Scientists looking for the genetic triggers that lead to Alzheimer's have identified five more, doubling the number linked with the mind-wasting disease.
If drugs or lifestyle changes could be devised to counter these genetic variations, more than 60 percent of Alzheimer's cases could be prevented, according to the researchers, whose work was published in the journal Nature Genetics on Sunday.
But those discoveries could be at least 15 years away, they said.
Alzheimer's is the most common form of dementia, a fatal brain disease that affects memory, thinking, behavior and the ability to handle daily activities. It is increasingly placing a heavy burden on societies and economies across the world.
"We are beginning to piece together the jigsaw and gain new understanding," said Julie Williams from Cardiff University's center for neuropsychiatric genetics and genomics, who led the study.
"If we were able to remove the detrimental effects of these genes through treatments, we hope we can help reduce the proportion of people developing Alzheimer's in the long-term."
The researchers said the genetic variants they found highlight specific differences in people who get Alzheimer's, including variations in the immune system, the ways the brain handles cholesterol and lipids as well as a process called endocytosis which removes toxic protein from the brain.
Alzheimer's Disease International predicts that as populations age, dementia cases will almost double every 20 years to around 66 million in 2030 and 115 million in 2050, with much of that rise happening in poorer nations.
"What's exciting is the genes we now know of — the five new ones, plus those previously identified — are clustering in patterns," Williams said at a briefing in London.
Scientists suspect genes can explain 60 to 80 percent of the risk of late onset Alzheimer's, the kind that occurs with age.
To find these new gene variants, Williams and an international consortium of fellow researchers looked at data from 25,000 people with Alzheimer's disease and 45,000 healthy people who were used as "controls."
They found that common gene variants called ABCA7, EPHA1, CD33 and CD2AP and MS42A were linked with an increased risk of developing the disease. "These five genes now show compelling evidence of association with Alzheimer's disease," she said.
Previous studies over the past few decades have established that gene variants known as CLU, PICALM, CRI, BIN1 and APOE are also linked to Alzheimer's risk.