Something clever goes here

Jeremy and I do crosswords together at lunch because we wanted to get a jump on being old, I guess. I can't tell you how often someone sees me doing a puzzle and informs me that crosswords prevent Alzheimer's. This is a little true - the way it was explained to me was that doing activities that increase the number of neural pathways can delay the onset of Alzheimer's symptoms because it takes Alzheimer's a longer time to chew through the extra pathways. Or something like that.
I would guess that doing crosswords prevents Alzheimer's much like eating blueberries prevents cancer. Maybe, possibly, eventually, a little bit.
So here's the question: if we know that we can at least have a better chance of avoiding dreadful diseases by doing little things like eating more blueberries and spending a few minutes a day on a crossword, why don't we? Is it a delayed gratification thing? Or are blueberries just that hard to eat?