WASHINGTON — In the largest-ever genetic analysis conducted on Alzheimer’s disease, an international group of researchers has identified 11 new genes associated with the disorder, doubling the number of known gene variants linked to it.

The International Genomic Alzheimer’s Project, a collaboration of two groups in the United States and two in Europe, scanned the DNA of 74,076 older volunteers from 15 countries – including people with and without the disease – to look for subtle gene variants involved in late-onset Alzheimer’s, the most common form.

The study, which appeared Sunday in Nature Genetics, provides additional evidence of the involvement of certain genes in Alzheimer’s, such as one connected to the abnormal accumulation of amyloid protein in the brain, which has been associated with the disease. It also finds new gene-related risk factors that may influence cell functions.

The 11 new genes join a growing list of known gene variants associated with late-onset Alzheimer’s. Until 2009, only one had been identified; with the new findings, the list reached 22.

The identification of so many new genes offers promising new avenues to finding drug therapies, said Gerard Schellenberg, a professor of pathology at the University of Pennsylvania and the head of the Alzheimer’s Disease Genetics Consortium, one of the participating U.S. groups.

“Not all are good drug targets, but the longer the list of genes that you know are implicated in a disease, the more likely you are to find one that might be a good candidate for a drug,” he said, adding that it could take 10 to 15 years to develop drug therapies based on the new findings.

The study, which was supported in part by the National Institute on Aging and other components of the National Institutes of Health, also identified 13 additional gene variants that it said merit further investigation.

Marilyn Miller, program director for the Genetics of Alzheimer’s Disease at NIA, said the large scope of the study, with so many participants from so many countries, was key to its success in identifying so many new genes. “Alzheimer’s is obviously a complex disease,” she said, “and because it is so complex, it is only because of this broad-based collaborative effort that we’ve been able to begin to find potential solutions to tackle the disease.”

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