The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight.
Level 4 - case-series / case-control
Longitudinal twin study comparing a single spaceflight astronaut to a single genetically matched ground control
PubMed 30975860 · doi:10.1126/science.aau8650
What was done
One monozygotic twin astronaut was longitudinally monitored before, during, and after a 1-year mission aboard the International Space Station, while his identical twin remained on Earth as a genetically matched ground control. The study evaluated multiomic, physiological, molecular, and cognitive outcomes across both subjects.
What was found
The abstract reports no exact numeric values. Observed spaceflight-specific changes included decreased body mass, in-flight telomere elongation, genome instability, carotid artery distension, increased carotid intima-media thickness, ocular structural changes, transcriptional and metabolic shifts, altered DNA methylation in immune and oxidative stress pathways, altered gut microbiota, and postflight cognitive decline. Within 6 months post-landing, average telomere length, global gene expression, and microbiota composition returned near baseline, though an increased frequency of short telomeres and persistent disruption of some gene expression remained.
Why it matters
This study provides an unprecedented multiomic catalog of how year-long spaceflight affects human biology relative to a genetically identical terrestrial control, identifying candidate physiological risks for future long-duration exploration missions.
Limits
The sample size is limited to one astronaut and one control twin (n=2), preventing statistical generalization to broader populations or separation of idiosyncratic responses from universal spaceflight physiology. Uncontrolled environmental variables between flight and ground environments could not be fully matched.
Cited by
- supports Astronauts on the International Space Station for six to twelve months experience accelerated DNA damage and chromosomal instability due to radiation exposure.