Book Summary • Why We Sleep: Unlocking the Power of Sleep and Dreams - by Matthew Walker

Mr Walker should have called his book “Go the F*CK to sleep” because he continuously talks about how we don’t get enough sleep even though there are many, many benefits to sleep. Sadly, that book-title was already taken.

“Why we sleep” is a great read, here are my takeaways. There are a lot, because it’s a great book.

You need 8 hours of sleep, but you don’t get it

Humans need more than seven hours of sleep each night to maintain cognitive performance. More than a third of individuals in industrialized societies sleep less than five to six hours a night during the week.

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.

There is a lot of “sleep procrastination” caused by late-evening television and digital entertainment. Even a hint of dim light—8 to 10 lux—has been shown to delay the release of nighttime melatonin in humans.

Sleep == good

AMAZING BREAKTHROUGH! Scientists have discovered a revolutionary new treatment that makes you live longer. It enhances your memory and makes you more creative. It makes you look more attractive. It keeps you slim and lowers food cravings. It protects you from cancer and dementia. It wards off colds and the flu. It lowers your risk of heart attacks and stroke, not to mention diabetes. You’ll even feel happier, less depressed, and less anxious. Are you interested?

Not sleeping is bad, m’kay

In short: if you don’t sleep enough, you’ll become a lazy, uncreative, unattractive, fat and forgetful person, who’ll die a lot sooner than those that do sleep.

Mid-day naps are good

Alcohol bad

Caffeine is everywhere and stays in your body long time

How sleep works

There’s a lot of information in the book on how sleep works, which is all a great read. In short: when it comes to information processing, think of the wake state principally as reception (experiencing and constantly learning the world around you), NREM sleep as reflection (storing and strengthening those raw ingredients of new facts and skills), and REM sleep as integration (interconnecting these raw ingredients with each other, with all past experiences, and, in doing so, building an ever more accurate model of how the world works, including innovative insights and problem-solving abilities).

The last two hours of sleep are precisely the window that many of us feel it is okay to cut short to get a jump start on the day. But these are very important hours!

Differences children and adults

As a parent myself, I found this information very important:

Society greatly disadvantages evening types

So teenagers are ‘evening types’ and they are greatly disadvantaged: they have to get up early to go to school and are sent to bed when they are not tired. However, they are not the only ones!

Evolution of sleep

How to sleep better

To successfully initiate sleep your core temperature needs to decrease by 2 to 3 degrees Fahrenheit, or about 1 degree Celsius. For this reason, you will always find it easier to fall asleep in a room that is too cold than too hot, since a room that is too cold is at least dragging your brain and body in the correct (downward) temperature direction for sleep.

When you get out of the bath, those dilated blood vessels on the surface quickly help radiate out inner heat, and your core body temperature plummets. Consequently, you fall asleep more quickly because your core is colder. Hot baths prior to bed can also induce 10 to 15 percent more deep NREM sleep in healthy adults.

Wake up only once. If you do use an alarm clock, do away with the snooze function, and get in the habit of waking up only once to spare your heart the repeated shock.


Read the book, there’s loads more interesting insights in there!