Astronauts Sunita Williams and Butch Wilmore stuck in space: How can it affect their health? Experts explain

When NASA astronauts Sunita Williams and Butch Wilmore boarded the Boeing Starliner for an eight-day space mission in June, little did they know they would have to spend much more time at the International Space Station (ISS). Due to critical issues with the Starliner spacecraft, it was deemed unfit for their return to Earth due to which the astronauts have been stranded in space for more than two months now without any definite timeline of their return. Experts have warned that this prolonged stay in space can pose significant health risks.

NASA revealed last week that Williams and Wilmore may have to wait until February 2025 as the agency considers using SpaceX's Crew Dragon to bring them home. However, a final decision has not yet been made.

In the wake of this situation, we speak to health experts who highlight the changes the body undergoes upon entering space and the health hazards one may face due to prolonged exposure to elements like microgravity and radiation in space.

Changes in the body
A person's body undergoes significant changes upon exiting the Earth's atmosphere and entering space.

Explaining these changes, Dr Atul Narayankar, Consultant Medical Oncologist, Wockhardt Hospitals, Mira Road, says, "The absence of gravity over there can be mentally and physically exhausting making it challenging to survive. One's muscles and bones tend to become weaker, causing distress. The fluids present in the body such as blood start to shift upward towards the brain which can cause several life-threatening complications."

"This includes complications like decreased blood pressure, increased heart rate, dizziness, fluctuation in body temperatures, dehydration, swelling of the face, shock, respiratory distress, weakness, changes in vision and sleep apnea. Several astronauts who visit space often experience space motion sickness which is kind of similar to sea sickness. This is because your brain often finds it difficult to adjust to a completely new environment," he adds.

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The change in environment also causes changes in the brain. Dr. Amrut S D, Associate Consultant Neurology, Manipal Hospital, Goa, explains how space affects brain health.
1. Fluid shifts: One of the first changes astronauts experience in space is a shift in bodily fluids due to microgravity. On Earth, gravity pulls fluids downward, but in space, they redistribute towards the head. This fluid shift increases pressure in the brain and eyes, potentially leading to vision problems and altered brain structure.
2. Brain structure changes: Studies using MRI scans have shown that long-term spaceflight can cause structural changes in the brain. The ventricles, which are spaces in the brain filled with cerebrospinal fluid, tend to expand, and there may be changes in the white matter, which is crucial for communication between different brain regions.

Stressing how vision is affected in space, Dr. Smit M. Bavariya, Cataract Surgeon at Dr. Agarwal's Eye Hospital, Wadala, says, "In space, fluids shift towards the head, which can increase intracranial pressure and affect the shape of the eye and the optic nerve. This can lead to visual disturbances."

Effects of radiation exposure and microgravity
While ISS has shields to protect astronauts from harmful radiation, they are not untouched by its effects. Prolonged exposure to radiation and microgravity can affect physical as well as brain health.

"When travelling outside Earth's protective atmosphere, astronauts are exposed to cosmic rays and solar energetic particles, which can put them at a greater risk of cancer and damage to vital organs over time and even impact their neurocognitive functions, raising concerns about astronauts' decision-making abilities during long-duration missions," Dr. Narayankar states.

Dr. Amrut highlights the risks these elements pose to brain health.
1. Radiation risks: Space is filled with cosmic rays and solar radiation, which are much stronger than what we experience on Earth due to the lack of atmospheric shielding. Prolonged exposure to this radiation can damage brain cells and DNA, leading to an increased risk of cognitive impairments, neurodegenerative diseases and even brain cancer.
2. Inflammation and oxidative stress: Radiation exposure can trigger inflammation and oxidative stress in the brain, leading to cellular damage and accelerating aging processes. These effects can impair learning, memory and other cognitive functions.

Risk of cancer
Dr. Narayankar informs that prolonged exposure to harsh and sensitive environments in space can increase the risk of cancer.
"This is because the radiation in space is much more intense compared to the Earth. Over time, it can invade your cell's DNA resulting in genetic mutation. This can lead to the development of cancer," he explains.

