Review: Why We Sleep, by Matthew Walker

Russ Allbery eagle at eyrie.org
Sat Oct 28 20:34:18 PDT 2017


Why We Sleep
by Matthew Walker

Publisher: Scribner
Copyright: October 2017
ISBN:      1-5011-4433-2
Format:    Kindle
Pages:     341

The world is full of theories, and corresponding books, about things
that will make you healthier or prevent disease. Nearly all of them are
scams, either intentional or created through the placebo effect and the
human tendency to see patterns that don't exist. The rare ones that
aren't have a certain pattern: they're grounded in our best
understanding of biology, align with what our body wants to do anyway,
have been thoroughly studied using proper testing methodology, and
don't make money for powerful corporations.

I'm fairly sure this is one of those rare ones that isn't a scam. And,
if so, it's rather important and worth your attention.

Matthew Walker is a professor of neuroscience and biology at the
University of California at Berkeley, where he's the founder of the
Center for Human Sleep Science. He's not a doctor; he started medical
training, but (as he says in the book) found himself more attracted to
questions than answers. He's a professional academic researcher who has
been studying sleep for decades. This book is a combination of summary
of the current state of knowledge of academic sleep research and a
plea: get more sleep, because we're literally killing ourselves with
the lack of it.

Walker opens the book with a discussion of the mechanisms of sleep: how
we biologically fall asleep and why, how this has changed over time,
and how it changes with age. Along with that, he defines sleep: the REM
and NREM sleep cycle that you may have already heard of, how it
manifests itself in most people, and where dreams fit in. The second
part then discusses what happens when you sleep, with a focus on what
goes wrong when you don't. (Spoiler: A lot. Study after study, all
cited and footnoted, has found connections between sleep and just about
every aspect of mental and physical health.) The third part does the
same for dreams, fitting them into the picture along with a scientific
discussion of just what's going on during dreams. The fourth and final
part tackles the problem: why don't we get enough sleep, and what can
we do about it?

I will warn in advance that this book will make you paranoid about your
sleeping patterns. Walker has the missionary zeal of an academic who
has sunk his teeth into something really important that society needs
to take into account and will try to drown you in data, analysis,
analogies, and sheer earnestness until you will believe him. He wants
you to get at least seven, and preferably eight, hours of sleep a
night. Every night, with as little variation as you can manage.
Everyone, even if you think you're someone who doesn't need as much
sleep (you're probably not). There's a ton of science here, a great
popularization of a whole field of research, but this is also a book
that's trying to get you to do something.

Normally, that sort of book raises my shields. I'm not much of a
believer in any book of the general genre of "most people are doing
this basic part of life wrong, and should do it my way instead." But
the hallmarks of good science are here: very widespread medical
consensus, no corporate interest or obvious path to profit, and lots of
studies (footnoted here, with some discussions of methodology —
although not the statistical details, which will require looking up the
underlying studies — and careful caveats where studies indicate
correlation but may not find causes). And Walker makes the very telling
point early in the book that nearly every form of life on the planet
sleeps in one way or another (defined as a daily recurring period of
time during which it doesn't respond to outside stimulus), which is a
strong indicator of universal necessity. Given the vulnerability and
loss of useful hours that come with sleep, one would expect some
species to find an evolutionary path away from it if it were
dispensable. But except for extremely short-lived species, we've never
found a living creature that didn't sleep.

Walker's argument for duration is also backed up by repeated studies on
human capability before and after various quantities of sleep, and on
studies of the sleep phases in various parts of the night. Study after
study used six hours as the cutoff point and showed substantial
deterioration in physical and mental capabilities even after only one
night of short sleeping. (Reducing sleep to four hours is nearly
catastrophic.) And, more worrisomely, that degradation is still
measurable after "catching up" on sleep on subsequent nights. Sleeping
in on weekends doesn't appear to fully compensate for the damage done
by short-sleeping during the week.

When Walker gets into the biological reasons for sleep, one starts to
understand why it's so important. I think the part I found the most
fascinating was the detailed analysis of what the brain is doing while
you sleep. It's not inactive at all, even outside of REM sleep. Walker
and other sleep researchers have done intriguing experiments showing
how different parts of the sleep cycle transfer memories from short to
long term storage, transfer physical skills into subconscious parts of
the brain, discard short term memories that the conscious brain has
tagged as being unwanted, and free up space for new knowledge
acquisition. REM sleep appears to attempt to connect otherwise
unrelated memories and bits of knowledge, inverting the association
normally works in the brain, thus providing some concrete explanation
for sleep's role in creativity. And (this research is fairly new), deep
NREM sleep causes temporary physical changes in the brain that appear
to be involved in flushing metabolic waste products away, including the
plaque involved in Alzheimer's.

