I don't normally post PubMed abstracts, but this is an interesting study. The researchers conclude that longevity is an independent prerequisite for the development of Alzheimer's, but is not genetically related to the condition. Your longevity genes will not make you more likely to get Alzheimer's in any way other than by living longer. This is important because - if validated by more and larger studies - it means that there are less likely to be hidden complications relating to Alzheimer's when extending the healthy human life span. The study suggests that Alzheimer's is not like cancer in this respect, and this is a good thing.