let me bring in "washington post" national political correspondent karen tumulty.>> what do medical experts say, why does it seem that just about every president goes through this rapid aging process? >> you know, there has actually been studies done on this, and a few years ago, a researcher named michael i believe you pronounce it roisand at the cleveland clinic determined that presidents in office thanks to the stress and the isolation, age two years for every one year that the rest of us are living through. but interestingly enough, they tend to live longer than most men of their eras. the journal of the american medical association said that the typical president who dies naturally tends to live 11 years longer than the average man of his era. >> ronald reagan and gerald ford lived to be 93. jimmy carter and george h.w. bush are both 88. do they explain why? my first thought was they have great health care. >> that is one of the reasons. and let's face it, men who get to be president tend to be well educated, they tend to be relatively wealthy and they have ac