New test helps people predict when they may get Alzheimer's disease

Study of genetic data from more than 70,000 people leads to creation of Alzheimer’s ‘risk score’

Katie Forster
Tuesday 21 March 2017 18:59 GMT
People with the highest PHS score were found to have an earlier than expected age of onset of the disease by up to 10 years
People with the highest PHS score were found to have an earlier than expected age of onset of the disease by up to 10 years (Getty)

New forms of genetic testing could allow people to discover their risk of developing Alzheimer’s at a particular age, scientists have said.

An individual’s genetic data can be used to estimate how likely they are to develop the debilitating disease in the future, according to a new study published in Plos Medicine.

Alzheimer’s disease is the most common form of dementia, which mainly affects people over 65 and can cause a deterioration in memory, thinking and behaviour.

Dementia affects 850,000 people in the UK and recently overtook heart disease to become the leading cause of death in England and Wales.

Rahul Desikan, a researcher from the University of California, analysed genetic data from more than 70,000 elderly people, some who had Alzheimer’s and some who didn’t.

By identifying known genetic risk factors for the disease in each person’s genetic “fingerprint”, he and his team created a scoring system known as the polygenic hazard score (PHS).

What is dementia?

The researchers then combined this score with statistics on the incidence rates of the disease to predict an individual’s Alzheimer’s risk and even predict the age of the onset of the disease.

They tested their risk calculations in two independent groups of patients and found people with the highest score were several times more likely to develop Alzheimer’s than those with lower scores.

People with the highest PHS score were also found to have an earlier than expected age of onset of the disease by up to 10 years.

“Our genetic risk score may serve as a ‘risk factor’ for accurately identifying older individuals at greatest risk for developing Alzheimer’s, at a given age,” Dr Desikan told The Independent.

“This score may also be helpful for identifying non-demented older individuals at greatest risk for developing Alzheimer’s neurodegeneration.”

Dr Desikan said while there may be “justified fear” among patients about finding out they have a disease for which there is currently no cure, “knowing your ‘personalised’ risk for Alzheimer’s can really help with planning for the future.”

“For example, if you know that you are at elevated risk for this disease, you may want to make decisions on making a will, getting your finances in order, figure out when to stop driving and perhaps reprioritise your life,” he said.

Dr James Pickett, head of research at the Alzheimer’s Society, said the study was “fairly successful at predicting the likelihood of someone developing dementia over the coming year”.

He said the study, which focused primarily on individuals of European descent living in the US, “needs to be tested further in mixed, non-US populations”.

“This genetic risk score could help identify people to take part in research studies, but is not opening a door to genetic testing for dementia risk in the clinic,” he added.

“For anyone concerned about dementia the first step is to visit your GP. If you’re looking for ways to reduce your risk, remember what’s good for your heart is good for your head, and it may be possible to lower your risk by staying active, eating well and learning new skills.”

Early diagnosis of dementia can help patients receive treatment to help with symptoms more quickly and help them and their families to develop coping strategies, which in some cases can save lives.

Professor Paul Morgan, director of the Systems Immunity Research Institute at Cardiff University, said the study “adds to the strong evidence that an approach that takes into account the polygenic nature of Alzheimer’s disease can be a useful way of aiding risk prediction”.

“As effective therapies emerge, the approach might be used more widely to enable early intervention in those at highest risk,” he added.

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