Book Summary: Why We Sleep
This post is about the learnings I got from the book “Why We Sleep” by Matthew Walker. Before I dive into that, let me preface this article with my personal experience with sleep. If you’re not interested in the personal story, and just want to get the TLDR on the book, click here.
Preface
I’ve always thought sleep was important. I never understood the people who claimed “I will sleep when I am dead”, as if sleep was a weakness of the human race (or the entire animal world), and we should be ashamed of ourselves for giving ourselves proper sleep.
Okay, I’ll admit there was a period in my life where I haven’t taken sleep seriously. I bet you had too (maybe even now).
High-school
In high school, I oftentimes stayed up late, because I was an avid gamer. This was a problem, because I had to wake up at 5:30am, so that including my 1 hour commute, I could get to school in time. The first class usually started at 8am (which is way too early for studying, but that’s for another discussion).
I was always a bit tired, but at least I could recoup some of the lost sleep during the bus ride (I can literally sleep anywhere). I never thought much of the lost sleep as a cause for me being tired. I honestly couldn’t connect the two at that age. I just thought, being tired, was… you know, normal. I counter balanced it with some energy drinks (highly not recommended).
When I brought the topic up with one of my friends (also high schooler), he said something along the lines of:
“If I’m always tired either way, I might as well sleep less, so that I have more time for other stuff (like gaming).”
This seemed logical at sixteen years old. From this point, I worried even less about my lack of sleep, thinking “I’d be tired either way”. I doubled down on video games, sometimes playing till 2am.
During the summer, my usual sleep routine was between 3-4am till 11-11:30am. The first meal of the day for me was usually the 2nd or 3rd meal for my other family members.
I was not the only one with this problem. Many of my friends had done the same.
University years
Fast forward to university, my sleep schedule got even worse. Yes, I woke up later than before, usually around 8 or 9am, but I also went to bed much later. The culprit around this time had not been video games, but rather, partying.
During the last 1 years of uni, my sleep got a little bit better, although I must admit, not intentionally. I just naturally started to party less and less as I matured, and didn’t have that much interest in gaming either. So there was less night-time distraction, which resulted in an improvement in my sleep.
The funny thing is, nobody bat an eye. Yes, my parents were initially adamant that I sleep at 10pm, but who can control a raging teenager, full of hormones, right? They eventually gave up. I did not even once hear the importance of sleep during my school years, as best I remember.
Adult years
Many people’s sleep suffers throughout their adult years. This is usually due to having to wake up early for work, and then also staying up late watching TV shows or movies (or doing whatever else). Fortunately, for me, this has been the opposite. As I started working, it was work-from-home. Yes, I’ve had meetings, but those weren’t starting usually before 10:30am, so if anything would cause me to sleep poorly, it wasn’t going to be my work hours. I’ve had periods where I’ve stayed up late, but I could always make up for it by sleeping in more.
I started learning about the importance of sleep by crossing a random YouTube video once. Since then, I’ve been interested in the topic. I mean if we spend 1/3 of our lives sleeping, we might as well learn some about it, right?
My sleep got better with each year since. This is not a result of adapting a single habit, or mindset, but rather getting exposed to more and more information about how good sleep is for you, and implementing some habits that I found useful. I will share what I’ve learned with you today (most insights come directly from the book, while others I’ve picked up online).
Why We Sleep
“Why We Sleep” is a book, that I believe, summarises perfectly well on why sleep is important and how to get good sleep. It is not the only material that has taught me the importance of sleep, nor the habits that might make it better. I watched countless YouTube videos on the topic, read a good number of articles. This post will try to summarise the book, as well as give you some more insights that I’ve learned along the years.
Keep in mind, this blog post is just a brief summary. If you want to understand more about sleep, and its importance, I highly encourage you to read the book. It’s seriously good!
Seriously, why do we sleep??
Our bodies constantly work all day. Even if you don’t lift a finger, your internal organs are working day and night. Your brain, is also an organ, and works really hard. As such, anything that works all day needs some “time off” or “rest”. Sleep is a process, in which your body party turns off, so that it can redirect energy from some activities to other activities, such as healing, regeneration, memory consolidation etc.
It’s funny, because many people think sleep is a waste of time. They think it’s a weakness that we need so much sleep that we spend 1/3 of our lives lying in bed. In fact, there is a famous saying that goes:
“I’ll sleep when I’m dead!”
If we spend this much in bed, and we are effectively defenseless during that time, wouldn’t you think mother nature (or evolution, call it whatever you will), had a pretty damn good reason for not eliminating it still?
If sleep, its quality and its amount was negotiable, evolution would be slowly enabling us to sleep less and less. But it is not happening. Our ancestors (to our best knowledge) slept just as much, as we do. Yes, they might have had other sleep habits, such as sleeping at different times, or even splitting sleep up into 2 chunks. They, nevertheless, did not sleep less or more, than we do. If there is any difference as to why we might sleep a tiny bit less than them, it’s the trap of modernity and corporate grind culture. Certainly not physiological reasons.
