The waterfall graph in the middle of this article is worth looking this up.

To summarize report, there's not anything you can do to avoid old age dementia because its causes are not understood.

The biggest attendant factors are vision or hearing loss. Note that these factors are merely attendant, not stated as causative.

There are no significant pharma treatments.

The "surprise" finding was that the examination regime produced improved cognitive "scores" in both the mediated group and the control group. And these improvements persisted until death. In other words, the study is a complete mess.

Takeaway: the mind is going to go along with the body.