I think the quote ties in with what else we know about Alzheimers: it tends to develop in those with smaller social circles, in those who experience less novelty and less healthy lifestyles. If the person is out in society learning a new language, meeting new people, learning a new instrument, exercising their minds' regenerative capacities, that's a great "counter" to aging.
If they're sitting at home, not driving anywhere, watching cable news all day, that's a recipe for rutted-grooves of thought and deterioration of the mind.
I tend to drive relatively little, visit fairly few distinct places, and generally take the same route each time I visit them. I'm also not a huge fan of night driving. I don't think I drive particularly slowly or make too many abrupt changes (I've never had an accident involving another car, am never the slowest one on the freeway, and have never had a complaint from any of my passengers).
The interesting part for me here is that these behaviors do, in fact, reflect a neurological issue I have with visual/spatial processing. In a nutshell, I get lost easily, because it takes me much more time to associate visual landmarks with a travel route than the typical human. I suspect my dog has a far, far better sense of direction than do I. :P
I'm not even close to old enough to have preclinical signs of Alzheimer's, yet, but I shall have to remember to remind my doctors of my visual-spatial issues in a few decades when I am.
Got a bit of a victim-blamey vibe here. Intuitively it makes sense that if you're more active and social, you don't get Alzheimer's - but it's also pretty tough to separate correlation and causation. Does being shut-in cause Alzheimer's, or do people end up being shut-ins because of Alzheimer's? Intuition is often wrong.
If they're sitting at home, not driving anywhere, watching cable news all day, that's a recipe for rutted-grooves of thought and deterioration of the mind.