Is dementia/alzheimer's a disease of modern times or always been around. i don't ever want to get it when i'm old anything i can do to lower risk?

Hopefully you won't: ....have anything to worry about by the time you get up to the typical age when people start having degenerative changes in their brains leading to AD. Hopefully, we will either have a vaccine, medication, or be able to do brain transplants to correct the problems! Yes, it's existed since the dawn of time though it was only named a century ago. Lots of things u can do now but none proven to work