Thanks for the review!
I am only halfway through the book, but I am already firmly resolved to highly prioritize 8 hours of sleep each night.
I would encourage everyone to read the book while experimenting with getting enough sleep consistently (e.g., for a week), and see for yourself whether the short-term benefits are worth it.
Maybe my assessment is not accurate, but it seems to me that "8 hours of sleep each night is extremely beneficial (relative to other stuff you could do)" is not a mainstream belief among Less Wrong readers. (Though I could find examples, e.g., http://www.thebayesianconspiracy.com/2018/06/61-biohacking-101/ and https://www.lesswrong.com/posts/KsrTZtu48qdkAeSht/a-few-tips-on-how-to-generally-feel-better-and-avoid .)
I would love to hear that I am completely wrong here, but if I am not, then why is that? Isn't the evidence for the benefits of sleep as overwhelming as the book describes it?
Even after correcting for the book's bias toward favoring sleep (note that I am not qualified to assess the existence/size of such bias), the evidence still seems overwhelming to me.
A few things that I would add to your great summary:
The book gives another argument for the huge benefits of sleep, which I find quite intuitive:
Addressing the question of why we sleep from an evolutionary perspective only compounds the mystery. No matter what vantage point you take, sleep would appear to be the most foolish of biological phenomena. When you are asleep, you cannot gather food. You cannot socialize. You cannot find a mate and reproduce. You cannot nurture or protect your offspring. Worse still, sleep leaves you vulnerable to predation. Sleep is surely one of the most puzzling of all human behaviors.
On any one of these grounds—never mind all of them in combination—there ought to have been a strong evolutionary pressure to prevent the emergence of sleep or anything remotely like it. As one sleep scientist has said, “If sleep does not serve an absolutely vital function, then it is the biggest mistake the evolutionary process has ever made.”
Yet sleep has persisted. Heroically so. Indeed, every species studied to date sleeps.
I think this quote from the book is also of particular interest to Less Wrong readers:
You Do Not Know How Sleep-Deprived You Are When You Are Sleep-Deprived
The third key finding, common to both of these studies, is the one I personally think is the most harmful of all. When participants were asked about their subjective sense of how impaired they were, they consistently underestimated their degree of performance disability.
(As mentioned in another comment, I think the studies that Walker refers to here are these two:
The Cumulative Cost of Additional Wakefulness: Dose-Response Effects on Neurobehavioral Functions and Sleep Physiology From Chronic Sleep Restriction and Total Sleep Deprivation ( https://academic.oup.com/sleep/article/26/2/117/2709164 )
Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose‐response study ( https://onlinelibrary.wiley.com/doi/full/10.1046/j.1365-2869.2003.00337.x )
I would summarize the following quote by "You might believe that your current state is close to your optimal state, but you just forgot (or never knew) how much better life could be if you got enough sleep consistently":
Similarly problematic is baseline resetting. With chronic sleep restriction over months or years, an individual will actually acclimate to their impaired performance, lower alertness, and reduced energy levels. That low-level exhaustion becomes their accepted norm, or baseline. Individuals fail to recognize how their perennial state of sleep deficiency has come to compromise their mental aptitude and physical vitality, including the slow accumulation of ill health. A link between the former and latter is rarely made in their mind. Based on epidemiological studies of average sleep time, millions of individuals unwittingly spend years of their life in a sub-optimal state of psychological and physiological functioning, never maximizing their potential of mind or body due to their blind persistence in sleeping too little.
In chapter 7 (Too Extreme for the Guinness Book of World Records) Walker mentions a research by David Dinges which seems kind of similar to what you described. I didn't find a reference in the book, but I found this highly cited paper, which seems to me like the one he was referring:
The Cumulative Cost of Additional Wakefulness: Dose-Response Effects on Neurobehavioral Functions and Sleep Physiology From Chronic Sleep Restriction and Total Sleep Deprivation
https://academic.oup.com/sleep/article/26/2/117/2709164
Walker mentions a research by Gregory Belenky with almost identical results that was published around the same time. I found a highly cited paper which seems to me like the one he was referring:
Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose‐response study
https://onlinelibrary.wiley.com/doi/full/10.1046/j.1365-2869.2003.00337.x
TL;DR
Walker has a sub-title "you do not know how sleep-deprived you are when you are sleep-deprived" in chapter 7, so you can guess what the researches above found.
No thanks. Knowing I helped you out is exactly the right reward for me :)