The book Why We Sleep: Unlocking the power of sleep and dreams came to my attention after listening to many podcast interviews with the Author Matthew Walker.

In truth, you can get most of the content of the book just by listening to the interviews with the author in many podcasts or in Matthew Walker’s own podcast. I have added a link to all those in the Other resources section of this post. So, after reading this post, I would recommend checking out the podcasts linked at the end of this post.

Let’s now see more about the book Why We Sleep

This post is part of the series Learnings from books where my goal is to share what I learned from the book that I read. It is a mixture of review and summary with a bit of my opinion and point of view. But, as reviews, these learnings can say more about me than the book itself, so I trust that you the smart reader will take it with a grain of salt.

Learnings from Why We Sleep

The book is good, it is written in a way that the reading is fluid and fun. I really enjoyed reading the book. It talks about many pieces of research that confirm the information provided by the author. You are gonna see many examples, that help us understand the information better.

The main message that I got from the book is the importance of sleep. The author shows what sleeping does to our body and our mind and also show what bad sleep does also does to us.

For me, my main takeaway is that we should give ourselves between 7 to 9 hours of opportunity to sleep every night, with consistency, and try to go to bed without caffeine, alcohol, or exposure to lights.

Importance of sleep

According to the book, two-thirds of adults throughout all developed nations fail to obtain the recommended eight hours of nightly sleep. This means that more than half of adult society is sleep deprived. Even though “sleep is the single most effective thing we can do to reset our brain and body health each day”

Sleep makes you live longer, improves your memory, and makes you more creative. It makes you look more attractive and healthy. 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. Having enough sleep will help you feel happier, less depressed, and less anxious.

The risk of not sleeping enough

There are many effects of not sleeping enough. Consistently sleeping less than six or seven hours a night can significantly harm your immune system and increase your risk of cancer by more than double. Inadequate sleep is also a significant lifestyle factor that can determine whether you are at risk of developing Alzheimer’s disease. Even a moderate reduction in sleep for just one week can disrupt your blood sugar levels to such an extent that you may be classified as pre-diabetic. Additionally, insufficient sleep raises the likelihood of your coronary arteries becoming blocked and brittle, putting you on a path toward cardiovascular disease, stroke, and congestive heart failure.

Sleeping little also has the propensity to make you fatter, as “too little sleep swells concentrations of a hormone that makes you feel hungry while suppressing a companion hormone that otherwise signals food satisfaction.”

But it is not only physical the effect is not enough sleep, sleep disruption further contributes to all major psychiatric conditions, including depression, anxiety, and suicidality.

Circadian rhythm and sleep pressure

Every person has an internal clock that is called the Circadian Rhythm, this clock helps your body knows when to be awake and when you want to be asleep. It is approximately one day, but not precisely one day. As our internal clocks are not exactly one day, the sunlight adjusts our internal clocks to precisely 24 hours.

This internal clock is different for each person, and around 40% of the population is morning type (wake up earlier), 30% are evening type (wake up later) and the rest fall between.

But circadian rhythm is not the only factor that determines when you want to sleep and when you want to be awake. The other one is “sleep pressure” which is a chemical called adenosine.

As the day progresses and you stay awake, the chemical “sleep pressure” in your body builds up, leading to increased feelings of drowsiness. The interplay between this pressure and other factors determines your level of alertness and focus during the day, as well as how easily you’ll fall asleep at night and the quality of your sleep.

Caffeine and its effect on sleep

After reading the book, I stopped drinking coffee after 12 PM. Caffeine works by blocking (occupying) the receptors of sleep pressure (adenosine). Sleep pressure builds up as you are awake, the more time you are awake, the more sleep pressure you have in your system. By blocking the receptors, you don’t feel the pressure so your body has more resistance to sleep.

As caffeine is hijacking and occupying these receptors, caffeine blocks the sleepiness signal normally communicated to the brain by adenosine. Tricking you into feeling alert and awake, despite the high levels of adenosine that would otherwise seduce you into sleep.

Ok, so we understand how it works, but what is the effect? As the author tells, “Sleep will not come easily or be smooth throughout the night as your brain continues its battle against the opposing force of caffeine. Most people do not realize how long it takes to overcome a single dose of caffeine, and therefore fail to make the link between the bad night of sleep we wake from in the morning and the cup of coffee we had ten hours earlier with dinner."

So, not having caffeine in our body (or having less possible) will help us sleep faster and better.

Are you getting enough sleep?

To find out, the author cites two questions that can help you answer that:

  1. “After waking up in the morning, could you fall back asleep at ten or eleven a.m.? If the answer is “yes, you are likely not getting sufficient sleep quantity and/or quality”

  2. “Can you function optimally without caffeine before noon? If the answer is “no”, then you are most likely self-medicating your state of chronic sleep deprivation.”

