One of my friends had a mother and maternal aunt who got dementia, so she was tested for the gene. She didn't have it.

I've heard that exercising our brains help stave off dementia.

I don't know if you've read The Salt Path, but the author's husband, who was diagnosed with a degenerative disease with no cure, walked 630 miles, camping out and really roughing it, and brain scans later showed his brain had forged new neural pathways. He was supposed to be dead and he's still alive and doing well several years later.