Polygenic score modifies risk for Alzheimer's disease in APOE ε4 homozygotes at phenotypic extremes

Alzheimers Dement (Amst). 2021 Aug 5;13(1):e12226. doi: 10.1002/dad2.12226. eCollection 2021.


Introduction: Diversity in cognition among apolipoprotein E (APOE) ε4 homozygotes can range from early-onset Alzheimer's disease (AD) to a lifetime with no symptoms.

Methods: We evaluated a phenotypic extreme polygenic risk score (PRS) for AD between cognitively healthy APOE ε4 homozygotes aged ≥75 years (n = 213) and early-onset APOE ε4 homozygote AD cases aged ≤65 years (n = 223) as an explanation for this diversity.

Results: The PRS for AD was significantly higher in APOE ε4 homozygote AD cases compared to older cognitively healthy APOE ε4/ε4 controls (odds ratio [OR] 8.39; confidence interval [CI] 2.0-35.2; P = .003). The difference in the same PRS between APOE ε3/ε3 extremes was not as significant (OR 3.13; CI 0.98-9.92; P = .053) despite similar numbers and power. There was no statistical difference in an educational attainment PRS between these age extreme case-controls.

Discussion: A PRS for AD contributes to modified cognitive expression of the APOE ε4/ε4 genotype at phenotypic extremes of risk.

Keywords: Alzheimer's disease; Alzheimer's disease dementia; apolipoprotein E; dementia resilience; genetic modifiers; polygenic risk score.