Astronauts more likely to die from heart disease

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Ronald Evans, who went to the moon as part of the Apollo 17 mission, died of a heart attack in 1990. New research suggests radiation exposure during the return mission may have made him more susceptible to cardiovascular disease.
Credit: NASA

Wannabe Mars astronauts take note: blasts of radiation from deep space may be why Apollo astronauts are more likely to die from heart problems than their low-orbiting and Earth-bound counterparts, a new study suggests.

Researchers from the US, led by Florida State University’s Michael Delp, examined how astronauts and cosmonauts died and found three of the seven who visited the moon died from cardiovascular disease – four times higher than those on the space station or on Earth.

Australasian Society of Aerospace Medicine’s Gordon Cable, who was not involved in the study, says he’s surprised the study was able to draw statistical significance from so few cases and with a gender bias – no women have set foot on the moon.

But, he added, the link was interesting since radiation is generally associated with cancer and reproductive issues.

“I think it’s exactly these sort of studies that we need to be doing as we are considering deep space exploration and long duration missions to the moon and to Mars,” he says.

On Earth, the planet’s protective magnetic field deflects charged particles – such as electrons and protons – that rain down on us from the sun and outside the solar system.

But once outside the shield, astronauts and cosmonauts are exposed to those particles.

Spacecraft do have radiation shields but they don’t block it all. Astronauts on the space station, in 2002, were subject to around one millisievert of radiation each day – the equivalent of a year’s worth of radiation on Earth.

And astronauts travelling to the moon, much further than the space station’s orbit and so even more unprotected from radiation, were exposed to around 1.2 millisieverts each day.

So Delp and his colleagues compared the cause of death for seven Apollo astronauts to 35 astronauts who got as far as low Earth orbit, and another 35 astronauts who didn’t leave Earth.

Three of the seven Apollo astronauts died from cardiovascular disease, making their risk around four times higher than for an astronaut flying at relatively low altitudes or not at all.

Cosmic radiation, the researchers write, is a major player in cardiovascular disease in astronauts as it damages the cells lining blood vessels.

To add weight to their theory, they replicated the amount of radiation the Apollo astronauts experienced on mice in labs and observed that after six months – or 20 human years – the mice developed damaged arteries, known to lead to cardiovascular disease.

But space radiation fluctuates. The sun occasionally spews out solar flares – sudden flashes of energy – often followed by an unusually massive blast of plasma in what’s called a coronal mass ejection. They’re also hard to predict.

Cable says the sudden burst of radiation from the sun while astronauts are travelling to Mars could also see some serious health effects.

“Trying to mitigate risks in a spacecraft is difficult. The problem with shielding on the spacecraft is it’s weighted and every single kilogram you take into space is hugely expensive,” he says.

“I think NASA might also need to see what can be done medically to treat patients and somehow create an immunity to radiation. But that technology doesn’t exist.”

The study was published in the journal Scientific Reports.

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