A blood test measuring levels of a protein called p-tau217 may help predict if seemingly healthy older adults are at risk of developing Alzheimer's disease within five to 10 years, according to research published in JAMA and presented at the Alzheimer's Association International Conference in London.
The findings suggest that this test could become a valuable tool for accelerating drug development by identifying individuals at high risk for clinical trials focused on Alzheimer's treatments or preventative strategies.
Large clinical trials are already underway to test drugs that could prevent or delay the onset of Alzheimer's. If these treatments prove effective, an accessible method for identifying suitable candidates will be crucial.
Identifying At-Risk Individuals
The study analyzed data from 2,684 older adults who were cognitively healthy at the time of enrollment in long-term Alzheimer's studies. Participants underwent the p-tau217 blood test and received annual cognitive checkups. Between 2004 and the previous year, approximately 478 individuals developed cognitive impairment.
Researchers found that symptom-free older adults with very high levels of p-tau217 had a 38% risk of developing cognitive impairment within five years, a risk that rose to 78% over a 10-year period. Conversely, those with very low p-tau217 levels showed a low risk of cognitive impairment over the same timeframes.
The p-tau217 test is thought to measure a form of tau protein that correlates with the buildup of amyloid plaques in the brain, a hallmark of Alzheimer's disease, and provides clues about the formation of tau tangles, another key indicator.
"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," said Dr. Reisa Sperling of the Mass General Brigham Neuroscience Institute, the study's senior author.
Cautions and Future Directions
While the study's findings are considered strong, experts not involved in the research advise caution. Some noted that only a small fraction of participants were tracked for the full decade, making the 10-year risk estimate less certain than the five-year estimate. Additionally, factors such as the risk of death from other causes or the presence of vascular dementia due to heart problems could influence predictions, according to Drs. Suzanne Schindler of Washington University in St. Louis and David Wolk of the University of Pennsylvania.
Schindler and Wolk, in a commentary published in JAMA, stated that the blood tests are "not yet precise enough to guide individualized prognosis" but acknowledged that the new work provides a "crucial piece of the puzzle."
Researchers emphasize that the p-tau217 test is not yet recommended for widespread use in healthy individuals seeking to assess their future risk. Sperling advises, "Wait and get tested when you can potentially do something about it." She added that at present, lifestyle recommendations such as eating well, sleeping adequately, exercising regularly, and staying mentally engaged remain the primary advice for maintaining cognitive health.
Experts like Jessica Langbaum of the Banner Alzheimer's Institute discourage individuals with a family history of Alzheimer's from seeking the test at this time. She noted that while a predictive blood test would be valuable, its utility would be maximized if effective treatments become available to help individuals before symptoms manifest.