Book Review: Why We Sleep, by Matthew Walker

While not quite as well-written or as interesting (or surprising) as Breath by James Nestor, Why We Sleep by Matthew Walker is an important book.

I am not crazy about the amount of time he spends on certain subjects but he does an excellent job of emphasizing the importance of sleep. In fact, he hammers this point home over and over again, which is good because we humans obviously haven’t gotten it. As I love to say,

Humans are bad at the fundamentals.


As an example, Dr. Walker points out that sleep deprivation is considered torture by most of the countries of the world and outlawed as a practice. Even more interestingly, the United States has not outlawed this as a torture practice.

Yet apparently over 1/3 of adults in most developed countries obtain less than the recommended 7 to 9 hours of sleep necessary for normal function.

So let’s break down Dr. Walker’s main points:

  1. Sleep is important for energy
  2. Lack of sleep is hurting us
  3. Common things disrupt our sleep
  4. We can improve our sleep

Sleep is important for energy

One of the more fascinating points for me was the actual reasons why we sleep – the science behind why we sleep – hence the title. We apparently did not know why we had to sleep up until recently. (In fact when I called my doctor friend to ask him about sleep as a pillar for our energy. He said that we don’t know why we have to sleep; it’s still a mystery to science. But now we do know and it’s a rather recent discovery.)

At a high-level, here is why sleeping is important:

  1. Our circadian rhythms establish a baseline of when we’re going to feel tired and when we’re going to feel energized.
  2. There is a ‘sleep pressure’ that builds within our body the longer we go without sleep. This sleep pressure is created by something called the suprachiasmatic nucleus and the sleep pressure builds up like a debt we owe and cannot be cleared without sleep. (This is the effect the caffeine blocks, for better and for worse.)
  3. Multiple rejuvenating functions occur during sleep which restore our cells to higher functioning abilities and clear our minds of certain thoughts, kind of like an old computer hard drive being reformatted.

Lack of sleep is hurting us

Not getting enough sleep can have a plethora of horrible effects on our health:

  • weakening our immune system, substantially increasing our risk of certain forms of cancer and Alzheimer’s disease
  • disrupting blood sugar levels so profoundly that we would be classified as pre-diabetic
  • causing fatigue (which obviously is why I’m reading this book)
  • increasing weight gain (another interest of mine)
  • even causing hallucinations and impaired driving (as much as drinking alcohol!)

And the list goes on and on

Common things disrupt our sleep

Alcohol has a hugely disruptive influence on our sleep, in particular our REM sleep. In fact, alcohol is so disruptive that alcoholics have been known to start dreaming while they are awake. These hallucinations and the lack of sleep caused by alcohol can literally drive you crazy. This is a common mistake people make about alcohol. People think it helps you fall asleep. Nope. What it actually does is knock you unconscious which is different than being asleep. Your brain is not resting during alcoholic unconsciousness. Your body is not being restored and your brain is not being reformatted. It also wakes you up later in the night and causes other disruptions.

Second, caffeine causes us to lose sleep. The half-life of caffeine in our body is longer than most people think, up to 10 hours. Caffeine blocks the sleep pressure from being sensed by the body but does not actually eliminate the Sloan sleep pressure. Leslie pressure builds and builds but you can’t feel it. So when you drink too much caffeine or the caffeine wears off, we crash. Also, if all the caffeine has not worn off by the time you try to lay down, you will have difficulty sleeping. This makes us more tired the next day and we drink more caffeine and the vicious cycle continues.

Third, our lighting has disrupted our sleep. Whether it is the screens we watch at night or the LED lights or even the old incandescent lights, we have confused our brains with lighting past sunset and our bodies can be confused out of our circadian rhythms. We must learn to turn off our screens at least an hour before bedtime minimize LED lighting, and try to avoid Bright lights before going to bed.

Fourth, and most simply we as a culture must learn to value sleep more. Our culture seems to honor those who sleep less and looked down upon extra sleep as laziness. However this book proves and study after study that people who sleep more are healthier, more productive, and more energetically.

So what can we do about it?

We can improve our sleep

Dr. Walker recommends 12 tips for improving our sleep. I don’t want to ruin the book for you so I’ll only put my top favorite tips here and which ones I experimented with.

  1. sleep tape – this was a carryover for me from the Breath book (read that book review here). Sleep tape both helps with your nasal breathing, lowering nighttime trips to the bathroom, and improving deep sleep. The science behind this is interesting and I would encourage you to read either book if you want to understand more. I have tried this and there is a definite correlation between improved deep sleep and using sleep tape.
  2. digital sunset – Dr. Walker recommends turning off all sources of blue light at least an hour before bedtime. Blue light disrupts our natural circadian rhythms. The science behind this is fascinating, if you want to read the book. Suffice it to say that this was challenging for me at first. My family often watched TV up until about 30 minutes before bedtime. However the kids love playing board games or card games, so we have switched to doing that more often. This ends up being a 4-hour digital sunset for me since I have to drive home, help with dinner, eat dinner, play with the kids, before reading bedtime stories. This also has had a positive correlation on my sleep. [Bonus: I also replaced our bedside lamp lightbulbs with low blue light lightbulbs since my son and I read for 30 minutes before bedtime. Apparently the new LED lightbulbs have a higher than normal amount of blue light which is disturbing our sleep even more (although they are saving the environment).]
  3. reduced caffeine and fluids at night – I didn’t realize the caffeine had a half-life of nearly 10 hours. I often would have a green tea in the afternoon around three or 4 PM. I thought my cut off for caffeine was around 4 PM but realized that it was getting earlier the older I grow. So it was not surprising to me that I needed to move my caffeine intake up to around lunch. Dr. Walker also recommends limiting liquids after 5 PM in general if you want to reduce nighttime visits to the bathroom. I have done so and have seen a nice decrease in those as well.
  4. other changes – Other changes that I have made (but are more difficult to track their effectiveness for various reasons) are:
    • having blackout curtains in the bedroom,
    • using a massage gun to relax in the evening,
    • wearing blue-blocking glasses if we watch TV,
    • lowering the temperature at night in the bedroom,
    • using a saline nasal rinse before bed,
    • wearing Breathe-Right strips while I sleep,
    • using a humidifying mist at night with essential oils, and
    • reducing certain foods at night time like pizza and marinara sauce in general.

I believe these various changes have helped as well but they are more difficult to track and I can’t in total confidence recommend their efficacy.

As an update, after reading Quench, I have also started to eat more hydrating foods, which paradoxically helps reduce the urge to urinate at night.

So, if you found any of this interesting or would like to read more, you can pick up Dr. Walker’s book here.

Thanks for reading! I will be working on finishing the main Sleep pillar page next.

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