Image : NASA

Excessive exposure to the Sun’s harmful rays is an occupational hazard endured by astronauts, who run the risk of contracting cancer and heart disease as a result. At least that’s what we thought. New research shows that astronauts aren’t dying prematurely, but scientists caution that long duration missions will pose serious risks.




A study published today in Scientific Reports failed to associate exposure to space radiation with an increased risk of death from cancer or cardiovascular disease among both astronauts and cosmonauts. It’s a surprising, if not encouraging, result, as it was long assumed that exposure to damaging ionizing radiation would eventually come back to haunt astronauts in the form of diseases later in life, and possibly an early grave.

That said, the lead author of the new study, Robert Reynolds from Mortality Research & Consulting, Inc., in California, cautioned that longer duration missions further away from Earth’s protective magnetic field, such as a mission to Mars, are likely to be dangerous and potentially life shortening.


For the new study, Reynolds and his colleagues performed a statistical analysis of publicly available historical data. A total of 418 spacefaring individuals were included in the study, including 301 astronauts and 117 cosmonauts.

The study considered all NASA astronauts since 1959 and all Soviet or Russian cosmonauts since 1961, all of whom experienced a trip to space prior to July 2018 in the case of astronauts and December 2017 for cosmonauts. The average follow-up period for astronauts was 24 years and for cosmonauts it was 25 years.

A total of 89 deaths were recorded, 53 of them astronauts and 36 cosmonauts. These individuals died from various causes, but Reynolds and his team were only interested in two particular causes of death: cancer and cardiovascular disease, as those conditions had the potential to be linked to radiation exposure. Among astronauts, 30 percent died from cancer and less than 15 percent died of heart disease. The stats were a bit different for cosmonauts, half of whom died of heart disease and 28 percent from cancer.

“If ionizing radiation is impacting the risk of death due to cancer and cardiovascular disease, the effect is not dramatic.”


These stats may seem both high and alarming, but Reynolds’ analysis suggested these figures were nothing out of the ordinary. No trend or hiccup could be detected in the data pointing to a common cause of death, namely exposure to radiation. “If ionizing radiation is impacting the risk of death due to cancer and cardiovascular disease, the effect is not dramatic,” concluded the authors of the new study.

But these are “historical doses of space radiation,” as the authors described it. Aside from the Apollo missions, astronauts and cosmonauts in low Earth orbit were still protected by the Earth’s magnetic field. The situation in the future, when astronauts journey deeper into space, will be markedly different, as noted in the new study:

It is important to note that future missions of deep space exploration will likely offer much greater doses of space radiation than have historical doses, which will lead to a different risk profile for future astronauts and cosmonauts. In the years to come it is imperative that epidemiologists continue to surveil the astronaut and cosmonaut populations for potential harmful effects of exposure to space radiation, using methods both novel and familiar. Doing so will be integral to supporting human ambitions for further exploration and eventual colonization of our solar system.


Sadly, a mission to Mars could take years off a person’s life, barring the development of shielding or special spacesuits. NASA research from 2013 concluded that, without sufficient protection, Martian-bound astronauts would get peppered by as much radiation as they’d receive from a full-body CT scan about once a week for an entire year.


A round-trip voyage to Mars would consequently expose astronauts to two-thirds of allowable lifetime exposure. And that doesn’t include time on the Martian surface, with its pitifully thin atmosphere and weak magnetic field.

The new research is encouraging for astronauts venturing to low Earth orbit, but given our desire to venture beyond, we’ll need to develop some viable solutions.