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An analysis of the physical characteristics of astronauts who develop vision problems after long missions in weightlessness has found that heavier body weight increases the risk.
The research team examined data collected by NASA from astronauts who had made long-duration space flights (averaging 165 days). The data included the astronauts’ sex and pre-flight height, weight, waist and chest size, as well as information about post-flight eye changes. The findings were related to body weight, not body mass index. They found that none of the female astronauts analyzed—who weighed less than the males—returned to Earth with symptoms of SANS. To rule out sex differences as a cause for the disparity, the researchers also examined the men’s data separately. “Pre-flight weight, waist circumference and chest circumference were all significantly greater in those who developed either disc edema or choroidal folds. This was still true when only the male cohort was analyzed,” the researchers wrote. “The results from this study show a strong relationship between body weight and the development of ocular changes in space.”
That such small differences in weight can make such a difference suggests again that adding just a small amount of artificial gravity, rather than 1g, might mitigate these issues. No tests of this however have ever been done, mostly because the engineering is complex and expensive. For humans we would need to build a vessel large enough that any rotation would be unnoticed. If the vessel is small it must rotate faster and the body’s inner ear gets confused. However, if we only need to simulate a tiny amount of gravity the spin rate can be reduced, simplifying the engineering.