Two things that age many people prematurely are lots of exposure to the sun and cigarette smoking. Genetics play a role, of course, as well as other external factors. Stress, if its extraordinary, does it too. Look at all of the recent presidents when they took office and when they left. They all aged more than 4 or 8 years.

Also, absent extreme circumstances, those of African descent seem to age better than Caucasians. Hence the phrase: Black don't crack.