It takes the number of identified genes associated with Alzheimer's disease to 10-the new genes affect three ways the body works and goals for treatment.
If the effects of all 10 could be eliminated the risk of developing the disease would be reduced by 60%, research published in nature Genetics says.
The international team warns, however, new treatments would be 15 years away.
' Clueless 'The disease is seen as up to 80% genetic. The first gene associated with the disease, APOE, more than 17 years ago was discovered but no new genes were discovered until 2009.
As Professor Kevin Morgan, of the University of Nottingham, said: "we were basically clueless."
The newly discovered genes affect three processes in the body: the way it deals with fat and cholesterol; the mechanism by which brain cells handle large molecules (Endocytosis); and the immune system.
???Continue reading the main story immune system genes: CLU CR1, ABCA7, CD33 support and EPHA1 Fat processing genes: APOE, CLU and PICALM genes: ABCA7Cell membrane, BIN1, CD33 support and CD2APCardiff University of Professor Julie Williams, who led the international study, said: "what I find exciting is that we have found specific gene processenwe now have precise objectives to identify treatments."They said that if the effects of these genes can be removed than the number of cases could be reduced by 60%.
"There are 500,000 people with Alzheimer's disease [in the United Kingdom] so if you could prevent 60% that would be 300,000 people," she said.
Ageing of the populationProf Morgan said: "this disease is devastating, people are desperate for any hope or further. I have no doubt that it will come, but the time frame is 10 to 15 years. "
The disease is a growing problem in the context of an ageing population. Alzheimer's disease society predicts that the number of people with dementia will reach a million by 2021.
Health economists believe all that the costs for the United Kingdom is £ 23bn of dementia every year.
Rebecca Wood, chief executive of Alzheimer's research United Kingdom, which part-funded the study, said: "these findings are a step in the direction of beat dementia.
"We are still looking for ways to stop this devastating condition, but this work is likely to spark off new ideas, collaborations and more research.
Dr. Susanne Sorensen, head of the research of Alzheimer's society, said: "these two robust studies mark an exciting development for scientists hope to identify a cause and find a cure for Alzheimer's disease.
"Although these studies will give us no nearer to predict who might be at greater risk of developing Alzheimer's disease, they will give scientists clues as how Alzheimer's disease might develop, especially their identification may also lead to the development of new drug treatments in the long term."