Down Syndrome & Alzheimers

So I'm doing a paper for AP A&P , we're on the nervous system. Anyway, I was assigned Alzheimers and apparently, Most people with Down Syndrome develop Alzheimers. Scientists think Alzheimers is caused by the Apolipoprotein E (APOE) gene because it is present in almost all Alzheimers patients. So, according to this website, People with Down Syndrome get 2 copies of APOE in addition to their extra copy of chromosome 21. The 21st chromosome contains the APOE gene.

Edit: I left out a piece I apologize. APOE comes in many forms, APOE(subscript)4 is the one that causes Alzheimers. People with APOE(4) have the highest risk of developing Alzheimers.

If I find more info I will add an update but I thought it was interesting and wanted to share.