NASA to study astronauts’ CV health

NASA is conducting a 5-year study to determine how oxidative stress and inflammation triggered by space flight affect the CV health of astronauts.

Steven Platts, PhD, NASA Johnson Space Center investigator, told Cardiology Today that biomedical research is being conducted on the International Space Station regularly, but this is the first study that will not only follow the long-term effects of space travel on CV health effects, but also collect preflight and in-flight data from 12 volunteer astronauts.

Platts said NASA monitors potential risks to astronauts, identifies gaps in knowledge and seeks to find countermeasures to avoid or mitigate those risks. The current study, Cardio Ox, will attempt to identify CVD risks.

“For astronauts we have two CV risks,” he told Cardiology Today. “One is orthostatic intolerance after space flight; it is well-known, and we’ve been studying it for decades. The other is the risk of arrhythmias during or following space flight.”

The presence of long-term CVD risk following space travel is currently unknown; Platts said NASA researchers are looking for answers.

Astronauts face numerous oxidative stress challenges and conditions that can cause inflammation. They are also exposed to much higher levels of radiation than normal conditions on Earth — although not as high as residents living near nuclear disaster sites such as Chernobyl might encounter. Platts said many of the studies analyzing the effects of radiation on CVD have been conducted at very high-exposure sites, making the current research novel. In fact, he said, these data could be useful in planning for human visits to Mars.

In addition, Platts said astronauts are under intense amounts of physical and emotional stress during space flight and while working aboard the space station. During extravehicular activity, astronauts are exposed to increased levels of oxygen.

“Are we increasing their lifetime risk of CAD incidence?” he asked. “Given our environment … we’re hoping that if we see something, it will lead to either more research or better information to give our ground-based counterparts.”

To determine risks and identify changes to astronauts’ CV health, the researchers plan to test blood and urine samples for biomarkers that indicate stress, such as cytokines, cortisol, fibrinogen and neopterin. They will also look for CV biomarkers, such as myeloperoxidase, PGF2a and glutathione peroxidase. Samples will be collected before launch, 15 and 60 days after launch, 15 days before returning and shortly after returning. Companion ultrasound tests will be conducted both on the space station and over 5 years following space flight to compare the thickness of the astronauts’ carotid artery walls.

“We’re assessing structure and function as well, using ultrasound,” Platts said. “We’re also doing a functional study of the brachial artery using flow-mediated dilation,” which he said would only be conducted pre- and post-flight for practical reasons. These results will be compared to the biomarkers as well.

Though the results of Cardio Ox may have implications for practicing cardiologists, Platts said the study population is small, and the average astronaut is a male in his 40s who is generally more fit than the average person.

“If these very healthy people who have been screened like crazy can still have these issues, then how does that relate to the rest of the population? It’s always a challenge to interpret those data.”

Platts said the amount of time each volunteer will spend in space over the next 5 years is unknown; therefore, many variables cannot be controlled.

“With space flight, we have a hard time controlling for some things,” he said. “We have to let them do their jobs, so we do the best science we can under those circumstances.” – by Shirley Pulawski