Interesting article from science@nasa.com. Einstein's Twin Paradox, developed from the Theory of Relativity, tells us that two brothers, one an astronaut and one on Earth would age differently if the astronaut brother travelled through space. The astronaut would not age as quickly as rapid space travel (at near light speed) would change the rate at which time progresses.
However, some researchers, according to the article, disagree with this hypothesis, instead believing that the astronaut brother would indeed age more quickly. The reason - long exposure to cosmic rays and increased radiation would damage Telomere strands in the chromosomes causing the body to age more rapidly.
Sounds logical, but I have a problem with the title of the article. Einstein's theories are focused on time, not on genetics and the bodies ability to replicate itself, so to say "was Einstein wrong" is a bit of a misnomer. The theory is still sound.