A five-minute neck scan could predict cognitive decline 10 years before symptoms appear, according to scientists.
Researchers suggest the quick scan of blood vessels may become a routine part of screening for people at risk of dementia if the results are confirmed in larger studies.
The scan identifies whether the vessels in the neck are stiffening, diminishing their ability to protect more delicate vessels around the body from the powerful physical pulses of blood generated by the heart.
Ageing and high blood pressure can cause this stiffening, which over time will weaken the protective effect given by healthy, elastic vessels.
As a progressively stronger pulse travels into fragile vessels it could cause structural changes in the brain's blood vessel network, as well as minor brain bleeds called mini-strokes.
All of these can contribute to the development of dementia.
Dr Scott Chiesa, post-doctoral researcher at UCL, said: "These findings demonstrate the first direct link between the intensity of the pulse transmitted towards the brain with every heartbeat and future impairments in cognitive function.
"It's therefore an easily measurable and potentially treatable cause of cognitive decline in middle-aged adults which can be spotted well in advance."
A group of 3,191 middle-aged men and women volunteered in the study, which began in 2002.
All were given an ultrasound which measured the intensity of the pulse travelling toward their brain, and were monitored for 15 years, with researchers testing their memory and problem-solving ability.
The 25% of volunteers with the highest pulse at the beginning of the study were about 50% more likely to exhibit accelerated cognitive decline over the next 10 years when compared with the other participants.
Researchers defined cognitive decline as a noticeable and measurable reduction in cognitive abilities, including memory, language, thinking and judgement skills.
It can be one of the first signs of dementia, but not everyone with those signs will develop dementia.
The UCL team plan to use MRI scans to check if the individuals who showed signed of decline also show structural and functional changes.
They will also test whether the scan can improve existing "risk scores" which predict dementia.
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Professor Metin Avkiran, associate medical director at the British Heart Foundation, which co-funded the research, said further research was needed to check whether lifestyle changes and medicines to reduce pulse wave intensity also delay cognitive decline.
The research is being presented to the American Heart Association Scientific Sessions conference in Chicago.