Apollo Astronaut Excess CV Deaths Blamed on Cosmic Radiation During Lunar Voyage

August 09, 2016

HOUSTON, TX — The 24 Apollo astronauts who voyaged to the moon are unique among humans for having left the shielding of earth's atmosphere and Van Allen belts against the high-energy cosmic rays of deep space. The price for that may have been a sharply raised risk of cardiovascular disease, including CV death, argues a new report that compared their deaths with those among demographically similar astronauts, including those who got only as far as low-earth orbit and those who never participated in an earth-orbital or lunar mission[1].

In addition, say researchers, experiments that simulated weightlessness and cosmic-radiation exposure in rats and looked at their physiologic effects found evidence of "sustained vascular endothelial cell dysfunction."

They say that their observations suggest "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."

If the findings reflect what happens in humans, chronic vascular endothelial dysfunction induced by the so-called "high atomic number and energy" (HZE) particles that contribute to cosmic rays may promote coronary atherosclerosis in space travelers who voyage beyond the earth's natural protections, according to the authors, led by Dr Michael D Delp (Florida State University, Tallahassee).

In their largely speculative report, published July 28, 2016 in Scientific Reports, the group argues that endothelial dysfunction secondary to unusual cosmic-radiation exposure may be responsible for the seemingly much higher CV mortality among deceased Apollo astronauts who went to the moon compared with astronauts who never traveled beyond lower-earth orbit.

Mortality (%) Due to CV Disease in Deceased Flight Astronauts and Reference Groups.

End points CV death Death from cancer Death from accidents
Reference groups
US population sample aged 55–64 (n=338,127) 27 34 5
Nonflight astronauts (n=35) 9a 29 53a
Flight astronauts
All flight astronauts (n=42) 17 31 43a
Astronauts limited to low-earth orbit (n=35) 11a 31 49a
Apollo lunar astronauts (n=7) 43b 29 14
a. P <0.05 vs US population age 55-64
b. P <0.05 vs nonflight astronauts

The findings, they write, "suggest that human travel into deep space may be more hazardous to cardiovascular health than previously estimated."

The group compared mortalities from cardiovascular disease, cancer, and accidental causes in 35 deceased members of the US astronaut corps who had not undertaken an earth-orbital or lunar mission (nonflight astronauts) and 42 deceased astronauts whose flights had been limited to low-earth orbit or who had traveled to and orbited the moon in the Apollo program.

Although it included mortality figures for a US reference population, the analysis is noteworthy for including the nonflight astronauts as a more relevant reference group. The authors note that members of the astronaut corps consistently "have substantially higher incomes, levels of education, general fitness, and lifelong access to medical care, all of which are factors known to contribute to high levels of health and well-being."

With such a reference group, the findings "demonstrate that previous conclusions suggesting the risk of death due to CVD is lower among flight astronauts are no longer tenable."

In the analysis, the seven deceased Apollo astronauts who made the moon voyage, according to the authors, had received an average 0.59 cGy of radiation during the trips, about half of which was from cosmic rays.

The authors declared no relevant financial relationships.

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