Space is deadly – but perhaps not as much as we thought NASA

Space exploration is a risky business. As well as the physical dangers, radiation from the sun and cosmic rays is thought to put astronauts at a higher risk of cancer and heart disease in later life.

But a new study that looked at whether astronauts are dying early from these conditions found no sign. “We haven’t ruled it out, but we looked for a signal and we didn’t see it,” says Robert Reynolds of Mortality Research & Consulting, City of Industry in California.

So far, not enough of the space-goers have died from these conditions to just compare their age of death with that of others. Instead, Reynolds’ team used a statistical technique on survival figures for 301 US astronauts and 117 Soviet and Russian cosmonauts.


Of the total group, 89 have died to date. Three-quarters of cosmonaut deaths were due to cancer or heart disease, while only half of the astronaut deaths were, probably because there have been more fatal accidents in the US space programme, such as the Challenger shuttle disaster.

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Down here on Earth, getting heart disease doesn’t make you more or less likely to also get cancer – the two conditions develop relatively independently of each other. But if radiation exposure were causing a surge in both conditions amongst people who have been to space, then the higher rate of death from one illness would be dampened by the higher rate of the other – because anyone who dies from heart disease cannot also die from cancer.

Reynold’s team plotted the space-goers’ deaths over time as survival curves – which show the rate at which a particular group is dying – for each disease, and found no sign of this dampening effect.

However, that doesn’t rule out that radiation could be giving the astronauts a higher rate of one condition but not the other – for instance, if it caused cancer but not heart disease.

And future space-goers who go further afield would be exposed to higher levels of radiation, says Reynolds, meaning it could still affect the health of anyone going to Mars.

Journal reference: Scientific Reports, DOI: 10.1038/s41598-019-44858-0