My Mother's Mom Died Of Alzheimers. She Has 7 Siblings

My mother's mom died of alzheimers. She has 7 siblings who are all over 50yrs old and the oldest seems to be exhibiting symptoms of alzheimers. Does this disease put my mom at a higher incidence for getting this disease. My mom has recently seen a late night info-mercial about a substance called cabria that claims to prevent alzheimers, is this true?