 Life on Earth is insulated from the harmful effects of galactic cosmic rays and solar particle events through particle deflection by the Earth’s magnetosphere and shielding by Earth’s atmosphere. With the exception of the Apollo lunar missions, manned spaceflight has taken place exclusively in LEO where atmospheric protection from space radiation is essentially absent, but protection by the Earth’s geomagnetic field is present. First long-term study into health of Apollo crews shows deep space missions might take their toll, exposing astronauts to blood vessel-damaging radiation 
 
 Travelling to the moon, Mars or beyond could dramatically increase an astronaut’s risk of dying from cardiovascular disease, the first research into the long-term health of Apollo spacemen has revealed. The mortality rate for CVD among all US flight astronauts, including both LEO and Apollo lunar astronauts, was not different than that in the non-flight astronauts. However, when considered as a separate group, the Apollo lunar astronauts, the only group of humans to have traveled outside of the Earth’s protective magnetosphere, demonstrate a higher mortality rate due to CVD compared to both the cohort of astronauts that did not travel into space, as well as astronauts who remained in LEO (Fig. In the first by Peterson et al.22, it was reported that of the 20 deceased US astronauts from 1959–1991 the causes of death were due to circulatory disease (10%), cancer (5%), accidents (80%) and other causes (5%). This comparison group was part of a Longitudinal Study of Astronaut Health initiative by the National Aeronautics and Space Administration (NASA) to better assess the occupational health risks of astronauts, since the health characteristics of astronauts and the overall environment in which they train at Johnson Space Center were deemed to be different from that of the general US population24. “Part of the reason why this cardiovascular effect has never been uncovered is because you are always looking and comparing [astronauts with] a general population,” he said. While traveling from LEO to the Moon and back, the Apollo lunar astronauts traversed regions of geomagnetically trapped electrons and protons known as the Van Allen belts and, depending on the duration of their mission and the specific activities in which they were engaged (e.g., lunar surface and intravehicular Command and Lunar Module activities), were continuously subjected to varying levels of high-energy cosmic rays31. Furthermore, LEO astronauts do not exhibit significant differences in mortality compared to non-flight astronauts. “That corresponds with what we saw with the low Earth orbit [astronauts] - they may have problems immediately when they come back, which we know they do, but they recover.” 
 
 Richard Hughson, of the University of Waterloo in Canada, who has studied the effect space travel on the cardiovascular systems of astronauts, described the new research as “fascinating”. With previous studies showing that both radiation and weightlessness can, in the short term, damage the blood vessels of the mice, the researchers waited 6-7 months before investigating the effects - a period equivalent to around 20 human years. These data indicate that the long-lasting effects of simulated weightlessness and space radiation on vascular endothelial function are the result of the radiation exposure and are not due to an interaction with weightlessness. While Hughson notes that the sample size for the Apollo lunar astronauts is very small, he believes the study puts forward a plausible suggestion for why lunar astronauts appear to be succumbing cardiovascular disease at a higher than expected rate. A team of researchers looking into the fate of the Apollo astronauts has discovered that their rate of death from cardiovascular disease is four to five times higher than that seen for astronauts of the same era who only flew in low Earth orbits, or who never flew on an orbital mission at all. While no difference was seen when the rate was compared to that of the general population, Delp believes that is most likely because astronauts are very fit and healthy, whereas the members of the public suffer from a wide range of conditions that could increase their risk of cardiovascular disease. RELATED: NASA's Scotty Kelly Grew 2 Inches After a Year in Space 
 
 Of the 24 Apollo astronauts who flew around the moon on nine missions, eight have died.
– Planning a trip to the moon? You might want to think about heart health first. According to a study published in Scientific Reports, travel in deep space dramatically raises the risk of cardiovascular disease. Florida State University researchers looked at America's Apollo astronauts, who are the only people ever to have gone to deep space, and found that they were four to five times more likely to die of cardiovascular disease than other astronauts, NBC News reports. Eight of the 24 Apollo astronauts have died, and of the seven deaths looked at, three, including Neil Armstrong, were from cardiovascular disease. That works out to roughly 45%, compared with around 10% among astronauts who either remained in low Earth orbit or never went to space at all. The study suggests that leaving the Earth's protective magnetosphere, which deflects cosmic radiation, even for short periods can do long-term damage to the cardiovascular system, according to the researchers. They say that since astronauts are selected from some of the most physically fit people around, the link wasn't uncovered until the Apollo crews were compared to other astronauts instead of the general public. Former NASA astronaut Jeff Hoffman says the implications are clear: Space travel needs to be fast. "We can't shield against high-energy cosmic radiation, not with our current mass-limiting capabilities, but it does re-emphasize the importance of getting to Mars as quickly as possible," he tells the Guardian. (Last month, NASA started an experimental fire on a cargo vessel.)