They call the article “5 ways to keep Alzheimer’s away”, but it really talks about 6. After mentioning the recent Journal of the AMA article which found ginkgo biloba of no help in warding off dementia, it mentions others with some support.
Certainly, physical exercise and mental exercise are helpful and probably have the least conflicted evidence behind them, so they are easy to recommend. Physical exercise has been shown to keep folks sharp and to at least some extent improve established dementia. I also agree with the article that the mental exercise needs to be varied (“cross training” they call it, with the analogy of only doing pushups developing only the arms). Social interaction should also be included this category. It stimulates the mind and the body and is clearly good for the psyche, a trifecta of anti-dementia goodness.
Their other recommendations have a bit more checkered evidence backing them up. They recommend antioxidants (e.g. vitamins A, C, and E) which have some support, but overdoing them (particularly vitamins A and E) may not be good and may cause some harm. But do remember “all things in moderation”. Also recommended are phosphatidylserine supplementation, fish-oil supplements, and adding curry to your diet. I think the support is slim for these, but for the most part they are not likely to cause harm. I think the curry (e.g. in Indian food, one of my favorites) is a particularly fun and tasty way to work against dementia, so go for it.