Did Yoda have Alzheimer's in his last years?

Yoda in the new movies and Yoda in "Empire Strikes Back" are two very different people in personality. This suggests that he might have lost it in his final years since he looks overly giddy and somewhat annoying when he talks to Luke. On the other hand, the Yoda of the past (well, of the new movies - I know it is confusing) is so mature and everything. If you come to think about it, he is over 700 years old or something, so it is conceivable that he might have had some kind of neural disorder at that stage of his life. I call upon all Star Wars fans to ponder about this issue.