black and white digital art of an astronaut

7 Significant Health Issues Every Off-Planet Astronauts Endure During Space Missions

Published on March 27, 2024

Imagine you’ve just stepped off a plane after a grueling 10-hour flight. Your body feels weary, your muscles ache, and you can’t shake off the fatigue that clings to you. This is a sensation many of us have experienced and can easily relate to. Now, let’s take a giant leap from this familiar scenario to the realm of astronauts orbiting our planet. Here, in the vast expanse of space, the absence of gravity presents an entirely different set of challenges.

In the microgravity environment of space, the human body undergoes changes that no commercial airline passenger would ever encounter. While a long flight might leave us feeling tired and stiff, prolonged exposure to space can have profound and lasting effects on the human body. From the weakening of muscles to the alteration of bodily fluids, the impact is far-reaching.

In this article, we’ll be looking at the long-term health impacts of space travel, and talk about how the human body adapts, or struggles to adapt, to this extraordinary environment. But before we get into this, let’s mention the main reasons for these health concerns.

The Triple Threat in Space Travel

Radiation Exposure

In space, astronauts are exposed to higher levels of cosmic rays and solar radiation, as Earth’s atmosphere provides a protective shield against these on the surface. Despite the ISS being equipped with specialized radiation shielding materials, astronauts are still exposed to a larger amount of radiation than most people do. Overtime, this exposure can increase the risk of cancer, damage the nervous system, and cause other health issues.

Microgravity Effects

The microgravity environment in space can lead to various health problems. Our body are adapted to function under the gravity pull of the Earth. Once that gravity is no longer affecting our bodies, its normal functions are thrown out of balance and can cause various effects. These include muscle atrophy, bone density loss, and fluid redistribution in the body, which can affect vision and other bodily functions.

Psychological Stress

Being in a confined space for extended periods, away from family and familiar surroundings, can lead to psychological stress and issues like depression and anxiety. The isolation and unique stressors of space travel can significantly impact mental health. Now, it’s one thing to be in a space station orbiting the earth, its another to be in a transit between Earth and Mars, which takes about 6 months to complete. On the ISS, you can see our beautiful from the windows, whilst on your way to mars, astronauts will onlybe able to see distant stars.

Bone & Muscle Loss

In the microgravity environment of space, astronauts experience reduced mechanical strain on their skeletons compared to Earth. This leads to bone demineralization and loss of strength. Astronauts can lose 1-2% of their bone mass each month in space, which is significantly faster than the 0.5%-1% annual loss experienced by older adults on Earth.

Over a six-month period, this can accumulate to a 10% loss in bone mass. This rapid demineralization increases their risk of fractures and prolongs healing time. It can take up to four years for astronauts to regain normal bone mass after returning to Earth.

Similarly, muscles also deteriorate in space due to lack of use and resistance they would normally encounter on Earth. This muscle atrophy contributes to overall weakness and can complicate physical tasks and re-adaptation to Earth’s gravity. This is the main reason why astronauts cannot walk when landing on Earth and are carried by support staff or assisted with mobility aids until they regain their strength and adapt back to Earth’s gravitational forces.

Current solutions to mitigate these effects

To mitigate these effects, astronauts on the International Space Station (ISS) engage in 2.5 hours of daily exercise, including strength training exercises like squats, deadlifts, rows, and bench presses using a resistive exercise device. They also use a treadmill and an exercise bike for cardiovascular workouts. Lastly, astronauts take dietary supplements to maintain bone health, which is a critical aspect of their carefully planned space food menu.

astronaut exercising onboard the ISS

Fluid Redistribution and Vision Impairment

Another significant issue astronauts face in microgravity is the redistribution of bodily fluids. On Earth, gravity pulls fluids downwards, but in space, these fluids tend to move towards the head. This can cause facial puffiness and increased intracranial pressure, leading to vision problems known as spaceflight-associated neuro-ocular syndrome (SANS). These vision changes can include flattening at the back of the eye, inflammation of the optic nerve, and changes in refractive error.

Current solutions to mitigate these effects

Regular monitoring of eye health through visual acuity tests, intraocular pressure measurements, and imaging techniques like optical coherence tomography (OCT) and MRI. Medical therapies may include medications like acetazolamide for managing cerebral pressures.

Nutritional supplements are provided to address potential enzymatic deficiencies. Targeted exercise regimes are used to maintain physical health and influence fluid dynamics. Simulating Earth-like gravitational environments through methods like lower body negative pressure helps counteract the effects of microgravity. “Space Anticipation Glasses” are provided to manage vision changes.

