寝る時のベストポジションとは？
What I've Learned
日本に住むアメリカ人のYouTuberが学びを解説する人気チャンネル。
食事、健康、能力開発などの内容が多く、動画編集にセンスが感じられる。
いくつかのスマッシュヒット動画があり、是非見てほしい。
文章ボリュームは多いが、論理的な展開+動画により理解しやすい。
今回は寝る時の体制に関する考察。
仰向け、横向き、うつ伏せ、どの態勢が一番良い睡眠につながるのでしょうか？
それでは今日も楽しんで動画を見ていきましょう！
00:00
Will the real Randy Gardner please stand up?
00:07
In 1964, high school student Randy Gardner successfully stayed awake for 11 days and
00:13
24 minutes, setting the world record for the longest a human has gone without sleep.
00:19
Over the several days awake, Gardner experienced everything from mood changes, memory lapses,
00:23
random hallucinations to temporarily losing the ability to identify objects and recall
00:29
words.
00:31
But you don’t have to stay awake for multiple days to experience detriments from sleep,
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as Neuroscientist Matthew Walker will tell you.
00:38
"I would like to start with testicles.
00:42
Men who sleep 5 hours a night, have significantly smaller testicles than those who sleep 7 or
00:51
more."
00:52
In his book “Why we Sleep,” Walker explains the ins and outs of just how bad too little
00:56
sleep is not only for your reproductive, cardiovascular, and immune health, but learning and cognition
01:02
as well.
01:03
Interestingly, lacking sleep even affects you socially.
01:07
-“...so we just published a study demonstrating that sleep loss will trigger viral loneliness."
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As Walker is explaining here in this interview with Rhonda Patrick, this paper he authored
01:18
demonstrated that people are much less comfortable with people being close to them after they’ve
01:23
been sleep deprived.
01:24
They even put people in an MRI scanner and found that the brain is lighting up in a way
01:29
that makes you more suspicious of people and less able to understand their intentions.
01:34
Now, one of the things that was striking to me that Matthew Walker said was that you cannot
01:39
recover a sleep debt.
01:41
You can’t just “catch up on sleep” by sleeping for 12 hours on a Saturday after
01:46
3 nights of sleeping poorly.
01:48
So, if we only have one chance at sleep, then sleep quality or the efficiency of sleep must
01:55
be very important even if you’re getting the recommended 8 hours a night.
01:59
There are many things you can do to improve sleep quality and I’ve discussed this in
02:03
another video, but what I’ve been curious about lately is sleeping posture.
02:09
What is the best position to sleep in and, what is the best kind of pillow?
02:13
Or should we even use a pillow?
02:16
This question has bugged me for a while because I’ve tried all kinds of pillows including
02:20
this thing that’s supposed to keep your head from rolling to one side but I’ve never
02:23
been 100% satisfied.
02:24
“Oh, man.
02:25
You want a bad night?
02:27
Try sleeping on one of these.”
02:30
The first thing I thought might be worth looking at is how other primates sleep.
02:34
A quick google image search of “sleeping primates” - shows a lot of them sleeping
02:38
on their side.
02:40
As Charles Nunn explains, what the great apes have in common with humans is that they all
02:44
build some sort of comfortable nest or sleeping platform each night.
02:49
Humans have different bone structures from apes of course, but I thought it would still
02:52
be interesting to consider the position they sleep in most often.
02:56
This 2015 study, monitored the sleeping patterns of 5 Orangutans for two years.
03:02
They found that orangutans spent 3 times more of their sleeping time on their sides than
03:07
they did on their backs.
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Now While digging into human research, I had trouble finding papers that specifically looked
03:13
at how sleep position affected sleep quality.
03:15
And, I couldn’t find any papers comparing sleep quality when people used a pillow versus
03:21
when they didn’t use a pillow.
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But we can of course use a bit of logic and make some inferences based off the data that
03:26
we do have.
03:28
So I figure a sleep posture that promotes good sleep quality would have to (1) Prevent
03:32
snoring and (2) at least not impede the glymphatic system.
