Gene test that gives 15-year warning of Alzheimer’s

A GENETIC test has been developed which could give a 15-year advance warning that a person is likely to develop Alzheimer’s disease.

The breakthrough in early diagnosis of degeneration of the brain could help those at high risk plan for their future as well as boost scientists’ understanding of the disease.

Around one million people in the UK are expected to be suffering from Alzheimer’s by 2025.

Lead researcher Dr Rahul Desikan, of the University of California, San Diego, said the genetic test was able to predict at what age someone could develop Alzheimer’s – called their polygenic hazard score.

The authors found that the score was a strong predictor of the age the disease would strike, the progression from normal ageing to Alzheimer’s and the brain deterioration associated with it. Those with high scores had developed Alzheimer’s ten to 15 years earlier.

Dr Desikan said: ‘ For any individual, we can calculate your annualised risk for developing Alzheimer’s disease. That is, what is your yearly risk for Alzheimer’s disease onset, based on your age and genetic information.’

During trials using a data- base of 70,000 patients, the risk score was found to predict with 90 per cent accuracy the age at which Alzheimer’s patients had contracted the crippling disease.

The test is based on 33 genetic variations, of which two – called APOE variants – have a big role to play in triggering Alzheimer’s. The other 31 have much smaller roles but can combine to increase the genetic risk.

Senior author Anders Dale, professor in neurosciences at the University of California, said: ‘The polygenic hazard score provides a novel way not just to assess an individual’s lifetime risk of developing Alzheimer’s but to predict the age of disease onset. Polygenic testing can better inform prevention and therapeutic trials and be useful in determining which individuals are most likely to respond to therapy.’

A limitation of the study is that the score has been based on people of European descent – making it less accurate for other ethnic groups.

Dr James Pickett, head of research at the Alzheimer’s Society, said: ‘Preventing the development of dementia symptoms is the holy grail of Alzheimer’s research but to succeed we need accurate methods to predict who is most likely to develop the condition. This study’s approach was fairly successful, but needs to be tested further.’

Dr Rosa Sancho, head of research at Alzheimer’s Research UK, said: ‘This study does not suggest that having a high polygenic hazard score means you will definitely develop Alzheimer’s, nor does a low score mean you are immune. Genetics is only part of the story – we know lifestyle factors also influence our risk of developing Alzheimer’s.’

‘Holy grail of research’