The number of people with Alzheimer's disease is set to grow
Two potentially key genes linked to the development of Alzheimer's disease have been uncovered by UK researchers.
It is the first gene clue to the condition in 16 years and has prompted scientists to rethink their theories on how the disease develops.
The genes were pinpointed in a study of 16,000 DNA samples and are known to be implicated in inflammation and cholesterol breakdown.
It is hoped the Nature Genetics study will open the way for new treatments.
The last and only gene to be linked to the common form of Alzheimer's disease is APOE4 gene, which has been the focus of much research.
Data from the latest work, a team effort of several UK universities, was shared with French researchers who identified a third gene, CR1, also reported in the journal.
The two genes uncovered by the UK team - CLU and PICALM - are both known to have protective roles in the brain.
Changes in the genes may either remove that protective effect or turn the "protectors into attackers", the researchers said.
One of the team, Professor Kevin Morgan from the University of Nottingham, explained that the pathways highlighted by the discovery include those involved in the turnover of cholesterol and part of the immune system involved in inflammation.
"These new pathways highlight potential new avenues for treatment using conventional drugs.
"The question now is if we lower cholesterol and reduce inflammation, could we modify the risk of people getting Alzheimer's disease."
There are 700,000 people living with dementia in the UK, a number predicted to reach 1.7 million by 2050.
Study leader Professor Julie Williams, who is also chief scientific adviser to the Alzheimer's Research Trust, said the research would provide "valuable leads".
"We have been looking at a specific theory about Alzheimer's disease but our data shows that there are different things going on.
"We do not really understand what causes common Alzheimer's disease.
"In a few years' time we might have a very good idea of the full picture."
The study was carried out by teams in Cardiff, London, Cambridge, Nottingham, Southampton, Manchester, Oxford, Bristol and Belfast and further research involving 60,000 people is being planned for the next year.
Rebecca Wood, chief executive of the Alzheimer's Research Trust, said: "At a time when we are yet to find ways of halting this devastating condition, this development is likely to spark off numerous new ideas, collaborations and more in the race for a cure."
Dr Susanne Sorensen from the Alzheimer's Society said the work was exciting.
"These discoveries will enable scientists to follow new avenues of investigation as they piece together the causes of Alzheimer's disease - likely to be a mixture of genes, lifestyle and life events."