Three Entire Apollo Space Programs
Apollo Space ProgrammeReuters

Apollo astronauts are five times more likely to die from heart attacks as a result of deep space radiation, a scientist has claimed. In the first study looking at mortality of Apollo astronauts, Michael Delp from Florida State University looked at the cause of death of those who have died since the space programme ended in 1972.

The findings, published in Scientific Reports, showed that 43% had died from cardiovascular problems. This is four to five times higher than the risk faced by no-flight astronauts and those who have only been to low Earth orbit.

Delop said his study provides an insight into how space travel affects the body. This is an area of increasing interest to scientists, as Nasa and other space agencies look to carry out long-duration spaceflights, such as manned missions to Mars.

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

During the Apollo space programme, there were 11 manned flights to space. Nine of these went beyond Earth's orbit. Astronauts are highly educated and have access to some of the best medical care in the world. This means their health is generally better than that of the general population.

To tease out how space travel has affected astronauts, Delp compared those who had left Earth's orbit to those who had not. His findings showed a vastly increased risk of death from cardiovascular disease.

He also showed how mice reacted to a comparable dose of radiation to what the astronauts would have been exposed to. After six months, or 20 mice years, they showed impaired arteries. In humans, this can lead to heart disease. As a result, Delp believes deep space radiation can increase the risk of cardiovascular disease.

"If such results translate to the human condition, then long-term dysfunction of the vascular endothelium induced by charged HZE [high atomic number and energy] particles could be a major contributor to the development of atherosclerotic cardiovascular disease in astronauts," he wrote.