Genetic test could predict age of Alzheimer's onset

A genetic test based on 31 genetic markers could be used to predict at what age an individual is likely to develop Alzheimer's disease.

Researchers from the US and Norway have analysed data from over 70,000 elderly people — some with Alzheimer's and others without — and developed a risk scoring test called the polygenic hazard score (PHS).

'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 Rahul Desikan of the University of California told The Independent.

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

Alzheimer's disease, the most common form of dementia that mainly affects people over 65, is highly heritable and known to be associated with genes such as APOE. But other genetic variants may collectively account for an individual's risk for developing the disease, according to the study which was published in PLOS Medicine.

The researchers initially identified almost 2000 small genetic differences known as single nucleotide polymorphisms (SNPs). They then ranked these differences for influence and created the PHS test based on 31 SNP markers and two APOE variants.

Through testing two independent groups of people, they found that individuals with the highest scores were several times more likely to develop the disease than those with lower ones. Additionally, these individuals were found to have an earlier than expected age of the disease's onset by up to 10 years, even in individuals who did not have an APOE variant associated with Alzheimer's disease.

'Knowing your "personalised" risk for Alzheimer's can really help with planning for the future,' said Dr Desikan. The authors add that continuous PHS testing could better inform prevention and therapeutic trials, and help determine which individuals are most likely to respond to therapy.

Dr James Pickett, head of research at Alzheimer's Society, said: 'This study's approach was fairly successful at predicting the likelihood of someone developing dementia over the coming year, but 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.

While genetics can influence the chances of developing Alzheimer's, other factors such as a healthy diet and regular exercise that improves blood circulation can also reduce the risk, said Dr Rosa Sancho, head of research at Alzheimer's Research UK.