Alzheimer's and genetics: what your family history actually means for your embryos

If you've watched a parent start forgetting names, you've probably asked yourself the question most doctors won't give you a straight answer to: Could I pass this on to my children?

Yes. You very likely could. And the degree to which that's true is bigger than most people realize.

Alzheimer's isn't mainly a lifestyle disease, and it isn't random. Between 60% and 80% of the variation in who gets Alzheimer's is explained by genetics. That makes it one of the most heritable common diseases we know of, more heritable than type 2 diabetes or heart disease. And for about 1 in 36 people of European descent, the genetic component isn't a "risk factor" at all. It's closer to a guarantee.

That last group is the part most families never hear about. And it's the part that matters most if you're going through IVF, because this risk is visible at the embryo stage, and it varies between your embryos.

APOE4: the gene everyone should know about

Everyone has two copies of a gene called APOE. The most common version, APOE3, carries average Alzheimer's risk. APOE2 is slightly protective.

And then there's APOE4.

One copy of APOE4 roughly triples your risk compared to someone with two copies of APOE3. But two copies? A 2024 study in Nature Medicine looked at over 10,000 people with two copies of APOE4. The prevalence of Alzheimer's was significantly higher in this group, and the average age of onset was younger. By age 65, nearly all of them had abnormal amyloid levels. Seventy-five percent had positive amyloid PET scans. The underlying pathology was the same as typical Alzheimer's, but the penetrance was near-complete — almost everyone with this genotype developed the disease.

For about 2-3% of the population, Alzheimer's isn't a probability. It's a trajectory.

And APOE4 isn't even the whole story. Researchers have identified 75 distinct genetic risk loci that each contribute to Alzheimer's risk independently. A genetic risk score built from these variants shows a 1.6 to 1.9-fold difference in risk between the lowest and highest risk deciles, even after you remove APOE entirely. Two children from the same parents can have dramatically different Alzheimer's risk profiles simply based on which parental alleles they happened to inherit.

That's the window where genetic risk can actually be addressed — during IVF, before transfer.

The drug pipeline won't save your grandchildren

When families learn their Alzheimer's risk is genetic, the next question is always: "Won't there be a treatment by the time it matters?"

It's a reasonable hope. But it deserves an honest answer.

The first generation of anti-amyloid antibodies (lecanemab and donanemab) are real scientific progress. Lecanemab slowed cognitive decline by 27% over 18 months in clinical trials. That's not nothing. But the side effects are severe, and here's the cruel part: they're worst in the people who need the drugs most. In APOE4 carriers, ARIA rates reach up to 40% for brain swelling and up to 28% for brain bleeds. Post-marketing data has confirmed this in the real world, with FAERS reporting 46 deaths among 1,286 adverse event reports. APOE4 homozygotes are at the highest risk.

The people most genetically destined for Alzheimer's are the ones most likely to be harmed by the only approved treatments.

And the drugs only work if you catch it early. Around 90% of Alzheimer's patients aren't diagnosed early enough to benefit. They cost $26,500 to $32,000 per year, require regular brain scans, and deliver a modest slowing of decline. Not prevention. Not reversal.

We're not making an argument against pharmaceutical research. We're describing where things actually stand. If you carry APOE4 and you're planning a family, the question isn't whether future drugs will eliminate your children's genetic risk. They won't. The question is whether there's a window where that risk can actually be addressed.

There is. And it closes earlier than most people think.

You can test for this before embryo transfer

APOE4 inheritance is straightforward. If you carry one copy of APOE4 and one copy of APOE3, each embryo you create has a roughly 50/50 chance of inheriting either version. It segregates like a coin flip. Some of your embryos will carry it. Some won't.

During IVF, a small number of cells can be biopsied from each embryo at the blastocyst stage. Those cells contain enough DNA to determine which embryos carry APOE4 and which don't. Polygenic embryo screening (PGT-P) can identify this, along with the broader polygenic risk from those 75+ other loci. If you want to see how we screen for Alzheimer's risk specifically, you can explore our screening tool or learn more about embryo screening.

Embryos from the same IVF cycle are biologically siblings, which means within-family validation is the right test for whether screening can distinguish between them. We've validated 17 disease polygenic scores on sibling pairs. Sixteen out of 17 showed no decrease in predictive performance within families, with all ratios of within-family to population-based effect size greater than 0.9. Alzheimer's was among the top performers.

The polygenic risk score for Alzheimer's doesn't capture all genetic risk. APOE dominates the signal, and environmental factors, stochastic processes, and unmeasured rare variants all play a role. A lower polygenic score doesn't mean a child won't develop Alzheimer's. A higher score doesn't mean they will. These are probability estimates.

But partial information that genuinely distinguishes between embryos is still information worth having. Especially for a condition where 7.2 million Americans over 65 are currently living with the disease, and the post-diagnosis options remain limited.

Nobody is talking about this

We reviewed over 133 posts in Alzheimer's caregiver communities. Zero mentioned embryo screening, PGT-P, or polygenic risk scoring.

Zero.

The families who could benefit most from knowing this technology exists don't know it exists. People are watching their parents lose their memories, and the best advice they're getting is "stay cognitively active," "eat more fish," and "get your shingles vaccine" (which has been shown to reduce dementia risk). That's not wrong. But it's missing the forest for the trees.

If you've got Alzheimer's in your family and you're going through IVF, or even considering it, this is worth a conversation with someone who actually understands polygenic screening. Not a generic genetic counselor (most aren't trained on PGT-P), but someone who works with this data every day.

If you're curious about what your family's Alzheimer's risk means for embryo screening, reach out to our team. You can also see which traits and conditions Herasight screens for, or explore whether embryo screening makes sense for your situation.