Using a device that measures brain activity, a team at the University of Birmingham were able to measure how quickly an individual responded to words they were shown on a computer screen.
They found that those who responded more slowly had an increased chance of developing Alzheimer’s within three years.
The study, which was carried out in conjunction with scientists the University of Kent and University of California and published in the journal Neuroimage Clinical, could pave the way for new methods of determining a patient’s risk of developing Alzheimer’s. The disease currently affects 1 in 14 over-65s in the UK.
Dr Katrien Segaert, part of the University of Birmingham team, said: “Crucially, what we found in our study is that this brain response is aberrant in individuals who will go on in the future to develop Alzheimer's disease, but intact in patients who remained stable.
"Our findings were unexpected as language is usually affected by Alzheimer’s disease in much later stages of the onset of the disease.
“It is possible that this breakdown of the brain network associated with language comprehension in patients with mild cognitive impairment could be a crucial biomarker used to identify patients likely to develop Alzheimer’s disease.
The team now hopes to expand the study to a larger group of people to see if a slower reaction when presented with a word it is a specific predictor of Alzheimer's or rather a general precursor to dementia.
Dr Segaert said: "The verification of this biomarker could lead the way to early pharmacological intervention and the development of a new low cost and non-invasive test using electroencephalogram [the test that detects electrical brain activity] as part of a routine medical evaluation when a patient first presents to their GP with concern over memory issues.”
The study involved 25 people, some of whom were healthy and others of whom had mild cognitive impairment (MCI) or Alzheimer’s.
MCI is not a type of dementia but sufferers have minor problems with mental abilities such as memory. The condition affects up to 20 per cent of people over the age of 65.
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