In June 2026, the journal Nature Genetics published one of the largest genetic studies of Alzheimer's disease and related dementias so far. It pooled 52 studies, with about 128,700 people who had dementia or a parent or sibling with it, and about 850,000 people without. It found 91 regions of the genome tied to dementia risk, and 16 of them had never been reported before.
That study is why we rebuilt our Cognitive Health & Memory report this autumn, and rebuilding it meant looking closely at APOE, the gene most people have heard of when it comes to memory. APOE is also a clear example of something we work with every day. DNA files from different companies, and even from different years of the same company, don't all read the same markers, so some files carry both of the markers needed to read APOE and some don't. You can check yours in a couple of minutes.
First, a quick look at what the new research found, because it's more hopeful than a headline about dementia genes might sound.
The new map of memory genes has more on it, and much of the risk can still change
A region of the genome is a stretch of DNA where certain variants show up more often in people with a condition. Finding 91 of them gives researchers a fuller picture of which body systems are involved, such as how the brain clears waste proteins, how its immune cells behave, and how fats and cholesterol move around.
Two things are worth keeping in mind. Everyone in the study was of European ancestry, so the map is less complete for people of other backgrounds. And genes are only part of the story. In 2024 the Lancet Commission on dementia, a long-running panel of researchers, estimated that around 45 percent of dementia cases could in principle be prevented or delayed by addressing 14 risk factors that can change over a lifetime. Blood pressure, LDL cholesterol, hearing loss, physical activity, smoking and social isolation are among them. That figure describes whole populations and can't promise anything to one person, but it's a good reminder that a lot of what shapes your memory later in life is in your hands.
Of all the regions on that map, one has stood out for decades, and it's the one people tend to feel nervous about: APOE.
APOE is read from two markers, and you need both
APOE makes a protein that carries cholesterol and other fats through your blood and your brain. It comes in three common versions, called e2, e3 and e4. You get one copy from each parent, so your type is a pair, like e3/e3 or e3/e4. The Alzheimer's Association estimates that between 40 and 65 percent of people diagnosed with Alzheimer's carry e4. If that number makes your stomach drop a little, hold on to the next sentence too. Carrying e4 raises the odds without settling the outcome, and plenty of people with e4 never develop the disease.
Your APOE type is worked out from two markers, which are single spots in your DNA where people can differ. They're called rs429358 and rs7412, and they sit very close together on chromosome 19. Each one changes a single building block of the protein, and together they tell you which versions you carry.
| rs429358 | rs7412 | Your APOE pair |
|---|---|---|
| TT | CC | e3/e3, the most common |
| CT | CC | e3/e4 |
| CC | CC | e4/e4 |
| TT | CT | e2/e3 |
| TT | TT | e2/e2 |
| CT | CT | usually e2/e4 |
With only one of the two, you're missing half the answer. rs7412 alone can tell you whether you carry e2, but it can't tell e3 from e4. rs429358 alone can spot e4, but it can't separate e2 from e3.
Two markers sounds simple enough. The catch is that your file has to contain both of them, and not every file does.
Not every DNA test reads the same markers
It's easy to assume a DNA test reads all of you. Consumer DNA tests actually read a fixed list of several hundred thousand markers on a chip, and each company chooses its own list. The lists overlap a lot, which is why one report can work with files from several companies. They don't match exactly, though, and a company can change its list when it moves to a new version of its chip.
Here's a real example. An AncestryDNA file downloaded in late 2022 was run on the company's V2.0 chip. It has about 669,000 markers, and rs429358 is among them, but rs7412 isn't there at all. Public chip listings show some other Ancestry chip versions do include rs7412, and one guide to finding your APOE status says Ancestry files have generally left it out since 2017. Files from other companies vary in the same way. So whether your test includes both APOE markers depends on the company and on when you tested.
If that makes you wonder about the rest of your file, a missing marker doesn't mean the rest of it is wrong. Each file has its own set of gaps, and for a few markers, APOE among them, a gap matters a lot.
The nice thing is that you don't have to take anyone's word for what's in your file, ours included. It's a plain text file, and you can look for yourself.
How to check your own file in two minutes
Before you look, take a moment to decide whether you want to know. An APOE result is the kind of information some people would rather not have, and that's a completely reasonable choice. Two US genetics bodies advise against APOE testing to predict Alzheimer's, because it says little about what will happen to any one person, and say any genetic testing for Alzheimer's should come with genetic counselling. If you'd rather not see it, skip ahead to the next section.
