I think the evidence goes deeper than that. Humans with downs syndrome, which duplicates the APP gene, evince symptoms of Alzheimer's as they reach their 40s.
Genetics is important, but lots of current research in biology reduces everything to genetics. Paradoxically, when twin studies have shown environmental factors typically make an equally important contribution towards disease onset.
For example, consider type 1 diabetes (T1D). Lots of research tries to understand genetic risk factors. Despite this being so difficult to translate into treatment, as its many small effects past the top 3 genes, and twin studies show 50% is contribution from the environment.
So very recently, someone said OK the immune system is a classifier that takes sets of little protein chunks in a tissue microenvironment and decides whether its seeing self or something foreign and acts accordingly. Then, your own microbiome has to do something to avoid immune immune responses, as the immune system is only pre-trained using your own DNA. Then, let's assume your microbiome has to mimic (copy) some of your DNA to signal self to the immune system.
And it turns out it is true [1]. Lots of bacteria mimic insulin. And when those bacteria end up being classified as non-self, you also destroy your pancreatic beta cells, which produce insulin.
There's good evidence for lots of other diseases. For example, multiple sclerosis [2]. The first paper cites other diseases, including Alzheimer's that look like mis-classification induced by dysbiosis in the microbiome or an infection.
