Florida State University researchers have published some disquieting results of a long-term study of former Apollo Astronauts. According to their research published in Scientific Reports, these astronauts are dying of cardiovascular ailments at a much higher rate than the general population.
The FSU researchers compiled health data of 42 former astronauts, seven of which were former Apollo crew members. The rates of cardiovascular disease-related deaths among the Apollo astronauts were statistically significant enough for the researchers to theorize that exposure to deep space, such as in the Apollo missions, is behind the increased mortality:
Results show there were no differences in CVD [(cardiovascular disease)] mortality rate between non-flight (9%) and LEO [(low-Earth orbit)] (11%) astronauts. However, the CVD mortality rate among Apollo lunar astronauts (43%) was 4–5 times higher than in non-flight and LEO astronauts.
The mechanism behind the high rates of mortality is thought to be exposure to galactic cosmic radiation that is much more concentrated in deep space than in low-Earth orbit. To test that hypothesis, researchers subjected mice to high levels of the same type of radiation experienced by deep space astronauts such as the Apollo crews. After six months of radiation exposure, the mice showed symptoms of the same types of cardiovascular diseases as the Apollo astronauts:
[...] results from these animal studies demonstrate that space relevant irradiation induces long-lasting vascular dysfunction of the type known to presage the development of atherosclerotic cardiovascular disease.
Despite the mice displaying similar symptoms of cosmic radiation exposure, researchers believe that the radiation alone is not the culprit in the Apollo astronauts’ increased mortality. According to their research, the metal hulls of spacecraft can create unique nuclear interactions when bombarded with charged particles such as cosmic radiation. The FSU researchers in this study are now teaming with NASA to conduct further research into the effects of cosmic radiation and the causes of the increased mortality.
These results are worrisome for aerospace firms currently organizing trips to Mars, such as the proposed 2018 mission planned by SpaceX. Russia, China and the European Space Agency are all planning expeditions to the moon which could expose their astronauts to deep space radiation. Unless scientists find a way to protect astronauts, future deep space missions might have to be crewed entirely by robots.