My grandmother has been diagnosed with the early stages of dementia. is this disease hereditary and if not, what can i do to prevent it?

Incomplete data: Research seems to suggest a genetic contribution but it is of uncertain strength and not to a single or even simple set of genes. Living longer has increased the numbers of people who decline cognitively but causes differ. Some are gradual and easier to deal w/. Some rapid and frightening. Healthy living in all respects is the best prevention-like strategy, but no one knows. If we did, Wow!