A systematic review of the clinical records from the United States National Alzheimer Coordinating center revealed that diabetes is linked to earlier cognitive decline during aging in APOE2 and APOE3 carriers, but not in APOE4 carriers, in which the effect of diabetes was negligible, perhaps because APOE4 carriers are already more prone to suffer vascular impairment and cognitive decline [581]. The gene discussed is APOE; the disease is Mental deterioration.