Risks to astronauts on extended missions include vision impairment, weakened bones and radiation exposure. There are also psychological risks from facing danger while being stuck inside a small craft.
“Astronauts should be small such as 70 lbs. midgets. Smaller and lighter life support and suits save space and food etc.
Put two on a fast rocket to Mars, land and return. A mini mission. Small is the solution. Alan Shepard was 115 lbs but need micro people. 50 lbs. small will win the space race.” - comment from PBSisBest Org