03:36
For now, let’s look at snoring.
03:38
What’s happening during snoring is that air flow is being partially blocked by tissues
03:42
in the airway, as evidenced by a… snoring sound.
03:46
I think more often than not, people would assume that snoring is mostly a nuisance to
03:50
one’s sleeping partner and the effect on sleep quality is not enough to cause alarm.
03:55
However, A study from 2003 looking at 1,144 school children separated the kids into either
04:01
“always,” “frequently,” “occasionally” and “never” snoring.
04:05
What they found was that in the kids, snoring “always” was significantly associated
04:10
with poor academic performance in mathematics, science , and spelling.
04:14
And snoring “frequently” was also significantly associated with poor academic performance
04:19
in mathematics and spelling .
04:22
Another study from 2001 found that children with lower academic performance in middle
04:26
school are more likely to have snored during early childhood.
04:30
Another study from 1994 showed that between age 4 and 7, “Daytime sleepiness, hyperactivity,
04:36
and restless sleep were all significantly more common in the habitual snorers than in
04:41
those who never snored.”
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And Yet another study from 2005 titled “Snoring predicts hyperactivity four years later”
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shows that “snoring and other symptoms of sleep-disordered breathing are strong risk
04:53
factors for future emergence or exacerbation of hyperactive behavior.”
04:57
I could go on with several more studies showing children who snore secrete less growth hormone,
05:03
how snoring is associated with headache and daytime sleepiness as well as high blood pressure,
05:07
heart attack and stroke but we can get into the full details in another video.
05:11
For now,
05:12
Here’s two recent nights from just the other week tracking my sleep with the app “snore
05:16
lab.”
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Here’s a night where I snored a lot… and slept about seven hours, and here’s a night
05:26
where I slept less about 6 and a half hours barely snored at all - most of what the app
05:32
picked up was me rustling around and my air conditioner turning on and off.
05:37
As indicated by the orange frowny face, I distinctly remember being very groggy this
05:41
particular morning when I snored alot, but quite refreshed this morning when I didn't
05:46
snore that much.
05:48
One pretty clear example of snoring being disruptive to sleep quality is the fact that
05:52
it seems to wake me up - On the nights that I do snore, the recording will show that the
05:57
snoring sometimes wakes me up enough to rustle around or change positions.
06:23
This 2013 review on “positional therapy in position-dependent snoring” explains
06:28
that it’s often observed that snoring is usually worse when sleeping on the back and
06:32
better when sleeping on their side.
06:34
And, several papers have shown that sleep apnea gets worse when people sleep on their
06:39
backs.
06:41
During the American War of Independence and later during World War I , soldiers were advised
06:45
to wear their rucksacks on their backs while sleeping to keep them on their side and avoid
06:50
sleeping on their backs.
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This would prevent snoring and making their position known to the enemy.
06:56
Papers from 1984 and 1996 found that people snore worse on their back, and this one
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2003 study found that snorers snore less on their side
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So far, it looks like sleeping on one’s side or at least avoiding sleeping on your
07:10
back would be good for sleep quality.
07:14
This study from 1983 found that ”Consistently, poor sleepers spent more time on their backs
07:19
with their heads straight.”
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Now what about pillows?
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There are several types of pillows and most of the ones advertised to improve sleep quality
07:28
aim to support the neck.
07:30
There is a natural curvature in the neck, a lordosis, and you can lose that and develop
07:34
something called flat neck syndrome.
07:37
This is developed presumably from looking down all the time, probably at your smart
07:40
phone or using a pillow that is too high.
07:43
But if we want to sleep on our sides, we shouldn’t need to worry about having the perfectly shaped
07:49
pillow and just get one that keeps your neck from bending too much while you sleep on your
07:52
side.
07:54
Moving on, to further evaluate sleep positions that promote good sleep quality, the position
07:59
should be good for glymphatic transport.
08:02
In the body, we have something called the lymphatic system that helps with each organ’s
08:06
problem of waste clearance - this network of vessels extends through the body and collects
08:11
cellular debris, proteins and other waste from the spaces between the cells so it can
08:16
be disposed of.
