Compared to the most common and relatively neutral E3 allele [90,91,92,93], the ApoE4 allele poses the highest risk for AD [92,108,109,110], CVD [91], and preE [106,107,111], by influencing tauopathy, while the ApoE2 allele is thought to offer protection against AD [92,108,109,110] and preE [88,106]. Here, APOE is linked to Alzheimer disease.