As a surgeon who is 48, I will say that on my transplant rotation ( I am not a transplant surgeon ) the theory of the safety of donation was in the Vietnam War era data that said that soldiers who lost a kidney from injury were at no increased risk of renal failure as the general public given similar risk factors. I know that if you have hypertension or diabetes, it is near impossible to donate a kidney as they have a high propensity to develop renal failure. I have not researched the literature about the war data, but that is what I was told.
That isn't really a fair comparison. There's a selection bias among kidney donors (they must pass some minimal health requirements) and are at a lower risk than the general population.