08:18
The brain however, does not have lymphatic vessels that it can use for waste clearance.
08:22
As Neuroscientist Jeff Iliff explains in his TED talk, this doesn’t make much sense considering
08:27
the adult brain uses about 25% of the body’s energy budget and generates a considerable
08:33
amount of metabolic waste.
08:35
“So how then does the brain solve its waste clearance problem?
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The brain’s solution to the problem of waste clearance, it was really unexpected, it was
08:47
ingenious.”
08:48
“So the brain has this large pool of clean, clear fluid called cerebrospinal fluid.
08:55
We call it the CSF."
08:57
The CSF fills the space that surrounds the brain and wastes from inside their brain make
09:01
their way out to the CSF which gets dumped along with the waste into the blood.”
09:06
In the brain, there is a specialized network of plumbing that organizes and facilitates
09:11
the cleanup process.
09:14
You can see that in these videos...
09:15
The frame on your left shows what’s happening at the brain’s surface and the frame on
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your right shows what’s happening down below the surface of the brain within the tissue
09:23
itself.
09:24
The blood vessels are labeled in red and the cerebrospinal fluid that’s surrounding the
09:28
brain in green.
09:30
“...and as it flushed down into the brain along the outsides of these vessels, it was
09:34
actually helping to clear away, to clean the waste from the spaces between the brain’s
09:41
cells.”
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What’s interesting is that all this is happening when you’re asleep - the video on the left
09:47
shows how much of the cerebrospinal fluid is moving through the brain of a mouse while
09:50
its awake - barely anything.
09:53
But when the animal goes to sleep, the CSF rushes into the brain to rinse and clean it
09:59
out.
10:00
Alzheimer’s disease is an example of how important this sleeping brain cleanup procedure
10:05
is.
10:06
A hallmark of Alzheimer’s disease is the build up of a peptide called amyloid beta,
10:10
and the glymphatic system helps clear this stuff out of the brain.
10:15
The research on sleeping position affecting glymphatic transport is very limited, but
10:19
this 2015 study had rodents sleep on either their side, back or stomach and were monitored
10:26
via magnetic resonance imaging.
10:28
They found that “glymphatic transport was most efficient in the lateral position”
10:33
- on their side.
10:34
Dr. Maiken Nedergaard said: "It is interesting that the lateral sleep position is already
10:39
the most popular in humans and most animals — even in the wild — and it appears that
10:44
we have adapted the lateral sleep position to most efficiently clear our brain of the
10:49
metabolic waste products that built up while we are awake.”
10:52
One interesting thing about this study is that it specifically looked at clearance of
10:57
the Alzheimer’s protein Amyloid beta and found that removal of it was most efficient
11:02
in the side sleeping position.
11:05
Now This is just in rodents, but this study was looking at how sleep position could affect
11:09
neurodegenerative disease in humans.
11:12
This study strapped a small device with an accelerometer to the participant’s heads
11:16
to monitor what sleeping positions they were in and for how long.
11:20
They found that those people spending more than two hours sleeping on their back a night
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was significantly more frequent in those with neurodegenerative disease.
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Those with neurodegenerative disease spent nearly twice as much time on their backs while
11:32
sleeping - controls spent around 30% of their sleep on their backs, those with NDD spent
11:38
around 50% of their sleep on their backs.
11:44
The Hadza of Tanzania are often interesting to look at as their lifestyle is thought to
11:49
be similar to that of prehistoric humans.
11:51
I couldn’t find studies specifically on their sleeping position, but this brief video
11:56
talking about a study on the Hadza’s sleep patterns shows most of them sleeping ...on
12:00
their side.
12:02
So, the data is limited but it’s enough at least for me to want to try and sleep on
12:06
my side more.
12:08
However… the problem is that you can’t just say “OK time to sleep on my side because
12:12
Ulysses McGill said so.”
12:13
"How's my hair?"
12:15
People unconsciously change their sleeping position multiple times throughout the night.
