A disturbing new study that found American astronauts of the Apollo Program from 1961 to 1972 are more prone to heart attack deaths illustrates the dangers of deep space radiation. This is the first study looking at the mortality of Apollo astronauts.

The men of the Apollo Program that landed the first humans on the Moon in 1969 are experiencing higher rates of cardiovascular-related deaths thought to be caused by their exposure to deep space radiation, said the study conducted by Professor Michael Delp, Florida State University Dean of the College of Human Sciences.

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The Apollo program consisted of 11 manned flights into space between 1968 and 1972. Nine of those flew beyond Earth's orbit into deep space. Twelve Americans landed on the Moon with 12 others having either orbited the Moon or journeyed into deep space.

In a new paper in Scientific Reports, Delp found out the astronauts who traveled into deep space as part of the Apollo Moon missions were exposed to levels of galactic cosmic radiation not experienced by any other astronauts or Russian cosmonauts. That exposure is now manifesting itself as cardiovascular problems.

"We know very little about the effects of deep space radiation on human health, particularly on the cardiovascular system," said Delp. "This gives us the first glimpse into its adverse effects on humans."

Delp found that 43 percent of deceased Apollo astronauts died from a cardiovascular problem. That's four to five times higher than non-flight astronauts and astronauts who have traveled in low Earth orbit.

Of the 24 men who flew into deep space on the Apollo lunar missions, eight have died and seven were included in the study. The eighth -- Edgar Mitchell -- died after the data analysis was completed.

Delp and his colleagues also exposed mice to the type of radiation that Apollo astronauts would have experienced. After six months -- the equivalent of 20 human years -- the mice demonstrated an impairment of arteries that is known to lead to the development of atherosclerotic cardiovascular disease in humans.

"What the mouse data show is that deep space radiation is harmful to vascular health," said Delp.

Delp is working with NASA to conduct additional studies on the Apollo astronauts regarding their cardiovascular health.

Delp's research is of special interest now as the United States and other nations, plus private organizations, make plans for deep space travel to the Moon, the asteroids, Mars and its moons.

NASA has unveiled plans for U.S. orbital missions around the moon from 2020 to 2030 in preparation for a manned flight to Mars. Russia, China and the European Space Agency are all looking at lunar missions. And SpaceX, owned by Elon Musk, has proposed landing humans on Mars by 2026.

As a group, astronauts are highly educated and have access to top medical care, meaning their healthcare outcomes are generally better than the general population. But the group of men in the Apollo program experienced different environmental conditions than anyone else in the world when they traveled into deep space.

Tagsastronauts, Apollo Program, moon, cardiovascular-related deaths, Professor Michael Delp