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It is a well-known stereotype that older people sleep less than younger folks, often rising at like, 4AM.
一个众所周知的刻板印象：老年人比年轻人睡得少，经常在凌晨4点左右起床。
But even though it's a stereotype, there does seem to be some truth to this.
但即便这是一个刻板印象，但似乎确实有一定的道理。
Like, surveys have found that many seniors wake multiple times in the wee hours before finally rising at the crack of dawn.
比如，调查发现，在破晓时分起床前，许多老年人会在凌晨醒来多次。
This doesn't happen because their bodies need less shut-eye, though; older adults need just as much sleep as younger ones.
但这并不是因为他们的身体需要更少的睡眠；老年人和年轻人需要同样多的睡眠。
And although sleep can be disrupted by many things associated with aging, like pain or medication, that's not the full story, either.
虽然与衰老相关的许多事情会干扰睡眠，比如疼痛或药物治疗，但这也不是全部。
Instead, studies suggest there are some fascinating and sometimes bizarre reasons older adults may wake up with the chickens.
相反，研究表明，有一些有趣的，有时是奇怪的原因导致老年人醒的比鸡早。
Including this stuff called brain sand. Which is even weirder than brain sand sounds.
其原因包括这种叫做脑沙的东西。它比大脑和声音更奇怪。
The general explanation here is that something changes with your circadian rhythm as you get older.
一般的解释是，随着年龄的增长，你的昼夜节律会发生变化。
That's the roughly 24-hour cycle your body is on, which affects everything from when you get tired to when you poop.
你的身体内大约是24小时的周期，它会影响你是什么时候疲劳，什么时候排便等一些事情。
But regarding what changes, the explanations vary. A lot. Some of these ideas are pretty straightforward.
但是关于什么变化，解释各不相同。解释很多。其中一些想法非常简单。
For example, there's evidence that dying brain cells may play a role. Hormone changes are also on the table.
例如，有证据表明死亡的脑细胞可能是一个原因。激素变化也在讨论之列。
See, over the course of a day, your brain triggers the release of hormones into your blood that regulate your body's internal clocks.
在一天的过程中，你的大脑触发激素释放到你的血液中，从而调节你身体内部的时钟。
These hormones result in certain proteins being produced and broken down on a 24-hour cycle,
这些激素会导致某些蛋白质在24小时的周期内产生和分解，
and that influences things like when you naturally wake up in the morning.
从而影响你早上自然醒来的时间等事情。
So if something changed with those hormones, it makes sense that your sleep schedule would, too.
因此，如果这些荷尔蒙发生了变化，你的睡眠时间表也会发生变化，这是有道理的。
And according to some evidence, that's what happens in older adults.
根据一些证据，这就是老年人的情况。
Studies have found that as people age, more of these proteins are produced earlier in the day,
研究发现随着年龄增长，很多这些蛋白质是在早期产生的，
which could trigger seniors to rise and shine in the wee hours.
这可能会促使老年人在凌晨起床。
Some scientists hypothesize that a hormone or some other molecule in the blood is responsible for this.
一些科学家假设是血液中的一种激素或其他分子引起了这些。
And although it sounds reasonable to begin with, there's also a really weird study backing this up.
虽然这听起来很合理，但也有一项奇怪的研究支持这一观点。
In an experiment published in 2011, researchers took skin cells from eighteen people in their 20s
在2011年发表的一项实验中，研究人员从18名20多岁的人身上提取了皮肤细胞，
and grew them in blood serum from eighteen people between 56 and 83 years old.
并将它们培养在56岁至83岁的18人的血清中。
Serum that, presumably, had this age-dependent hormone or molecule in it.
血清中可能含有这种依赖年龄的激素或分子。
And suddenly, the younger cells started producing proteins earlier in the day, behaving like they were forty years older!
突然之间，年轻的细胞开始在一天的早些时候产生蛋白质，表现得就像它们老了40岁一样！
Which is quite the result. Now, more specifically than just "hormones," it's also possible that melatonin could be involved here.
这就是结果。现在，更具体地说，不仅仅是“荷尔蒙”，褪黑激素也可能参与其中。
That's one of the hormones that regulates sleep.
这是调节睡眠的荷尔蒙之一。
Several studies have found that melatonin levels decline with age, and the reasons why vary from reasonable to almost ridiculous.
几项研究发现，褪黑激素水平会随着年龄的增长而下降，其原因合理的、近乎荒谬的，都有。
Like, it seems to happen partly because certain brain receptors and enzymes associated with melatonin dwindle,
比如，其发生的部分原因可能是与褪黑激素相关的大脑受体和酶减少了，
and possibly because the brain uses more melatonin over the years.
并且也可能是因为这些年来大脑使用了更多的褪黑激素。
But this might also be caused by something in the pineal gland called "brain sand."
