I had heard about Why We Sleep, Matthew Walker’s book on the importance of sleep and the science behind it, on Tim Ferriss’s podcast with Amanda Palmer. To paraphrase, she said that the book changed her life, and left her wondering why she had never learned anything meaningful about sleep before then. I made a note to read it after hearing to that.
I’m extremely glad to have read the book. Walker lays out the importance of sleep so clearly that it seems unbelievable that any individual could deny themselves sleep, let alone the majority of our society. Walker dissects studies that link things like Alzheimer’s, stress, memory and happiness to the quality of a person’s sleep, and leaves very little room to doubt his ultimate hypothesis: That sleep is a key component to overall health and wellbeing, and we need to start making efforts to prioritize it.
Some notes:
- Daylight savings: Heart attacks, strokes, and car accidents all spike in the day following daylight savings, and then return to their daily average in the days following. If simply losing one hour of sleep is so trivial (a case made by many people sleeping 5-6 hours a night) then that spike is very difficult to explain.
- Losing NREM vs. REM sleep: The first half of a full night’s sleep is dominated by NREM (non-REM) sleep, when the body repairs and regrows tissues. The second half is dominated by REM sleep, which is associated with learning, memory and your mood. For that reason, if you are cutting your night’s sleep short (say, going to bed at 12am and waking up at 6am) you are not reducing your NREM and REM sleep evenly – you’re disproportionately affecting your REM sleep.
- Effects of caffeine: Adenosine is a chemical that gradually builds in your body throughout the period of each day that you are awake, and then clears out as you sleep. It is effectively a drowsiness chemical. When you drink coffee, or other caffeine, it is blocking your body’s adenosine receptors, making them perceive your body as being less drowsy than it is. When the caffeine wears off, you are left with a significant buildup of all the adenosine that your body has accumulated but that has not yet clung to the receptors, leaving you to crash. Caffeine also takes far longer to truly wear off then I had thought, meaning that even if you are able to fall asleep after drinking a coffee at 5pm or so, the chemical will still be in your body and still be affecting how you sleep.
- Effects of alcohol: No surprise that alcohol results in a poor night’s sleep. Anyone who has woken up after a late night at 6am with a beating heart and racing thoughts will know what I’m talking about. Walker makes it clear than even one or two drinks will impact how you sleep, and more importantly will cut into your REM sleep, affecting your ability to retain information and memories. Seems like a bad trade off just for a drink.
- Techniques for sleeping better: This should be a refrigerator magnet for everyone in the US. Go to bed at a consistent time each night. Don’t take long naps in the early evening, or you will deplete the adenosine required to make you fall asleep that night. Don’t look at blue light (or be in a bright room) before bed or you will confuse your body’s circadian rhythm. Don’t spend non-sleeping time in bed. Don’t eat right before bed. Don’t drink a lot of liquids right before bed or you will cut into your sleep to go to the bathroom. Sleep in cool temperatures. Don’t drink alcohol (period, but particularly not every night and not in high doses). Don’t drink caffeine past noon. I’m sure there are more.
- No such thing as catching up on sleep: This one was crucial for me. Sleep cannot be regained. If you sleep five hours a day during the week, losing significant chunks of your REM sleep, bingeing on the weekends will not make up for that lost chunk of sleep. You will still see impacts to your mood and memory.
- Sleep is critical to eating well: Study participants who slept poorly ate a few hundred calories more than their peers who slept well, which would lead to significant weight gain if continued throughout an entire year. Sleep is just as important as eating and exercising when it comes to maintaining good health.
- Teenager sleep deprivation: Teens see their circadian rhythms shift backwards (later sleep times, later rise times) as their bodies are developing, but often the time they start school is before the sun has come up. That results in them sleeping less than almost anyone in society, at a critical time in their development. Parents in particular are critical of teens sleeping in, mainly on the weekends, but what they fail to recognize is how sleep deprived their children are.
Links to Matthew Walker’s interviews with Peter Atia: