Long Trips to Space Linked to Possible Brain Damage

在太空长期停留可能会导致脑损伤

Five space travelers had elevated levels of proteins in the blood often seen in people with head trauma and neurodegenerative diseases.

五位太空旅行者血液中的蛋白质含量增高。这种情况经常会出现在有头部创伤和神经退化症的病人当中。

Over the past several years, scientists have published research suggesting that people’s brains change after spending longer than a few months in space. These studies started because astronauts experienced issues like vision problems and swollen optic nerves upon returning to Earth after long missions.

在过去的数年里，科学家们所发表的研究论文表明，如果在太空中停留的时间超过数月，人的大脑就会发生改变。这些研究始于宇航员在太空中经过长时间停留并在返回地球后出现视力问题和视觉神经肿胀问题。

Researchers are now wondering whether these extended trips to space damage the brain. In a new study of five male cosmonauts (Russian astronauts), researchers looked at levels of different proteins in the blood that are often also seen in people with some sort of head trauma or brain disease. They found that on average, the cosmonauts had higher levels of some of the proteins in the three weeks following the mission than before. 

研究人员们目前正在思考长时间停留在太空是否会对大脑造成损伤。在一项新的关于5名男性航天员（俄罗斯航天员）的研究中，研究人员观察了他们血液中的各种蛋白质的含量。血液中的这些蛋白质往往也会出现在存在某类头部创伤或大脑疾病的人群中。研究人员发现，在太空任务结束后的三周内，宇航员血液中某些蛋白的含量要比去太空之前有所升高。

Cosmonaut：航天员

Dr. Donna Roberts, a neuroradiologist at the Medical University of South Carolina in Charleston who did not contribute to the new paper, said that more studies need to be done to determine if these changes are clinically significant, but that the new paper is “an example of the type of tests we need to start doing more of” to better understand the effects of the brain’s changes during long-duration spaceflight.

Donna Roberts博士是查尔斯顿南卡罗莱纳医学院的一名神经放射学医生，Donna Roberts并未参与新论文的发表。Roberts博士表示，要想了解这些变化是否具有临床意义，还需要进行更多的研究。但是，新论文里的测试就属于我们需要更多进行的测试，这些测试可以帮助我们更好地了解在长时间太空飞行过程中大脑变化的结果。

Neuroradiologist：神经放射学医生

The effects of long-term space travel on humans

长时间太空旅行对人类的影响

For over twenty years, humans have been visiting the International Space Station, which orbits Earth more than 200 miles above the planet. A typical trip lasts about six months. The space station is in free fall around Earth, so people on the space station experience a state of near weightlessness. Such “microgravity” is thought to be the main cause of a number of changes the human body can experience while in spaceflight, including the loss of muscles and bone density.    

在过去20多年的时间里，人类一直都会前往太空空间站。太空空间站在地球上空200多英里处围绕地球旋转。前往空间站通常需要大约6个月。空间站围着地球进行惯性运动，因此空间站上的人们会体验到一种接近失重感的状态。这种微重力被认为是太空飞行中使人体发生变化的主要原因，包括肌肉和骨密度流失。

Orbit：沿轨道运行；围绕…运动

In the last couple of years, brain imaging has also revealed a loss in volume of grey matter, which contains the cell bodies of neurons, and an increased volume of cerebrospinal fluid. Roberts, who uses imaging to study the effect of spaceflight on the brain, has published research showing that in some people who have had long missions on the ISS, their brain has moved up in their head towards the top of their skull, and cerebrospinal fluid occupies more space below and in the center of the brain. 

在过去的数年里，大脑成像也显示出大脑灰质的含量有所减少（灰质中含有神经元细胞体）以及脑脊液的含量有所增加。Roberts利用脑成像来研究太空飞行对大脑的影响并发表了研究论文。论文显示，某些在国际空间站执行长期任务的宇航员的大脑会朝颅骨上方移动，因此脑脊液会在颅骨下方占据更多的空间并会位于大脑的中央。

But researchers don’t know what these brain changes might mean for people’s health and cognition. Dr. Peter zu Eulenburg, a co-first author of the new study, published online Oct. 11 in JAMA Neurology, said the previous studies raised questions: “Is there any damage to the brain? Is this really harmful for the cosmonauts?” 

