Study Finds New Genetic Link to Alzheimer’s Disease : Medicine: Discovery may allow doctors to predict who is most likely to get the common form of ailment.

Researchers have linked the most common form of Alzheimer’s disease to a gene that helps process cholesterol, enabling them to identify some patients virtually certain to develop the mind-destroying disease in their elderly years.

In research on 42 families where late-onset Alzheimer’s is common, scientists at UCLA and Duke University found that 90% of people with two copies of a gene variant called APOE-4 develop the disease by the age of 80. More than half of the people with one copy of the gene develop Alzheimer’s by the age of 75. APOE-4 is a subtly altered version of the gene APOE, which is normally present in most people.

Scientists have previously found two other genes associated with Alzheimer’s, but both were linked to a rare form that strikes at a very early age. Researchers are excited about the new discovery, reported today in the journal Science, because it is the first gene linked to the more common form of the disease, which strikes older people.

Alzheimer’s progressively destroys the mind and eventually kills. About 2.5 million Americans are thought to suffer from the disease. There is no known cure.

Dr. Zaven S. Khachaturian, director of Alzheimer’s Research at the National Institute of Aging, said the findings have caused “a great deal of excitement” among Alzheimer’s researchers because they link the most common form of the disease with a specific gene factor, APOE-4, that can be measured.

“It could become a very important diagnostic tool,” Khachaturian said. “We may be able to screen for this and be able to make judgments about whether a person’s likelihood of getting the disease is high or low, or early or late. It has that potential.”

Additional studies to verify the findings will be required before the conclusions can be applied to the general population, Khachaturian said.