I think 41's dis-countenance is tied into the company's he's with, rather than being based on a physical ailment. He really does not thrive around bubba.
I would imagine it is hard for him to be around Bubba, especially since Bubba was so disrespectful to him when they were running in 92. He would never address him as President Bush, always Mr. Bush. It would make me so mad! Clinton absolutely has no grace. He reminds me of an uncle that everyone is ashamed of because he comes to the reunions smashed and talking trash, but when the uncle wins the lottery he becomes the favorite of the family. They tolerate him because he's the cash cow.