What is space anemia? Other complications Sunita Williams, Butch Wilmore are likely to face due to prolonged stay in space

Sunita Williams and Butch Wilmore's extended space stay has raised several health concerns. Longer stay in space affects eyes, cardiovascular system, bone density and cognitive health.
Experts are also talking about a threat to the DNA of the astronauts, who probably won't be able to return to the earth anytime soon. Prolonged exposure to space radiation can also destroy the red blood cells.
Space radiation, consisting of high-energy particles, can cause DNA strand breaks and mutations, potentially leading to genetic disorders. Radiation and microgravity conditions can impair blood cell production and function. The oxidative stress from radiation may damage red blood cells (RBCs), leading to premature breakdown and anemia. Microgravity can also affect fluid distribution, impacting RBC production.
According to NASA, on Earth, our bodies create and destroy 2 million red blood cells every second. During six-month space missions, the bodies of the astronauts studied were destroying 3 million per second, or 54% more than was typical before flight.
Researchers explain that the shifts in body fluids in space leads to changes in RBCs in the body. Astronauts lose up to 10 percent of the liquid in their blood vessels. Red blood cell destruction or hemolysis continues to occur as long as astronauts stay in space.
“Space anemia has consistently been reported when astronauts returned to Earth since the first space missions, but we didn’t know why,” said study author Dr. Guy Trudel, a rehabilitation physician and researcher at The Ottawa Hospital and professor at the University of Ottawa told BBC. “Our study shows that upon arriving in space, more red blood cells are destroyed, and this continues for the entire duration of the astronaut’s mission,” he added.
A study published in the Journal of the American Heart Association, analysed the blood samples of 14 NASA astronauts who took five- to 13-day missions to the International Space Station between 1998 and 2001. The scientists took the blood samples 10 days before the launch, the day of their return and three days after the landing and found increased levels of free-floating mitochondrial DNA in the blood on the day of landing and three days after, ranging from two to 355 times higher than pre-space travel.

"Deep space exploration is dangerous for many reasons, but we need to know as much as possible about the adverse health effects so we can protect humans from stressors before, during and after exploration-type space missions," as per a report published in the American Heart Association quoting Goukassian, a professor of cardiology at the Icahn School of Medicine at Mount Sinai in New York City.
Astronauts Barry "Butch" Wilmore and Sunita "Suni" Williams were originally scheduled to spend a little more than a week aboard the International Space Station as part of the debut crew flight test of the Starliner.