3 questions for astronauts in space on the health impacts of a long-duration mission

What happens to the human body in space? Over 60 years after the first human left Earth on a 108-minute mission, we’re still learning.

Andreas Mogensen, with the European Space Agency, and Jasmin Moghbeli, with NASA, launched to the International Space Station (ISS) in August for a six-month mission. They spoke with Yahoo Life about some of the health challenges that can occur while in space for a long-duration mission.

"One of the things I've felt for the month and a half that I've been up here is just a general stuffiness that comes from the increased blood volume to the head," says Mogensen, who is on his second spaceflight following a 10-day mission in 2015. "You just kind of feel a little bit congested constantly. But apart from that, I don't think there are any significant health challenges that I've noticed."

Mogensen and Moghbeli are expected to return home around February 2024 and may clock some changes when they touch down on Earth.

Experts are already aware of some health challenges, such as bone and muscle loss due to weightlessness in microgravity; vision changes, also due to weightlessness, which may cause blood and cerebrospinal fluid to shift upward and prompt eye swelling and blurry vision; and psychological challenges that can occur from spending prolonged time onboard a confined, isolated space.

Many of the physiological changes appear to be temporary. Astronaut Scott Kelly, for example, grew about 2 inches taller during his nearly one-year stay on the ISS, thanks to the lack of gravity that caused his spinal discs to expand; it took less than two days back on Earth for his height to return to normal.

But other changes might last longer; months after his return to Earth, Kelly’s immune system was still on high alert; short-term memory and logic tests showed a decline in cognitive performance; and genetic mutations caused by increased radiation exposure while in space were still present — which could mean a slight increase in cancer risk over his lifetime.

There are still so many unknowns about the health consequences of space travel, particularly because so few people have done it. Women have been underrepresented (since its inception, NASA has selected 299 male and 61 female astronaut candidates) making women’s health even harder to study. Research was published in 2014 on whether space affects men and women differently, specifically calling for the selection of more female astronauts.

One disproven myth, for example, postulated that zero gravity would cause “retrograde” menstrual flow, “causing blood to accumulate in the abdomen and cause infections.” In a now-infamous exchange, Sally Ride, who in 1983 became the first American woman to go to space, said she was asked by engineers if 100 tampons would be enough for a one-week mission.

Spaceflight can also be psychologically taxing. A 2021 study cites the most frequent mental health symptoms as emotional dysregulation, cognitive dysfunction and the effects of chronic sleep deprivation.

However, Moghbeli and Mogensen say the remarkable experience of being in space makes it easy to stay upbeat (despite spending months in a relatively confined space — an international crew of seven people live and work in an area larger than a six-bedroom house).

“The work that we do is interesting and we have the opportunity to look down at our beautiful planet in the evenings and in our free time,” Mogensen says. “And so all in all, it's just an incredible experience. Of course, we are away from our families and our friends for long periods of time, but we have good opportunities to stay in contact with them through various communication means. So it's not as challenging as a lot of people believe it to be.”

“Maybe we're just lucky and we got a great crew, but we all get along really well and so that makes not just working together but also living together a lot of fun," Moghbeli says. "This is an absolute once-in-a-lifetime experience. And for me personally, one of the most challenging things has been the thought of leaving this experience not knowing if I'll ever get to come back, and it feels like time is just kind of flying by. And while I do certainly miss my husband and my daughters back home and all my friends and family, overall, it's just such a unique opportunity, and I'm just trying to soak it all in.”

Read on for more from Moghbeli and Mogensen, who spoke to us via Zoom from space.

1. How do you stay healthy and physically fit while in space?

Mogensen: We do a mix of cardio and muscle-strength-building exercises in order to maintain our muscle mass and our bone density. Being weightless, we simply don't need our muscles or our bones, and so our body is smart and says, "Well, there's no need to spend energy maintaining it if we don't need it." So that's why we have to exercise, and hopefully it also means that when we return to Earth, our rehabilitation will be minimal. Most astronauts do return to Earth and need minimal rehabilitation.

We’re able to minimize the loss of muscle mass and bone density by our excellent exercise regimen up here. We exercise two-and-a-half hours a day. We have a stationary bicycle, we have a treadmill, and then we have a strength-conditioning device — basically, a machine where we can do all sorts of muscle exercises like squats, dead lifts, bench press, curls, anything like that.

2. What are researchers hoping to learn from your six-month mission to inform the health of astronauts on even longer trips in space — like eventually a mission to Mars?

Moghbeli: We're constantly learning more about the impacts of spaceflight on the human body. There’s such a small number of people in the grand scheme of things that have flown in space, so it's often hard to pinpoint whether something is a causal factor or not.

We have certainly seen that we've been able to provide countermeasures through exercise to maintain our bone density, but the bone structure seems to change a bit. We've definitely been interested in studying the impacts to our eyes, and understanding better — I don't think we quite do yet — when we start talking about longer missions, what that impact will be to our eyes, the fluid shifts.

One thing a lot of kids ask me is, "Oh, are you going to be younger than all of us when you come back from space?" But actually, we find it might actually age us a bit more up here. So I think we're really still gaining an understanding of all those things.

3. Hundreds of men but only a few dozen women have gone to space. Jasmin, what do you think is the biggest misconception people have about women and their ability to complete a spaceflight, and how do you hope your mission changes that?

Moghbeli: Each individual has their own strengths and weaknesses — it's not just men and women. But when you start to generalize, there are certain characteristics about women that you could say are more advantageous for space. And you could do the same for certain characteristics that are more characteristic of men.

I think this is slowly changing over time, but we've lived in a world where the standard is often men, and then anything else is a deviation from that. Over time, we've done a better job of adapting. We've seen now multiple times women come up here — myself and Loral O’Hara are up here right now.

It's easy to connect and relate to someone that in some way looks like you or you feel some connection to that person. So I'm just hoping as people see more women up here — especially the next generation — I hope they realize that they can do this as well, and we just continue to build that.