But we know the common cold is caused by viruses, not chilly air.

但是我們知道普通感冒是由病毒引起，而不是因為寒冷空氣。

So, why does this old wives' tale hang around?

那麼，這個無稽之談為什麼還會流傳下來？

It's probably because colds are more common in colder weather.

這大概是因為感冒在寒冷的天氣裡較為常見。

But as far as scientists can tell, that's not because you feel cold.

但就科學家所知，那並不是因為你感到寒冷。

There are lots of better explanations for why colder weather increases your odds of getting sick.

有關冷天為什麼會增加你生病的機率，有許多更好的解釋。

The connection between temperature and illness isn't simple.

溫度和疾病之間的聯繫並不簡單。

Even though colds and other respiratory illnesses are more common in colder months, not all of them spike in the dead of winter, when it's coldest.

儘管感冒和其它呼吸道疾病在寒冷的月份更常見，但它們並不會都在寒冬最冷時達到高峰。

And the most direct studies we've done haven't found a relationship between feeling cold and catching a cold.

而我們所做過最直接的研究並沒有發現感覺寒冷以及感冒之間的關聯。

For example, in a randomized controlled trial published in 1958, researchers divided nearly 400 people into rooms that were either 27 degrees, 16 degrees, or -12 degrees Celsius.

舉例而言，在 1958 年發表的一項隨機對照試驗中，研究人員將近 400 人分配至溫度攝氏 27 度、16 度或零下 12 度的房間裡。

Then they put virus-infected mucus up some of their nostrils.

他們接著把有病毒感染的粘液放在受試者的鼻孔裡。

But the temperature didn't make a difference⏤in every room, just over a third of the volunteers that received the infected mucus got sick.

但是，溫度並沒有什麼差別，在每個房間裡，感染黏液接收者當中，只有超過三分之一的人感冒。

One study from 2005 did find that people who had their feet soaked in freezing-cold water reported more cold symptoms in the days afterward compared to a control group.

2005 年的一項研究確實發現將腳浸泡在冰水中的人與對照組相比，在事後幾天回報有更多的感冒症狀。

But it's hard to tell how much of that was influenced by subjects thinking they'd be more likely to get a cold.

但是很難說這其中有多少是受到受試者自以為更有可能感冒的影響。

If feeling cold really does make you more likely to get sick, there are a couple of ideas that might explain it.

如果感覺寒冷真的使你更容易生病，有幾個可能解釋它的想法。

One hypothesis argues that even though the cold doesn't weaken your immune system overall, it might lower the defenses in your respiratory system specifically.

一種假說認為，即使感冒並沒有削弱你整體的免疫系統，它也可能會降低你呼吸系統的防禦能力。

And in a paper published in 2016 in the journal "Medical Hypotheses",

而在 2016 年發表於《醫學假設》雜誌的一篇論文中，

a microbiologist suggested that viruses lie dormant for extended periods of time in our bodies, then get activated when the temperature drops.

一位微生物學家提出，病毒在我們體內長期潛伏，然後在氣溫下降時被激活。

But there are lots of problems with those ideas, and the vast majority of research shows that simply being cold doesn't make you more vulnerable to catching colds.

但這些想法有很多問題，而絕大多數的研究都表示，單純的寒冷並不會讓你更容易感冒。

Instead, there are other aspects of cold weather that might increase your chances of getting sick, like the fact that the air is super dry.

相反地，寒冷天氣可能增加你生病的機率可能有其它的面向，例如空氣超級乾燥這件事。

Colder weather is associated with lower humidity because at lower temperatures, the air can't hold as much water.

寒冷的天氣與較低的溼度有關，因為在較低的溫度中，空氣不能持有同樣多的水。

When humidity is high, the droplets of virus-infected grossness that we breathe out or sneeze out or cough out of our bodies stay large and drop to the floor relatively quickly.

當溼度較高時，我們從體內呼出、透過噴嚏打出、咳出的病毒會維持大小並相對快速地下降到地面。

But in dry air, they break up into smaller particles and can float around for hours.

但在乾燥的空氣中，它們會分解成更小的分子，並能漂浮數小時之久。

Plus, the lack of moisture can dry out the mucus lining in your nose, which might make it easier for viruses to get past that line of defense.

此外，缺乏水分會使你的鼻腔內的粘液變乾，可能使病毒更容易越過這道防線。

Another potential problem is that some people don't get enough sunlight in the winter, making them run low on vitamin D.

另一個潛在的問題是，有些人在冬季沒有得到足夠的陽光照射，使得維生素 D 低下。

Since vitamin D helps power your immune system, lower levels mean lower defenses against viruses.

由於維生素 D 有助於為免疫系統提供動力，較低的水平意味著對病毒的防禦能力降低。

And then there's the fact that human behavior changes during colder months.

還有一個事實是，人類的行為在較冷的月份會發生變化。

We're more likely to stay indoors, which means we're more frequently touching stuff infected people touched, and breathing in the remnants of their sneezes.

我們更可能待在室內，表示我們更頻繁地接觸了被感染者接觸過的物件，並吸入他們噴嚏的殘餘物。

So, researchers are still trying to pin down all the different ways cold weather may or may not affect how likely you are to catch a cold.

所以說，研究人員仍在試圖判定寒冷天氣可能影響你感冒機率的不同方式。

But the best way to avoid catching one isn't necessarily by throwing on another layer or drying out your hair before running out the door.

但是，避免被傳染感冒的最佳方式並不見得是外出前多穿一件衣服或是擦乾頭髮。

It's washing your hands with soap, not touching your face with unwashed hands, and staying away from people you know are infected.

而是用肥皂洗手、不要用沒洗過的手摸臉，並遠離你知道受感染的人。

Thanks for watching this episode of SciShow!

感謝收看本集 SciShow 節目！

And a special thanks to our patrons on Patreon who help us keep the heat running all winter and contribute by asking questions like this one.

並特別感謝我們在 Patreon 上的贊助人，他們幫助我們在整個冬天保持熱量，並透過提出像這樣的問題做出貢獻。

To submit your own questions, you can head over to patreon.com/scishow.

要提交你自己的問題，可以前往 patreon.com/scishow。