"Why We Sleep: Unlocking the Power of Sleep and Dreams" by Matthew Walker is a deep dive into all things sleep. Walker provides us with a scientific foundation for most of what is known about these two essential parts of life. In this summary we'll be giving a high level view of the topics contained within this great book.
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Our bodies have a Circadian Rhythm. It is our Internal clock, like the beating of a drum. It is always running even if we can't see the sun.
Our body temperature shifts with our circadian rhythm as well, this is one of the main ways your body knows when it is "time to sleep"
Not everyone’s rhythm is the same. Some people are "Night Owls" naturally staying up late and waking up late. Others are "Morning Larks" who sleep early and rise early. Neither one is better or "less lazy" than the other.
Newborn babies don't have a strong circadian rhythm. Teens typically have a later circadian rhythm compared to adults which explains the all too common contention between tired parents and "rebellious and lazy" teens.
Adenosine
Adenosine is the chemical that builds up in our brain causing tiredness. Caffeine blocks adenosine and is both a stimulant and addictive.
NREM vs REM Sleep
NREM Sleep, or Non Rapid Eye Movement Sleep, occupies the majority of the first half of a nights sleep. It dances in a delicate cycle with REM Sleep, switching between the two about every 90 minutes.
REM sleep is most dominant in the last half of the night.
Dr. Walker theorizes that the uneven pattern between NREM and REM is necessary to "remodel and update our neural circuits at night"
If you get only 6 hours of sleep (as opposed to the ideal 8 hours) you don't lose 25% of your REM sleep but rather between 60-90%.
Walker classifies awake time as reception, NREM as reflection, and REM as integration of key learning that we do every day.
Humans have much more REM sleep when compared to other species like birds. REM dense sleep allows us to sort and connect information we collect as well as come up with creative solutions. Walker also claims it allows us to understand complex emotions and work together like no other species has.
Consistent REM sleep develops our emotional IQ, or in other worse, our ability to regulate our emotions.
Part 2: Why should you Sleep
Learning, Practice, & Sleep
"Sleep-the-night-after" learning has been shown to improve memory retention by between 20 and 40%.
Walker claims Practice does not make perfect. Practice with a good night sleep makes perfect. He tells a story of a piano player whose brain was able to "iron out" the mistakes of a complex sequence of notes he had been struggling with. This was also tested in a study with people trying to type a complex sequence of numbers without mistakes. Sleep refined the bad "muscle memory."
Sleeping shifts memories from hippocampus (short-term) to cortex (long-term) and creates space for more knowledge.
Sleeping not only helps us remember things, but forget things. A complex parse of our memories happens at night which is one of the reasons our brains are so efficient.
Drunk and Drowsy Driving
Getting consistently 6 hours of sleep a night for 10 nights is all it takes to become as impaired as someone who hasn't slept in 24 hours.
In 2 studies cited in the book, participants were unable to tell how impaired they were. Essentially, when you are sleep deprived you may not know you are sleep deprived.
Sleeping for fewer than 4 hours the night before driving increases your chance of a crash by 12x.
Drowsy and drunk driving combined is an extremely dangerous thing to do. The effects of each impairment combined multiplicatively and were found to be 30x more likely to drive off of the road.
Memory, Disease, and Appearance
Pulling an all-nighter is a terrible idea when it comes to learning. Students who pulled all-nighters were 40% worse at recalling "crammed" facts
Lack of sleep is becoming recognized as a factor that could contribute to Alzheimer's disease.
Sleep is also tied to Heart Disease, Obesity, the reproductive system, the immune system
Part 3: How and why we Dream
Dreams, Dreams, Dreams
MRI allowed the first scientifically grounded visualization of the brain during dreaming (REM Sleep).
Scientists have been able to correctly predict the general "form" of someone's dream after seeing the brain activity.
Dreaming is one of the few times where a key stress related chemical called noradrenaline is shut off from your brain
Dreaming tunes our ability to correctly perceive emotions.
Dreaming & Creativity
Dmitri Mendeleev had a dream which led to him organizing the elements into the periodic table we know today.
Rolling stones' Keith Richards had the opening lines of "Satisfaction" come to him in a dream
Mary Shelly was inspired to write Frankensteinfrom a dream she had.
Part 4: From Sleeping Pills to Society Transformed
Sleep Disorders
Somnambulism refers to any kind of sleep disorder involving movement like sleep talking, sleep eating, and sleep walking. We don't fully understand what causes somnambular episodes.
Insomnia is not the same as being sleep deprived. Sleep deprivation is when you are able to sleep, but you don't give your self enough opportunity to sleep. Insomnia is when you try to sleep but can't. There are various forms of insomnia including chronic and paradoxical insomnia.
Paradoxical insomnia is when a patient has slept much better than they believe, creating an illusion between actual rest and perceived rest. Often times these people are treated as hypochondriacal.
Narcolepsy is a neurological disorder which includes daytime sleepiness, sleep paralysis, and cataplexy.
Sleep disorders are almost never solved with sleeping pills. People suffering with these or any other sleep disorders should consult a sleep scientist.
Healthy Sleep Habits
Modern light fixtures and all electronic screens have an overwhelming amount of blue light. This blue light can delay your natural release of melatonin which helps you fall asleep.
Alcohol is a sedative and being sedated is not the same as being asleep. Alcohol actually disrupts and fragments your sleep and causes you to wake up for brief moments of time.
A general rule for what temperature to sleep at is around 65° F (18.3° C). If you recall from part 1, a lower temperature is how your circadian rhythm tells your body when it is time to sleep.
There are no current or past medications that create natural sleep. They cause grogginess and more of a sedation then actual sleep and rest. Sleeping pills have also been linked to many harmful diseases and generally are not worth the risk.
Sleep and Society
Walker says, "A study across four large US companies foudn that insufficient sleep cost almost $2,000 per employee per year in lost productivity. That amount rose to over $3,500 per employee in those suffering the most serious lack of sleep".
Some companies have started to offer sleep incentives like cash prizes for getting good sleep. Walker recommends this but to structure it so that you get extra time off (or other reward) with consistent good sleep.
Almost 40% of public high schools start before 7:20am which is terribly difficult and almost cruel for teenagers. Remember that teens' circadian rhythms naturally shift later than most adults.
Research has shown that later school start times reduce behavioral problems, increase class attendance, and reduces substance abuse.
Walker has a vision for better sleep in our society and encourages everyone to contribute to good changes where they are able to. He argues that technology, one of the main culprits to bad sleeping habits, can be used to create even better sleep situations for the world through developments in smart lighting, health tracking, and of course sleep research.
Appendix
The appendix to the book covers 12 tips to get better sleep
Stick to a Sleep Schedule
Exercise is great but not too late in the day
Avoid caffeine and nicotine
Avoid alcoholic drinks before bed
Avoid large meals and beverages late at night
Avoid medicines that delay or disrupt sleep
Don’t take naps after 3pm
Relax before bed
Take a hot bath before bed
Dark bedroom, cool bedroom, gadget free bedroom
Have the right sunlight exposure
Don’t lie in bed awake
Conclusion
Thank you for reading our summary of "Why We Sleep: Unlocking the Power of Sleep and Dreams" by Dr. Matthew walker. We hope you learned something from it! We'd highly suggest listening to our podcast episode about this book. In it, Robert and Chayse dive into their personal experience reading this book and what things from it they have been able to implement in their lives.
