Article image

Bad news for first Mars colonists: Space travel is proven to weaken the immune system

Space travel is incredibly difficult, and being an astronaut is a demanding job. It appears that it may have even more challenges than previously thought.

According to recent research, space travel puts astronauts at higher risk of infections due to weakened immune systems. For example, while onboard the International Space Station (ISS), astronauts often have to deal with issues such as skin rashes and various diseases.

Strangely, these space travelers seem to shed more live virus particles while in space. Viruses like Epstein-Barr, varicella-zoster responsible for shingles, herpes-simplex-1 responsible for sores, and cytomegalovirus are all more prominent. This led researchers to question whether our immune systems weaken during space travel.

Dr. Odette Laneuville, an associate professor at the Department of Biology at the University of Ottawa is the lead author of the new study.

He explains, “The expression of many genes related to immune functions rapidly decreases when astronauts reach space. But when they return to Earth after six months aboard the ISS, the opposite happens.”

How the space travel study was conducted

The team of researchers looked closely at the gene expression in leukocytes, or white blood cells, of 14 astronauts. This group included three women and 11 men.

These astronauts stayed on the ISS for between 4.5 and 6.5 months from 2015 to 2019. Blood samples were drawn from the astronauts at 10 different points. This occurred once before flight, four times in flight, and five times after they returned to Earth.

Through their research, they discovered that 15,410 genes were expressed differently in the leukocytes. They were able to identify two clusters of these genes, with 247 in one cluster and 29 in another, that changed their expression in a synchronized manner over the time period studied.

The first cluster of genes decreased in space and then increased when back on Earth. The second cluster had the opposite reaction. Most of these genes code for proteins related to immunity in the first cluster and cellular structures and functions in the second.

What was learned about the immune system during space travel

The research suggests that a trip to space leads to changes in gene expression. This results in a weaker immune system.

“A weaker immunity increases the risk of infectious diseases, limiting astronauts’ ability to perform their demanding missions in space. In space, astronauts have limited access to medical care, medication, or evacuation if an infection or immune-related condition becomes severe,” says Dr. Guy Trudel, a rehabilitation physician and researcher at The Ottawa Hospital and professor at the Department of Cellular and Molecular Medicine of the University of Ottawa.

However, there’s a bit of good news. Most genes in either cluster returned to their pre-flight levels within one year after returning to Earth, typically within a few weeks.

But this research also points to a potential risk. Returning astronauts might have a higher risk of infection for at least a month after landing back on Earth. The time it takes for their immune resistance to fully recover may depend on many factors. These include age, sex, genetic differences, and past exposure to pathogens.

The researchers believe that the changes in gene expression in leukocytes in microgravity may be due to a phenomenon called ‘fluid shift’. This refers to the redistribution of blood plasma from the lower to the upper part of the body.

This includes the lymphatic system, leading to a reduction in plasma volume of 10%-15% within the first few days in space. Large-scale physiological adaptations, including altered gene expression, are thought to accompany this fluid shift.

How do we boost astronauts’ immune systems for space travel?

So, what’s next? Laneuville says, “The next question is how to apply our findings to guide the design of countermeasures that will prevent immune suppression while in space, especially for long duration flights.”

Preventing the progression towards severe symptoms through early detection of both immune dysfunction and sub-clinical inflammation can improve the health of astronauts. This is especially true during long missions.

Understanding these changes in the immune system is not just about keeping astronauts healthy. It could also have significant implications for future space travel.

As humanity looks to venture further into space, and potentially even colonize other planets, ensuring the health and wellbeing of astronauts is absolutely crucial. And that’s not just about making sure they have enough food and water. It’s also about understanding the more subtle effects that living in space can have on the human body.

Much more data is needed to find a solution

The research team, led by Laneuville, continues to study these changes in the immune system and how they can impact an astronaut’s health. With these findings, they are closer to understanding how space travel affects the immune system.

While the findings present challenges, they also offer hope. The immune system’s ability to recover once an astronaut returns to Earth is encouraging. Much more research is needed to understand the exact timeline and factors affecting this recovery.

However, this study opens the door to the development of strategies to help boost the immune system of astronauts, both in space and after they return to Earth.

In the future, we might even see the development of new medical treatments or interventions that can be used in space. These would be designed specifically to help astronauts deal with these changes in their immune system. The lessons learned from this research could eventually benefit not just astronauts, but all of humanity.

In essence, Laneuville, Trudel, and their team are pushing the boundaries of our knowledge about human health in space. They’re not just contributing to the exciting field of space exploration, but also to the broader fields of immunology and gene expression.

As we continue to explore the final frontier, their work is sure to have far-reaching impacts on our understanding of human health and resilience.

The Canadian Space Agency funded this important research.

More about health hazards of space travel

Space travel, while an exciting frontier for exploration and scientific discovery, presents significant health hazards to astronauts. Here are some of the key health risks associated with space travel:


The reduced gravity environment in space leads to several physiological changes in astronauts. These include muscle atrophy (weakening and shrinking of muscles), bone density loss, cardiovascular deconditioning (reduced heart muscle size and blood volume), and fluid shifts in the body, potentially leading to vision changes.


In space, astronauts are exposed to significantly higher levels of radiation than on Earth, which increases their risk of developing cancer and other illnesses. This radiation can also cause acute effects such as nausea, vomiting, fatigue, skin injuries, and changes in the blood.

Psychological Stress

The confined and isolated environment, coupled with the inherent risks and stresses of space missions, can lead to a variety of psychological and behavioral issues, including anxiety, depression, and interpersonal conflict.

Altered Sleep Cycles

The different light-dark cycles in space, along with the stressful environment, can disrupt astronauts’ sleep patterns, potentially leading to fatigue and performance decline.

Visual Impairment

Some astronauts experience changes in vision after space travel. This is believed to be due to fluid shifts in the body due to microgravity, leading to a condition known as Spaceflight Associated Neuro-ocular Syndrome (SANS).

Immune System Changes

As demonstrated by the research mentioned in your previous questions, space travel can alter the functioning of the immune system, potentially making astronauts more susceptible to infections.

Increased Exposure to Infectious Organisms

The ISS is a closed environment, meaning microorganisms can circulate more easily. In addition, studies have suggested that some bacteria can become more virulent in microgravity.

Space Travel Environment

The spacecraft environment itself can pose risks. For example, the air is different, with higher levels of carbon dioxide, which may impact cognitive function. Additionally, astronauts could potentially be exposed to chemicals used in the spacecraft.

Re-adaptation to Earth’s Gravity

When astronauts return to Earth, they often experience issues like dizziness, blood pressure changes, and weakened muscles and bones.

It’s important to note that mitigating these health risks is a major focus of space agencies like NASA. Ongoing research is focused on understanding these health hazards.

In addition, scientists are working to develop countermeasures to ensure the safety and health of astronauts during long-duration space travel. Such countermeasures include exercise regimes, nutritional strategies, psychological support, and medications to help manage these potential health issues.

News coming your way
The biggest news about our planet delivered to you each day