Sleep is essential for:
- repairing bodily damage,
- healing tissues,
- strengthening immune system,
- conserving and restoring energy,
- consolidating memories and experiences,
- flush out toxins that accumulate during wakefulness.
(just to name a few)
Some animals even evolved so they could sleep with half of their brain, while the other half is actively working. Some even can sleep while moving (i.e. swimming). If sleep was not important, why would evolution work in ways to enable these animals to sleep even when it’s “inconvenient”?
We sleep, so that we may stay alive. Recent studies found that sleeping less increases the chance of diabetes, cancer, dementia, bone and muscle loss. Sleep is essential for our bodies to keep working. It is not something that’s negotiable, not even close. Sleep is crucial for cognitive function, emotional well-being and physical recovery.
How do we, and how should we sleep?
Our sleep is mainly influenced by something that we call the “circadian rhythm”.
Circadian rhythm refers to the natural, internal processes that regular the sleep-wake cycle in living organisms, typically following a 24 hour cycle. It is observed in animals, plants, and even some microorganisms.
The primary external cue that influences circadian rhythm is light. Exposure to light during the day helps regulate the sleep-wake cycle, while darkness signals the body to prepare for sleep.
People’s circadian rhythm varies. This is why some people identify as “night owls”, while some say they’re “morning people”. Not everyone needs to sleep at the exact same time to have quality sleep. The reason for this is probably coming from the fact that our ancestors had to stay awake during the night to watch predators and guard the camp. The “watchers” naturally developed a tendency to sleep later and wake up later, while the other people developed a tendency to sleep and wake up earlier.
Disruptions to circadian rhythms, such as those caused by shift work, jet lag or irregular sleep patterns can lead to degradation in sleep quality, or even sleep, metabolic and mood disorders.
Darkness
There are various signals that tell your body, that now would be a good time to go to sleep. As I’ve already mentioned, darkness is one of those. When you’re seeing less light, your body naturally produces more hormones that signal your body to “get sleepy”. This is why looking at your phone at 11pm is probably not a good idea (or at any other device for that matter, with some exceptions). Devices emit blue light, which signals to your body: “no need to get sleepy, there is light, so it must be the middle of the day”.
Cold
Another signal is temperature. The outside temperature naturally lowers during the night, which also signals the body to wind-down and sleep. Since it’s been a while since we’ve slept outside, we need to make sure our rooms are colder during the night. This might mean turning off the heating, or using AC. Using less layers of sheets also works. (Just be careful with humidity levels, as AC can make the air drier. Use a humidifier if you notice that by the morning your throat and nose are too dry.)
Sleep pressure
Sleep pressure is another big factor in sleep-wake cycles. Sleep pressure uses the hormone called adenosine to signal tiredness and sleepiness to your body.
Adenosine builds up during the day, and gets cleared out during the night. If you have more sleep with better quality, more adenosine clears out. If you have poorer sleep or too little sleep, adenosine remains from the previous day in your system. This is why sleeping less usually has a “crash” after a couple days or weeks. Your body experiences such high adenosine levels, that it can’t keep anymore, it must rest and clear it out. The fancy term people usually use for built up adenosine is “sleep debt”.
All nighters are terrible for you. Your adenosine levels cannot reset. You might feel a spark of energy as the sun comes up (because of your circadian-rhythm), you’ll feel awful in the afternoon as almost two full days worth of adenosine is in your body.
Caffeine (among other things) blocks receptors that sense the presence of built-up adenosine. Caffeine does not stop adenosine from building up. You are tired, you just don’t feel it. People who get enough quality sleep experience less benefit from drinking caffeinated drinks. If your adenosine is cleared out from a good night’s sleep, caffeine has much lesser of an effect (also different people have different reactivity to caffeine). Older people break down caffeine slower than young people.
Caffeine half life is 6 hours on average. It is usually recommended to stop consuming caffeine 12 hours or more before bed (14-16h is even better, or… not consuming caffeine in the first place, but this is not a post against caffeine - use it responsibly).
Sleep cycles
Our sleep has something called “sleep cycles”. This includes deep sleep, REM sleep, and light sleep. The majority of deep sleep happens early on in our circadian-rhythm. The majority of REM sleep happens after we’ve been asleep for a while.
Different sleep cycles have different purposes. Deep sleep is the most restorative sleep stage. It is essential for tissue growth, muscle repair, immune system strengthening. REM sleep is associated with dreaming and heightened brain activity. REM sleep plays a crucial role in processing emotions and experiences. It is also important for memory consolidation. It supports brain development and builds new neural pathways. Light sleep is what connects REM and deep sleep together.
Generally the more deep and REM sleep you get, the better.
