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Five more genes linked to Alzheimer's are discovered

April 04, 2011|By Marissa Cevallos, HealthKey

Alzheimer’s, the brain disease that saps away not just memories but, gradually, identity, is now a little less mysterious. In two large studies of more than 54,000 people, scientists have found five new genes linked to the disease. 

Think of the genes as clues to the underlying causes of Alzheimer’s. Those causes are still unknown, but scientists have long suspected they involve tangled strands of protein and protein plaque in the brain. Some of the most recently discovered genes add evidence that cholesterol plays a role in the disease, others that inflammation of the brain is an important player.

In one study, a large U.S. team -- led by geneticist Gerard Schellenberg at the University of Pennsylvania School of Medicine, identified four additional genes that each add risk to eventually developing Alzheimer’s.

In the second study, led by scientists in Europe, researchers helped confirm those findings and added a fifth gene to the new roster. Until now, researchers had identified only five genes linked to Alzheimer’s, so the latest pair of studies doubles the grand total to 10.

Scientists found the genes by comparing DNA extracted from tissue samples of Alzheimer’s patients with those of healthy people of the same age. They looked for genes that popped up more frequently in the DNA of Alzheimer’s patients. Schellenberg’s group analyzed more than 11,000 people with Alzheimer’s and about as many elderly folks without dementia. Three other consortia brought the total to 54,000 people.

Possessing one of the newly discovered genes doesn’t drastically change someone’s odds for developing Alzheimer’s -- 10% to 15% at most, reports the New York Times. An already known gene, APOE, is still the best predictor, that story says, explaining that if a person has one copy of APOE, his or her risk is 400% greater; two copies and the increased risk of Alzheimer’s balloons to 1.000%. 

About 5.4 million Americans live with Alzheimer’s, a number predicted to rise to 16 million by 2050.

Reality Check: Finding a gene is still many steps away from making a drug or even predicting whether a person will develop the disease.  The gene is simply a hint to scientists about where they ought to conduct more research. After all, the path to preventing Alzheimer’s—an enormously complicated disease—has been marked by false hopes and disappointment.

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