What if anything can be done to prevent Alheimers?

At this point in time, the evidence regarding Alzheimer's disease, or more accurately, dementia in elderly people, seems to be that to some extent, it is a cardiovascular disease. Likelihood of becoming demented is decreased by the same measures that lead to decreased likelihood of heart attack or stroke. So -- EXERCISE (the cure for everything!), healthy cardio-friendly diet, and exercising your brain as well by staying active and challenging your brain by learning new things. There is some evidence that statins (cholesterol-lowering drugs) may lessen the likelihood of developing dementia.

The cause of Alzheimer's disease specifically is not yet known and appears to be heavily influenced by genetics.