APOE and Alzheimer disease: Sporadic Alzheimer’s disease (AD) accounts for more than 95% of all AD cases and the APOE4 allele of apolipoprotein E (apoE) is the greatest genetic risk factor; two copies of the APOE4 allele increase AD risk up to 15-fold relative to APOE3. APOE4 carriers account for more than half of AD patients and APOE4 accelerates onset of cognitive impairment by 7-9 years per allele[1,2].