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.