Things that prevent dementia: ballet, full-body coordination activities. Protecting your hearing, hearing loss is sequentially prior to dementia; reading lips helps if you are already deaf (looking at you, EDM kids). There is a specific frequency of light that can demolish brain-plaque in mice, not sure what the results are in humans but plaque is perhaps 30-40% the alzheimers equation in humans in my current understanding.
This is one of the reasons I think building your life around a car is not a good idea. It's of course the most common thing to do especially in the U.S.. but once you get a car, in order to maximize its value you have to maximize its use, which inevitably means more hours sitting down. Not everyone has that luxury but I would just blame society for condoning building everything around driving, even dating.