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Variant linked to Alzheimer's may make you smarter

Sarah Dingle reported this story on Tuesday, February 16, 2010 12:41:00

ELEANOR HALL: The discovery that you have a genetic predisposition to Alzheimer's disease could hardly be regarded as positive news.

But now a United States based neuropsychologist has found that the genetic variant linked to Alzheimer's can also improve the brain function of carriers when they are younger.

The research results have surprised specialists both here and overseas as Sarah Dingle reports.

SARAH DINGLE: Assistant professor Duke Han from Rush University has been researching Alzheimer's disease for years but even for him these results were unexpected.

DUKE HAN: I thought I actually made some sort of major mistake so I went back and did the analysis over and over again, just because I was sure that it should been the opposite.

SARAH DINGLE: Professor Han's work examined epsilon 4, a variant of a particular gene known as apolipoprotein E or APOE. The epsilon 4 variant is the best established genetic risk factor for Alzheimer's disease.

DUKE HAN: We looked at young people in the military who sustained a mild to moderate head injury and we predicted that people who had this APOE, epsilon 4 allele would do worse after a head injury just because it seems to be associated with Alzheimer's disease and at least in older people it seems to be associated with worse outcomes after head injury.

However when we did the analysis we actually found the opposite. That people who had this particular genetic trait actually fared better at least from a cognitive standpoint. The one difference being that this population that we looked at was actually fairly younger.

SARAH DINGLE: He says other papers have found young students with the epsilon 4 variant tend to be associated with better school marks and had some superior memory results.

Professor Han says to explain this, he turned to evolutionary biology.

DUKE HAN: Came across this concept of antagonistic pleiotropy - that certain genes can actually have opposite affects across the lifespan. That they can convey a benefit earlier in life and then convey some sort of risk in later in life and that is why it is still represented in our gene pool if you will.

LYNETTE MOORE: Well it's a real irony that the gene variant which seems to cause a greater risk of dementia in older age actually may help younger people, that same gene.

SARAH DINGLE: Lynette Moore is from Alzheimer's Australia.

LYNETTE MOORE: That is an interesting piece of research that we'll have to watch for further studies. It does, as I say, seem a little at odds with that theory that if you work your brain harder you build up more of those brain connections and that gives you a bit of protection because of that brain reserve you carry into older age.

SARAH DINGLE: She says it doesn't change the message that keeping your brain active may help reduce the risk of Alzheimer's disease.

LYNETTE MOORE: The relationship between these risk genes and lifestyle, that is a critical area for research. We need a whole range of research to try to get the answers to the risk associated with Alzheimer's and the cure.

SARAH DINGLE: Professor Han says epsilon 4 could be a good place to start.

DUKE HAN: If we can come to an understanding of how that happens then theoretically we might be able to actually affect that process later in life, whether it be the delay of the downside of possessing that trait or the increase of the good side and just translating that to older age.

SARAH DINGLE: He says seeing epsilon 4 as a beneficial genetic trait instead of a cause for concern could make a crucial difference.

ELEANOR HALL: Sarah Dingle reporting.

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