Blood Test Could Predict Alzheimer’s a Decade Early
A blood test that detects a protein linked to Alzheimer’s disease may predict brain decline up to ten years before symptoms appear, according to a new study. The research found that healthy older adults with elevated levels of the protein p-tau217 had a 78% risk of developing cognitive impairment over a decade.
The findings are set to be presented at the Alzheimer’s Association International Conference in London, the world’s largest annual gathering of dementia scientists. Experts say the test could pave the way for earlier treatment to prevent dementia.
Study Details and Key Findings
The US study collected data from nearly 2,700 healthy adults with an average age of 70. Participants provided blood samples and were monitored over time, completing memory, thinking, and daily functioning tests.
People with very high levels of p-tau217—more than twice the average measurement—had a 78% risk of progressing to cognitive impairment within ten years and a 38% risk within five years. Those with moderately elevated levels had a lower but still significant risk: 15% over five years and 45% over ten years.
The blood tests provided predictive information beyond that obtained from brain scans and genetic testing.
Expert Commentary
Maria Carrillo, chief science officer and medical affairs lead at the Alzheimer’s Association, said: “This is the future of Alzheimer’s care, targeting the earliest stages of the disease, including in its silent stage before memory issues arise. This is when treatments may have the greatest benefit—perhaps even keeping people from ever experiencing dementia symptoms.”
Study leader Professor Rachel Buckley, an expert in neurology at Mass General Brigham and Harvard Medical School, added: “Our findings provide some of the clearest evidence yet that elevated p-tau217 levels may help detect dementia risk years earlier—even in adults with no noticeable memory or thinking problems.”
Implications for Future Treatment
Dr Carrillo noted: “Identifying people at risk earlier could fundamentally change how we diagnose, treat, and prevent dementia, with far-reaching health, happiness, and cost implications for patients, families, healthcare systems, and society.”
Professor Buckley said: “Once verified, these blood tests could be used to recruit patients for clinical trials of treatments to prevent cognitive decline and dementia. In the future, when treatments are approved for use early in the disease process, these tests could help guide monitoring, treatment decisions, and counselling for patients and families.”
UK Context and Expert Views
A blood test for p-tau217 is also being evaluated in the UK. Researchers at University College London began recruiting patients last August.
Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, said blood tests were “the most promising development in dementia diagnosis research.” He added: “In the future, this tool could support clinicians to identify people at risk and support them to take steps to reduce their risk or even access preclinical treatments as they become available.”
Dr Sara Rodrigues, senior research manager at Alzheimer’s Research UK, cautioned: “At present, blood tests identify changes in pathology associated with Alzheimer’s disease, but they haven’t been validated to predict whether a person will go on to develop the condition. It is important to note that in the study nearly a quarter of people with low levels of p-tau217 still went on to experience declines in memory and thinking. This suggests further research is needed to understand how to interpret these results.”
Limitations and Next Steps
The researchers noted that p-tau217 alone could not fully predict an individual’s risk and longer-term studies will be needed. The test could one day help patients access treatment before dementia develops.