12:19
One study found that over the course of 1 night, subjects changes positions as many
12:23
as 20 to 40 times per night.
12:26
So how can we get ourselves to stay on our sides, or at least bias ourselves to select
12:31
that position more often as we rustle around at night?
12:35
In 1984, the journal CHEST published a letter written by a patient’s wife.
12:40
She had cured her husband’s snoring problem by inserting a plastic ball into a pocket
12:44
sewn on the back of a T-shirt to prevent her husband from sleeping on his back.
12:49
In fact, there’s a type of therapy called “positional therapy” designed to keep
12:53
patients off of their back - all kinds of things from a backpack with a softball inside
12:58
to a ball in a sock on the back to a shark fin type thing to alarms that ring when you
13:03
roll on your back.
13:06
So ... what if pillows are making sleeping on our backs artificially too comfortable?
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That is, let’s say you lay down to sleep, but you simply don’t use a pillow.
13:16
Laying on your back might become a little less comfortable now that your neck and head
13:20
aren’t cradled in a cushy comfortable cushion.
13:22
What’s going to be the more comfortable position?
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Probably sleeping on your side because you can support your neck with your shoulder or
13:29
a pillow made out of your arm and hands.
13:32
Surprisingly, there was one paper that addresses this directly.
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In this paper by Michael Tetley titled “Instinctive sleeping and resting postures: an anthropological
13:42
and zoological approach to treatment of low back and joint pain,” he argues that forest
13:46
dwellers, nomads and tribal peoples suffer from few muscoskeletal problems because they
13:51
sleep in a “natural” posture without a pillow at night.
13:56
According to Tetley, he has “organised over 14 expeditions all over the world to meet
14:00
native peoples and study their sleeping and resting postures.
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They all adopted similar postures and exhibited few musculoskeletal problems.”
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He says tribespeople often do not like having their photographs taken so he demonstrates
14:13
most of the postures himself.
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What was interesting about this paper is that none of the positions he’s presented show
14:20
people sleeping on their backs.
14:25
So the data on this topic is limited, but based on what I did find, so far it seems
14:30
that the side position is the better position for cleaning out your brain and preventing
14:34
snoring from impeding your sleep, and ditching the pillow might be the way to get yourself
14:40
to spend more time in that side position.
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That’s the idea anyway.
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It’ll probably take some time to adjust to sleeping without a pillow and I’m not
14:48
saying this is realistic for everyone - if you don’t snore, and you wake up feeling
14:52
refreshed and are without back or neck pain in the morning there’s probably no need
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to change your routine.
14:58
Also maybe you could figure out some other way to keep yourself on your side during the
15:01
night without ditching your pillow.
15:04
Actually I’ve been sleeping without a pillow for about a week now and I can’t say I’m
15:07
waking up drastically more refreshed, but I haven’t woken up with a stiff neck or
15:12
back yet - something that would usually happen every other day.
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But I don’t really know if this way of sleeping is keeping me on my side like I was thinking,
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so I’m planning to track a couple weeks of sleeping like this with a wearable device
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and hopefully one of those baby monitor type see in the dark cameras.
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I’m planning to post updates on my instagram every now and then, and at the end of the
15:35
experiment, I’ll post a thorough video on youtube letting you know how it all went.
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And, If any of you would like to join me in the sleep experiment, I’ll post in the description
15:43
how I plan to do it.
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Also, if any of you have done a sleep tracking experiment yourself in the past, please let
15:49
me know in the comments or on instagram what you used to track your sleep.
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This video was sponsored by Kenhub - which is where most all the anatomical images used
15:59
in this video came from.
16:01
If you're a medicine, nursing, or physiotherapy student and want a way to drastically reduce
16:06
the frustration involved with packing ridiculous amounts of anatomy information into the thing
16:10
between your two auditory ossicles, you should definitely check out Kenhub.
16:15
With hundreds of engaging videos, interactive quizzes, complete articles and a full atlas
16:19
with stunning images, Kenhub is the best tool for learning anatomy I've come across and
16:24
it actually makes the process fun.
16:26
Check out Kenhub at kenhub.com
