"If we were able to remove the detrimental effects of these genes through treatments, we could reduce the proportion of people developing Alzheimer's by 20 percent," Williams told a press conference in London. "In the U.K. alone this would prevent just under 100,000 people developing the disease."

Robert Green, a neurologist and clinical research expert in Alzheimer's at Boston University, cautions that the predictive value of the new studies is less than for APOE. "The risk factor they provide is in the small-effect category, like markers for common diseases such as diabetes or heart disease.

"The discoveries are exciting for research," he says. "They are novel and were largely unsuspected and will help us fit together a few more pieces of the puzzle of what causes Alzheimer's, and possibly how to treat it."

A co-author of the Welsh study, Michael Owen, who is director of the Center for Neuropsychiatric Genetics and Genomics at Cardiff University, adds that the collaborators on the project are planning a much larger study involving 60,000 participants. Through this they hope to both confirm the significance of the new markers and unearth additional ones.

"It's also possible that in the future we might be able to use the results of genetic tests as part of a battery of indicators to identify those who might benefit from early intervention with new therapies," Owen says. "Though I should stress that the current genes on their own are not strong predictors of risk and are not suitable for risk testing."