Research has found that deep sleep happens more before midnight. If you want to get more deep sleep, it is crucial to go to sleep preferably latest at 10pm. If you go to sleep after midnight, your deep sleep will suffer.
To maximise deep and REM sleep, focus on winding down before bed, decreasing your heart rate and stress levels. If you carry stress into your sleep, your body naturally experiences less deep and REM sleep. Less stress means more relaxation, which means more deep and REM sleep. You also need to make sure that you sleep enough, so that there is time for your body to go into these cycles for enough amount of time.
Snoring or sleep apnea can affect deep and REM sleep, a lot. If you constantly feel tired even though you’re sleeping enough, it might be a sign that you’re snoring or have sleep apnea, and your body simply cannot get enough deep and REM sleep during the night. To find out if you are snoring, there are free iOS and Android apps that record audio throughout the night. To find out if you have sleep apnea, visit your doctor, they’ll likely recommend to do a sleep study.
Interruptions to sleep
People think that when they go to bed at 11pm and wake up at 6am, they must have slept 7 hours. I mean, it’s logical, isn’t it?
Sadly, it doesn’t work that way. Even if you don’t seemingly remember waking up, we all experience mini-wake-ups during our sleep. Even if each of these only lasts 10 seconds or a minute, it is an interruption nevertheless. Each of these interruptions means less deep and REM sleep. The amount which you’ve actually spent asleep is most likely less than the amount you’ve spent in bed. This is called “sleep efficiency”. Younger adults usually have 95+% sleep efficiency, this decreases as we age.
You need to take this into account when planning for your sleep. Aiming for half an hour or an hour more time in bed will usually get you your planned sleep amount. I.e. if you intend on sleeping 8 hours, be in bed for at least 8:30 (watching Netflix in bed doesn’t count).
Summary / Takeaways
The above do not reflect all insights from the book, they rather summarise what I thought was most important in understanding and getting good sleep.
Many things affect sleep, however focusing on a few important things can drastically improve our sleep quality. In my experience these are the most important things when it comes to good sleep:
- Sleep consistently (same bedtime, same wake up time every day)
- Sleep enough (varies for each person, min. recommended 7+ hours)
- Reduce blue light before bed (blue light blockers, less screen time)
- Sleep in a dark, cold room
- Avoid caffeine 12 hours before bed
- Avoid alcohol and other drugs completely
- Don’t eat 3-4 hours before sleep (digestion is disruptive to sleep)
- Don’t exercise 3-4 hours before bed (except for light yoga or walking)
- Don’t do stressful activities before bed (no fighting with spouse)
- Do relaxing activities before bed (warm shower, reading a book, yoga)
Others will tell you other “pro tips” or “magic formulas”, but the truth is, if you focus on these basics, you’ll get much better sleep than the vast majority of people. Sleep doesn’t need to be complicated and involve a 3 hour morning and evening routine.
How do you know you’re doing a good job sleeping?
Measuring sleep has gotten more and more accessible in the recent years. You don’t need expensive, huge machines to do it. Of course, the devices that exist are limited in capability, but in my experience they’re seriously good nowadays. I am not affiliated with any of the recommendations here, I’ve used all of these products and found them genuinely useful.
Some sleep trackers that are good:
- Whoop (screenless sports band)
- Oura (smart ring)
- Apple Watch (+ third party app like AutoSleep, Bevel or Athlytic)
These tools (and there are probably other similar ones as well) can help you a lot in figuring out your personal sleep patterns and potential problems. They’re not magic pills, so don’t expect them to be 100% accurate, but in my experience they’re pretty accurate. I’ve used them to monitor my sleep habits and quality. They also act kind of as an “accountability” mechanism. They gamify sleep, and motivate you to get better scores by keeping better sleeping habits. For some people they might cause them to stress to much over their scores and sleep, if this is you, stop using these products because it might actually harm your sleep if you stress too much over your morning scores. ;)
Now
Nowadays I feel like my sleep is amazing. I’ve watched my patterns for years, measured my sleep for years, and I can tell you, good sleep doesn’t take 20 habits and a 3 hour wind-down routine. I’ve followed basic principles such as consistency. I also pay a lot of attention to reducing stressful stuff before bed. No horror movies, exercise, bag of potato chips or the like. The lower my HR is before bed, the better I sleep. HR is usually a good indication of overall bodily stress. The 20/80 rule definitely applies to sleep habits. Change the most important things and watch how your sleep becomes better, and you become a more relaxed, productive, and overall happier human being. If there is one magic pill in life that can make you feel better, it’s better sleep.
Thank you to Matthew Walker for writing “Why We Sleep”. I highly encourage you to read the book.
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These blog posts are mainly written for myself so that I can improve my writing, but if some people find it and even just 1% of those find it useful, it accomplished more than I’ve ever wanted it to.
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