Blood Test Predicts Alzheimer’s Risk Years in Advance
A recent study suggests a blood test that analyzes a single protein could forecast an individual’s risk of developing Alzheimer’s-related cognitive issues up to a decade before any symptoms appear. This research was highlighted at the Alzheimer’s Association International Conference (AAIC) 2026 in London. It shows that older adults with elevated levels of the biomarker p-tau217 have about a 78% chance of cognitive impairment within 10 years, even if they currently show no memory or thinking problems.
Currently, nearly 7 million Americans are living with Alzheimer’s disease. This number could nearly double to about 13 million by 2050 without any significant medical breakthrough, according to the Alzheimer’s Association.
‘Tremendous Promise’ but Caution Needed
Dr. Manisha Parulekar of Hackensack University Medical Center in New Jersey indicates the test may change how doctors assess the risk of Alzheimer’s. “A single blood test to detect Alzheimer’s predisposition in cognitively healthy individuals holds tremendous promise,” Parulekar noted to Newsweek. She mentioned that it might extend risk assessment from specialty clinics to primary care settings. This could allow for early, personalized interventions focusing on factors like blood pressure, sleep, and physical activity. Furthermore, it could accelerate recruitment for prevention trials to test early interventions in delaying or preventing the disease.
However, Parulekar warned that a positive result, in the absence of a cure, may cause psychological distress, anxiety, and anticipatory grief. Concerns also include potential insurance discrimination and unequal access to future care. She emphasized that responsible implementation should involve structured counseling and equitable access to interventions alongside robust support infrastructure.
Research Findings
The research team analyzed blood samples from nearly 2,700 adults, average age 70, who were cognitively healthy. These samples came from six significant Alzheimer’s research groups and clinical trials. It represents one of the largest studies of its kind. Participants were monitored for an average of nearly five years, with some followed for over a decade using standardized memory and cognitive function tests.
Individuals with p-tau217 levels more than double the average faced a 78% risk of cognitive impairment within 10 years and about a 38% risk within five years. Those with moderately high levels had a 15% risk over five years and 45% over 10 years. The blood test’s predictive value surpassed what brain scans and genetic testing alone could provide.
P-tau217 is a modified form of the tau protein, which aggregates in the brain in Alzheimer’s, closely connected to cognitive decline. It also correlates with amyloid beta levels, another Alzheimer’s hallmark, making it an effective marker for both processes.
Lead study author Rachel F. Buckley from the Mass General Brigham Neuroscience Institute and Harvard Medical School stated that the findings are some of the clearest evidence yet that higher p-tau217 levels can predict dementia risk years beforehand, even in adults without visible memory or thinking problems. The test could aid in choosing patients for treatments aiming to prevent cognitive decline.
Researchers emphasize that the biomarker alone does not fully predict individual risk. Factors like age, genetics, kidney function, obesity, and ethnic background can influence both biomarker levels and dementia risk. More diverse studies and extended follow-up periods are necessary to improve long-term risk assessments. The FDA has approved the p-tau217 blood test for clinical use in the United States. In 2025, the FDA cleared the Lumipulse G pTau217/β-Amyloid 1-42 Plasma Ratio by Fujirebio as the first in vitro diagnostic blood test to assist in diagnosing Alzheimer’s disease.
Newsweek contacted the study authors for further details.
Buckley, R. F., et al. (2026). Prognostic Value of Blood-Based P-Tau217 Levels for Progression to Cognitive Impairment. JAMA. doi:10.1001/jama.2026.12556.
Contact Newsweek editors on this story: Marc Vargas and James Debens.