An absolute must read for everyone!!! This book made me realize how little awareness there is on the importance of sleep. School curriculums cover a variety of topics including sex education, health & fitness, drug use, etcâŚ. However, I donât know of any country that covers sleep, a fundamental component of our daily routine, comprising almost a third of our entire lives, in their educational curriculum.
This book is the best source of information Iâve encountered on the topic of sleep. It is extremely well balanced between scientific information, actionable advice, and ongoing empirical evidence from recent studies. Unlike other books Iâve tried to read related to neuroscience, this one is neither too scientifically terse, nor too âhand-wavyâ.
My biggest takeaway was that if we do everything right in life (eat well, exercise, meditate, stay focused, work smart/hard, etcâŚ), the fruits of our labour wonât be nearly as large if we also donât also supplement it with sufficient sleep. A lack of sleep will cause you to gain weight more easily, make you more emotionally unstable, make it more difficult to remember things, lead to less creative ideas, and make it more difficult to improve in whatever mental or physical goals one may have.
My favorite anecdote from the book was one about Thomas Edison. He was supposedly a short night time sleeper, but a habitual daytime napper. During his naps, he would hold a metal bearing in his hand. The moment he would fall asleep, which naturally caused him to lose muscle tone, the sound of the dropping ball caused a noise loud enough such that he woke up. Upon waking up, he immediately wrote down all the ideas that came to his mind.
As a software engineer, I kept drawing comparisons between sleep and garbage collection. There is no such thing as a good software, and similarly, there is no such thing as a good biological organism. It kind of works, evolves over time, hacks and workarounds keep building on top of each other, and common patterns emerge. In order for a dolphin to achieve NREM sleep underwater, they can only do so with half a brain at a time. Some people may see this as a brilliant evolutionary adaptation, but another way of looking at it is as a hack where a mission critical system canât shut down, but is also out of resources.
Iâve seen a lot of âfaux-scienceâ related to sleep over the years, but Matthew Walkerâs book is by far the closest thing we have have to a âSleep Bibleâ. He makes it very clear throughout the book how much more there is to learn. The state of research on sleep is still in its infancy, and it feels as though he is constantly alluding to a sequel that may come out in a couple decades. One thing is clear though: sleep is one of the most important factors we can and should control. It is crazy to think that humans are the only animals who deprive themselves of sleep, especially given that itâs ânear impossibleâ (according to the author) to simply catch up on lost sleep.
====== Notes Below ======
Pro Tips For Good Sleep
Complete darkness - buy blackout curtains if necessary
Take a hot bath to relax and reduce your inner body temperature before sleep
Reduce the temperature of your surroundings to approximately 18.5C
Avoid caffeinated drinks up to 8 hours before bedtime
Donât be too full, nor too hungry
Wash your hands and face before bed to reduce the temperature of your extremities.
Larks vs Night Owls
I typically sleep between 11:30pm and 7:00am. As a Lark, Iâve always looked at Night Owls as people who constantly procrastinate and canât commit to a reasonable day/night schedule. Shamefully, I have to admit what a poor point of view that was⌠From an evolutionary standpoint, Night Owls were the ones who kept guard at night while the Larks went to bed early. This is a brilliant evolutionary survival tactic. It is very sad that Night Owls are forced to deprive themselves of sleep by adapting to the âmodern day standardsâ of the start and end of a workday. This can only lead to health issues and this is why flexible work hours are so much better.
Larks or Night Owls, humans also evolved to have a mid afternoon nap. This is often why energy levels dip in the afternoon, and why the â4 oâclock coffeeâ is a known widespread concept. It it sad that our society is depriving us of thisâŚ
The Chemistry Of Sleep
Melatonin, adenosine and caffeine are the three key chemicals involved in either promoting or inhibiting sleep.
Adenosine is a chemical that builds up while we are awake, and is dissipated away while we sleep. On days when we are very active (i.e. a long hike), it builds up faster, which explains why we are exhausted by the end of the day. Similarly, if we donât get a full night of sleep, an insufficient amount of it dissipates away, which is why we remain tired.
