My FIL has it and it is really sad. There are different types. His began with small strokes in the brain over time and it is called dementia, but it all becomes Alzheimer's in the end.
All sorts of interesting theories are out there why it seems to be on the rise in the United States--everything from diet to presence of a virus. On an AD support board I visit, it is amazing how many of those who developed the disease also had pneumonia at some stage in their lives. I think the theory is like that of chicken pox, which can show up as shingles later in life. Whatever it is, I told my sons to shoot me if I ever develop it.
I have relatives on BOTH sides of my family who contracted Early-Onset Alzheimer's . Imagine being totally senile before you're 50, as happened to an uncle of mine. If I contract this and there's still no cure-I intend to Take Matters Into My Own Hands.
I hope your son doesn't take you seriously and end up in trouble! But yes, it's a very sad disease. It's like it steals you before you die.
susie