If you do want to look:
- Find your raw data file. It's the text file you downloaded from your testing company, usually inside a zip. Unzip it if needed.
- Open it in a plain text editor, not a word processor. It's a long file, so give it a moment.
- Search for rs429358, then for rs7412. Each marker you have sits on its own line, with the marker name, the chromosome (19), a position number, and then your two letters.
- Read what you find. If both lines are there with letters, use the table above. Your file may show them as two letters together, like CT, or as two separate columns, like C and T. The order doesn't matter. If you see A and G where the table has T and C, your file is reading the opposite strand of DNA: swap A for T and G for C before you look them up.
Here's what you might find:
- Both markers, with letters. You can read your pair from the table.
- A line that's there but has no letters, written as -- in some files and 0 0 in Ancestry files. The test looked at that spot and couldn't get a clear reading for you.
- No line at all. Your file doesn't include that marker, either because your version of the test doesn't read it or because the company leaves it out of the download.
If your file came from Ancestry, there's one more thing to know. SNPedia, a public genetics database, says that, going by its users' files, Ancestry data always reports rs429358 as TT, even for people whose files from other companies show CT. So a TT at rs429358 in an Ancestry file doesn't rule out e4.
Whatever you found, or didn't, APOE is only one gene, and the same file can tell you a lot more.
What our report does with the file you have
The Cognitive Health & Memory report reads more than 160 markers across 38 genes, so APOE is one part of a much bigger picture. For APOE itself, it works with whatever your file contains.
- Both markers in your file. The report reads your APOE pair directly.
-
Only rs7412. If your file also has a neighbouring marker, rs2075650, in a gene called TOMM40 right next to APOE, the report uses it. One version of it tends to travel with e4, so it can give a rough estimate. In a public reference set of about 2,500 people, we found it picked up about 7 in 10 e4 carriers of European ancestry and about 9 in 10 of East Asian ancestry, but only about 1 in 4 of African ancestry.
It also flags some people who don't carry e4: about 1 in 6 of those it flags in European ancestry, and about half in African ancestry. A 2024 study of American adults found the same drop, with the marker tracking e4 far less closely in Black and Hispanic participants than in white participants. That's why the report calls this reading an indication rather than a confirmation.
-
No rs7412. The report can't show an APOE type, and everything else in it works as usual. That's the case for the 2022 Ancestry file above.
If your file or the report shows e4, especially two copies, talk to your doctor or a genetic counsellor. They can help you work out whether a clinical APOE test would be worth doing for you, and what it would and wouldn't change.
Whichever of these describes you, the most useful part comes next, because most of it doesn't depend on your APOE type at all.
What's worth doing whatever your type
Your APOE type may change how strongly some of this applies to you, but the list itself stays the same.
Watch the fat on your plate. In a UK trial that recruited people by APOE type, those with one e4 copy showed a rise in C-reactive protein, a blood marker of inflammation, on high saturated fat diets compared with a low-fat diet. In people with two e3 copies the change was too small to count as a real effect. When DHA, an omega-3 fat from fish, was added to the same diet, triglycerides (a type of blood fat) in the e4 group fell 30 percent compared with a low-fat diet, against 17 percent in the e3 group. The trial was small, with 88 people, and it measured blood markers rather than memory, so it's a hint more than a verdict. For APOE, the report's list leans toward a Mediterranean-style diet, omega-3 fats and walnuts, and away from saturated fat and added sugar.
Know your blood pressure and cholesterol. High blood pressure is on the Lancet Commission's list, and high LDL cholesterol joined it in 2024. Both are numbers you can ask about at your next appointment.
Stay active, look after your hearing, and see people. Physical activity, treating hearing loss and staying socially connected are all on the same list, and none of them depend on any marker in your file. A walk to lunch with a friend can cover three things on this list at once: the walk, the company, and what's on your plate.
You can do all of this without a DNA test. What a test adds is knowing which of it to put first for you, and that's what the Cognitive Health & Memory report is built for. It reads your APOE markers, whichever your file has, along with more than 160 markers across 38 genes in eight areas, from cholesterol and blood pressure to how your brain clears waste proteins and how well you use B vitamins. Then it turns them into a ranked, food-first plan for memory and brain health. It doesn't tell you whether you'll develop Alzheimer's disease. It reads your file in your browser, and your DNA file is never uploaded or stored.
See what's in the Cognitive Health & Memory report
And if you've decided you want to look, you can take the first step tonight for free. Open your raw file, search for rs429358 and rs7412, and in two minutes you'll know what your test can and can't tell you about APOE.