"There's a potential risk of developing leukemia (cancer of blood-forming cells), sarcoma (cancer that develops in the connective tissues of the body), and thyroid (abnormal growth of cells in the thyroid glands) cancer among space astronauts. However, more concrete research is needed to prove the risk of cancers due to staying in space for prolonged periods," he adds.

Risks to brain health
According to Dr. Amrut, prolonged stay in space can affect neurological and psychological health in the following ways:
1. Cognitive decline: Prolonged exposure to the space environment can lead to cognitive challenges such as impaired memory, attention, and decision-making skills. These effects are thought to be linked to the changes in brain structure and the stress of living in a confined, isolated environment.
2. Sleep disruption: The absence of a natural day-night cycle in space can disrupt circadian rhythms, leading to sleep problems. Poor sleep can exacerbate cognitive decline and negatively impact mood and overall mental health.
3. Psychological stress: The isolation, confinement and distance from Earth can lead to increased psychological stress, which can affect cognitive function and overall brain health.

Impact on vision
According to reports, Sunita Williams underwent an extensive eye scan as she was believed to be facing eyesight issues. It is common for astronauts to have vision problems due to conditions like Spaceflight Associated Neuro-ocular Syndrome (SANS).

Dr. Bavariya explains, "SANS is a condition observed in some astronauts that affects the eyes and the brain. It involves changes in vision, including blurred vision, difficulty focusing and changes in the shape of the eye. It is caused by increased intracranial pressure, which results from fluid shift in microgravity and affects the optic nerve and the eye's structure."

Informing about the criticalness of the condition, he says, "SANS can be quite detrimental as it affects astronauts' vision and can impact their ability to perform tasks that require precise visual acuity. The long-term effects are still being studied, but significant visual changes can impact an astronaut's quality of life and their ability to complete missions effectively."

"To mitigate the effects of SANS, research is ongoing into various countermeasures. These include wearing pressure garments, adjusting sleep positions and using medications. In some cases, visual health monitoring and eye exercises are being explored to help manage or reduce symptoms," he concludes.

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Other health risks
Dr. Amrut highlights other health risks associated with bones and muscles, heart and the nervous system.
1. Bone and muscle loss: In the microgravity of space, bones and muscles do not bear the usual weight they do on Earth, leading to atrophy. Astronauts can lose up to 1% of their bone mass per month and muscle strength declines as well. This weakening can affect posture, movement and overall physical health.
2. Nervous system impact: The nervous system, which relies on the proper functioning of muscles and bones for movement and coordination, can be disrupted. The vestibular system, which controls balance, can become confused in microgravity, leading to disorientation and difficulty in movement coordination.
3. Cardiovascular changes: The heart muscle can weaken due to reduced workload in space, affecting blood circulation and potentially leading to dizziness or fainting when astronauts return to Earth's gravity.

Preventive measures
Going to space requires one to be extensively prepared not only in terms of knowledge of the mission but also important health measures to be taken. While this is a large and evolving area of study involving both doctors and space scientists, health experts suggest some preventive measures to minimise health risks in space.

Dr. Narayankar
1. It is imperative for astronauts to use protective shielding made from materials such as polyethylene or water, which are effectively known to absorb and scatter harmful particles and lower various health risks in astronauts. Innovative spacecraft designs incorporate these materials into walls and equipment for ensuring safety.
2. Opting for flight paths during solar minimums can minimise exposure to cosmic rays. Try to monitor radiation levels and adjust the schedule based on fluctuating radiation conditions in different areas of the spacecraft.

Dr. Amrut
1. Exercise regimens: To combat bone and muscle loss, astronauts follow strict exercise routines, including resistance and cardiovascular training, to maintain physical health.
2. Radiation protection: Spacecraft are designed with shielding to minimise radiation exposure, and astronauts may take medications or antioxidants that help protect against radiation-induced damage.
3. Cognitive training: Engaging in cognitive tasks and mental exercises during missions can help keep the brain sharp and mitigate cognitive decline.
4. Psychological support: Regular communication with loved ones, access to mental health professionals and recreational activities are important for managing the psychological stress of space travel.