Researchers are conducting what is believed to be the largest study yet of genes which cause Alzheimer's disease.
It is estimated there are over 700,000 people in the UK with dementia
Led by experts at Cardiff University, it will involve analysing DNA samples from 14,000 people from the UK and US.
Scientists will scan the entire human genetic blueprint, known as the genome, to compare the samples.
They will be looking for changes in the genetic code that either pre-dispose people to dementia or protect them from the disease.
Samples from 6,000 patients with late-onset Alzheimer's and 8,000 "healthy" volunteers will be collected.
By matching genetic variations to both groups, the researchers hope to find previously unknown mutations that contribute to the risk of developing the disease.
The team led by Professor Julie Williams from Cardiff University will use a technique known as "genome-wide association scanning" to analyse the DNA samples.
"Alzheimer's is a genetically-complicated story involving many genes, so we need large sample sizes to make sure any genetic links that we find are not mere coincidence," Professor Williams said.
"With access to 14,000 DNA samples, our study is the largest genetic study ever to look at Alzheimer's and will undoubtedly produce some valuable insights into what causes this devastating illness.
"It's very likely that we will find some unexpected associations.
"We know already that certain genes are involved in more than one form of dementia and that even genes that affect cholesterol level can be a risk factor for Alzheimer's.
Possible symptoms of the disease
Becoming confused about where they are or wandering off and becoming lost
Becoming muddled about time and getting up at night because they are mixing up night and day
Putting themselves or others at risk through their forgetfulness, such as omitting to light the gas
Behaving in ways which may seem inappropriate, such as going outside in their nightclothes
Source: The Alzheimer's Society
"We need to build a complete picture of the different pathways that lead to the disease. With this knowledge, we should, in time, be able to derive tangible clinical benefits."
The Alzheimer's Society estimates that there are currently more than 700,000 people in the UK with dementia.
It is estimated the figure will double over the next 20 years as the population ages.
The project is being funded with a £1.3m donation from the Wellcome Trust, Britain's largest medical research charity.
Professor Richard Morris, head of neurosciences and mental health at the Wellcome Trust, said: "It is essential that we develop our understanding of the underlying causes of the disease, and genome-wide association scans offer a powerful tool to do just this."