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Friday, January 11, 2019

Review: Why We Sleep

I picked up Why We Sleep thinking that this might be one of those "stupid pill" books for me. After all, not only am I a sleep apnea victim, I'm one of those lucky people who've slept quite well all his life. My CPAP therapy has made it such that I only really need slightly less than 7 hours of sleep a night, and I've never needed an alarm clock! I also read The Promise of Sleep, written by the pioneer of sleep studies.

But wow, what a difference 9 years makes. Sleep science has advanced quite a bit, and a lot of my knowledge was obsolete. For instance, Dement's book mentioned that you shouldn't be afraid of sleeping pills. We now know that sleeping pills just sedate you, and don't actually generate sleep of the natural kind. There's also better therapies available for insomnia now, chiefest of which is CBT-I Cognitive Behavioral Therapy for insomnia. Wow.

There are way more practical tips in this book on how to get better sleep. In particular, setting a bedroom temperature lower is counter-intuitive:
 The need to dump heat from our extremities is also the reason that you may occasionally stick your hands and feet out from underneath the bedcovers at night due to your core becoming too hot, usually without your knowing. Should you have children, you’ve probably seen the same phenomenon when you check in on them late at night: arms and legs dangling out of the bed in amusing (and endearing) ways, so different from the neatly positioned limbs you placed beneath the sheets upon first tucking them into bed. The limb rebellion aids in keeping the body core cool, allowing it to fall and stay asleep. (Pg. 276)
Yup. Please show this to your Asian mom who keeps tucking you back into your blanket after you've fallen asleep. While you're at it, you might want to get her to lower the nightime thermostat:
A bedroom temperature of around 65 degrees Fahrenheit (18.3°C) is ideal for the sleep of most people, assuming standard bedding and clothing. This surprises many, as it sounds just a little too cold for comfort... (Pg. 277)
Another tip is to take a hot bath just before bed. I've had doctors advise me to take a hot shower before bed before, to wash away pollen and other allergens so I don't introduce them into bed. But the reason for how the hot bath works is counter-intuitive:
A luxury for many is to draw a hot bath in the evening and soak the body before bedtime. We feel it helps us fall asleep more quickly, which it can, but for the opposite reason most people imagine. You do not fall asleep faster because you are toasty and warm to the core. Instead, the hot bath invites blood to the surface of your skin, giving you that flushed appearance. When you get out of the bath, those dilated blood vessels on the surface quickly help radiate out inner heat, and your core body temperature plummets. Consequently, you fall asleep more quickly because your core is colder. Hot baths prior to bed can also induce 10 to 15 percent more deep NREM sleep in healthy adults. (Pg. 279)
This is amazing stuff. Prof Walker also debunks several past theories about why sleep evolved biologically:
 Sleep, it turns out, is an intensely metabolically active state for brain and body alike. For this reason, theories proposing that we sleep to conserve large amounts of energy are no longer entertained. The paltry caloric savings are insufficient to outweigh the survival dangers and disadvantages associated with falling asleep. (Pg. 175)
We also now know that sleep-deprivation is its own form of Dunning-Kruger: Sleep deprived individuals perform worse, but don't know that they perform worse, so don't know that they're sleep deprived, which encourages them to think that they don't need to sleep more!
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. (Pg. 137)
All in all, this is an amazingly good book, and well worth your time. Highly recommended!

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