What is the link between ApoE4 and Alzheimer’s?

There are three versions of ApoE. There’s ApoE2, ApoE3 and ApoE4. ApoE3 is the most common version in the population and that is what we would consider to be a neutral risk. If you have ApoE2, some research suggests that is a protective factor in the development of Alzheimer’s. ApoE4 increases your risk for developing Alzheimer’s. There are two versions: You get one copy from each of your parents. You could have any combination of the two. We know that there is an increased risk with one version of ApoE4—many studies say 2–5 times the risk, and then if you have two copies, or one from both of your parents, then it’s about 12–15 times the risk.