Review of Why We Sleep: Unlocking the Power of Sleep and Dreams

Book: Why We Sleep: Unlocking the Power of Sleep and Dreams by Matthew Walker. Rating: ⭐️⭐️⭐️⭐️⭐️.

Amazing book! It has the potential to be life-changing for me.

When I started reading it, my review was around 3 stars. This book is not easy to read and sometimes (especially in the beginning) it feels boring. It took me some time to engage in the topic. I think I felt the same when reading Deep Work.

Now that I finished the book, I’m glad I was able to persevere reading it because there is a lot of good advice backed by science here. I still remember when during university years, I decided to study C++ (the programming language) from 0 am to 3 am every Wednesday (had to wake up at 8 am max). It was “the only time I had,” and I wanted to go the extra mile to learn something new and exciting. After some months doing this, I realized it was not so productive, and until this day, I remember almost nothing of what I studied.

I never gave that much importance to sleep and always tried to “optimize” the time awaken. After many years of experiments, I found that 7 hours of sleep was enough for me. I’m glad it was not less than that, or I would feel worse now.

The best part of this book is the significant number of scientific studies referenced. It’s not some article you read online that is interpreting some research in their way and telling you that you only need on average 6.7 hours of sleep a day. In this book, you will know dozens of scientific studies, their methods, and conclusions.

These kinds of books written by scientists are fantastic (and sometimes boring… It can’t be perfect) to help you draw your own conclusions based on serious researches available until now. I would totally recommend this book if you don’t take sleep seriously and is interested in something that is free and can drastically improve your life.

I did some sleep experiments in the past, but I will probably reboot all of them. My experiments start now! :)

Here are my notes for this book:

