The head of our Geropsych department spoke briefly about where he believes treatment will trend for the next decade or two. He doesn't see much on the horizon that cures or even slowly reverses the symptoms, but there is increasing evidence of things that slow the progression. Inflammation in the brain is one of the problems because it interferes with amyloid clearance. (I mostly understand that, but if you want more you should go ask your mother.) Acetaminophen isn't great for inflammation in general, but it's pretty good for brain inflammation. It might slow the progress of the illness 20%. So that goes into the cocktail when you start showing symptoms. Vitamin E, maybe another 5%, Fish Oil, another 5-10% - he blithely said "and there's a half dozen other things that might or might not have a small effect." Always the problem at this stage, when many things look plausible and promising, but somehow don't pan out.
So we get that up to 40%, which doesn't sound huge, but actually, it is. If you can slow dementia, people can live at home a little longer. If you show symptoms at 90, it can be the difference between having to go to assisted living at 96 instead of 94. As there is general deterioration anyway, that might mean you get to die at home, which is what most people want; or in assisted living with more freedom instead of a nursing home. Slowing the symptoms means the mind stays ahead of the body, and you have your wits about you.
As I am overweight and smoked for 35 years I can be pretty sure my body is going before my mind, but this may apply to the rest of you.
So why not start on prophylactic tylenol now? Because it's bad for your liver, and 40 years of it is a burden you don't want to put on it. Some parts of any Alzheimer's cocktail will be similarly problematic over decades - but as a few-years strategy when you're already showing symptoms, the balance of risks shifts quickly.