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  • (intro music)

  • It is a well-known stereotype that older people sleep less than younger folks, often rising at like, 4AM.

  • But even though it's a stereotype, there does seem to be some truth to this.

  • Like, surveys have found that many seniors wake multiple times in the wee hours before finally rising at the crack of dawn.

  • This doesn't happen because their bodies need less shut-eye, though; older adults need just as much sleep as younger ones.

  • And although sleep can be disrupted by many things associated with aging, like pain or medication, that's not the full story, either.

  • Instead, studies suggest there are some fascinating and sometimes bizarre reasons older adults may wake up with the chickens.

  • Including this stuff called brain sand.

  • Which is even weirder than brain sand sounds.

  • The general explanation here is that something changes with your circadian rhythm as you get older.

  • That's the roughly 24-hour cycle your body is on, which affects everything from when you get tired to when you poop.

  • But regarding what changes, the explanations vary.

  • A lot.

  • Some of these ideas are pretty straightforward.

  • For example, there's evidence that dying brain cells may play a role.

  • Hormone changes are also on the table.

  • See, over the course of a day, your brain triggers the release of hormones into your

  • blood that regulate your body's internal clocks.

  • These hormones result in certain proteins being produced and broken down on a 24-hour cycle, and that influences things like when you naturally wake up in the morning.

  • So if something changed with those hormones, it makes sense that your sleep schedule would, too.

  • And according to some evidence, that's what happens in older adults.

  • Studies have found that as people age, more of these proteins are produced earlier in the day,

  • which could trigger seniors to rise and shine in the wee hours.

  • Some scientists hypothesize that a hormone or some other molecule in the blood is responsible for this.

  • And although it sounds reasonable to begin with, there's also a really weird study backing this up.

  • In an experiment published in 2011, researchers took skin cells from eighteen people in their

  • 20s and grew them in blood serum from eighteen people between 56 and 83 years old.

  • Serum that, presumably, had this age-dependent hormone or molecule in it.

  • And suddenly, the younger cells started producing proteins earlier in the day, behaving like they were forty years older!

  • Which is quite the result.

  • Now, more specifically than justhormones,” it's also possible that melatonin could be involved here.

  • That's one of the hormones that regulates sleep.

  • Several studies have found that melatonin levels decline with age, and the reasons why

  • vary from reasonable to almost ridiculous.

  • Like, it seems to happen partly because certain brain receptors and enzymes associated with melatonin dwindle,

  • and possibly because the brain uses more melatonin over the years.

  • But this might also be caused by something in the pineal gland calledbrain sand.”

  • Buckle up, because this stuff is about to get fascinating.

  • The pineal gland is a soybean-sized organ in the center of your brain, and it releases

  • melatonin and plays a big role in your circadian rhythm.

  • So, it's pretty important.

  • But something weird happens to it as people age: In this gland, calcium deposits can form.

  • Now, calcification occurs in other organs, too.

  • But the pineal gland has the highest rate of calcification of any organ in the body.

  • One study found that in people aged forty to seventy, up to twenty-eight percent of

  • the pineal gland could be studded with these chunks of calcium, also known as brain sand.

  • It's little rocksin your brain!

  • Scientists don't really know why these deposits happen, either.

  • Some hypothesize it might be caused by vascular inflammation or reduced oxygen in the brain,

  • both of which can occur more as people age.

  • These scientists think either of these things might be causing stem cells in the pineal

  • glandthat is, cells that can turn into other typesto transform into cells that

  • produce bone.

  • That's right.

  • Pineal calcification might be similar to the production of bone in the brain.

  • Which should not be a thing!

  • For now, at least, that's just speculation.

  • Still, researchers do know that brain sand reduces the amount of melatonin in the fluid around the brain and spinal cord.

  • And that can lead to insomnia and other sleep disturbances, including waking up super early.

  • So, from dying cells to hormones to brain sand, there are tons of ideas about why older adults tend to rise so early.

  • And it's possible that multiple factors might be at play here.

  • In any case, there are so many ideas that some scientists speculate there might be an evolutionary reason behind all this.

  • It's called thepoorly sleeping grandparent hypothesis.”

  • It's the idea that, back when most humans slept outside or in relatively open environments,

  • it was beneficial for some people to stay up and remain vigilant for lions and other predators.

  • And as a result, we evolved circadian rhythms that changed with age and ensured someone was always awake to act as a sentinel.

  • This idea is cool, but it is just a hypothesis.

  • It's completely possible that our sleep schedules evolved for a different reason, or as a matter of chance.

  • But it does kind of make you think: If older people have internal alarm clocks to save

  • their families from man-eating lions, that's a pretty heroic reason to get up early in the morning and go to Denny's.

  • Thanks for watching this episode of SciShow!

  • We're able to make content like this thanks to our patrons on Patreon, who not only have

  • formed a delightful community, but also ask great science questions.

  • If you're a patron, you can submit a question to our QQ inbox, and we'll check it out

  • and maybe make an episode like this answering it.

  • This is the best way to send us questions, but even if you're not a patron, we'd

  • still love to hear what you're curious about.

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多くの高齢者が早起きするワイルドな理由 (The Wild Reasons Many Older People Wake Up So Early)

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    林宜悉 に公開 2021 年 01 月 14 日