Sunita Williams' return: Vision impairment, kidney stones, other health fears

As American astronauts Butch Wilmore and Sunita Williams are on their way back to Earth after nine long months in space, experts are contemplating the health risks they could face, which can range from bone and muscle deterioration, radiation exposure and vision impairment among others.

But experts also warn that besides the well-known dangers that can be managed, there are some other risks that still remain a mystery.

As humans push deeper into the solar system, plumbing the mysterious depths of space, there are bound to be more side-effects that astronauts will have to face.

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ISS missions

International Space Station (ISS) missions typically last six months. But some astronauts stay up to a year, and researchers are confident in their ability to maintain astronaut health for that duration.

According to Rihana Bokhari, an assistant professor at Center for Space Medicine at Baylor College, though Williams and Wilmore's nine-month stay got a lot of attention, it is quite par for the course.

"The best results we have to show that we're being very effective is that we don't really have a fracture problem in astronauts when they return to the ground," Rihana Bokhari, an assistant professor at Center for Space Medicine at Baylor College, told AFP.

But Bokhari added that bone loss was still detectable on scans.

Exercise regimen

A two-hour daily workout keeps the astronauts in shape, medical experts say.

To counter the lack of gravity in space, astronauts use three exercise machines on the ISS. This includes a 2009-installed resistance device that simulates free weights using vacuum tubes and flywheel cables.

Balance disruption is another health issue, said Emmanuel Urquieta, vice-chair of Aerospace Medicine at the University of Central Florida. In the report, she is quoted as saying that this happens to every single astronaut, even those who go into space just for a few days.

Kidney stones

Astronauts are expected to retrain their bodies during NASA's 45-day post-mission rehabilitation programme.

Experts also point to another challenge known as "fluid shift" – in which bodily fluids get redistributed toward the head in microgravity. This can increase calcium levels in urine, raising the risk of kidney stones.

Fluid shifts may also contribute to increased intracranial pressure, altering the shape of the eyeball and causing spaceflight-associated neuro-ocular syndrome, causing mild-to-moderate vision impairment.

Radiation levels

Another theory suggests raised carbon dioxide levels are the cause.

Radiation levels aboard the ISS are higher than on the ground as it passes through the Van Allen radiation belt. But earth's magnetic field still provides significant protection.

The shielding is crucial, as NASA aims to limit astronauts' increased lifetime cancer risk to within three per cent. However, missions to the Moon and Mars are all set to give astronauts far greater exposure, said an astrophysicist, according to reports.

Artificial gravity

Future space probes can provide some warning time for high-radiation events, such coronal mass ejections – plasma clouds from the Sun – but cosmic radiation remains unpredictable.

Artificial gravity, created by rotating spacecraft frames, can help astronauts stay functional upon arrival after a nine-month journey to Mars.