BBC Science has an article where
experts ranked 400 jobs by their dementia risk. Those least likely to die from Alzheimer's were taxi drivers and ambulance drivers. The reason behind this seems to be that constant spatial and navigation processing tasks might offer some protection from Alzheimer's.
The authors do have one caveat: While researchers found that taxi and ambulance drivers were less likely to die of Alzheimer's, they were also more likely to die young.
That's an issue because Alzheimer's is a disease that becomes more likely the older you get. If people in those professions aren't living long enough to get Alzheimer's, that could explain some of the results.
"The paper isn't an advert for becoming a taxi driver - unfortunately they're dying earlier" Spiers says. "Importantly, however, the researchers reran their analysis correcting for age and still found a significant effect."
It seems using your brain other than for existence might help stave off mental decline.