Heterozygous carriers of ε4 allele have about a 2 to 3-fold higher risk of developing AD compared to homozygous ApoE3 carriers, while for homozygous ε4 allele carriers the risk increases about 10-fold compared to non- ε4 carriers [107] and 40–65% of all AD patients are carriers of at least one copy of ApoE4 [108]. Here, APOE is linked to Alzheimer disease.