Blood test could predict Alzheimer's cognitive decline years early, international study finds

The study, led by scientists at the Mass General Brigham Neuroscience Institute, combined data from six observational studies and clinical trials across North America, Japan, and Australia. It focused on whether a blood test measuring p-tau217 can reliably predict whether a person with normal cognitive function will eventually develop symptoms.

The analysis included 2,684 older adults who showed no signs of cognitive impairment at enrollment. Participants had their blood analyzed for p-tau217 and underwent positron emission tomography (PET) brain scans. Annual follow-up assessments tracked cognitive changes over a period stretching from 2004 to 2025, during which around 478 participants developed impairment. The research found a strong relationship between high p-tau217 levels and the onset of these problems. The biomarker remained significantly associated with cognitive impairment after researchers accounted for amyloid-beta plaques, and its predictive value also extended beyond known genetic risk factors such as APOE4.

Despite the strength of the association, lead author Rachel F. Buckley, PhD, said the work's value lies in estimating individual risk. "What really sets this work apart is that it estimates an individual's level of risk for cognitive impairment," Buckley said. "We harmonized data across six cohorts, creating a large and varied data set, and still found consistent results showing how p-tau217 informs risk over time." Senior author Dr. Reisa Sperling cautioned that the tests are not currently recommended for routine screening of people without symptoms. "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," Sperling said. "Today, our medical advice would remain the same regardless of test results: exercise regularly, maintain a healthy diet, and prioritize sleep and overall wellness."

The long-term goal, Sperling explained, is for Alzheimer's risk assessment to follow the model of cardiovascular prevention. "Our long-term goal is to get us to where cholesterol testing is in predicting your risk of a heart attack," she said. Several clinical trials are already investigating whether disease-modifying therapies can benefit people who have biological signs of Alzheimer's but have not yet experienced cognitive impairment. If those trials prove successful, the p-tau217 blood test could serve as a tool to identify who might benefit most from early intervention.