Alzheimer’s blood test could detect symptoms years before diagnosis

A blood test could detect Alzheimer’s decades before symptoms appear, a study suggests.

Researchers said the findings show Alzheimer’s may be present in midlife and already linked to cognitive differences.

While more research is needed, experts said using blood tests to pinpoint changes in the brain earlier could be incredibly valuable.

The researchers said: “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.”

Alzheimer’s happens when the proteins amyloid and tau abnormally build up in the brain.

For the study, researchers measured the levels of two amyloid biomarkers, as well as p-tau217, in the blood of 1,350 people without dementia in the US.

The average age of participants was 61.

Analysis found high levels of the biomarkers in 86 people, which were associated with worse cognitive performance, accelerated decline in verbal memory and slower processing speed in tests taken five years apart.

Researchers said the results build on previous studies with 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.

A separate study also suggested a new way of performing brain scans could detect tau protein tangles before symptoms appear.

Researchers compared Flortaucipir, a radioactive tracer used in PET scans, with a newer agent called MK6240.

The study of 682 people in the US and Canada found MK6240 identified more than twice as many tau-positive cases as Flortaucipir in early tau regions.

Flortaucipir, also known as Tauvid, is licensed in the UK but not routinely used on the NHS.

It is estimated that about a million people in the UK have dementia, with the figure expected to rise to 1.4m by 2040.

Alzheimer’s, the most common form of dementia, makes up between 60 per cent and 80 per cent of cases.

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.”