Variants in the ApoE gene are the strongest genetic risk factor there is for developing Alzheimer’s disease. Inheriting the E2 allele decreases the number of plaques, while inheriting the E4 allele increases the number of plaques and raises the risk of developing Alzheimer’s disease – for those unlucky individuals who have two copies, that risk jumps by 12-fold. E4 carriers also start developing the disease decades earlier than those with E2 alleles.