APOE3/3 prevalence
Approximately 55% of the population carries the E3/E3 genotype, considered the wild-type reference, while 20–25% carry E3/E4 and only 1–2% are E4/E4 homozygotes.
Snapshot · The Peter Attia Drive
#395 - Brain lipidology: understanding APOE, cholesterol homeostasis, Alzheimer's disease risk, and the effects of lipid-lowering therapies on brain health | Tom Dayspring, M.D.
Explore episode
Jun 8, 2026
Where this was said
APOE genotype, apoE isoforms, and Alzheimer's disease risk
At 51:43 · chapter starts 48:45
Peter explicitly distinguishes APOE the gene (written in all caps) from apoE the protein (written with a lower-case 'apo'), a nomenclature distinction that often causes confusion. Tom explains that the ApoE protein comes in three isoforms — E2, E3, and E4 — differing by just one amino acid, but that single substitution changes the protein's ability to bend and bind, altering its function as a ligand on lipoproteins. Since individuals inherit one allele from each parent, six genotype combinations are possible. Peter provides the population frequencies: roughly 55% are E3/E3 (wild type), 20–25% are E3/E4, and 1–2% are E4/E4. E2/E2 is exceedingly rare. The risk associated with Alzheimer's disease scales nonlinearly: E3/E4 individuals face approximately 2–3 times the risk of E3/E3 carriers [1] — Peter Attia "A single amino acid difference between ApoE isoforms changes the protein's shape and function. Carrying two E4 copies raises Alzheimer's ri…" 49:35 , while E4/E4 homozygotes face 8–12-fold higher risk. Earlier estimates of 20–25-fold for E4/E4 have been revised downward as studies have matured. The underlying reason — which the next chapter will elaborate — is that the ApoE4 protein is structurally inferior at its job of transporting cholesterol to neurons.
What APOE Genotype Actually Means for Alzheimer's Risk
A single amino acid difference between ApoE isoforms changes the protein's shape and function. Carrying two E4 copies raises Alzheimer's risk 8–12-fold over the E3/E3 baseline — a near full-log increase — because the ApoE4 protein is structurally inferior at delivering cholesterol to neurons.
APOE3/4 Alzheimer's risk elevation
Individuals with one copy of APOE4 (E3/E4) have approximately 2–3 times higher Alzheimer's disease risk compared to E3/E3 carriers.
APOE4 homozygote Alzheimer's risk
People carrying two copies of the APOE4 allele (E4/E4) face an 8–12-fold increase in Alzheimer's disease risk compared to E3/E3 carriers, a near full-log elevation in risk.
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