但是，研究人员还不清楚大脑的这些变化对人类健康和认知有哪些影响。Peter zu Eulenburg是新研究的第一合作作者，该项新研究于10月11日由JAMA neurology发布在网上。他表示，此前的研究提出了一些问题：“这些变化对大脑是否有损害？这些变化是否真的对宇航员有害？”

Looking at blood for signs of brain damage

通过血液发现大脑损伤的迹象

To look for evidence of brain injuries, zu Eulenburg and his colleagues measured the levels of five different proteins in the blood of five male cosmonauts both before and after approximately six-month trips to the space station. 

为了寻找大脑损伤的证据，zu Eulenburg和他的同事在五位宇航员前往空间站之前和前往空间站后大约6个月对他们血液中5种不同的蛋白质水平进行测量。

These proteins are biomarkers that “can tell us about the status of the brain without opening up the brain,” said Keisuke Kawata, a neuroscientist at Indiana University Bloomington. Kawata, who studies repetitive head impacts and did not contribute to the study, said that the best fluid for studying biomarkers is cerebrospinal fluid in the brain and spinal cord, but accessing it requires an invasive spinal tap. Drawing blood is much easier, and blood “is the second-best biological fluid to test the brain health,” he said.

这些蛋白质是生物标记物。这些生物标记物“可以让我们在不用打开大脑的情况下了解到大脑的状态”，Keisuke Kawata，印地安那大学伯明顿分校的一位神经科学家表示。研究重复性大脑影响的Kawata并未参与此项研究。他表示，研究生物标记物的最佳液体是大脑和腰椎中的脑脊液，但是对其进行评估需要进行侵入式的腰椎穿刺。抽血则要容易得多，而且血液也属于“仅次于脑脊液的、衡量大脑是否健康的生物液体”，他表示。

spinal tap：腰椎穿刺

The biomarkers in the study can be used “to indirectly evaluate the extent of damage” due to neurodegeneration or a traumatic injury, said zu Eulenburg, who is a neurologist and professor of neuroimaging at the German Center for Vertigo and Balance Disorders. Neurofilament light chain, for example, is a structural protein that maintains neurons’ axons, which transmit signals to other neurons. 

研究中的生物标记物可以用来“间接评估由于神经退变或创伤性损伤”所导致的受伤程度，zu Eulenburg表示。Zu Eulenburg是眩晕和平衡障碍德国中心的一位神经成像学教授和神经学家。比如神经微丝轻链就是一种维持神经元轴突的结构蛋白，其可以将信号传递给其他神经元。

traumatic injury：创伤性损失

Vertigo and Balance Disorders：眩晕和平衡障碍

Neurofilament light chain：神经微丝轻链

In a healthy person, “you shouldn’t be detecting much of those structural proteins in the blood,” Kawata said. But if someone has a neurodegenerative condition, the proteins dislodge from the neurons and can get into the bloodstream.

对于一个健康的人，“你的血液中应该不会检测到大部分这类结构蛋白，”Kawata表示。但是，如果一个人存在神经退变方面的疾病，神经元中的蛋白会移动并进入血液中。

Interpreting the results

结果解释

The researchers measured five proteins 20 days before launch and calculated the average level for each protein across the five cosmonauts. They then compared this to the average level one day, one week, and 20 to 25 days after the cosmonauts returned to Earth. 

研究人员在发射任务开始前20天测量了5种蛋白质并计算了5位航天员身体中每种蛋白质的平均含量。然后，研究人员将这一结果与宇航员返回地球后第1天、第1周和第20-25天的平均蛋白质含量进行对比。

Two of the proteins had elevated levels both one day and one week after the missions. These levels dropped over the next two weeks, but remained above the cosmonauts’ baseline level from before the missions. A third protein wasn’t significantly elevated in the first week after returning and had dropped below the baseline after three weeks, so it wasn’t indicative of potential brain damage. For the final two proteins, the researchers typically look at the ratio of one to the other. The ratio dropped after the cosmonauts returned, a trend that is sometimes seen in people with a neurodegenerative condition. 

