Why Type-A people might want to sleep more: a summary of Why We Sleep

Matthew Walker’s Why We Sleep has been one of the most impactful books I’ve read this year. Was first made aware of the book on Peter Attia’s podcast, and then received 3 independent recommendations to read the book from friends.

I read the book cover-to-cover, and took copious notes. Sharing a summary of these here both as a reference for myself, and in hope that it might move fellow Type-A people to prioritize sleep a little more.

Basic Sleep Patterns

There are essentially three kinds of sleep, which I will quickly highlight to make the rest of this post easier to read:

My sleep pattern on July 11, 2019 (as recorded by Fitbit)

1. Rapid Eye Movement Sleep (REM Sleep): This typically becomes more prominent in the early hours of the morning and is reflected in light blue color in the image above
2. Light Sleep (Stage 1/2 Non-REM Sleep): This is important for physical recovery and for rest. It is represented in the mid-hue blue color in the image above
3. Deep Sleep (Stage 3/4 Non-REM Sleep): This is important for memory, physical replenishment, and hormonal regulation

Sleep as a catalyst for learning

There have been a number of (well-replicated) studies that show the impact of sleep (specially REM sleep) for learning. I won’t link to the studies here, but will present some of their findings:

1. Deep sleep helps remove unnecessary neural connections. REM sleep strengthens useful neural connections. If you’re trying to learn and internalize new concepts, getting 7+ hours of good quality sleep is becomes a huge advantage
2. Deep sleep helps transfer and make safe newly learned information into long-term storage sites of the brain. REM sleep takes these freshly minted memories and begins colliding them with the entire back catalog of your life’s autobiography. I.e, REM sleep tends to be strongly linked to creativity
3. Practice, with sleep, makes perfect. Offline learning (letting your brain learn while you asleep after practicing through the day) tends to be more effective than online learning (simply powering through the task without sleep)
4. REM sleep fuels creativity. Deep sleep helps transfer and make safe newly learned information into long-term storage sites of the brain. But REM sleep takes these freshly minted memories and begins colliding them with the entire back catalog of your life’s autobiography

There are a number of studies that demonstrate this. In the interest of transparency — I have not looked at the studies myself, and am assuming that the author has not mis-represented them in his book:

• The working memory span is affected by sleep deprivation. When sleep deprived (42 hours of sleep deprivation) participants in a study were asked to remember a nonsense word and locate it among a number of similar words, the length of time they could hold it in their working memory decreased by 38% compared to rested individuals
• When students were given tests to learn the assignment of a 100 random names to random faces, those who had an afternoon nap outperformed those without an afternoon nap by 20%
• For athletes, sleep is important both before and after the game. A number of NBA players that voluntarily tracked their sleep saw a double digit percentage improvement in their rebounds, assists, points, and distance run (adjusted for time on court) when they slept atleast 7 hours before the game compared to days when they slept for less than 7 hours

Sleep deprivation and emotional reactivity

Sleep deprivation is strongly linked to psychotic disorders. It is unclear if this link is causal (i.e., does sleep deprivation trigger psychotic disorders, or do the onset of psychotic disorders cause sleep deprivation), but the link is fairly clear.

1. The amygdala (emotional centre of the brain) and the striatum (the hedonic centre of the brain associated with impulsivity and reward) becomes hyperactive with less sleep. They get decoupled from the rational control of the pre-frontal cortex
2. REM Sleep increases our ability to recognise and successfully navigate the kaleidoscope of socioemotional signals that are abundant in our culture — such as overt/covert facial expressions, major and minor bodily gestures, and mass group behaviour
3. Lack of sleep is as a key lifestyle factor determining whether or not you will develop Alzheimer’s Disease. Alzheimer’s is associated with the buildup of a toxic protein called beta-amyloid. These are flushed out while sleep because glial cells shrink by up to 60% to let cerebrospinal fluid to its work and flush out the toxic protein. But without deep NREM sleep, this doesn’t happen effectively

Impact of sleep on longevity

As we approach midlife, the body begins to deteriorate and health resilience starts its decline. The impact of insufficient sleep on our cardiovascular system escalates.

1. Adults 45 years or older who sleep fewer than 6 hours a night are 200 percent more likely to have a heart-attack or stroke in their lifetime, compared to those who are sleeping 8 hours a night
2. When adults with no existing signs of diabetes or issues with blood sugar were limited to sleeping 4 hours a day for just 6 nights, they were 40% less effective at absorbing a standard dose of glucose (compared to when they were fully rested)
3. Sleep has a significant impact on your immune system. In a study where individuals where exposed to the common flu virus, half the individuals sleeping an average of 5 hours an hour the week before were infected. However, only 18% of those with 8 hours of sleep the week before were infected

Takeaways and tips for better sleep

Reduce constant electric and LED light

The presence of light delays the onset of melatonin (a hormone that signals the brain to go to sleep) in humans. In particular, light receptors that perceive “daylight” are particularly sensitive to blue light. These are prominently present on LED screens.

Takeaway: Remove screens from your bedroom, and don’t use your phone/laptop for atleast 30 minutes before going to sleep

Regularize temperature

To successfully sleep, your core temperature needs to decrease by 2–3 degrees Fahrenheit. For this reason, you’ll find it easier to fall asleep in a room that is too cold rather than too hot. Fading light and a drop in core temperature signal to the brain that it must sleep. For this reason, splashing cold(ish) water on your face before sleeping is a good idea to help you get to sleep faster.

Note that drop in thermal temperature is a more important marker for sleep than absolute thermal temperature. So it’s generally a good idea to have the aircon in your bedroom at a lower temperature than that in your living room.

Bedroom temperature of 18–19 degrees celsius is ideal for sleep for most people — assuming standard bedding and clothing

Avoid caffeine in the evening

Caffeine makes you feel more alert by blocks receptors of a neurotransmitter called Adenosine. Adenosine signals to the brain that it should go to sleep. Because caffeine does not reduce Adenosine concentration and only blocks receptors, it wreaks havoc on your circadian rhythym when consumed at a time when adenosine concentration might be high.

For this reason, it’s a good idea to have caffeine in the morning (when your adenosine concentration is going down anyway), but a terrible idea to have it after 4PM. Caffeine has a half life of 6 hours. Consuming it in the evening will wreak havoc on your circadian rhythm.

Avoid alcohol before sleeping

A lot of people like to use a glass of wine or whiskey as a nightcap. But the kind of sleep (as measured by EEG sensors) that alcohol induces is far closer to that of a light anaesthetic than natural sleep.

Alcohol is one of the most powerful known suppressors of REM sleep. When the body processes alcohol, it generates aldehydes and ketones. Aldehydes, in particular, will block REM sleep. This is one reason why alcohol before sleep is particularly bad for those trying to learn new skills. If you must have alcohol for social reasons, try to consume it in limited quantities, and have it in the early evening instead of late at night.

Disagree and/or have counterclaims? Let me know!

I’m no expert on the matter, and am trying to relay the takeaways I had from the book because I honestly believe they could help other people. If you have counterclaims for the ideas raised in this post, please do let me know so I can research them for myself and update this post accordingly.

I’m a tech startup founder, human-optimisation junkie, and machine learning enthusiast. Do leave a note on Twitter (rishdotblog) or email me at rishabh@loki.ai to give feedback, or just say hi! :)