What are some ways to prevent alzheimer's disease?

Unclear: We don't really know how to do it fully. But there are some correlations which point to some value: exercise, and mental activities, especially educational completion, seem to protect. Foods include, red wine, cold water fish, mediterranean diet, fruit and vegetable juices, coffee, and perhaps vitamins and neutraceuticals (but beware of claims!).

Partially: The most important is controlling you blood pressure and cholesterol level. It is also important to have physical exercise and keep mentally fit. Some studies indicate that drinking in moderation, eating fish and dark chocolate might decrease the risk.