NASA's Twins Study confirms spaceflight can: damage DNA; change how thousands of genes are expressed; increase the length of telomeres (the caps that protect chromosomes); thicken carotid artery walls; and increase inflammation. However, over 90% of the changes returned to normal post-flight.

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NASA's Twins Study confirms spaceflight can: damage DNA; change how thousands of genes are expressed; increase the length of telomeres (the caps that protect chromosomes); thicken carotid artery walls; and increase inflammation. However, over 90% of the changes returned to normal post-flight.