Sustainable Pace

October 21st, 2020

Why We Sleep - Unlocking the Power of Sleep and Dreams (Matthew Walker, 2017)

Matthew Walker is a neuroscientist and sleep researcher. Why We Sleep is a comprehensive collection of insights into why sleep should be given more attention. To me it has been a revelation. Sleep affects our well-being so much, it should be a number one priority to get right, even before addressing exercise and nutrition. This book is full of interesting bits and pieces, and I pick a few that were most interesting to me.

Sustainable Pace

Circadian rhythm and adenosine

It's not like everyone has the same sleep patterns. Sleep is dependent on the circadian rhythm and the levels of adenosine in your body. Let's talk about circadian rhythm first.

You may have heard of people being either owls or larks, meaning they either prefer to go to bed late and rise late, or go to bed early and rise early. But it isn't as fixed as it seems, as for example a teenager's circadian rhythm significantly shifts into owl territory. So it's no use getting upset about teenagers going to bed late - in fact it's even harmful to have early school start times. Another thing about the circadian rhythm is, that it is hardly ever exactly 24 hours, it is slightly longer, in some people more than an hour longer - these people really have a hard time getting enough sleep.

Adenosine is another big factor - it is a molecule, and it's concentration in our blood stream builds up over the day. The more adenosine you have, the more tired and drowsy you are. If levels are too high, you fall asleep. However, you can block reception of adenosine for example by caffeine intake - by drinking coffee you can suspend sleepiness, but not avoid it. As the effect of caffeine wears of, adenosine has built up in the background and hits you especially hard.

You should try to keep your circadian rhythm and adenosine level in sync, in order to be sleepy enough to actually fall asleep when the time is right. If you don't, you might never be really tired and also never be really awake. I liked the term sleep pressure that is used in the book - without enough pressure, sleep will not happen.


Apparently good sleep has a great impact on how well we learn, and this book cites a lot of interesting studies. Apparently both NREM and REM sleep have their own effect, NREM sleep boosting more factual learning, while REM sleep is responsible for creativity and connecting the dots, so to speak. The expression "to sleep on it" exists in almost any language - so sleeping is known to improve learning long before there was scientific evidence.

If you are learning intensely, not sleeping enough actually makes big portions of the effort futile. This is especially interesting, as early school times often prevent a good sleep and slow down progress significantly. Also alcohol consumption severely degrades your learning success. Because alcohol does not help you sleep well, but is more of an anaesthetic, your sleep quality is decreased, even though you're not aware of it. Even if you consume alcohol several nights after the learning experience, it still affects it - in fact it is so detrimental that Walker recommends no alcohol at all, the science is that clear about it. The same goes for sleeping pills, by the way.

Sleep deprivation and catching up on lost sleep

A common pattern seems to be to sleep too little during the week, and catch up sleep during the weekend, hoping to restore the balance this way. However, Walker makes a compelling argument that you can never catch up on sleep. When you lose hours of sleep, they are irrevocably lost. So establishing a habit of going to sleep and waking up at the same times each day is a good idea. It should be a really stable pattern. When you look back in history, before electric light was invented, this was the norm - nowadays you really have to protect your sleep times vigilantly.

Sleep deprivation has actually a similar effect as alcohol consumption - studies have compared intoxicated learners with sleep deprived learners, yielding in similar results. This is especially interesting when you realize how many people still drive a vehicle when being sleep deprived - there is no easy way to measure if a driver was sleep deprived, but their capabilities are comparable to a drunk driver, who are now being severely persecuted.

Insufficient sleep also dulls your perception - studies have shown that people choose less challenging tasks at work when being sleep deprived. People also eat more quantities of food, and adding to that, food of less quality. Especially sugars are craved when people have not slept enough. So insufficient sleep severely impacts other aspects of health.


There is so much more I could quote from this book - it's a treasure trove of insightful studies and recommendations. To me Matthew Walker's book on sleep has been an eye-opening experiencing (pun intended)!

For most of the time I just took sleep for granted and didn't really given it much thought - it was just there. I didn't pay much attention if I was having too little or low-quality sleep. After having read this, I try to give sleep the same amount of awareness than I give the hours I'm awake.

Walker often references the National Sleep Foundation, and they actually have a lot of great guidelines. If there is only one, read the one about healthy sleep tips - so much great advice there!

How is your sleeping? What has helped you sleep better? Get in touch and let's discuss! Especially if you have experience monitoring your sleep with a device like a FitBit or Nokia Sleep, I would be happy if you could share your learnings with me.