His gut microbiome showed altered bacterial proportions, although the overall bacterial diversity was intact.

A decline in cognitive efficiency was reported.

To study the influence of microgravity, radiation and confinement in long-duration spaceflight, NASA selected twins Scott and Mark Kelly for a unique mission. Scott went to space while Mark was chosen as the control to stay on earth for comparison.

Under stressful situations, normally, there is a change in genetic expression.

Telomeres, are the “caps” that protect the ends of DNA strands.

This study was in no way conclusive or predictive, because of the very small sample size(just one pair of twins), a short study period, just to name a couple of reasons.