但这也可能是由松果体中的一种叫做“脑沙”的东西引起的。
Buckle up, because this stuff is about to get fascinating. The pineal gland is a soybean-sized organ in the center of your brain,
系好安全带，因为这东西会让人着迷的。松果体是大脑中央一个大豆大小的器官，
and it releases melatonin and plays a big role in your circadian rhythm. So, it's pretty important.
它释放褪黑激素，并在你的昼夜节律中起着重要作用。所以它是相当重要的。
But something weird happens to it as people age: In this gland, calcium deposits can form.
但随着年龄的增长，它会发生一些奇怪的变化：在这个腺体里，会形成钙沉积。
Now, calcification occurs in other organs, too. But the pineal gland has the highest rate of calcification of any organ in the body.
现在，钙化也发生在其他器官。但是松果体是身体中钙化率最高的器官。
One study found that in people aged forty to seventy, up to twenty-eight percent of the pineal gland
一项研究发现，在40到70岁的人群中，多达28%的松果体
could be studded with these chunks of calcium, also known as brain sand. It's little rocks… in your brain!
可能布满了这些大块的钙，也被称为脑沙。就是你脑子里的小石头！
Scientists don't really know why these deposits happen, either.
科学家们也不知道为什么会有这些沉积物。
Some hypothesize it might be caused by vascular inflammation or reduced oxygen in the brain, both of which can occur more as people age.
一些人猜测它可能是由血管炎症或大脑缺氧引起的，随着年龄的增长，这两种情况会发生得更多。
These scientists think either of these things might be causing stem cells in the pineal gland —
这些科学家认为这两种情况都可能导致松果体中的干细胞——
that is, cells that can turn into other types — to transform into cells that produce bone. That's right.
也就是说，细胞可以转化成其他类型的细胞——转化成产生骨骼的细胞。没错。
Pineal calcification might be similar to the production of bone in the brain.
松果体钙化可能类似于大脑骨骼的产生。
Which should not be a thing! For now, at least, that's just speculation.
这应该不算什么事！至少现在，这只是猜测。
Still, researchers do know that brain sand reduces the amount of melatonin in the fluid around the brain and spinal cord.
尽管如此，研究人员确实知道，脑沙会减少大脑和脊髓周围液体中褪黑激素的数量。
And that can lead to insomnia and other sleep disturbances, including waking up super early.
这会导致失眠和其他睡眠障碍，包括起得超级早。
So, from dying cells to hormones to brain sand, there are tons of ideas about why older adults tend to rise so early.
所以，从死亡的细胞到荷尔蒙再到脑沙，关于为什么老年人起得这么早有很多想法。
And it's possible that multiple factors might be at play here.
这可能是多种因素共同作用的结果。
In any case, there are so many ideas that some scientists speculate there might be an evolutionary reason behind all this.
无论如何，有这么多的想法，一些科学家推测这背后可能有一种进化的原因。
It's called the "poorly sleeping grandparent hypothesis."
这被称为“祖父母睡眠不好假说”。
It's the idea that, back when most humans slept outside or in relatively open environments,
这个观点认为，在大多数人还睡在户外或相对开放的环境中的时候，
it was beneficial for some people to stay up and remain vigilant for lions and other predators.
对一些人来说，对狮子和其他食肉动物保持警惕是有益的。
And as a result, we evolved circadian rhythms that changed with age and ensured someone was always awake to act as a sentinel.
结果，我们进化出了昼夜节律，随着年龄的增长而变化，确保人们总是醒着，充当哨兵的角色。
This idea is cool, but it is just a hypothesis.
这个想法很酷，但它只是一个假设。
It's completely possible that our sleep schedules evolved for a different reason, or as a matter of chance.
我们的睡眠时间表完全有可能是出于不同的原因，或者是一种偶然。
But it does kind of make you think: If older people have internal alarm clocks to save their families from man-eating lions,
但它确实会让你想到：如果老年人有内部闹钟来保护他们的家人免受食人狮子的伤害，
that's a pretty heroic reason to get up early in the morning and go to Denny's.
那么这是一个很英勇的理由，让你一大早就起床去丹尼餐厅。
Thanks for watching this episode of SciShow!
感谢收看本期节目！
We're able to make content like this thanks to our patrons on Patreon, who not only have formed a delightful community,
多亏了我们的赞助人，我们才能制作这样的节目，他们不仅形成了个令人愉快的社区
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
还询问了很多很棒的科学问题。如果你是其中之一，你可以通过邮箱提交你的问题，我们会进行查看
and maybe make an episode like this answering it.
可能还会制作视频回答你的提问。
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.
这是向我们提问的最好方法，但即便你不是成员之一，我们仍愿意倾听让大家好奇的问题。
You can leave your science questions in the comments below, if you see one you like, you can give it an upvote,
大家可以在下方留下你的问题，如果你看到喜欢的，你可以给它投票，
and we'll do our best to check them out.
我们会尽我们最大的努力查看它们。
