JOHN DANKOSKY: This is Science Friday. I’m John Dankosky sitting in for Ira Flatow.

Hundreds of people have flown in space since cosmonaut Yuri Gagarin orbited the earth in 1961. But of those hundreds, the 24 who flew the Apollo missions are the only people so far who have left the protection of the earth’s magnetosphere, which shields us from most of the radiation entering the solar system. New research published this week compares those 24 astronauts to those who never left low Earth orbit and concludes that interplanetary travel may boost the risk of heart attacks and strokes up to five times the risk for astronauts that stay closer to home.

We’re taking a look at that research, plus the bigger picture of how time and space affects astronauts bodies. How can we help to keep them healthy on these long voyages as NASA and SpaceX get ready to send people to Mars? We want to hear from you. What are your questions about space travel and the body? Our number is 844 724 8255. That’s 844 SCI TALK. You can always tweet us at Sci Fri.

My guests are Dr. Michael Delp he’s Professor and Dean in the College of Human Sciences at Florida State University and author of the new research about the Apollo astronauts. Welcome, Dr. Delp.

MICHAEL DELP: Thank you. It’s great to be with you.

JOHN DANKOSKY: Also with us today is Dr. Jeffrey Sutton. He’s President and CEO of the National Space Biomedical Research Institute and Director of the Center for Space Medicine at Baylor College of Medicine. Welcome, Dr. Sutton.

JEFFREY SUTTON: Thank you very much.

JOHN DANKOSKY: So first of all, Dr. Delp, let me turn to you and talk about these alarming statistics– a five-fold increase in the risk of cardiovascular problems for Apollo astronauts. How did you reach this finding?

MICHAEL DELP: Well, I think first, in starting the study, we were looking at the fact that the International Space Station is scheduled to be decommissioned in 2024. And really, around the world, a lot of countries, space organizations, and even corporations have talked about plans to send humans back to the moon and on to Mars within a 10-year time frame from now. And so the question came up– are there any long-term effects of going into deep space to humans? And the Apollo lunar astronauts are the only humans to have done that.

We wanted to look and see what their cause of mortality, or cause of death was. And so even though there are 24 Apollo astronauts, really what we looked at were the seven that had died since 2015. And we found that they did have a higher mortality rate due to cardiovascular disease, a higher five-fold higher than astronauts who never flew into space, as well as the astronauts that remained in low Earth orbit.

JOHN DANKOSKY: Of course, 24 total astronauts is a pretty small sample size. So how can we conclude anything from these seven deaths?

MICHAEL DELP: Well, you can’t make definitive conclusions. And we say that in the paper– that this is an observation. It is a small sample size. And any conclusion you draw– it cannot be definitive. But it was statistically significant. And we also felt like it was difficult to ignore the possibility that space travel may be having this adverse effect on the cardiovascular system, even with this small number. And one of the things about research and space is very frequently we are dealing with small numbers, be them human studies or animal studies.

JOHN DANKOSKY: You also did some studies on mice around this as well.

MICHAEL DELP: Yes. What we found was that we had some– these were all ground-based studies. We simulated a weightlessness. We looked at space radiation. And then we combined the two, looking to see if there was an interaction.

And then after these treatments, we waited six to seven months, which was the rough equivalent to 20 human years to see if there were any long-lasting effects. And what we found was that there was some dysfunction of the blood vessels in the radiation treated animals, but not the simulated weightlessness. And that was the only effect that we found that really had this long-term sustained effect. And so from that, we concluded that space radiation may have these effects on blood vessels that may predispose these vessels to the formation of plaque.

JOHN DANKOSKY: Dr. Sutton, I’d like to get your reaction. What stands out to you about this research?

JEFFREY SUTTON: Well, I think the research is very important because it demonstrates how one can go about looking at the hazardous effects of space radiation. Space radiation is different than the radiation that we’re exposed to here on Earth where we are protected by the magnetosphere.

And as we look at different systems in the body, not only at the cardiovascular system as Dr. Delp has done, but also at the brain, at blood, at bone, at other tissues and organs, and also look at the effects of space environment on human adaptation and risks that can take place beyond those caused solely by radiation or the interaction, for example, as Dr. Delp was talking about between microgravity and radiation.

