A groundbreaking study published Wednesday in JAMA suggests that a simple blood test could identify apparently healthy older adults who are likely to develop Alzheimer's disease within the next five to ten years. The research, presented at the Alzheimer’s Association International Conference in London, marks a potential shift in how clinicians and researchers approach early detection of the devastating neurological disorder.
The test measures levels of a protein called p-tau217, a form of tau that correlates with amyloid plaque buildup in the brain—a hallmark of Alzheimer's. Among 2,684 symptom-free participants tracked over up to a decade, those with the highest p-tau217 levels faced a 38% risk of cognitive impairment within five years, skyrocketing to 78% by ten years. In contrast, individuals with very low levels had minimal risk.
Dr. Reisa Sperling, the study's senior author from Mass General Brigham Neuroscience Institute, emphasized that the findings are not yet a green light for widespread screening. “Wait and get tested when you can potentially do something about it,” she said, noting that currently, lifestyle changes like diet, exercise, and social engagement remain the best advice for those worried about Alzheimer's. The test is already used to diagnose Alzheimer's in people with cognitive symptoms, but its predictive power in healthy individuals is a new frontier.
The research underscores a critical conundrum: many people harbor amyloid plaques without developing dementia. Sperling explained that the blood test offers clues about the tipping point where amyloid triggers abnormal tau tangles, leading to symptoms. “This is a gradual process where amyloid and tau build up in the brain, and this blood-based biomarker is telling you how far you are in that process,” she said.
Large clinical trials are already testing drugs aimed at preventing or delaying Alzheimer's, and a predictive test could streamline enrollment of high-risk participants. If any of these therapies prove effective, doctors would need a reliable way to identify who should take them. However, experts caution that the test is not yet precise enough for individual prognosis. Drs. Suzanne Schindler of Washington University in St. Louis and David Wolk of the University of Pennsylvania, in an accompanying JAMA commentary, noted that factors like competing mortality risks or vascular dementia could cloud predictions. They called the work “a crucial piece of the puzzle” but stressed that the blood tests “are not yet precise enough to guide individualized prognosis.”
Jessica Langbaum of the Banner Alzheimer’s Institute in Phoenix said she already fields requests from people with family histories of Alzheimer's seeking the test, which she strongly discourages for now. “These findings are quite strong,” she said, adding that a predictive test would be “really important” only if ongoing studies yield a drug that can help before symptoms begin. The study also highlighted that only a small fraction of participants were tracked for a full decade, making the 10-year estimate less reliable than the five-year projection.
The findings arrive amid broader efforts to improve Alzheimer's detection and treatment. For context, Captain Chesley “Sully” Sullenberger recently revealed his early-stage Alzheimer's diagnosis, underscoring the disease's reach even among high-profile figures. Meanwhile, advances in other medical fields, such as the FDA's approval of the first gene therapy for sickle cell disease in young children, highlight the potential for targeted interventions once risk is identified.
For now, researchers urge caution. The p-tau217 test may eventually become a routine screening tool, but its role remains experimental. As Sperling put it, the goal is to give patients actionable information—not just a forecast of doom. “At this point, it wouldn’t change what I would tell someone to do,” she said. “I’d still tell them to eat well, sleep well, exercise a lot, and stay engaged.”
