individuals whose mother had alzheimer's disease, they had a phenomenal shrinkage or brain atrophy over those two years compared to the images of the other volunteers in the study. >> we're all getting older in this country, the whole country is getting much older at the moment. when people are worried this sort of thing, what should people be doing? do you look at mom and say does she have it, i have a higher risk? >> there are two important risks everyone has to know about. the obvious one is age. beginning at age 65, about 3% are at risk of getting alzheimer's disease. but, tom, with each five years of age, that risk doubles. by the time you're 85, the risk is now 50%. the other risk is family history. if someone in your immediate family already has alzheimer's, your risk jumps between 4 and ten fold so you can't change your genes and you can't change your family. so you need to identify what other things could you do to protect yourself as you get older so that even if you had the genetic chances of having