This is still a mystery for researchers. They think they know, and then the science changes.

There are many kinds of dementia. Vascular dementia is caused by vascular problems and is more common with people at risk for stroke and heart attack. Alzheimer's (they think) has to do with proteins, neurons and other things going wrong in the brain, but there are many other types of dementia, as well.

Genetics plays some role, but many who get dementia haven't inherited the tendency. One thing that seems certain is that "what is good for the heart is good for the brain." Therefore, exercise, good nutrition (antioxidants are showing promise, as does fish oil when it comes to supplements), using the brain in novel ways to exercise it, keeping free of knocking the brain around within the skull (i.e. some sports), and good social interaction are all ways to help prevent dementia. That said, many people do everything "right" and still get dementia.

Carol