This is not a book summary or review by any means, just some of the things that stuck with me. I highly recommend reading or listening to the entire book.
The book cover.
On the importance of sleep
Everyone needs 7.5-8hrs of sleep every night. There’s a very rare condition in which some people need only 6hrs, but you don’t have it (it’s extremely rare). You might be able to function on less, but it won’t be optimal (understatement) and it’s (very) unhealthy.
Even 30-60min of sleep deprivation per night has measurable negative impact on your cognitive ability the next day. Conversely, napping, even for 30 mins has a measurable positive impact on your cognitive ability.
Multiple days of even minor sleep deprivation adds up to terrible effect. Paraphrased: “Driving a car on a few subsequent nights of 6hrs of sleep is comparable to driving slightly drunk”.
Regular sleep deprivation, even if minor, measurably increases your risk of all sorts of diseases (cancer, cardiovascular, alzheimer’s) as well as the chance of getting sick from infectious diseases (e.g. flu, common cold).
Similarly, many ailments or impairments are caused or exacerbated by poor sleep hygiene but incorrectly diagnosed. If you have an ailment (acute or chronic), make sure to fix your sleep first.
We often hear of the “holy trinity” of health being Sleep, Diet and Exercise. While the 3 clearly interrelate, of those 3, you should priortize sleep. There’s irrefutable evidence that after a night of poor sleep, you’re much less likely to exercise and make (much) poorer food choices. This isn’t your fault, it’s your body’s way of compensating for the lack of sleep.
12 tips for better sleep, from the book’s Appendix.
Sleep and society
The cliché that some people are “morning larks” while others are “night owls” is true. 40% of the population reaches peak wakefulness early in the day (and naturally rises/goes to bed early), while 30% only reach it during the evening time (and naturally rises/goes to bed late). The remaining 30% is somewhere in between.
How the general populace is divided according to their chronotype - whether their natural peak wakefulness occurs towards the morning or evening. Data from the book.
Our societal structures and schedules hugely favor the morning types by early morning start times for school and work. This means that non-morning types (i.e. 60% of the populace) are structurally forced to function outside of their natural sleep patterns, with poor sleep and sleep deprivation as a consequence.
This means we’re leaving a lot of unused brain-power on the table of the non-morning types, while also systematically disadvantaging them. It’s also very likely that this causes unnecessary accidents and mistakes.
Teenagers are especially hard hit because they have a different circadian rythm than adults, shifted 2-3 hrs later than adults. As a consequence, having teenagers take tests (that can potentially influence their life’s direction) in the morning is a (very) bad idea - yet that’s what we do.
Overall, lack of sleep is hugely detrimental for our children (of all ages). For example, there are clear links between poor sleep hygiene and (incorrect) ADHD diagnoses in young children. Make sure your kids get enough sleep.
It’s a myth that people need less sleep starting in middle age, on the contrary. What is true, is that they often have a harder time going to and staying asleep for a variety of reasons.
It should be clear that the cost of poor sleep hygiene to society is huge: from the cost of sleep deficit related accidents and workplace mistakes to the opportunity cost of not capitalizing on well slept brains, to children’s lives being determined due to bad morning test scores.
It’s time that we all start taking sleep more seriously: from policy makers, to company leaders to all individuals, sleep should be a top priority. The evidence is overwhelming.