These are all very interesting and important problems if we’re going to be able to send humans on long duration exploration missions beyond low Earth orbit for extended periods of time.

JOHN DANKOSKY: And NASA looks at about 31 risk areas that they’ve been researching where astronaut health is concerned. One of them, of course, Dr. Sutton, that we’ve heard a lot about is how bones weaken in zero gravity, which means that astronauts need to have pretty rigorous exercise routines. How well has that worked out?

JEFFREY SUTTON: It’s actually worked out quite well. Certainly, it appears that the longer a person is in the weightless environment, the greater the risk for bone demineralization. And exercise along with good diet and nutrition– and there are actually some medicines that are effective as countermeasures, singularly and combined in mitigating the risks of bone.

But it’s complicated. Different astronauts have different individual susceptibilities and predispositions to bone loss. In other words, some lose bone greater than other astronauts do. Bone is lost at different rates in different parts of the body. Not surprisingly, those weight-bearing areas in the skeleton, for example, the upper portion of your thigh bone in the hip area and the pelvis tend to lose bone at a greater rate than non-weightbearing parts of the skeleton.

JOHN DANKOSKY: Some of the other things that we’ve read about that are interesting– like dust inhalation and a problem there. What’s going on with the lungs in space?

JEFFREY SUTTON: The lungs actually do quite well in space. What’s not known is what the effects, for example, lunar or Martian dust would be on the pulmonary system. Lunar dust, for example– since we’re talking about the astronauts who went to the moon– is a very unusual substance. It’s like fresh fractured quartz. And it tends to get stuck in the bronchial tree. And we need to understand better both the nature of the particular dust on the bodies that our astronauts are going to be going to to help prevent problems from occurring.

JOHN DANKOSKY: If you have questions about astronaut health, you can give us a call at 844 724 8255. That’s 844 SCI TALK. I’m talking with Jeffrey Sutton and Michael Delp and about what we know about the long-term effects of space.

Dr. Delp, getting back to this issue of radiation, a lot of people, I think, think about the problem of radiation being one tied to cancer. So what could be the other problems outside of that that we might be looking for? Obviously, you’re studying heart disease. But what else might radiation cause?

MICHAEL DELP: Well, there’s new evidence that it has neural effects. And so the neural tissue, the brain, and peripheral nerves may also have a susceptibility to it. In our study, we didn’t see any differences in mortality due to cancer in the Apollo astronauts relative to the other groups, but I don’t think they were in space long enough. And I think when we’re talking about humans going to the moon or to Mars and having a more prolonged stay, that time in space and the time that they’re exposed I think will be an important variable that will really require a lot more study.

JOHN DANKOSKY: We’ve got a question here from Ryan, who is calling from Fayetteville, Arkansas. Hi there Ryan. You’re on Science Friday.

RYAN: Hi. I was wondering if your team does research on physiological degradation of astronauts, if there’s any research going on about psychological or mental effects of prolonged space exposure, if that has a similar effect like some of the things that you’re studying.

JOHN DANKOSKY: Thanks for the question, Ryan. Dr. Sutton, you want to take that?

JEFFREY SUTTON: Sure. I’d be glad to. There’s a lot of work that’s done on the physiological adaptation and changes that take place when humans go into space. In fact, it’s pretty hard to think of a system in the body that’s not affected by weightlessness. Fluid shifts, cardiovascular system that we’ve been talking about, nervous tubular system, many, many different systems change.

With respect to behavior, the psychological effects, of course, the brain is the organ of psychology and as Dr. Delp was pointing out, we’re very concerned about brain health and ensuring astronauts have excellent performance throughout the duration of the mission. Behavioral and psychological and even psychiatric problems have taken place. They’re documented in the public literature. And there are some very interesting analog studies that have also been done.

