There's been a lot of hopeful news lately about Alzheimer's prevention/cure. One of the things that has been discovered is that a diabetes drug might help and trials may be completed within 15 years. According to Dr. Richard Isaacson the reasoning behind this is that sugar causes inflammation throughout the body. It is thought that changing your diet, limiting sugar (a high salt diet can also impact memory) and including these foods can reduce the risk of Alzehimer's.
Other recommendations are to fast two days a week for 14 hours (don't eat for 14 hours between dinner and breakfast) and also lower sugar and carbohydrates in your diet.