A straightforward blood test capable of identifying the signature proteins associated with Alzheimer’s disease could offer a revolutionary way to detect the condition decades before any symptoms manifest, according to new research.
The findings suggest that the neurological disorder may already be present in midlife and linked to subtle cognitive differences.
While further investigation is required, experts believe that utilising blood tests to pinpoint these crucial brain changes at an earlier stage “could be incredibly valuable”. Alzheimer’s is characterised by the abnormal accumulation of amyloid and tau proteins within the brain.
For the study, published in The Lancet, researchers analysed levels of two amyloid biomarkers and p-tau217 in the blood of 1,350 individuals in the US who did not have dementia, with an average age of 61.
The analysis revealed that 86 patients exhibited high levels of these biomarkers, which were correlated with poorer cognitive performance, an accelerated decline in verbal memory, and slower processing speeds in tests conducted over a five-year period.
Researchers noted that these results build upon previous studies involving 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.”
The team concluded that “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.”
In a separate study, also published in The Lancet, a novel brain scanning technique was proposed for detecting tau protein tangles before symptoms appear.
Researchers compared Flortaucipir, a radioactive tracer used in PET scans, with a newer agent named MK6240. The study, involving 682 patients across the US and Canada, found that MK6240 identified more than twice as many tau-positive cases in early tau regions compared to Flortaucipir. While Flortaucipir, known as Tauvid, is licensed in the UK, it is not routinely available on the NHS.
Dementia currently affects an estimated one million people in the UK, a figure projected to rise to 1.4 million by 2040. Alzheimer’s, the most prevalent form of dementia, accounts for between 60 per cent and 80 per cent of all cases.
Dr Jacqui Hanley, head of research funding at Alzheimer’s Research UK, commented on the studies: “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.”
She emphasised the potential benefits: “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 highlighted the current challenges in the UK, where “many people wait far too long for a dementia diagnosis, meaning they often miss out on these opportunities.”
She added: “This is why there’s so much excitement around the potential for blood tests, alongside other assessments. 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.”
While acknowledging the importance of detailed brain imaging for understanding the disease’s extent and stage, Dr Hanley noted that the tau PET scan study suggests “newer methods might detect Alzheimer’s-related changes earlier than existing techniques, which could enable earlier identification of disease and more precise selection of participants for clinical trials.”
She cautioned that “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.”
Looking ahead, the Blood Biomarker Challenge, a multi-million-pound initiative spearheaded by the Alzheimer’s Society, Alzheimer’s Research UK, and the National Institute for Health and Care Research, aims to make blood tests for dementia diagnosis available on the NHS by 2029.