Why We Sleep

by Matthew Walker
health reading

In my first years of university, I often found myself doing homework up to the early morning hours and then sleeping a few hours and starting the new day as if nothing happened. I knew that it wasn’t good, but only now I know how bad it was. Bad sleeping habits make you fatter, sicker, unhappier, more forgetful and prone to diseases shrinking your life expectancy with every night that you don’t rest well.

Why We Sleep by Matthew Walker, the director of UC Berkeley’s Center for Human Sleep Science, is filled with striking information about the effects of lousy sleeping habits. Walker explains how neglecting a good night rest affects our problem-solving abilities, memory, creativity, mental and physical health, as well as social feeling and empathy.

Even though Walker sometimes jumps very far from the correlation to causation in things such as the relation between sleep length and happiness, the book is still essential and alarming in many ways. Here are some facts that stuck with me and that you might be asking yourself even before reading the book.

How long do we have to sleep

You might think that you are a short sleeper, and 6 hours per night are enough for you, most likely, that’s not the case. Only less than 1 percent of people can sleep 6 hours and get the amount of sleep that their body needs; the rest is sleep-deprived and got used to it. The optimal amount of sleep is 7,5 - 8 hours every night. If that’s not possible for you, try to take a quick nap after the lunch, even though it can’t substitute the night sleep it’s still better than letting your tired body flow through the day without a rest.

Sleeping habits also change with age. The thing that I could closely relate to is that in the puberty, our sleeping cycle moves forward, making us want to stay up longer and sleep until later hours. The body often overshoots this shift, which might last up until adulthood. Thus it is very important to let your adolescent kids sleep long enough, which is often impossible with early school schedules.

What if we sleep less

Why We Sleep lays out so many negative effects of sleep deprivation that it would take more than ten articles to list them all. Things that take the highest toll are memory, concentration, creativity, and the overall state of health of your body. Walkers also links sleep deprivation to many diseases, why the linkage might not be as strong as he claims, what has been proven to be true over and over again is that being drowsy behind the wheel is as bad as being drunk.[1] Fatigue-related accidents are estimated to account for 20% of fatal car crashes. Driving after 24 hours without sleep is considered to be equal to driving with 0.1% alcohol in blood, the amount considered illegal in almost all countries.

How to improve your sleep

There are a few things you might consider doing to improve your sleep. First is avoiding blue light before going to bed. Blue light boosts your mood and energy, which is excellent throughout the day but is not desired in the evening when you want your body to relax and get ready for rest. Internally, your body thinks that the blue light is the natural light and it suppresses production of melatonin, a hormone that regulates our sleep-wake cycle by making us feel tired.

Secondly, you can create a better environment for the shut-eye phase of the night, make sure your room is dark, silent and cold, your body drops the temperature in the night and you will rest better if your body doesn’t have to work hard to do that. Optimal room temperature for sleeping is around 19 °C (65-66 °F).[2] If you like to take a hot bath before going to bed, however unpleasant, consider taking a cold shower at the end.

Last but not least, try to avoid alcohol before bedtime; contrary to the popular believe alcohol doesn’t improve your sleep, rather it induces the sleep but lowers the overall quality (mostly of the REM - rapid-eye-movement phase) to very low level. That’s also the reason why even after sleeping to the lunch hours after a party, you still feel tired, and your body asks for more sleep.

Why we sleep at all

After all, sleeping makes you - and all animals alike - vulnerable and unable to hunt, gather, reproduce, or eat. Why do we sleep then, and why hasn’t the evolution got rid of the sleep already? Because the upsides of sleep overweight the downsides severally. Sleep helps us regenerate and boosts our immune system, while we sleep the body gets rid of many toxic substances and enhances our abilities using the experiences obtained throughout the day. Overall, sleep makes us evolutionary more fit, just in ways that are not that easy to see.


Why We Sleep is both eyes-opening and eyes-closing book. Never have I been proven to be wrong in so many things by a book. Walker also encourages you to put the book often away and take a nap or go to sleep already, knowing how important sleep really is. I think we all should learn more about sleep - an activity we spend almost one-third of our lives at and yet know so little about. That being said, the books has its flaws and factual errors, you can read more about these for example in this article: Matthew Walker’s “Why We Sleep” Is Riddled with Scientific and Factual Errors.


Alexey Guzey wrote lengthy article titled Matthew Walker’s “Why We Sleep” Is Riddled with Scientific and Factual Errors that debunks and disputes many claims in the book, to name a few:

I definitely recommend reading the blog post as well as the discussions linked in the first paragraph.

Learn more about sleep


Title: Why We Sleep: The New Science of Sleep and Dreams
Author: Matthew Walker
ISBN10: 0141983760
ISBN13: 9780141983769