Ongoing research, including Earth-based studies, continues to inform new mitigation strategies. Additionally, operational adjustments on the ISS, such as reducing ambient CO2 levels and exploring remote medical procedures, are part of the comprehensive approach to managing SANS.

Breakdown of the immune system

Space travel also affects the human immune system. Research indicates that the stress of spaceflight can alter immune cell function, potentially making astronauts more susceptible to infections. The closed environment of spacecraft and space stations can also facilitate the spread of microbes.

In a recent study led by Daniel Stratis and Guy Trudel, researchers explored how long-duration space missions aboard the International Space Station (ISS) impact astronauts’ immune systems. The team closely monitored 14 astronauts, collecting blood samples during pre-flight, in-flight, and post-flight phases of their six-month missions.

Through RNA sequencing of leukocytes, significant transcriptome changes were observed. The study found 276 transcripts that varied notably, grouped into two clusters with distinct expression profiles correlating with the transition into and return from space. Initially, there was a notable decrease in immune-related gene activity, followed by a reactivation upon Earth re-entry.

These findings suggest a rapid adaptation of leukocytes to the unique conditions of space, characterized by an initial suppression of immune functions, followed by their reactivation upon return.

Current solutions to mitigate these effects

Addressing the issue of immune system modulation in space, scientists are now investigating potential strategies to counteract these effects. While the specific measures being explored by the team were not detailed in the study, it’s known in the broader scientific community that such strategies might include personalized medicine approaches, enhanced nutrition plans, targeted exercise regimes and a high level of cleanliness inside the spacecraft.

astronaut Alexander Gerst scrubbing the ISS interior

Sleep Disruption

Astronauts in space often face sleep disruption due to several unique challenges. In orbit, especially on the International Space Station, they encounter multiple sunrises and sunsets within 24 hours, disrupting natural circadian rhythms. This absence of a regular day-night cycle makes it hard to maintain a consistent sleep schedule. 

Spacecraft noise and confined living spaces also contribute to sleep difficulties, along with the effect of microgravity on the body makes it very difficult for astronauts to achieve the restful sleep necessary for optimal health. 

Sleep is vital for maintaining good health, as it allows the body to repair and regenerate. This restorative process includes healing damaged cells, boosting immune function, and regulating key hormones. 

During sleep, the brain consolidates memories and processes information, crucial for cognitive functions like learning, problem-solving, and decision-making. Lack of sleep can lead to various health issues, including weakened immunity, increased risk of chronic diseases, and mental health problems like depression and anxiety. New parents will know this very well. 

Current solutions to mitigate these effects

To mitigate sleep deprivation in space, space agencies have developed several strategies. 

  • They use specially designed sleep quarters that offer a dark, quiet environment to promote better sleep. 
  • Lighting systems that mimic the natural progression of daylight help regulate astronauts’ circadian rhythms. 
  • Scheduled sleep periods are strictly followed to ensure astronauts get enough rest. 
  • Astronauts are trained in relaxation techniques and sometimes use sleep aids under medical supervision. 
  • Agencies also monitor sleep patterns and adjust schedules accordingly to optimize rest.

astronaut Luca Parmitano asleep on the ISS

Psychological and Mental Health Issues

Isolation and confinement are major factors contributing to psychological stress in space. Astronauts are separated from their families and usual social networks, living in a confined space with the same individuals for extended periods. This can lead to feelings of loneliness, interpersonal tension, and decreased motivation.

The absence of natural environmental cues in space, such as changes in weather and the day-night cycle, can disrupt circadian rhythms. This disruption often leads to sleep disturbances, impacting mood, cognitive function, and overall mental health.

Workload and monotony also play significant roles. While astronauts have busy schedules, the repetitive nature of tasks, coupled with the lack of new stimuli, can lead to boredom and a decrease in task engagement.

The stress of constant vigilance, especially during critical mission phases or spacewalks, adds to the psychological burden. Astronauts must constantly be alert to potential emergencies or technical issues, leading to increased stress and anxiety levels.

A sense of distance from Earthly concerns and a feeling of disconnection, sometimes referred to as the “overview effect,” can lead to existential reflections, both positive and negative. While some astronauts report profound awe and a renewed perspective on life, others may feel an increased sense of vulnerability or philosophical angst.

