A simple blood test that measures hallmark proteins associated with Alzheimer's disease could detect the condition decades before symptoms appear, according to a study published in The Lancet.
Researchers measured levels of amyloid biomarkers and p-tau217 in the blood of 1,350 people without dementia in the US. High levels were found in 86 patients, linked to worse cognitive performance, accelerated verbal memory decline, and slower processing speed over five years.
The findings suggest Alzheimer's may be present in midlife and already associated with cognitive differences. The authors said the results support the concept that Alzheimer's begins decades before clinical symptoms emerge, highlighting the potential of blood-based assays for early detection.
A separate study in The Lancet found that a new PET scan tracer, MK6240, identified more than twice as many tau-positive cases as the existing tracer Flortaucipir in early tau regions, potentially enabling earlier detection of tau tangles.
Dr Jacqui Hanley of Alzheimer's Research UK said the studies add to evidence of progress in detecting biological changes earlier, which could be valuable for identifying people for clinical trials and future treatments. However, further research in larger and diverse groups is needed before routine use.
