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GPs will offer a new blood test that can spot Alzheimer's disease years before it strikes as part of a landmark trial.
In the largest UK study of its kind, more than 50 GPs in central and northern Scotland will make the test available to up to 500 patients, with hope it will soon be rolled out across the UK.
The tool looks for two proteins in the blood that are linked to the brain damage seen in dementia.
Studies have found that it can spot the condition more accurately than scans and other memory tests that are currently used, with some research suggesting it can flag these signs decades before symptoms appear.
The announcement of the project comes within 24-hours of US researchers presenting striking findings from a study involving a similar test at the Alzheimer's Association International Conference in London.
The paper, published in the medical journal JAMA, showed that a blood test looking for one of the same proteins as the Scottish tool could accurately identify a dementia patient a decade before symptoms struck.
Those with very high levels of the protein p-tau217 had a 78 per cent increased risk of developing the major killer within 10 years.
Patients with a moderately high score were 45 per cent more likely than average to be diagnosed.
The blood tests used in the Scottish research are looking for two proteins that are linked to the condition, p-tau181 and p-tau217.
Experts consistently use p-tau217 in Alzheimer's research because it is one of the most reliable indicators of the disease.
While it is a form of tau protein, which normally helps brain cells function properly, decades of research has found levels of p-tau217 tend to increase in Alzheimer's.
Scientists can identify higher levels of p-tau217 as they are associated with the build-up of beta-amyloid plaques – clumps of protein that form between brain cells – and tau tangles, twisted clumps of tau protein that build up inside brain cells.
P-tau181 is also widely used as an indicator - but p-tau217 is largely considered more accurate by experts.
Unlike in the American new study, the patients in the Scottish trial will already be showing signs of cognitive decline when they receive the test.
The aim is to assess the benefit of such a predictive tool for patients, as well as to offer support as early as possible so families can 'plan ahead'.
There are an estimated one million people in the UK living with dementia - of which Alzheimer's is the most common type - and by 2040 that figure is expected to climb to 1.4 million.
Around 90,000 people in Scotland are living with the degenerative brain disease, and 3,000 are aged under 65.
Dr Sheelagh Harwell, senior associate GP at GP-Plus in Edinburgh, is one of the medics participating in the Scottish study.
She said: 'The study heralds an exciting time in general practice as new diagnostic blood tests become available.
'Consultations are shifting from physicians discussing dementia risk with patients, to discussing brain health.
'An earlier diagnosis of Alzheimer's can aid patients with lifestyle modifications, allow them to access support sooner, and plan ahead.'
At present, the most accurate way to find out if you are at risk of dementia is through genetic testing - which is prohibitively expensive.
Australian actor Chris Hemsworth took a hiatus in 2022 after learning that he had inherited two copies of APOE4, dubbed 'the Alzheimer's gene', from his parents.
Studies show that having both copies increases the risk by 10 to 15 times. Having one copy can double a person's risk.
The Hollywood star, 42, received the shock diagnosis after taking a genetic test on the National Geographic documentary series Limitless with Chris Hemsworth.
'You're constantly thinking you're going to live forever, especially as a young individual. Then to be told that this might be the thing that might take you out was like, whoa - it kinda floored me,' Hemsworth said on the show.
Following the test, Chris made changes to his already extensive workout routines and now focuses more on his brain health.
In an interview with Men's Health, he said he was 'incorporating more solitude into his life' as well as focusing on cardio exercise rather than lifting heavy weights.
He said: 'I've always been pretty consistent with my exercise commitments, but lately I've really felt the importance of taking time for yourself without any outside voice or stimulation and making time for stillness.'
In the US study, scientists from Mass General Brigham and Harvard Medical School found that measuring levels of p-tau217 alone could help identify people at risk of Alzheimer's-related cognitive decline up to a decade before symptoms appear.
They followed nearly 2,700 adults - with an average age of 70 - who were cognitively healthy at the start of the study for almost five years on average, with some tracked for more than a decade.
Those with very high levels of the biomarker had an estimated 38 per cent increased chance of developing cognitive impairment within five years and a 78 per cent increased risk within ten years. People with moderately raised levels still faced a 15 per cent increased risk over five years and a 45 per cent risk over ten.
Researchers said the findings offer some of the clearest evidence yet that Alzheimer's risk may be detectable years before memory problems begin.
However, the experts stressed that p-tau217 cannot predict an individual's future on its own, and that age, genetics, kidney function, obesity and ethnic background can all influence biomarker levels and dementia risk.
Also presented at the conference was the announcement of a new trial into the potential of trontinemab, a revolutionary drug which scientists believe could 'reverse' Alzheimer's.
The study, known as PrevenTRON, will recruit cognitively healthy volunteers in countries across the world, including the UK, aged between 55 and 80.
The drug, which is administered as a monthly infusion, will be offered to about 1,600 people with no current memory problems but who are at high risk of the disease, having been found to have high levels of p-tau217 in the blood.
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