If you use the “I can sleep when I’m dead” there’s a big chance you will be dead sooner than later
Sleep makes us very vulnerable to everything but evolution kept is in almost all animals all those years, so it has to be very important
Sleep is the single and most effective way to reset our brain and body every day
The Circadian Rhythm duration is more than one day
Night owls are usually penalized by society by having a different gene. It’s not lack of effort that makes them not work well in the morning but their DNA.
40% of the population are morning people, 30% are night owls, and the rest are in between
Melatonin helps to pace the sleep cycle
Because our Circadian Rhythm is bigger than 24 hours, it’s easier to artificially stretch a day than shrink it
Jet lag happens when you travel through timezone but your circadian time is not adjusted yet
Caffeine is the only addictive drug we give to our children
Caffeine doesn’t kill the urge to sleep; it just blocks the signals of the level of adenosine for your brain. When the caffeine effect passes, you will probably have a caffeine crash because of the level of adenosine accumulated
Wake state is learning, NREM state is reflecting, REM state is integration (integrating neurons with each other)
Your eyeballs show your sleep state. If you see someone sleeping and moving their eyeballs left to right, they are in a REM state
Imagine the possibilities if we (humans) could rest our brain one side at a time like dolphins and birds. One side remains awake while the other sleep.
REM sleep recalibrate the emotion circuits in the human brain
Alcohol for pregnant women or women who breastfeed is bad because it passes to the child and affects REM sleep. REM sleep is important to the formation of the child’s brain and connection of neurons.
The same amount of alcohol present in the mother’s blood will be passed to the children when breastfeeding.
Deep NREM sleep happens a lot during adolescence, which improves cognitive capacity and decision making
The brain is less malleable or plastic during adolescence. That’s why kids can pick up a second language easier than adolescents. This explains why rationality is the last thing to appear in adolescents.
Deep NREM sleep is very important for adolescents
The circadian rhythm of children, adolescents, and adults are different. Children tend to sleep earlier, adolescents tend to sleep later, and adults kind of in the middle. Forcing an adolescent to sleep at 10 is like an adult going to sleep at 7
The lower is the sleep quality, the higher is the mortality risk according to research with adults
Sleep before you learn. There are studies showing that sleep helps your brain to retain more information. A nap at noon helps you to concentrate and store more information (20% more according to studies) while studying
We obtain most of our deep NREM sleep earlier in the night and most of our deep REM sleep and light NREM sleep later in the night
Early night sleep is the one who helps the most to retain fact-based memories
Sleep after learning is not a crucial way to store information, but it also helps to find memories you have but don’t remember
A pianist said to the researcher that there are moments when we can’t play a piece and go to bed, frustrated. The other day, he wakes up and just plays it. – it’s funny that it happened to me many times, playing instruments or even programming
It’s not practice that makes perfect, but practice + sleep. After one night of good sleep, subjects show great improvement when compared to the ones who didn’t sleep or got a bad night of sleep
During sleep, the brain fixes/automatizes motor problems you’re having during the day. That’s why the pianist doesn’t have the same motor struggles from the previous day after a night of sleep
Sleep is also important for body recovery and improvement. It’s especially true for sports.
Sixty years of academic studies don’t let me trust people who say, “I’m fine with 4 hours of sleep every day.”
After 16 hours awake the brain starts to fail. You need more than 7 hours of sleep to maintain cognitive performance. After 10 days sleeping only 7 hours a day, your brain is bad as if you were awake for one full day. 3 nights of sleep (more than a weekend BTW) are insufficient to recover after a week of short sleeping
Drowsy driving accidents are not really accidents because they have a cause and are predictable – :(
Don’t drive when you’re sleep deprived. If you REALLY, have to do that. Take a 30min nap in a safe place. Wait for 20-30 min and then continue for a while. It will not last long but reduces the chance of an accident.
A researcher invites anyone who says he/she can live well with short sleep to go to his laboratory for a 10 days stay, so he can show categorically the brain malfunctioning. Until this day, no volunteer could hold their claim
Emotions are intensified when you’re sleep deprived
People who sleep less have a greater chance of having Alzheimer
People who sleep less lose part of the “I’m satisfied” and gain more “I’m hungry” feeling
When sleep deprived we look for food with more calories
Freud described a dream as something coming from unconscious wishes that were not fulfilled – is it why we say that we have “a dream” of becoming/doing something?
Freud analysis of dreams is unscientific but he knew a scientific explanation will come someday
Dreams are a by-product of REM sleep as heat is a by-product of a light bulb generating light
Dreaming is like a night therapy
It’s not time per se which heal or wound, it’s time dreaming
When you’re sleep deprived, you can’t read emotions property and the world looks more frightening
REM sleep is great for creativity. Many songs were composed during REM sleep (satisfaction, yesterday, etc.)
The periodic table was conceived after days of struggle and one night of good sleep
Lucid dreamers may be the next iteration of Homo sapiens by focusing their dreams and improving particular areas of the brain
What if Alien abductions are just post-sleep paralysis? The symptoms are similar and they are usually reported at night
If you know you are carrying a gene that will kill you by not being able to sleep, would it change your will to have children and spread the disease?
In a study, sleep-deprived rats (10+ days) started losing body mass even when they were eating well. When core temperature decreases, mammals increase the metabolic rate. Because of the lack of sleep, they could not control the body temperature and were burning from inside out (metabolic increase)
There’s a study based on Hunter gathers that says humans only need 6.7 hours of sleep to live. When you look into the research, well-being, and life expectancy of the tribes researched, you get a different conclusion. (7-9 is still the recommended)
Sleep and time awake work together for a balanced life. It seems to be a good balance to have 16 hours of awake time and around 8 hours of sleep
We decide when it’s night and when it’s the day because of electricity and other artificial lights
Using an iPad (or any other LED device) to read before sleep reduces the creation of melatonin and directly influence the time and quality of sleep
Remove the blue light from your devices and use yellow lights at night to help to release melatonin.
Drinking alcohol at night also makes you feel exhausted the next day because of the lack of good sleep since alcohol affects your sleep in a bad way
A hot bath before bed helps sleeping better and have more deep sleep because your core will cool down right after
It’s possible that sleep pills contribute to increased death risk. Such experiments will never be conducted because they are considered too risky by the ethics committee.
Sleep and wake up at the same time every day
Sleep and exercise help each other. When you exercise, you tend to sleep better. When you have a great sleep, you have better performance exercising
Low-calorie intake (800) contribute to bad sleep
Avoid going to bed too full or too hungry. Avoid heavy sugar food before going to sleep
Early school start time is bad for children learning and education. If the goal of educate our children, we are failing in the most spectacular way with the current early start time model.
Resident doctors don’t sleep enough and takes them to eventually make possibly deadly mistakes.
We receive no education about the importance of sleep but receive some regarding sex, diet, and others (informal research)
Sleep appears to be a natural analgesic when done right.

12 tips for a good sleep

Stick to a sleep schedule every day. Set an alarm to go to sleep, not just to wake up
Exercise is great but it’s important to not exercise late in the day
Avoid caffeine (coffee, Coca-Cola, chocolate, and certain teas) and nicotine. The effects of coffee take 8 hours to vanish sometimes
Avoid alcoholic drinks before bed
Avoid large meals and beverages at night
If possible avoid medicines that affect your sleep
Don’t take naps after 3 pm. Late naps can make it harder to sleep at night
Relax before bed. Reading or listening to music should be part of your bed routine.
Take a hot bath before bed to reduce your body temperature (cool down after it). The bath can also help you to relax.
Dark bedroom, cool bedroom, devices free bedroom
Have the right sunlight exposure. Try to have morning sunlight for at least 30 minutes every day.
Don lie in bed awake. Anxiety to sleep can make it even harder to sleep.