[tupshin]

They haven't ruled out epigenetics causes, but they are talking about a very specific gene (APOE4) with an extremely strong correlation with Alzheimer's when two copies of the gene are present.

[odyssey7]

Does everybody with two copies get Alzheimer’s? If not, then there must be at least one additional ingredient / cause.

[tupshin]

> Not only were people with two copies of the APOE4 gene much more likely to develop the biological changes that lead to Alzheimer’s disease, similar to people with the other genetic forms of the disease, they were almost assured the diagnosis: Nearly 95% of the people in the studies with two copies of the APOE4 gene had the biology of Alzheimer’s disease by the time they were 82 years old.