Alcohol and why it destroys your sleep

Some people think of alcohol as a sleep aid, believing that alcohol helps them to fall asleep more easily, or even offers sounder sleep throughout the night. Both are untrue.

Alcohol is a sedative, it “sedates you out of wakefulness, but it does not induce natural sleep. The electrical brainwave state you enter via alcohol is not that of natural sleep; rather, it is akin to a light form of anesthesia.”

So you will “sleep” but not get all the benefits of sleeping. Worse, it will make you worse, as alcohol fragments sleep, littering the night with brief awakenings making the sleep not restorative, and making you tired the next day.

Also, “alcohol is one of the most powerful suppressors of REM sleep that we know of”. So even if you drink a moderate quantity of alcohol in the afternoon or night, it will deprive you of your dream sleep.

So in summary, alcohol makes you feel more tired the next, will prevent the solidification of memory, and will not allow you to handle your emotions on your REM sleep. There are more side effects than benefits.

Types of sleep

We basically have two types of sleep REM (Rapid-eye Movement) and NREM (Not Rapid Eye Movement). When we sleep we cycle between the two many times during the night at around every ninety minutes.

But the ratio between the two types changes during the night. ​​During the initial half of the night, a significant portion of our ninety-minute sleep cycles is dedicated to the profound NREM sleep phase, while the REM sleep phase is limited. However, as we progress toward the second half of the night, there is a shift in this pattern, the majority of our sleep time is occupied by REM sleep, and the NREM sleep phase is either reduced or absent.

REM

REM sleep is intimately connected to dreaming. It is in this phase that you have most of the dreams (even if you don’t remember them). The ones that are hallucinogenic, motoric, emotional, and bizarre experiences with a rich narrative come from REM sleep.

“REM sleep can therefore be considered as a state characterized by strong activation in visual, motor, emotional, and autobiographical memory regions of the brain, yet a relative deactivation in regions that control rational thought.”

NREM

Not REM (NREM) sleep is subdivided into 4 stages, stages 1 and 2 are light NREM and 3 and 4 are deep NREM.

NREM is associated with the process of solidifying memories and also filtering the banal daily things that we don’t need to store from the important things that we have to remember.

Should you nap?

According to the book, we humans are being of biphasic sleep. Meaning that instead of sleeping only a big bout of slumber at night, we should also take a nap of 60 to 90 minutes at the beginning of the afternoon.

“the true pattern of biphasic sleep-for which there is anthropological, biological, and genetic evidence, and which remains measurable in all human beings to date - is one consisting of a longer bout of continuous sleep at night, followed by a shorter midafternoon nap.”

How and why we dream

The book has an entire part about dreaming that is very interesting, but overall, the dream serves a few purposes.

Sleep, specifically REM sleep, is needed in order for us to heal emotional wounds. It serves as an emotional therapy. For example, if you had an emotional experience and after you dream about it, it will be easy for you to move forward with your life. It is not that you will forget the the memory, but it will not trigger the same emotional charge as before, so REM sleep in a way helps you disassociate the memory from its emotional charge of it.

Dreaming also helps us decode our daily experiences, helping us in improving our learning and even the learning of physical tasks.

Another benefit is the enhancement of creativity and problem-solving.

The book also covers many other subjects, like insomnia, sleeping pills, etc that I didn’t have space to cover here, so I recommend reading the book or listening to the author’s podcast.

Favorite quotes

These are my 5 favorite quotes from the book.

“the shorter you sleep, the shorter your lifespan”

… humans (and all other species) can never “sleep back” that which we have previously lost is one of the most important take-homes of this book,

“Under-slept employees are not only less productive, less motivated, less creative, less happy, and lazier, but they are also more unethical. “

“Sleep has proven itself time and again as a memory aid: both before learning. to prepare your brain for initially making new memories, and after learning, to cement those memories and prevent forgetting.”

“If you are about to undergo an elective surgery, you should ask how much sleep your doctor has had and, if it is not to your liking, you may not want to proceed. No amount of years on the job helps a doctor “learn” how to overcome a lack of sleep and develop resilience.”

Other resources

These are my learnings from the book Why We Sleep: Unlocking the Power of Sleep and Dreams, written by Matthew Walker. A special thanks to Vancouver Public Library (VPL) for allowing access to the book for free.

Happy reading!

Liked this post? Check out other posts part of the series Learnings from books where my goal is to share what I learned from the book that I read. It is a mixture of review and summary with a bit of my opinion and point of view