1) if you live long enough, you will get Alzheimer's, as the late-onset version is in many ways a symptom of aging
2) in 40 years, a HUGE chunk of the population is going to be older
wow, who'd a thunk it
There are things that exacerbate the onset of Alzheimer's, and the early onset version is thought to be an array of disorders that manifest in similar ways, which we dub "Alzheimer's", that are largely genetic.
Worried about Alzheimer's?
1) drink orange juice or other juices containing vitamin C. Even on glass a week exponentially reduces your chances of losing mental capacity later in life
2) stay mentally active. If you don't use it, you lose it. Areas of your brain that are not used die off. If you are constantly using your memory and cognitive skills, or in later life if you begin new hobbies and adventures, your brain will remain functional for a much longer time
3) smoke pot. Compared to all other synthetic medications aimed at preventing or slowing the onset of Alzheimer's, THC outperforms them in all categories. This is both the synthetic THC and natural THC found in marijuana.
These are of course only good for the late onset Alzheimer's, although I am not sure about the use of THC or vitamin C in postponing the onset of early Alzheimer's.