Three genetic mutations have been identified that could account for almost a quarter of cases of Alzheimer's disease, media reports suggest.
They are the first new genes to be linked to the condition for more than 15 years and represent a significant leap forward, with only four other genes previously linked to Alzheimer's.
Researchers at the University of Cardiff found two new mutations, clusterin (CLU) and PICALM, after studying 600,000 common DNA markers from 4,000 Alzheimer's sufferers and 8,000 healthy people.
French researchers found the third gene mutation, Complement Receptor 1 (CR1), in a separate study of more than 14,000 DNA samples.
Overall, the two studies found that clusterin (CLU) and PICALM may cause around 19 per cent of cases of Alzheimer's, with CR1 accounting for a further 4 per cent.
Are new Alzheimer's cures likely?
Professor Julie Williams, who led the UK research team, said the findings provided leads in the race to find treatments and cures for Alzheimer's.
'The CLU gene produces clusterin which normally acts to protect the brain in a variety of ways. Variation in this gene could remove this protection and contribute to Alzheimer's development.
'Clusterin also has a role in dampening down inflammation in the brain. Until now inflammation seen in the brains of Alzheimer's sufferers had been viewed as a secondary effect.
'Our results suggest the possibility inflammation may be primary to disease development.'
Dr Williams added that PICALM has an important role in controlling synapses, and changes in genes that affect synapses could have a direct effect on disease development.
What do other researchers say?
Dr Susanne Sorensen, head of research at the Alzheimer's Society, said the studies marked a 'really exciting breakthrough' in Alzheimer's research.
'In the next 10 years one million people will develop dementia but the government currently spends eight times less on dementia research than cancer research.
'This investment needs to be drastically increased so we do not miss out on the opportunity to build on these findings.'
- Three genetic mutations have been found that may cause 23 per cent of Alzheimer's cases.
- Findings suggest inflammation may be a primary cause of Alzheimer's.
- The researchers plan further studies on the genetic causes of Alzheimer's.