Neuroscience Explains: Can You Prevent Alzheimer’s If It Runs In Your Family? | Dr Tommy Wood | Be Well Moments

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0:10So my grandmother had Alzheimer's, so I'm always terrified as my siblings are and my mum that we might get dementia because it might run on the family and Alzheimer's. If you do have a genetic risk, is it still as, can you still prevent that? So say you get your DNA results back, which everyone was doing like five years ago, and they're like, yeah, you have the genetic kind of snip for Alzheimer's. Is it still preventable? So there's multiple different types of genetic risks for Alzheimer's disease. So maybe we should go through them one by one. So the original Alzheimer's disease, which when Alzheimer first described them was a collection of slightly obscure and very rare dementias that occurred in younger individuals.

0:58So before then we called what is now Alzheimer's disease, we called it senile dementia, which is essentially just dementia that occurs in old age, so after 65 years old. The cases that Alzheimer looked at were cases of dementia in individuals who are younger than that, sort of 30 to 50. Those tend to be, if they're early onset, as we call them Alzheimer's disease, or familial Alzheimer's disease, they're caused by a single genetic mutation to number of genes like the pre-senilins, pre-senilin 1 and 2, or the amyloid precursor protein. And those account for only 1 % of Alzheimer's cases. And they have a much more predictable course.

1:40They tend to onset in something like the 30s to 50s, and then there tends to be a relatively rapid decline after that. There are people who say they've worked with individuals who have those types of mutations, and at least have managed a slow decline through the use of lifestyle. But that's not really the kind of dementia that we're talking about. What we're talking about is late onset or sporadic Alzheimer's, which is 99 % of cases. That's, you know, if you had a family member with Alzheimer's, that's probably the type of Alzheimer's that they had. Then there are two, again, types of genetic risk we might talk about.

2:21One is related to the ApoE genotype. So ApoE4 is probably the single most common polymorphism that increases the risk of Alzheimer's disease. For those who don't know, apolipoprotein E is a protein that helps to traffic fats through the body. You have two copies, and you can have one of three types, two, three, or four. If you have one copy of ApoE4, you have something like a two to six times increase of risk of Alzheimer's disease. If you have two copies, it's something like six to 20 times on average. So we know that having or carrying at least a copy of ApoE4 increases risk of Alzheimer's disease in sort of modern westernized societies, but that's not necessarily the case around the globe.

3:14So there have been studies in the Bolivian Chimene, who are a hunter-gatherer group, in certain Native American groups, in the Nigerian Yoruba. In those studies, those individuals didn't have an increased risk of Alzheimer's disease. And there's even some data suggest that people of Italian heritage, so Sicilian Italian heritage, those when they're in Sicily, ApoE4 is not associated with an increased risk or the risk is much smaller, but then the risk is much larger once people of the same ancestry are in the US. So this suggests that even for ApoE4, there's an environmental component. And most of the evidence suggests that ApoE4 is mainly a risk multiplier.

3:56So we know what some of the risk factors are for Alzheimer's disease. They include smoking, alcohol, poor diet, sedentary lifestyle. In those who have at least one copy of APOE4, that risk seems to be magnified, but then they may also benefit more if they make those lifestyle changes. So you can never promise that by doing those things, you can completely eliminate all the risk, but all the evidence suggests that if you recreate or manipulate your environment such that you remove those risk factors or you moderate those risk factors as much as possible, you've probably reduced the risk associated with having a copy of APOE4 quite significantly.

4:39Then the final genetic risk could be a polymorphic risk. What's that? So we know that lots of genes can add up in little ways to increase your risk of dementia. So they have these things called polygenic risk scores, which might be hundreds or thousands of genes and each one just adds like a tiny little bit. So when you look at those who have high polygenic risk, so they might not have ApoE4, but just like lots of little risks add up, then again, regardless of your polygenic risk, you can still have a significant impact on your risk of dementia by making certain lifestyle changes. So pretty much across the spectrum of genes, dementia still seems to be preventable.

5:28And by that, I mean that at a large population level, you know, if everybody were to do this, we can prevent a large number of dementias. It's estimated to be somewhere around 40 to 50%. Some people say it could be more than that. So you can't promise one person that they could completely eliminate their risk, but you can substantially reduce your risk no matter what your genes, no matter what your genes are. thanks so much for listening to hear the full episode there's a link in the description