Nearly everyone who makes sperm does so constantly from puberty until death at a rate of millions of sperm per day.

每個能製造出精子的人從成熟後直到死亡，每天都會生產出數百萬的精蟲。

And people in their seventies, eighties or even nineties have been known to impregnate their partners, which might make it seem like a person's ability to get someone pregnant is the same, whether they're 20 or 85.

而就算是七八十歲，甚至是九十歲的人都還有能夠使伴侶懷孕的案例，不禁讓人覺得一個人讓人懷孕的能力似乎不管在二十歲或八十五歲都是一樣的。

But medical professionals have come to realize that that's simply not true.

然而醫學專家早已發現，事實並非如此。

Even if all of the parts involved are still working well in an older person, it turns out time does take a toll on their sperm.

即使老年人體內的各項機能齊全且功能正常，年紀的增長仍會使精子不再老當益壯。

A person's age matters because the stem cells that make sperm are constantly making copies of themselves and therefore their genomes, but no biological process is perfect.

人的年齡之所以會影響到精子，是因為製造出精子的幹細胞會不斷自我複製，而其中的基因組變也會一同被複製。然而世上沒有十全十美的生物學流程。

So when these stem cells make copies of their DNA, mistakes can occur.

這些幹細胞在複製自己的 DNA 時，有機會發生一些錯誤。

And with all of the cell divisions needed to turn out hundreds of billions of sperm, mutations accumulate over a person's lifetime.

而由於細胞分裂是製造出數千億精子的必經過程，突變的狀況便會在人的一生中不斷累積。

Plus, these copies go on to become sperm through a multi-step process called meiosis, where other errors, like improper chromosome sorting, can occur.

此外，這些細胞透過一種稱為減數分裂的多步驟流程來不斷分裂複製為精子，而在此過程中可能會發生如染色體排列不當等其他錯誤。

One of the most obvious effects of these mutations and errors is how sperm look.

而這些突變與錯誤所造成最顯而易見的結果，就是精子外觀的改變。

Sperm-makers of any age end up with a few sperm with misformed parts.

任何年齡層的「製精人」多多少少都會產出一些奇形怪狀的精子。

But these abnormal sperm become more common, the older they are.

但是隨著年齡的增長，這些畸形的精子會變得越來越普遍。

You might see more sperm with misshapen heads or tails as a person ages, morphologies which can impair the sperm's ability to fertilize an egg.

隨著一個人變老，你可能會看到有更多頭部或尾端外型扭曲的精子，而這種形態上的改變會損害精子使卵子受精的能力。

And older people also tend to have more sperm with large nuclear vacuoles.

老年人也往往有著更多巨大液泡的精子。

These are mostly empty pockets inside the sperm, which take up a substantial portion of the sperm's head.

這些液泡大多是精子細胞內的空腔，佔據了精子頭部相當大的空間。

And they seem to indicate that DNA damage is severe enough to likely impair the development of an embryo, if that sperm does successfully fertilize an egg.

而研究顯示如果這種精子成功地使卵子受精，當中帶有的 DNA 損傷可能會嚴重到危害到胚胎的發育。

Sperm from older people is also less motile, meaning they struggle to swim around and ultimately to fertilize eggs.

老年人的精子活動力也較為遲緩，代表它們很難游到卵子身邊並使其受精。

That's likely because of age-related changes in the epididymis, an organ that contains the narrow, tightly coiled meters-long tube where sperm finish maturing.

這可能是副睪隨著年齡增長而有所變化，而副睪內藏著狹窄而緊密纏繞著，數公尺長的輸精管，且是精子發育成熟的地方。

Some evidence suggests that the older the person is, the harsher the environment inside that tube is.

一些研究證據顯示，隨著年齡的增長，輸精管內環境也會越趨惡劣。

And that can damage the sperm's DNA and ultimately hamper their ability to produce the energy they need to move.

這可能會損害精子的 DNA，並傷害了精子產出前進的能量。

And even if sperm look normal and can find and fertilize eggs, they're not out of the woods.

即使精子看起來正常並且可以找到卵子並其受精，它們仍面臨著其他危險。

All of these aging related effects on sperm DNA can contribute to increased risks of infertility, difficult pregnancies and health conditions in the child, like rare birth defects, childhood leukemia, schizophrenia, and autism.

所有這些與衰老相關的精子 DNA 影響都會增加不孕症、難產和兒童健康狀況的風險，如罕見的出生缺陷、兒童白血病、精神分裂症和自閉症。

Damage to sperm DNA can also increase the risk of miscarriage in the first half of pregnancy, because most miscarriages during that time occur because the fetus has abnormal genes or chromosomes.

精子 DNA 損傷也會增加懷孕前期流產的風險，因為在這段期間內的流產原因多半是胎兒的基因或染色體異常所導致的。

Though, it's important to note the age-associated increase in risk for miscarriages, pregnancy complications and childhood health conditions are small, and overall the risks are low, and this is a relatively new field of study.

然而值得注意的是，因為年齡增加而導致流產、妊娠併發症及兒童健康問題的風險很小，整體來說風險很低，而且這是一個相對新穎的研究領域。

So there's a lot left to learn about the effects of age on sperm.

因此關於年齡究竟會對精子造成什麼樣的影響，我們還有許多仍有待研究的地方。

But from what we know so far, it's clear that sperm do change as a person gets older.

但單就我們目前所知道的，精子確實會隨著人的年紀增長而跟著改變。

I guess time takes its toll on everything.

只能說，時間真的會吞噬一切。

Thanks for watching this episode of SciShow.

謝謝收看本集的 SciShow。

If you like this episode, you might like the one that we have on why sperm count is dropping, so you can check that out next.

如果你喜歡這期節目，那你可能也會喜歡我們之間對於為何精子數量會下降的探討，所以接下來就去看看吧。

And, just so you know, we put out a new episode every single day, so make sure you see them all by clicking that subscribe button and ringing that notification bell.

然後提醒你一下，我們每天都會上傳新一集的節目，所以記得確保你有按下訂閱按鈕以及通知鈴鐺，讓你不會錯過任何一集節目。