有两种蛋白质的含量在任务结束后第1天和第1周有所增加并在接下来的2周有所下降。但是，含量仍然高于宇航员执行任务前的基准线。第三种蛋白在返回地球后的第1周并未明显升高。经过三周后，第三种蛋白下降至基准线以下，因此其并不能表明宇航员存在潜在的脑损伤。对于两种蛋白，研究人员观察了它们之间的比率。它们的比率在宇航员返回地球后有所下降，这一趋势偶尔会出现在有神经退变疾病的人群中。

zu Eulenburg said that the fact that some levels remained elevated for the entire three weeks was “very surprising,” and the results “verified brain injury as a consequence to long-duration exposure to microgravity.”

Zu Eulenburg表示，在整整三周内，某些蛋白质的水平仍然保持升高状态是“非常出乎意料的”，结果证明“长期暴露于微重力下会造成大脑损伤”。

“This is obviously a pilot study, but the data quality and the analytics are so robust that I have no doubt in the overall effect,” he said.

他说：“这显然属于探索性研究，但是数据的质量和分析学都十分具有说服力，所以我对总的结果持肯定意见。”

The seriousness of these effects remains uncertain. Roberts said the paper contains “initial data suggesting that there is some type of injury to the brain,” but cautioned that more work needs to be done to show the effect on astronauts’ health. Kawata said the paper is not evidence that if you go to space, you’re going to get Alzheimer’s disease, for example. 

这些影响的严重性仍属于未知状态。Roberts表示，论文含有“表明存在某类大脑损伤的初步数据”，但Roberts也审慎提出，要想具体了解其对宇航员健康的影响，则还需要完成更多的工作。Kawata表示，该论文并非证明，如果你前往太空，你就会患上帕金森。

Both Roberts and Kawata would like future studies to measure the biomarkers for longer than three weeks after astronauts return, as well as while they are on the space station, which would help determine if the elevated levels are due to time spent in microgravity, rather than the change in gravity upon return, or the intense force experienced during landing. 

Roberts和Kawata都赞成在宇航员返回地球后测定生物标记物的研究要超过三周并且还要在他们在太空站期间进行测定，这也许有助于测定蛋白质水平升高是由于在微重力下所持续的时间而不是在返回时重力发生变化或着陆时的巨大冲击力所导致的。

Roberts said understanding the cause of the elevated biomarkers would help space agencies figure out which sorts of measures would best counteract the effects. zu Eulenburg thinks time spent in microgravity is the most likely cause, since imaging studies have shown that changes in the brain don’t occur for people on shorter trips, so the elevated levels might start while astronauts are still in space. 

Roberts表示，了解生物标记物升高的原因也许有助于航天机构制定最佳的应对措施。zuEulenburg认为，在微重力状态下所持续的时间是最可能造成脑损伤的原因，因为脑成像研究显示，太空航行时间较短的宇航员的大脑并未发生变化，因此蛋白质含量的升高也许就是在宇航员还停留在太空时开始的。

Kawata said it shouldn’t be a big problem if biomarkers are only elevated for a couple of weeks in total. But zu Eulenburg said via email that three weeks of elevated levels are a sign of a “substantial” reparatory process. And other studies have shown that changes in the brain and cognitive effects last for at least several months after spending months in space, suggesting that elevated biomarkers could last longer than a couple of weeks. 

Kawata表示，如果生物标记物仅仅升高了总共几周，那么并没有什么大问题。但zu Eulenburg通过邮件表示，生物标记物水平在三周内升高就是“重大”修复的迹象。另一项研究也显示，在太空中花费数月后，大脑和认知的变化也会持续至少几个月，这表明标记物升高的持续时间也会超过数周。

“I would feel very cautious about doing a one-year mission aboard the [space station] without sufficient countermeasures in place," said zu Eulenburg. 

“如果没有充足的应对举措，我会对在空间站工作1年持审慎的态度，”zu Eulenburg表示。

Roberts said she feels confident that science will be able to find ways to protect astronauts from adverse effects. “Ultimately our goal is to become a multiplanetary species… but we have to be smart about it along the way.”

Roberts表示，她相信科学将可以找到保护宇航员免于副作用的方法。

“最终，我们的目标是成为多行星物种……但是在这一过程中，我们必须理智行事。”

原文来源：HOW STUFF WORKS  编辑&翻译：Sarah，译锐翻译