Because microgravity doesn’t pull enough fluids from the brains of astronauts, their vision changes for the worse, and some report getting “the stupids.” Not good.
NASA worked with REI to develop an experimental sleeping bag to literally suck on the lower body. So far, in Earth experiments, it seems to work. But the apparatus needs tweaks to be more comfortable, and suitable for space.
More:
https://www.cnn.com/2021/12/09/health/astronaut-vision-sleeping-bag-scn/index.html
— Rex
