The link between memory loss and Down syndrome is widely known; virtually all patients with Down’s demonstrate problems with thinking and memory by the time they reach 60 (NPR link). But recently, scientists have pushed this connection further, stipulating that people with Down syndrome actually represent the largest population predisposed to developing Alzheimer’s disease. “By the age of 40, 100 per cent of all individuals with Down syndrome have the pathology of Alzheimer’s in their brain,” says Michael Rafii, Director of the Memory Disorders Clinic at the University of California, San Diego.
It’s All in the Genes
The connection lies on the genetic level – specifically, in the production of chromosome 21, which Down’s patients by definition have an extra copy of. One of the genes in this chromosome controls the production of amyloid, the substance associated with the sticky brain plaque found in the brains of Alzheimer’s sufferers. One too many of this gene leads to excess amyloid, hence the predisposition to develop Alzheimer’s.
Even a few decades ago, the medical complications associated with Down’s meant people usually didn’t live long enough to experience dementia. But clinical advances are lengthening Down’s life expectancy to an average of 55-60 years, meaning an increasing number are being diagnosed – usually with early-onset Alzheimer’s, which strikes before 65. And yet not every Down’s patient will end up exhibiting full-blown Alzheimer’s symptoms, which scientists are still working to understand.
With Down’s patients living longer, scientists are being given exciting opportunities to test the efficacy of Alzheimer’s prevention drugs in a way they haven’t been able to before. Giving these medications to such a high-risk population means doctors are able to better quantify their effectiveness, leading to more useful data and, hopefully, better treatment options.
And finding a new drug that prevents Alzheimer’s in people with Down syndrome could conceivably help millions of people who don’t have the disorder. Scientists are working right now on a drug therapy that people could start taking in early adulthood to prevent ever developing Alzheimer’s.
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