Sunita Williams return: What health risks astronauts may face in space? ’Vision problem, bone loss, brain damage’

NASA astronaut Sunita Williams, who remains in space due to significant delay in Starliner's return, has been contributing to studies focused on analyzing the effects of spaceflight on the human body. She herself has been undergoing body tests at the International Space Station ever since she reached there on Boeing's Starliner spacecraft on June 6.

It's not unknown that humans in space experience microgravity and space radiation-induced health risks. But how does microgravity impact the human body? For more than 50 years, space agencies have been conducting research and studies to find answers. Taking this into account, it's now feared that Williams may be at health risk because of her longer-than-scheduled stay in space.

Sunita Williams, along with her colleague Butch Wilmore, launched aboard Starliner capsule on June 5. She was supposed to return within the week. However, software issues, helium leaks and thruster anomalies detected in the spacecraft have delayed the return of the two NASA astronauts.

NASA official said in a press conference on August 7 that they are weighing other options, other than Starliner, to bring back Williams and Wilmore. The official hinted that the duo may be brought back to Earth on SpaceX craft in 2025, but this has not been confirmed yet.

Vein scans in in space

Sunita Williams, along with her colleague Butch Wilmore participated in vein scans during her recent stay at the ISS. A press release from NASA on July 18 informed that doctors on the ground monitored in real-time as the pair took turns imaging each other’s neck, shoulder, and leg veins.

"Afterward, Wilmore scanned the veins of fellow NASA astronaut Matthew Dominick, helping researchers understand how microgravity affects the human body," the release added.

Meanwhile, NASA says it "is particularly interested in investigating how the body reacts to long-duration spaceflight as the agency plans for extended missions on the Moon and Mars."

What health risks do astronauts face in space?

NASA explains that in space, astronauts are exposed to varied and increased levels of space radiation. The radiation in space is different from what we experience on Earth. The source of these radiations are "particles trapped in Earth’s magnetic field, solar energetic particles from the Sun, and galactic cosmic ray".

On Earth, people are shielded against these radiations due to the planet’s magnetic field and atmosphere. However, the case is the opposite for those hovering in the space, where there is almost no atmosphere.

According to the US space agency, "increased risk of cancer and degenerative diseases, such as heart disease and cataracts have been observed in human populations exposed to radiation on Earth". It adds that health risks for astronauts from radiation exposure in space are mainly driven by long-term impacts.

Bone loss

NASA also explains about "Skeletal unloading". It says, “Skeletal unloading during extended stays in reduced gravity increases the risk for loss of bone density and strength. Astronauts can lose up to 1% to 2% of bone density per month in the hip and spine, compared to bone loss of 0.5% to 1% per year in post-menopausal women and much older men on Earth. This rapid bone loss can place the crewmembers at risk for bone fracture and risk of early-onset osteoporosis because of spaceflight.”

NASA also learned that without Earth’s gravity affecting the human body, weight-bearing bones lose on average 1% to 1.5% of mineral density per month during spaceflight.

"After returning to Earth, bone loss might not be completely corrected by rehabilitation; however, their risk for fracture is not higher. Without the proper diet and exercise routine, astronauts also lose muscle mass in microgravity faster than they would on Earth," it added.

Weakening of muscles

Meanwhile, the JAXA Human Spaceflight Technology Directorate says that staying for a long time in space could cause the weakening of muscles and bones, primarily in the legs and lower back. "Muscles weaken and bone mass decreases if you stay for a long time in space," it adds.

Space sickness

Besides, astronauts may also experience "space sickness" which may involve headaches, nausea, and vomiting, says JAXA Human Spaceflight Technology Directorate. It also warns of "weakening of the heart muscles" which can cause "dizziness when standing". The report says that astronauts can also experience intense stress.

Brain damage, vision problems

NASA says in a report in 2021 that the fluids in the body shift upward to the head in microgravity, which may put pressure on the eyes and cause vision problems.

Moreover, a study published in the scientific journal JAMA Neurology in 2021 revealed that "the negative changes" on the body due to long periods in space “include atrophic muscles, decreasing bone mass, deteriorating vision and altered bacterial flora in the gut.”

The study of five Russian cosmonauts, who had stayed on the ISS, revealed that spending a long time in space appears to cause brain damage.

Kidney stones

"If preventive or countermeasures are not implemented, crews may experience an increased risk of developing kidney stones due to dehydration and increased excretion of calcium from their bones," the US space agency adds.

What astronauts do to remain healthy?

Astronauts follow certain procedures, strategies, medications, exercise routines, etc. known as countermeasures to stay healthy and productive in space and after astronauts return to earth.

Besides, NASA is currently working on developing a medical data architecture for spacecraft that enables the capabilities of clinical decision support tools, which could use artificial intelligence and machine learning to further help diagnose and treat various illnesses.