Researchers say the studies, which analyzed the genes of more than 50,000 people in the United States and Europe, leave little doubt that the five genes make the disease more likely in the elderly and have something important to reveal about the disease’s process. They may also lead to ways to delay its onset or slow its progress.
“The level of evidence is very, very strong,” said Dr. Michael Boehnke, a professor of biostatistics at the University of Michigan and an outside adviser on the research. The two studies are being published Monday in the journal Nature Genetics.
For years, there have been unproven but persistent hints that cholesterol and inflammation are part of the disease process. People with high cholesterol are more likely to get the disease. Strokes and head injuries, which make Alzheimer’s more likely, also cause brain inflammation. Now, some of the newly discovered genes appear to bolster this line of thought, because some are involved with cholesterol and others are linked to inflammation or the transport of molecules inside cells.
The discoveries double the number of genes known to be involved in Alzheimer’s, to 10 from 5, giving scientists many new avenues to explore. One of the papers’ 155 authors, Dr. Richard Mayeux, chairman of neurology at Columbia University Medical Center, said the findings would “open up the field.”
And an expert who was not part of the studies, Dr. Nelson B. Freimer, who directs theCenter for Neurobehavioral Genetics at the University of California, Los Angeles, said there were now enough unequivocal genes for Alzheimer’s disease that researchers could make real progress in figuring out its biology. “This is a big, solid step,” he said.
An estimated 5.4 million Americans have Alzheimer’s disease, most of whom are elderly. According to the Alzheimer’s Association, one in eight people over age 65 have the disease.