Caffeine, which needs no introduction, binds to the same receptors as adenosine. Since the receptors get blocked, it temporarily prevents us from being tired. It is fascinating to think that this basic function has made it the second most traded commodity on earth, second only to oil.
Fun fact: The author mentioned a study done by NASA on spiders who were exposed to caffeine. Spiders on caffeine cannot make a spider web at all, which is a tad concerningâŚ
Melatonin is a hormone that âkicks off sleepâ and it only gets produced in complete darkness. The smallest bit of light, especially blue LED light produced by phones, inhibits melatonin production. This is one of the reasons why darkness is so vital for a good nightâs sleep.
One of the topics I wish the author had discussed in more depth are the quantitative numbers, limits, and impacts of drinking coffee or taking melatonin pills. How much coffee is too much? Are melatonin pills okay? If so, at what dosage?
NREM vs REM sleep
Our brain continuously switches between REM sleep and NREM sleep. In terms of information processing, a high level way of thinking about it is:
1. Wake state: reception of new information
NREM sleep: Storage of new information from short term to long term memory. Solidifies memories.
REM sleep: Integration of new data with old experiences. Creates creative connections.
As we get older, we get less and less deep sleep. More precisely, we lose approximately 80-90% of our deep sleep by the age of 80âŚ
NREM Sleep
Muscle tone is often maintained during NREM sleep, there is no dreaming, and that is primarily when growth hormone is secreted.
NREM sleep can be achieved with only half the brain if necessary. Dolphins, for example, achieve NREM sleep with half a brain at a time, because the other half is necessary to maintain life preserving activities in the water. Birds on a wire do something even more fascinating. The birds on opposite end of a long line sleep with half a brain, keeping one eye out for predators, while all the birds in the middle are able to get full sleep with both parts of the brain at the same time.
Birds on transcontinental flights achieve NREM sleep by taking ultra small naps (while flying) that last seconds. As short as this is, it is sufficient for whatever NREM sleep needs to do.
A 2006 German study sent electrical stimulus to the brain during NREM sync with a function that was in sync with that of the brain. This resulted in a 40% increase in memory! Even though these studies are still questionable and have a lot of work ahead, Iâm really excited for whatâs on the horizon.
REM Sleep
Rapid Eye Movement (REM) sleep is a special type of sleep that requires both parts of the brain. It is not present in amphibians or water based animals. It is the only time humans dream. It also completely parallelizes the body when a person enters this mode of sleep.
The main purpose of REM sleep, as far as we know, is creativity. A few of the most famous examples include the fact that the periodic table of elements conceived by Dmitri Mendeleev came to him in his sleep. John Lennon, amongst several other musicians, also claim to have come up with iconic songs in their sleep and recorded them, sometimes without recollection, immediately upon waking.
REM sleep parallelizes the body so we do not move or react to events happening in our dreams. It is worth mentioning that the Homo Erectus was the first dedicated group sleeper, because muscle tone cannot be lost when you are on a tree.
Sea animals cannot enter REM sleep since bodily functions are always necessary for survival underwater. Interestingly enough, some animals such as seals, who can live both under or above water experience little to no REM sleep while underwater and a normal amount when they are above.
Time Tracking during sleep
An unexplained phenomenon is time dilation during sleep. Some people claim to have lived a thousand years, while others experience a single minute throughout a full nightâs sleep. Simultaneously, our bodies are able to keep some sort of biological clock, which is why we often find ourselves waking up a couple minutes before the moment the alarm clock is set to go off.
Practice doesnât make perfect, practice+sleep makes perfect
Motor functions are improved in the last two hours of sleep.â¨â¨Anyone who is practicing a new skill (athletes who are training, babies learning to walk, musicians practicing a new piece, etcâŚ) need to sleep to solidify those skills. Individuals can practice a new skill the whole day and see little to no improvement towards the end of the day. It is likely that they may get tired or that their brain has not made the proper connections to master the skill. The last two hours of sleep, which a lot of people unfortunately miss, is the moment when these new skills are mastered. For example, the author mentioned a pianist who would only be able to âmasterâ a musical piece upon waking, rather than in the evening after a full day of training.
