APOE and Mental deterioration: The apolipoprotein (APOE) ε4 gene is the strongest genetic risk factor of late-onset dementia and particularly Alzheimer disease.1,2 Homozygous carriers of the APOE ε4 allele have an absolute risk of 50% by age of 85 years to develop dementia due to Alzheimer disease, compared with less than 10% in noncarriers.3 Insight into the potential pathways that mediate the effect of APOE on cognitive decline and dementia is important to unravel pathophysiology and to identify potential therapeutic targets.4