To which I counter: It may not stave off dementia, but that statement is complete and utter bullshit. Someone who makes a statement like that has clearly never bothered to solve a puzzle in their lives. Or, if they did, it was probably some piece of shit puzzle you might see in back of a shopping circular or Metro newspaper. (Again, anybody from Scribner wanna send me a copy of this book, please, hit me up. I'll be a fair and honest reviewer.)
We got copies of the San Francisco Chronicle while we were up in the sticks last week. (What? What is this thing you're talking about "copies of the San Francisco Chronicle?" Yes, believe it or not, there are places on Earth that don't have the Internet, and the people who live there get their news -- if they even care to get it at all-- a day later and from only one resource: a dead tree.) And on the puzzle page they had, count 'em, two crosswords. One appeared to be the L.A. Times puzzle, and I've mentioned before those are pretty solid work. A little on the easy side, but I'd hardly call them a cakewalk. All were themed, had some topical cluing/entries. No surprises, Rich Norris is a veteran editor.
The other puzzle, was clearly filled in and clued from a presorted computer database (I'm sure if there was a way to have the computer export it as well, they'd do that too). No innovation. Nothing topical. Zero freshness. I'm guessing if a life of crosswording is spent doing that dreck, there wouldn't be much thinking involved.
The average solver cannot get solve a Wednesday New York Times puzzle. It requires too much of them. And it only gets harder by four more levels of difficulty after that. Rote filling in of answers will not help you to solve these. They require intuition, logic, guesswork, general knowledge, spelling -- you name if. And if you want further proof that rote recall is necessary for solving all puzzles, I'll point you to the direction of Frank Longo's, Patrick Berry's and/or Emily Cox and Henry Rathvon's latest books. There isn't one tired repeater in any of those puzzles. They are all workouts.
Is working out every day going to make you live forever? I doubt it, but it'll probably make you healthier. Doing any challenging mental exercise is no different. If doing crosswords supposedly won't stave off dementia, I'll take my chances and have a blast doing so.