Brain may show signs of Alzheimer's long before symptoms appear

Despite appearing healthy, those with a genetic risk may fare worse on mental ability tests

A scientist looks at brain scan images. Photo: AP

Healthy people with a higher genetic risk of Alzheimer’s disease may show differences in their brain structure and fare worse on mental ability tests, research suggests.

Experts behind the study say the findings back the theory that signs of Alzheimer’s in the brain may be detectable before significant symptoms appear.

It is already known that people who have a parent or sibling with Alzheimer’s disease are more likely to develop it than those without a close relative who is affected.

People with more than one first-degree relative with Alzheimer’s are thought to be at even higher risk of developing it.

Alzheimer’s is a degenerative disease in which several brain regions are affected, but among the earliest includes the hippocampus, which is vital for processing memory and learning.

For the new research, published in the Neuropsychopharmacology peer-reviewed journal, University of Glasgow researchers used polygenic risk scores, which estimate a person’s genetic risk of developing a particular disease such as Alzheimer’s.

They calculated a genetic risk score based on a large number of mutations for 32,790 healthy adults without dementia from UK Biobank, a large-scale database.

They worked out that a person’s lifetime genetic risk of Alzheimer’s was associated with differences in brain structure and performance on mental ability tests.

“Our findings are novel because they show the effects of genetic risk may, to a certain extent, be apparent long before a clinical dementia diagnosis," said Rachana Tank, a lead author on the study.

“Although we cannot say for certain that these differences are early signs of dementia per se, it is important that we do further research in this area.”

Dr Donald Lyall, lecturer in public health at the University’s institute of health and well-being, said: “These findings could lead to a better, more meaningfully informative way of gauging Alzheimer’s disease risk than current methods of inquiring about a family history of dementia.

“Being able to identify individuals at risk of worse cognitive abilities and potentially accelerated decline could greatly improve diagnosis and treatment options in future.”

Fiona Carragher, director of research at the Alzheimer’s Society, said that the findings could greatly improve treatment of the disease.

“If we can accurately identify people at risk of developing Alzheimer’s disease later in life, it could be a real game-changer," Ms Carragher said.

“Early detection of those at a higher risk has the potential to pave the way for new treatments in the future and help researchers to understand what causes diseases like Alzheimer’s to develop.

“The scale of this study is significant. It adds further evidence to the theory that some brain changes associated with Alzheimer’s disease can start many years before symptoms such as memory loss.

“However, it only looked at people from a white European background. We need to better understand whether there are associations between different genetic risk factors and changes in the brain in people from other ethnic communities.

“Research will beat dementia, but we need more funding.

"The government must honour their commitment to double dementia research funding to provide hope for future generations. We owe it to the 850,000 people in the UK currently living with dementia.”