twenty-First Century

  • Few ideas how society can improve productivity, health and less road accidents by prioritizing sleep and right awareness


Twelve Tips for Healthy Sleep

  • Stick to sleep schedule. If only one advice you take this should be it.
  • Exercise is great, but limit before 2-3 hours before sleep/
  • Avoid Caffeine and Nicotine. Specially in late afternoon
  • Avoid alcoholic drinks before bed.
  • Avoid large meals and beverages late at night.
  • If possible, avoid medicines that delay or disrupt your sleep.
  • Don’t take naps after 3 p.m.
  • Relax before bed. Don’t over schedule 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.
  • Take a hot bath before bed.
  • Dark bedroom, cool bedroom, gadget-free bedroom.
  • 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.
  • Don’t lie in bed awake. If you are still awake after 25 min do some relaxing activity. The anxiety of not being able to sleep can make it more harder to fall asleep.
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