The last part of the book is probably the most concretely useful: what
can one practically do to get more sleep? There is quite a lot that's
proven effective, but Walker starts with something else: sleeping
pills.

Here, you can almost see the lines drawn by a lawyer around what Walker
should say. He stresses that he's not a medical doctor while laying out
study after study that all point in the same direction: sleeping pills
are a highly dangerous medical fraud that will shorten your lifespan
for negligible benefit in helping you fall asleep, while limiting your
brain's ability to enter true sleep. They're sedation, sedation is not
sleep, and the $4 billion dollar sleeping pill market is literally
making everything worse.

The good news is there is an effective treatment for insomnia that
works for many people; the better news is that it's completely free
(although Walker does suggest some degree of medical supervision for
serious insomnia so that some parts of it can be tailored to you). He
walks through CBT-I (cognitive behavior therapy for insomnia), which is
now the medically recommended primary treatment for insomnia, and takes
apart the pieces to show how they line up with the results of sleep
research studies. Alongside that are recommendations for improving
sleep for people who don't have clinical insomnia but who aren't
regularly getting the recommended amount of sleep. There are a lot of
interesting bits here (and he of course talks about blue LED light and
its relationship to melatonin cycles), but I think the most interesting
for me was that you have to lower your core body temperature by a
couple of degrees (Fahrenheit) to enter sleep. The temperature of your
sleeping environment is therefore doubly important: temperature changes
are one of the signals your body uses to regulate circadian rhythms
(cold being a signal of night), and a colder sleeping area helps you
lower your core body temperature so that you can fall asleep. (The
average person does best with a sleeping room temperature of 65F, 18C.)

There's even more in here: I haven't touched on Walker's attack on the
US tendency to push high school start times earlier and earlier in the
day (particularly devastating for teenagers, whose circadian rhythms
move two hours later in the day than adults before slowly returning to
an adult cycle). Or the serious problems of waking to an alarm clock,
and the important benefits of the sleep that comes at the end of a full
night's cycle. Or the benefits of dreams in dealing with trauma and
some theories for how PTSD may interfere with that process. Or the
effect of sleep on the immune system.

Walker's writing style throughout Why We Sleep is engaging and clear,
although sometimes too earnest. He really wants the reader to believe
him and to get more sleep, and sometimes that leaks around the edges.
One can also see the effort he's putting into not reading too much into
research studies, but if there's a flaw in the science here, it's that
I think Walker takes a few tentative conclusions a bit too far. (I'm
sure these studies have the standard research problem of being
frequently done on readily-available grad students rather than
representative samples of the population, although the universality of
sleep works in science's favor here.) Some of the recitations of
research studies can get rather dry, and I once again discovered how
boring I find most discussion of dreams, but for a first book written
by an academic, this is quite readable.

This is one of those books that I want everyone to read mostly so that
they can get the information in it, not as much for the enjoyment of
reading the book itself. I've been paying closer attention to my own
sleep patterns for the last few years, and my personal experience lines
up neatly with the book in both techniques to get better sleep and the
benefits of that sleep. I'd already reached the point where I was
cringing when people talk about regularly going on four or five hours
of sleep; this is an entire book full of researched reasons to not do
that. (Walker points out that both Reagan and Thatcher, who bragged
about not requiring much sleep, developed Alzheimer's, and calls out
Trump for making the same brag.) The whole book may not be of interest
to everyone, but I think everyone should at least understand why the
World Heath Organization recommends eight hours a night and labels
shift work a probable carcinogen. And, as Walker points out, we should
be teaching some of this stuff in school health classes alongside
nutrition and sex education.

Alas, Walker can't provide much advice on what I think is the largest
robber of sleep: the constant time pressure of modern life, in which an
uninterrupted nine hour sleep opportunity feels like an unaffordable
luxury.

Rating: 9 out of 10

Reviewed: 2017-10-28

-- 
Russ Allbery (eagle at eyrie.org)              <http://www.eyrie.org/~eagle/>


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