Researchers led by scientists at the Mass General Brigham Neuroscience Institute found that a blood test measuring phosphorylated tau 217 (p-tau217) can predict cognitive decline years before symptoms appear. The study combined data from six observational studies and clinical trials across North America, Japan, and Australia, tracking 2,684 cognitively normal older adults from as early as 2004 through 2025.
Among participants with very high p-tau217 levels, the estimated probability of developing cognitive impairment reached 38% within five years and 78% within 10 years, though the researchers noted that substantially fewer observations supported the 10-year estimate. The results were published in JAMA and presented at the Alzheimer's Association International Conference.
The biomarker provided predictive information beyond what other established risk factors could explain, including amyloid-beta plaques detected on brain scans and genetic risk factors such as APOE4. Rachel F. Buckley, PhD, a cognitive neuroscientist at Mass General Brigham, said the work "estimates an individual's level of risk for cognitive impairment" by showing "how p-tau217 informs risk over time."
However, researchers cautioned against routine testing in asymptomatic people. Reisa Sperling, MD, senior author and neurologist at Mass General Brigham, stated that "we do not yet have disease-modifying treatments for people who find out they are at high risk for developing cognitive impairment due to Alzheimer's disease, which is why we don't recommend currently available blood tests for asymptomatic individuals." Current medical advice for healthy people remains consistent: exercise regularly, maintain a healthy diet, and prioritize sleep and wellness.
The researchers acknowledged limitations, including potential selection bias in the participant population and the need for larger, longer-term studies to confirm findings and improve precision of individual risk predictions.