A genetic test that can predict your dementia risk

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What is the new genetic test that predicts dementia risk?

Ruth Fricker-Schmidt 0:02

This is an ABC podcast.

Norman Swan 0:06

Hello and welcome to this week's Health Report with me, Norman Swan. Today, a lot on testing of various kinds. Around a million colonoscopies are done on Australians each year, but are they being done well and on the right person? And just what is the right way to do bowel prep, the bit that everyone just loves? Not. Cancer gene tests are now more widely available, but an expert warns that deciding to have the gene test done is not a straightforward decision. CT scans of the heart, done in the right people, they can reduce the risk of dying of heart disease by up to a half. And using another gene test to predict your likelihood of developing dementia. From the number of people you see doing Sudoku puzzles from the train or bus, it's fair to assume that there's a lot of interest in trying to delay or prevent the onset of dementia as we age.

Norman Swan 0:54

But maybe looking for a specific gene is what we really need to do to avoid cognitive decline. A huge study in Denmark followed over 100,000 people for up to 10 years to compare their risk of dementia with the various versions of a gene called ApoE, I should say, that we might have been born with. Ruth Fricker-Schmidt is at the University of Copenhagen and was one of the researchers. Welcome to The Health Report, Professor Fricker-Schmidt.

Ruth Fricker-Schmidt 1:20

Thank you very much.

Norman Swan 1:22

So just tell us a bit about what we know about the APOE gene, since this is the cornerstone of your study.

Ruth Fricker-Schmidt 1:29

APOE is a well-known gene in dementia, actually also in cardiovascular disease. But APOE, a specific common variant that many of us carry, has been known as a risk marker for dementia for many years, actually since 1993. But our study here, we try to kind of make it a little bit more practical in order to include the genetics with other risk factors here, it's just age and gender, to make it more applicable for risk estimation. So what we do is actually to try to identify groups in the general population that have a little bit higher risk than the population at large, Because we want to kind of identify them so we can in the future target our prevention better and more efficient.

Norman Swan 2:19

So let's just go back to the ApoE gene because everybody carries the ApoE gene, but we don't all carry the same version of it. And it's only one version of it that's really associated with dementia and heart disease. That's the ApoE4, the four version. And you get one dose from your mum and one dose from your dad. And if you get a double dose, that increases your risk even more.

Ruth Fricker-Schmidt 2:40

That's right. And that's well known that this common variation, actually, 3% of us, we have two copies, one from the mother and one from the father in our genome. And that kind of confers this higher risk. But 25% of us, we carry one copy and we have also a little bit increased risk for both heart disease, actually, and dementia. But this is not so much different from other variation in the genome. You know, the entire variation is really what makes us different in risk estimations, both you know, for our blood biomarkers and externally, you could say.

Norman Swan 3:21

In terms of the environment and so on. So you look at a lot of different factors in these people in two different studies based in Copenhagen of the Danish population. So what did you find when you followed people through in different age groups relative to whether they were carrying one dose of the gene or two doses of the gene versus their age, their sex, smoking, diabetes and all that sort of thing?

Ruth Fricker-Schmidt 3:45

So if we look at sex first, we did divide it in women and men because that's, of course, of interest with regard to risk estimation because we have a different risk factor profile gender-wise.

How does the APOE‑4 gene variant affect a person’s chance of developing dementia?

Ruth Fricker-Schmidt 4:00

But even though it looks like there is a little bit increased risk in women, it's the same pattern in women and men. So we can say that that with regard to age, of course, the risk increases as we get older, we know that, but also the risk for the specific genetic groups increase as we get older.

David Newby 4:24

Ruth Fricker-Schmidt 4:24

that's not surprising, you can say, but this is just, you know, to quantify it a bit more precisely.