Introduction
Have you ever wondered what it is like to be an astronaut? They have to deal with an extreme environment very different than any on Earth. There is no gravity. It’s really cold. And astronauts are exposed to cosmic radiation. Researchers already know that astronauts lose muscle and bone in space. Their vision changes and their immune systems don’t work as well. These become huge problems during longer trips to space.

An astronaut’s genome, or DNA, can determine how they respond to space. Changes to their DNA may lead to adverse health effects. But researchers don’t have a good understanding of what actually happens to DNA in space. Studying telomeres may help. They are the “end-parts” of chromosomes that protect the ends of the DNA. Like the plastic tips on the ends of shoelaces! They keep the laces from getting tangled or frayed.

Researchers know that telomeres get shorter as people get older. This is related to normal cell division. Things like stress and smoking make telomeres shorter, too. Unhealthy environments can also cause telomeres to shorten. For example, places with air pollution or radiation exposure. The length of telomeres is linked to the risk of dementia, heart disease, and cancer. This makes them important to study for human health effects.

In 2015 NASA did a study on the twin astronauts Scott and Mark Kelly. Scott Kelly spent a year on the International Space Station while Mark Kelly stayed on Earth. Researchers studied the twins’ telomeres. Scott’s telomeres increased in length while in space. His telomeres then quickly shortened when he returned to Earth. In fact, Scott’s telomeres were shorter after the 1-year mission than before he went into space. We will have to wait to see what impact this has on his health in the future.

The NASA Twins Study gave researchers a lot of new information about astronaut health. But there were also limitations. To date, most astronauts have spent less than 20 days in space. Also, Scott and Mark Kelly are middle-aged white men. Spaceflight is becoming more common. So more people of different ages, sexes, ethnicities, and starting health will travel to space. There will also be more civilians instead of highly-trained astronauts. Some will be on short-duration trips, but some will be on longer missions. Some may even stay!

We wanted to know if telomere length changes occur in a more diverse population. And does telomere length change during a shorter trip into space? This information is important to ensure the future health and safety of humans in space.

Methods
We used the 2021 SpaceX Inspiration4 mission for our study. The mission was only 3 days long. The four crew members were all civilians and first-time flyers. And they were of different ages and sexes. We collected blood from each crew member 92 days, 44 days, and 3 days before their trip. We also collected blood during each of the days they were in space. Lastly, we collected blood again 1 day, 45 days, and 82 days after they returned to Earth.

We extracted DNA from all the blood samples. Then we measured the average telomere length.

Results
We saw that telomeres were longer during spaceflight (Fig. 1). This happened for all four crew members. We also saw that telomeres shortened quickly when they returned to Earth. This happened for three of the four crew members. At 45 and 82 days post-trip, we saw all four crew members’ telomeres gradually return to near normal length.

Discussion
The changes in telomere length for the Inspiration4 crew were like those seen in the NASA Twins Study. It is important to know that even short trips into space can change telomere length. And that it can happen in a more diverse group of people. We wanted to learn more about these changes. This will help us understand how they might cause problems for astronauts when they come back to Earth.

We think that telomere length changes because of cosmic radiation exposure. Radiation damages DNA. And it is everywhere in space. Spending more time in space also means more exposure. The International Space Station has shielding in frequently used areas. This helps protect the astronauts from some radiation. But what if humans want to travel to and/or stay on other planets someday? We need a better solution to reduce radiation damage.
Conclusion
Space is an extreme and dangerous environment. We don’t know a lot about how it can impact people’s health long-term, especially their DNA. The more we know, the better we will be able to keep our astronauts healthy.

There are several things you can do to stay healthy down here on Earth:
Eat healthy food with plenty of fruits and vegetables.
Get enough sleep.
Limit your stress. You can try meditation, do relaxing activities, and stay in touch with loved ones.
Reduce your exposure to toxicants like smoke, pesticides, and pollution.