Alcohol
Drinking alcohol in the evenings before bed is a very common and socially acceptable phenomena, so I was saddened to find out how bed it really isâŚ. Alcohol is one of he strongest inhibitors of REM sleep, which means that we canât make any new âbrain connectionsâ if we drink before bed. Moreover, drinking before bed can cause problems in the connections we make based on information we received from a few days ago. This means that if you were were preparing on Tuesday for a test thatâs happening the following Monday, drinking before bed on Friday night could have implications regarding how much information you retain. The only workaround for this is to drink sufficiently early in the day such that the alcohol is fully digested by the time you go to sleep. Brunch samosas anyone?
I know that being healthy during pregnancy is very important, but this book made me fear for every child whose mother has a glass of wine while theyâre pregnant. Alcohol can very readily transmits through the placenta layer. Seeing how fetuses spend almost all their time in REM sleep, and brain development is vital during pregnancy, any bit of alcohol can have huge longterm implications on the childâs development.
DD: Drunk Driving vs Drowzy Driving
The author pointed to several studies proving that drowsy driving is as bad, if not worse, than drunk driving. If driving is really a necessity, taking a 30 minute nap is the best thing you can do. The author does recommend to wait an extra 20 minutes after waking for the sleep inertia to dissipate. The author also mentioned that the equivalent of a breathalyzer for alcohol may be coming for sleep sooner than we might expect.
One of the interesting ideas that was brought up in this chapter is the fact that insurance does not take sleep patterns into consideration. Insurance companies look at age, health, fitness, and much more. Sleep arguably plays a much bigger role than all of those, so why is it so under the radar?
Emotion
The Amygdala, a part of the brain responsible for managing emotional balance, is a lot more responsive in sleep deprived patients. This might explain why sleep deprived humans are more likely to âsnapâ.
Thereâs a saying that âtime heals all woundsâ, but it very much seems that time, with the aid of sleep, is what ultimately heals wounds. It is near impossible to be mentally or emotionally stable without sufficient sleep.
The author mentions that there are studies which have shown how sleep deprivation can act as an antidepressant, but it seems to be true for a very small number of people. One of the reasons I loved this book is because the author constantly kept bringing up examples like these. He was able to simultaneously show how little and how much we know about sleep, and paved the way for a followup book sometime in the distant future :)
Cancer
Cancer was touched on several times throughout the book. The main takeaway was that less sleep leads to a higher risk of cancer and a shorter life span. There are humans case studies and rat experiments supporting this. However, I feel like almost anything nowadays leads to a higher risk of cancer, so Iâm not too sure how much to read into this…
Exercise
There wasnât a lot of evidence in the book suggesting that exercise leads to better sleep. Perhaps exercise causes more adenosine to build up in a shorter time period, which indirectly leads to better sleep. However, there was a directly correlation between sleep quality and exercise the following day. A bad nightâs sleep definitely makes it more difficult to exercise the following day.
Adolescence, Age and Sleep
The author spent a fair amount of time discussing the changes in sleep pattern sthat take place during adolescence.
The circadian rhythm in children runs on an early schedule. However, when children reach adolescence, during puberty, the timing of the supercharysmatic nucleus moves forward a lot. This causes teens to start going to sleep later and waking up later. The exact reasoning for this is not clear, but there are some theories that it is an opportunity for kids to spend more time away from parents and learn to be on their own.
Seeing how the brain continues to develop and mature into our mid 20s, an insufficient amount of sleep at this age can easily increase the likelihood of mental diseases in the future.
In adults, melatonin is released much earlier in the day, which is why itâs common for them to fall asleep on the couch.
Random Points
Some prisons implement the âno uninterrupted sleepâ policy. A method of holding people hostage and making them go crazy is simply by not letting them get uninterrupted sleep.
The longest period without sleep was removed from the Guinness book of world records. This shows how unhealthy of a task it is.
Modern MRI scanning techniques can detect the subject of our dream. It is very coarse, but some experiments can determine if a person is, for example, dreaming about a car.