A simple blood test that measures key proteins linked to Alzheimer’s may be able to detect the disease decades before symptoms appear, according to new research.
The study suggests Alzheimer’s may already be present in midlife and linked to measurable differences in thinking and memory, even in people without dementia. Experts say the findings are promising, though more research is still needed before the approach could be used routinely.
Alzheimer’s develops when the proteins amyloid and tau build up abnormally in the brain.
In the study, researchers in the US measured blood levels of two amyloid biomarkers as well as p-tau217 in 1,350 people who did not have dementia. The average age of participants was 61.
The analysis found that 86 people had high levels of the biomarkers. Those higher levels were linked to poorer cognitive performance, faster decline in verbal memory and slower processing speed on tests taken five years apart.
Researchers said the findings, published in The Lancet, build on earlier studies in older adults by “showing that evidence of Alzheimer’s disease neuropathology is present in midlife, although infrequent, and is already linked to measurable cognitive differences”.
They added: “These findings support the concept that Alzheimer’s disease begins decades before clinical symptoms emerge and highlight the potential value of plasma biomarkers for early detection in the general population.
“Identifying individuals with early Alzheimer’s disease neuropathology through accessible, blood-based assays could help target preventive strategies and clinical trials aimed at delaying or preventing the onset of dementia, with implications for both clinical practice and public health policy.”
A separate study, also published in The Lancet, points to another possible breakthrough, this time in brain imaging. Researchers tested a newer PET scan tracer called MK6240 against Flortaucipir, an existing radioactive tracer used to detect tau protein tangles.
That study, involving 682 people in the US and Canada, found MK6240 detected more than twice as many tau-positive cases as Flortaucipir in early tau regions, suggesting it may be better at spotting disease changes before symptoms begin.
Dementia affects about one million people in the UK, and that number is expected to climb to 1.4 million by 2040. Alzheimer’s is the most common form of dementia, accounting for between 60 and 80 per cent of cases.
Commenting on the findings, Dr Jacqui Hanley, head of research funding at Alzheimer’s Research UK, said: “These two studies add to a growing body of evidence showing progress in detecting the biological changes linked to Alzheimer’s disease much earlier in life, using a range of biomarkers from blood tests through to advanced brain imaging.
“Being able to identify these changes sooner than we can now could be incredibly valuable.
“If we can identify Alzheimer’s disease earlier on, it would open up opportunities for people to take part in studies of new treatments.
“We could also identify people who might benefit from disease-modifying treatments that are indicated for early-stage disease.”
Dr Hanley said accurate blood tests “could improve how a diagnosis is made, as they are less invasive, scalable and potentially more accessible than existing tools such as PET brain scans and lumbar punctures”.
She added: “As exciting as the results of these two observational studies are, we will need further research in larger and diverse groups of people before the approaches could be used routinely.”