Current solutions to mitigate these effects

To address these issues, space agencies provide comprehensive psychological support. This includes pre-mission training to equip astronauts with coping strategies, regular communication with family and mental health professionals, and post-mission debriefing and counseling.

Astronauts are also trained in group dynamics and conflict resolution to manage interpersonal issues that may arise within the crew. Team-building exercises and regular communication help maintain group cohesion.

Monitoring mental health is an ongoing process. Astronauts regularly complete psychological evaluations, and support is readily available if issues are identified.

Technological solutions, like virtual reality, are being explored to provide mental stimulation and a temporary escape from the confines of the spacecraft. This can offer a sense of normalcy and relaxation. Finally, off-world astronauts can bring a few personal items with them and they can video call their loved ones regularly.

astronaut playing saxophone in space

Cardiovascular Changes

In microgravity, astronauts experience a shift of bodily fluids towards the head. This headward fluid shift can cause facial puffiness and increased pressure on the brain and eyes. In response to this fluid redistribution, the body often decreases its total blood volume, as it perceives an overload of fluids. This reduction in blood volume, combined with changes in red blood cell production, can affect cardiovascular health.

The heart also undergoes changes. Typically, in microgravity, the heart doesn’t have to work as hard to pump blood throughout the body, which can lead to a decrease in overall heart muscle mass. This condition, known as cardiac atrophy, can impact the heart’s effectiveness in pumping blood, particularly once astronauts return to Earth’s gravity.

Current solutions to mitigate these effects

Astronauts maintain cardiovascular health through rigorous daily exercise, using specialized equipment designed for microgravity. Treadmills, stationary bikes, and resistance machines help preserve heart and blood vessel function, counteracting the effects of reduced gravity on muscle and bone density.

To manage fluid shifts in the body, astronauts may use lower-body negative pressure devices. These devices create a vacuum effect around the lower body, drawing fluids back towards the feet, and simulating the gravitational pull experienced on Earth. An experimental pair of pants was designed for this very purpose by a team of researchers. 

Diet and hydration are carefully monitored and regulated. Ensuring adequate fluid intake and a balanced diet rich in nutrients supports overall cardiovascular health and helps mitigate some of the effects of microgravity.

Before space missions, astronauts undergo extensive cardiovascular screening. This ensures they are in optimal health before encountering the unique stressors of space travel. Post-flight rehabilitation is crucial for returning astronauts. This includes a structured program of exercises and medical monitoring to help their bodies readjust to Earth’s gravity, especially to manage orthostatic intolerance.

Cosmic rays can impair the function of erectile tissues

In a recently published white paper by a team of scientists from Florida State University, it has been discovered that astronauts could face an increased risk of erectile dysfunction from long-duration space missions.

Their study, involving 86 rats, shows that the unique conditions of space, like microgravity and cosmic radiation, can significantly harm vascular tissues vital for erectile function. This revelation is particularly timely as agencies gear up for extended Moon and Mars missions.

Current solutions to mitigate these effects

While these findings add a layer of complexity to space travel’s health impacts, they also offer a silver lining. The study suggests antioxidants and enzyme inhibitors might help mitigate these effects, a crucial insight for future space explorers’ well-being.


In the pursuit of expanding human knowledge and exploring the unknown, astronauts willingly subject themselves to a multitude of risks and challenges. They face not only the immediate dangers of space travel but also long-term health effects that can linger for years after their return to Earth.

This leads us to an important consideration: the compensation and recognition these space explorers receive. Astronauts are often celebrated as heroes, pioneers venturing into the final frontier. However, when we consider the sheer magnitude of the risks they bear – both known and unknown – we must ask ourselves: Is the salary and prestige associated with being an astronaut truly reflective of the sacrifices they make?

As current space agencies’ plans involve going further into the solar system, these questions are becoming increasingly relevant, not just for current and future astronauts but for all of us as a society. How we value and support these brave individuals in their endeavors is a reflection of our commitment to understanding more about our place in the universe.

As a child, I always dreamed of becoming an astronaut and walking on the Moon, but now that I am a 36-year-old man with a wife and two young daughters, I am not so sure if this dream is worth the potential sacrifices and risks involved.

Now I ask you, would you consider the potential health risks, the time away from family, and the intense physical and psychological demands to be a worthy trade-off for the chance to be part of space exploration history?

Tom Urbain

Space exploration has been a fascinating subject for me since a very young age. As a child, astronauts were my heroes, so it was inevitable that a part of my website would be dedicated to astronauts and their space missions.

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