"How do you know if you have Alzheimer's?" said the front of the pamphlet. The answer inside was: "If you can't remember what you ate for lunch, you don't have Alzheimer's. If you can't remember whether you ate lunch or not, that's Alzheimer's."
But I have a hunch that such "old timer's" diseases start much earlier in life than we think. I'm convinced that senility starts in your 20s, when you wake up with a hangover and can't remember the last bar you went to the night before. That is followed by years of "Where did I leave my car keys?" and "I completely forgot about that pizza in the back of the fridge that is now covered in mold," and then to "I came into this room to get something — what was it?!"
The only reason these things don't start happening earlier than in your 20s is because when you were younger, you didn't drink, have a car, have your own fridge or own anything in the next room.