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Dementia predicted ‘up to nine years before diagnosis’ with new brain test

Scientists say they have developed a new method that can predict dementia up to nine years before diagnosis, with 80 per cent accuracy.

The test involves analysing the network of connections in the brain when it is in “idle mode” to look for very early signs of the condition.

Researchers from Queen Mary University of London said their method is better than memory tests or measurements of brain shrinkage, two commonly used tools to diagnose dementia. They said this technique has the “potential to fill an enormous clinical gap” by identifying people who are at risk of dementia and treating them before symptoms start to show.

The team looked at brain scans from more than 1,100 people from UK Biobank, a database containing genetic and health information from half a million people in the UK. They examined the patterns of connections in a brain network called the default mode network (DMN), which kicks in when the brain is in idle mode – where the mind wanders and is not focused on a particular task.

The researchers developed a model that was able to predict which people in this group would go on to be diagnosed with dementia.

Among the 103 people who had dementia, 81 had brain scans between five months and 8.5 years before being officially diagnosed. Their brain scans showed less connectivity in the default mode network compared with those who did not go on to develop dementia, the findings showed.

Professor Charles Marshall, who led the research team within the Centre for Preventive Neurology at Queen Mary’s Wolfson Institute of Population Health, said: “Predicting who is going to get dementia in the future will be vital for developing treatments that can prevent the irreversible loss of brain cells that causes the symptoms of dementia.

Although we are getting better at detecting the proteins in the brain that can cause Alzheimer’s disease, many people live for decades with these proteins in their brain without developing symptoms of dementia.

“We hope that the measure of brain function that we have developed will allow us to be much more precise about whether someone is actually going to develop dementia, and how soon, so that we can identify whether they might benefit from future treatments.”

The findings are published in the journal Nature Mental Health.

Scientists not involved in the research said there is an urgent need to improve the way people with the condition are diagnosed, as one in three people with dementia never receive a formal diagnosis, which will be even more important as dementia becomes a treatable condition.

However, they cautioned whether this method would prove successful in the long term.

Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, said while the research was able to identify structural changes in the brain before dementia symptoms appear, more studies are needed “involving diverse groups of people of different ages and ethnicities to fully understand the benefits and limitations of this MRI scan as a diagnostic tool”.

Tara Spires-Jones, FMedSci, president of the British Neuroscience Association and professor in the UK Dementia Research Institute at the University of Edinburgh, said that while this type of brain scan is useful, they are “not widely available nor are they perfect at predicting who will go on to develop dementia”.

Dr Sebastian Walsh, a Doctoral Fellow in Public Health Medicine at the University of Cambridge, said although the results are “potentially exciting”, the sample was small.

The time between brain scan and diagnosis was up to 9 years, but actually an average of 3.7 years, he added.

“Given delays in the way diagnoses appear in the UK biobank cohort, it is not surprising that the ’new’ cases of dementia actually had cognitive impairment at the time of the scans,” Dr Walsh said.

“So before we can be truly confident that this technology can predict dementia onset (rather than just be an early indicator it is present), it will be really important to see these findings demonstrated in bigger samples with a much longer delay between scan and onset of cognitive symptoms.”

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