The health of astronauts is in the limelight. First, NASA's Kelly report indicated gene changes from space life and was then followed up by new reports on brain shrinkage.
It is likely that the discourse on the health of astronauts will gain more traction. One of the reasons is the rise in space-faring nations and secondly the new push for extended manned missions to Mars and the moon.
As space missions take to the next level beyond the frontiers of Earth's protective magnetosphere to deep space radiation environment, the enhancement of health risks becomes inevitable.
Risks From Interplanetary Travel
In the case of interplanetary travel, astronauts are exposed to a number of radiation sources, which include ionizing radiation, solar particle events, galactic cosmic rays, and radiation trapped in the Van Allen belts.
In addition to proton radiation, heavier high atomic number and energy (HZE) ions such as 56Fe inflict damage to tissues and DNA.
Some studies have looked at mortality rates induced by cardiovascular disease (CVD), cancer, accidents and other causes of death.
The CVD risk is acute among astronauts because of the direct effects of space radiation and weightlessness caused to the arterial vasculature.
In one of the studies, astronauts were classified into three categories:
• Astronauts with no experience in orbital missions in space
• Astronauts who flew only in low Earth orbit (LEO)
• Apollo lunar astronauts who traveled beyond Earth's magnetosphere
Though the differences were narrow in the CVD mortality rate between novice non-flight astronauts (9 percent) and LEO (11 percent) astronauts, the CVD mortality rate was high among Apollo lunar astronauts (43percent), or four to five times more than non-flight and LEO astronauts.
A study carried out on mice under simulated weightlessness and space-relevant total-body irradiation on vascular responsiveness demonstrated vascular endothelial cell dysfunction from space-relevant irradiation. This causes a special kind of artery disease, adding to the risk of CVD among astronauts exposed to deep space radiation.
Kelly Twins Health Report
The above results of early studies are now getting endorsed by the NASA Twins Study, which probed effects on the human body after a long stint in space under zero gravity. The study made comparisons of data before, during and after the space mission of astronaut Scott Kelly with his own twin brother, Mark Kelly, a retired astronaut. It gave researchers a broad idea of the impact that space life makes on astronauts.
Results of the study were recently released. In the study, researchers scrutinized the health of the Kelly twins in terms of the immune system, bone density, gut microbiome and DNA changes induced by space life.
At the genomic level, they examined whether a "space gene" has been activated while Scott was serving in space. The genome sequencing of DNA and RNA from the twins' white blood cells showed Scott and Mark were having mutations unique to each of them with thousands of RNA molecules expressing differently.
Scott's DNA underwent a plethora of chemical modifications when he was in space, but turned normal when he came to Earth.
Mark's DNA also shifted during the study and attained normalcy at the end of the study. The researchers affirm that this is because of the sensitivity of genes to changing environments.
Impact On Brain
In the latest of astronaut health concerns, a study examining the brains of those returning from the International Space Station has been conducted.
Brain scans of 27 astronauts conducted by scientists at the University of Michigan before and after spaceflight showed visible changes. In the group, 12 spent a fortnight on shuttle flight missions and 14 spent six months on the space station. The MRI scans were obtained from the NASA Lifetime Surveillance of Astronaut Health program.
All the 27 brains showed increases and decreases in gray matter volume in different parts of the brain in line with the duration of time spent in space.
Device For Gravity
Meanwhile, there are efforts going on to mitigate zero gravity-related problems for astronauts. The latest experiment uses a vacuum cleaner-like device around the waist of astronauts to make them feel the weight on the lower body thanks to a hard suction force.
According to orthopaedic surgeon at the University of California, Alan Hargens, who had a role in developing the device, the lower body negative pressure (LBNP) device is an "early form of artificial gravity."
The device works in such a way that the person can exercise it at the normal body weight.
Space agencies have been looking to simulate gravity as weightlessness was compounding to health problems such as back pain, weakness of muscles and skeleton, and fluid pile-up in the upper part of the body.
Sometimes, astronauts returning to Earth have problems adjusting to pressure on the feet and buttocks.
"Crews get very little of this type of loading so their butts and feet are hypersensitive to touch after six to twelve months in space," said Hargens.
The device has been tested and proved useful to counteract muscle and skeletal issues. It was tested under prolonged bed rest for subjects as a proxy for low gravity situation.
