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Study asks if going to moon came with a downside of heart disease

Only 24 people have ever gone to deep space, or to the area beyond the Earth’s magnetic shield. These are the Apollo astronauts who flew to the moon, the last of whom did so in 1972.

Today, dreams of deep space exploration are surfacing again. Government space programs and private corporations alike have their eyes set on returning to the moon for longer visits and venturing beyond, to Mars, in the coming decades.

Michael Delp, a professor of human sciences at Florida State University, said researchers need to better understand and study the effects of deep space travel on the human body. “There are an incredible number of unanswered questions,” he said. “One of these is what deep space does to the cardiovascular system.”

In a paper published Thursday, a week after the 47{+t}{+h}anniversary of the first moon landing, Prof. Delp and a NASA-affiliated team of researchers examined how deep space travel may have affected the cardiovascular health of Apollo astronauts. Comparing Apollo astronauts who have died with other astronauts who either never flew in orbital missions or only flew in low Earth orbit, Prof. Delp and his colleagues found a higher rate of cardiovascular deaths among Apollo astronauts. Based on further research in mice, they suggest that the cause of cardiovascular disease in these astronauts may have been deep space radiation.

Their study, published in the journal Scientific Reports , is the first to look specifically at the long-term health of Apollo lunar astronauts.

However, experts also have concerns about the scientific legitimacy of studying an extremely small number of astronauts.

Small sample size

To date, only seven of the 24 Apollo lunar astronauts have died. Of those seven, three died of cardiovascular disease (Neil Armstrong, who flew on Apollo 11; James Irwin, who flew on Apollo 15 and Ronald Evans, who flew on Apollo 17).

The problem with a small sample size is that a one-person difference can drastically alter the statistics, said Jay Buckey, a professor of medicine and engineering at Dartmouth College who did not participate in the study.

For instance, at least one of the three Apollo astronauts who died of cardiovascular disease, Irwin, may have had cardiovascular problems before he left Earth. During his flight on Apollo 15, Irwin experienced a bout of heart arrhythmia, which was later noted in a NASA report as being possibly related to “pre-existing, undetected coronary artery disease.”

Unexplored risk factors could also explain why the other two Apollo astronauts died of cardiovascular disease, Prof. Buckey said. “Were they smokers? Did they have a family history of heart disease? Did they have high cholesterol? Those are all factors that could lead to heart disease, without having to bring galactic cosmic radiation into the mix,” he said. Because this study relied on a small number of astronauts and did not consider such risk factors, “it is not possible to determine whether cosmic ray radiation affected the Apollo astronauts,” Tabatha Thompson, a representative for NASA, wrote in an email.

Studies on mice

The epidemiology of Apollo astronauts is the novel portion of this study, but it is not the only one. The research on mice supports previous studies that have shown similar results, said Benjamin Levine, director of the Institute for Exercise and Environmental Medicine at Texas Health Resources and a professor at the University of Texas Southwestern Medical Center.

In their study, Prof. Delp and his colleagues exposed mice to simulated conditions of anti-gravity, cosmic radiation, or both effects combined. After half a year (the equivalent of 20 human years), they found that only the mice that had been exposed to radiation had sustained damage to their blood vessels. In particular, the researchers found damage to the lining of the blood vessels, which is typically the first indication of long-term heart disease leading to a heart attack or stroke.

The mouse studies provide some indication that radiation exposure may have affected the cardiovascular health of Apollo astronauts, Prof. Delp said. — New York Times News Service