What life in space does to the human body

Astronaut Scott Kelly retired after a year in space. Now doctors are busy analyzing what prolonged time in zero gravity meant for his health.

We speak with Volker Damann, a doctor at the European Space Agency and visiting professor at the International Space University. Over the years, he has provided medical supervision and training for many astronauts aboard the International Space Station (ISS).

ResearchGate: Medically speaking, what can we learn from Scott Kelly?

Volker Damann: With Scott Kelly we have a unique opportunity for research with twins. He and his brother are identical twins who’ve had the same occupation, the same career path. One of them was in space for a year, the other here on Earth, and both are taking part in the same study.

We hope to gain insight from Scott Kelly and his Russian colleague about how certain changes we know to expect after 3-6 months in space, such as bone loss, develop over longer periods. Does the calcium carbonate content of bones continue to diminish by one to two percent or is there a plateau? That’s of course important to know if we want to send people to Mars one day.

Generally speaking, we have only a handful of test subjects for space medicine research, and that’s a statistical problem. Long flights like Scott Kelly’s can show us whether the body adapts physiologically to weightlessness. The idea is to conduct these long flights every two years in order to gather more data.

RG: What kind of medical issues typically arise during spaceflight?

Damann: Fortunately, minor ones—that’s the good news. One thing we frequently see are foreign objects in astronauts’ eyes. At zero gravity, dust and dirt, things like breakfast crumbs, float around instead of falling on the ground. If a breadcrumb gets in your eye, that’s not much of a problem, but if it’s a shard of glass or metal it can be dangerous. Astronauts are trained to use ultrasound equipment to inspect the eye and remove foreign objects.

Skin problems like eczema are also common in space. At first, we were surprised to see that, but it can be explained by the lack of gravity. At zero gravity, there’s no convection. That means sweat on the skin doesn’t evaporate like it does here on Earth. It accumulates in the underarm and groin areas, providing an ideal environment for bacteria and fungus to grow. So there’s a need for different hygiene practices.

RG: Have there been medical problems that surprised you?

Damann: Yes, there’s another problem that affects the eyes, and we don’t yet know what causes it. Some astronauts experience changes to their vision: all of a sudden they need reading glasses, or others who usually wear glasses don’t need them anymore. The problem often occurs in only one eye. It turns out that the eyeball becomes dented from behind, compromising it. The problem is fortunately reversible, but it makes us wonder whether we’re dealing with a significant increase in cerebral compression and how this can be investigated non-invasively. This is a clinical problem that’s been hotly debated over the last few years. There are many studies being done at the moment, and all astronauts undergo three-Tesla MRI scans of their eye sockets before and after each flight. It’s something we’re a bit worried about, but it’s no reason to stop sending astronauts into space.

RG: What happens if a serious medical emergency occurs in outer space? Are astronauts trained to be able to assist their colleagues?

Damann: Astronauts’ medical training is comparable to that of a paramedic. They’re familiar with life-saving procedures like intubation and the use of a defibrillator. They can give stitches. They can provide dental care, perhaps do a provisional filling or pull a tooth in an emergency. They have access to a medical handbook—which is illustrated and captioned in Russian and English—so that they can take care of things even if they lose radio contact with Earth. The ISS also has an onboard pharmacy with everything you might find in your medicine cabinet. Additionally, there are prescription medications that are only used if a doctor—either on Earth or onboard if there is one—prescribes them.

RG: What about nutrition? Are there other dietary requirements in space?

Damann: The body needs less energy, because the stabilizing muscles that enable us to walk upright on Earth aren’t being used. The food is actually not that different than it is on Earth. It’s not all out of a tube or a tin like it used to be. On the Russian side, canned food is still common, but that’s cultural.

RG: In which areas of space medicine has there been particular progress recently?

Damann: One example is the rehabilitation of astronauts‘ muscular systems. They frequently complain of back pain and there were a few ideas about what might cause that. Astronauts become a centimeter or two taller at zero gravity, and we at ESA had a hypothesis: that the pain comes from the small muscles between vertebrae that enable upright posture and support the spine. They atrophy in space and need to be built up again. As a result, we reworked the astronauts’ entire workout program to specifically train these muscles before and after flight. It was very successful. That’s a little glimpse into the medical research we do.

RG: What other areas of research have the potential to significantly improve the health of astronauts during space flight for the future? 

Damann: If we want to keep exploring outer space, we need to make the crew medically more autonomous. Imagine you’re flying to Mars. The astronauts need to be able to help themselves. It’s good to have a doctor onboard, but how do you pick that doctor? He has to cover everything from dermatology to gynecology to surgery. That’s not easy. It’s a question we’re working on an answer to.

On Earth, medical education without Human Patient Simulators would be unimaginable. We’re considering whether we can individualize these simulators so that the software mimics the physiology of an individual astronaut. That way, a doctor or medic onboard could test certain procedures before conducting them on the patient.

RG: How do you think the human body would adapt to a lifetime in space? Would that even be possible from a medical perspective?

Damann: The human body is highly adaptive, but we have to find out what the limits to that are. Currently, astronauts conduct a mandatory two-hour workout program every day to keep their cardiovascular systems healthy and prevent bone loss. Of course, one could investigate what happens to astronauts who don’t exercise, but then you run up against ethical issues.

What we can do is keep extending the period astronauts spend in space to see how certain changes develop. Generally speaking, I do think a life in space is possible. The bigger medical question then would be whether people who’ve lived much of their lives in space could return to Earth.

Translated from German. This interview also appeared in Die Welt

Featured image: Scott Kelly during his time in space (NASA).