A groundbreaking blood test could one day identify healthy older adults at high risk of developing Alzheimer's symptoms years before memory loss begins, offering scientists a powerful new tool in the quest to halt the disease's progression.
Researchers announced on Wednesday that individuals with the highest levels of a blood marker called p-tau217 faced a 38% probability of developing cognitive impairment within five years, escalating to a 78% chance within a decade.
While the test is not yet ready for widespread clinical use, and experts caution against healthy individuals rushing to get screened, its immediate value lies in identifying volunteers for clinical trials. These trials aim to determine whether new drugs can effectively delay or prevent Alzheimer's disease.
Should these treatments prove successful, scientists believe a reliable method for identifying at-risk individuals before symptoms manifest will be crucial.
"Wait and get tested when you can potentially do something about it," advised Dr. Reisa Sperling of the Mass General Brigham Neuroscience Institute, the study's senior author. "At this point it wouldn't change what I would tell someone to do. I'd still tell them to eat well, sleep well, exercise a lot and stay engaged."
The findings, published in JAMA and presented at the Alzheimer's Association International Conference in London, are based on a study of 2,684 healthy older adults. Participants underwent blood testing and annual cognitive assessments over nearly two decades, during which 478 developed cognitive impairment.
The blood test measures p-tau217, a form of the tau protein closely associated with the accumulation of amyloid plaques and tau tangles, hallmarks of Alzheimer's disease. Researchers suggest the test pinpoints a critical "tipping point" in the disease process, where brain changes become significantly more likely to lead to memory loss and other 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," Sperling explained.
Experts not involved in the research acknowledged the findings as an important advance but urged caution. In an accompanying JAMA editorial, Drs. Suzanne Schindler of Washington University in St. Louis and David Wolk of the University of Pennsylvania noted the test's current limitations in predicting an individual's future with certainty, partly due to the relatively short follow-up period for some participants.
Nevertheless, they described the findings as "a crucial piece of the puzzle." Jessica Langbaum of the Banner Alzheimer's Institute confirmed that people with a family history of Alzheimer's are already inquiring about the test, though she does not recommend it outside research settings. She emphasized that a predictive blood test could become "really important" if ongoing clinical trials demonstrate that medications can prevent or delay Alzheimer's before symptoms develop.
