Important new insights into Alzheimer's disease have emerged from the discovery of a handful of genes that are strongly implicated in raising a person's risk of developing the brain disorder in later life.
The findings could eventually lead to a genetic test to predict the likelihood of suffering from Alzheimer's after a certain age, although the scientists behind the research warn that there will be difficult ethical dilemmas posed by a test for a debilitating and fatal disorder that has no cure or effective treatment.
A series of landmark studies published last night links five additional genes to Alzheimer's disease. This brings to 10 the total number of genes that are associated with the condition, which typically strikes after 65 and is marked by memory loss and dementia.
British researchers said the 10 genes accounted for about 20 per cent of the overall cause of Alzheimer's disease (about a third of the genetic contribution to the disease). If faults in all 10 genes could be corrected, it would eliminate about 60 per cent of Alzheimer's cases, scientists said.
Alzheimer's disease affects about 500,000 people in Britain but the number affected by dementia is growing rapidly with an ageing population – it is expected to reach 1 million by 2021. Sufferers need expensive, long-term care and the total "health burden" cost to society is estimated to be £23bn a year for the UK alone.
Scientists are attempting to understand why the ageing brain develops Alzheimer's by studying the entire genomes of elderly people with and without the condition. By doing this, the researchers are able to tease out changes to the key genes that exert an influence on a person's risk factor.
The latest studies, in Britain, the US and Europe and published in the journal Nature Genetics, scanned the genomes of about 60,000 people, identifying small genetic variations in the five genes that can now be linked with the disease. Eventually, this kind of research should lead to genetic tests that can estimate in middle age the probability of a person developing Alzheimer's.
Professor Mike Owen of Cardiff University's School of Medicine said: "At some point, I believe we're going to be able to predict this disease in middle age, because that's when we can intervene [to lower a person's risk]. However, if and when we do develop such tests, society's willingness to take them up and use them will depend largely on how useful they are in terms of treating the disease."