Personally, I have heard aluminum cookware, antiperspirants, lack of mental stimulation (ie. didn't read or work puzzles, or listen to radio enough). and now Fat. If six people lived in one household, as a Farm family, and one mother, and one of the sons developed Alzheimers, and nobody else in the family although they all ate exactly the same foods, I would look at genetic links. That seems to be at the heart of the matter. Like so many other mental affectations, like BiPolar illness, these seem to be passed down through the genes. One of my sons has ADHD and his Grandmother and a couple of cousins have ADHD, I'd be looking for genetic factors, exacerbated by life stressors, use of street drugs being the first which pops into my mind.