After Terry Pratchett and later my grandmother died from it, I'm a bit scared of Alzheimer's. There is a lot of evidence that shingles vaccines (particularly Shingrix) reduce dementia risk:

https://hn.algolia.com/?q=shingles

Furthermore, there was recently a study (published in Nature) suggesting that lithium deficiency could be a cause, since lithium orotate (a compound that reaches the brain) prevented it in a mouse model of Alzheimer's:

https://news.ycombinator.com/item?id=44825326

This also fits with the old observation that regions with more lithium in the water supply tend to have fewer cases of Alzheimer's.

So I take now lithium orotate capsules (with 1mg of elemental lithium) as a daily supplement. I will also get the Shingrix vaccine soon, even though my health insurance doesn't pay for it (it only does so for older adults), but it isn't that expensive.