For example, there was a 520 day isolation study done in a chamber in Moscow that was the first high fidelity simulation of a crewed mission to Mars. And what basically happens is that– first of all, crew tend to do generally very, very well, careful training and screening and teaming. Nevertheless, the environment’s harsh. And one does get concerned about common things– anxiety, a little bit of depression. And it’s important that we better understand how astronauts will function for long periods of time in isolated environments. There’s some work that’s been done and a lot more work that needs to be done.

JOHN DANKOSKY: I’m John Dankosky. This is Science Friday from PRI, Public Radio International.

Dr. Delp, one of the big mysteries that’s come up in recent years is the problems that many astronauts have developed with their vision. What exactly happens?

MICHAEL DELP: Well, I think some of them– and it’s particularly in long-term space flight that this has started to occur– and they lose a lot of their visual acuity. And NASA started noticing this. And they convened a meeting of national experts in 2010. And there’s been a lot of research effort once that problem was identified to really try to figure out exactly what it is. It certainly is related to the fluid shift. It’s been hypothesized that it may also have some bearing with the blood brain barrier, the lymphatics, possible venous congestion of blood, of blood leaving the brain area.

And the other interesting fact is– Jeff, you can correct me– is that it’s happened exclusively in men, that there have been no female astronauts or cosmonauts coming back with that.

JEFFREY SUTTON: Yes, that’s right. This is a newly recognized syndrome. And it’s probably been around for quite some time. It is of concern. We’ve been talking about radiation, which is the number one risk to astronaut health beyond low Earth orbit. Within low Earth orbit, this spaceflight induced intracranial hypertension visual alteration problem is the number one problem.

And Mike is absolutely right. This is a new syndrome. And speaking as a physician, over the span of your career, you don’t see new syndromes all that often. And it’s very interesting because of the male predominance. It’s been seen in the international crews.

And in addition to the changes in vision, many of the astronauts who are affected by this have changes in the retina itself. And that’s really the worrisome thing, that there is swelling of the optic disk. And there is folding that takes place in some astronauts, in the retina and also some areas that appear to be damaged. And some astronauts also may have some elevated intracranial pressure. And some of these changes may actually persist, even when astronauts return from the space environment.

So it is a mystery. And work is being done on this. And it’s a very important area for international collaboration to take place, to be able to better understand the mechanisms and also to mitigate this risk.

JOHN DANKOSKY: I’m wondering– just a couple minutes left, but Dr. Delp, about some of these other mysteries, if we want to send people to Mars sometime relatively soon, what are the other things we need to figure out? I mean, what are the other potential hazards for long-term life in space?

MICHAEL DELP: Well, I think– and this is something that I’m not an expert with– but spacecraft shielding, I know there are a lot of smart people out there that have talked about that.

But even things that we can control– I mean, Jeff talked about food and nutrition. A lot of experimental work still needs to be done about potential countermeasures, for example, to radiation and how nutritional needs can be met. For example, with antioxidants, even on earth a number of investigators have tested different antioxidant cocktails and many of them don’t work, but occasionally they do. And to find out why they do and what organ systems are they effective in.

JOHN DANKOSKY: Dr. Sutton, a quick last thought– something else you think we might need to figure out before we send people off to Mars?

JEFFREY SUTTON: Well, I think we have to figure out how we’re going to take care of these folks. You know, there’s an old saying in medicine that common things are common. So if you send a group of folks away, they’re going to have to be able to have ways in which they can take care of each other. So we’re looking at a relatively autonomous medical care and health care delivery system with the abilities to make remote diagnosis and to have treatments and to think about new ways that are maybe rather disruptive and revolutionary, involving, for example, 3D printing of resources that can be helpful in treating folks.

And we’ll have to learn also, very much, of how to, quote unquote, “live off the land” of how to be able to support ourselves. So imagine going on expedition. And it’s complicated.

JOHN DANKOSKY: We all watched the Martian. I guess that’s one way to do it. I want to thank Dr. Jeffrey Sutton at the Center for Space Medicine at Baylor University and also President and CEO of the National Space Biomedical Research Institute, Dr. Michael Delp, Professor and Dean of Human Sciences at Florida State University. Thank you both very much.

MICHAEL DELP: Thanks to you.

JEFFREY SUTTON: It’s been a pleasure. Thank you.

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