Blood Test Could Predict Alzheimer’s Years Before Symptoms Begin

A groundbreaking study from Washington University School of Medicine in St. Louis has revealed that a simple blood test could predict not only a person’s risk of developing Alzheimer’s disease but also estimate when symptoms will first appear.

The research, published in the journal Nature Medicine, focuses on a specific protein called p-tau217, which forms “tangles” in the brain that disrupt communication between nerve cells. In healthy brains, tau helps stabilize nerve cell structure, but its abnormal accumulation is a hallmark of Alzheimer’s disease.

Researchers analyzed data from more than 600 older adults enrolled in two long-term Alzheimer’s research projects. By comparing blood samples with participants’ cognitive performance over several years, the team discovered that p-tau217 levels rise in a “remarkably consistent” pattern long before memory loss begins.

“We show that a single blood test measuring p-tau217 can provide a rough estimate of when an individual is likely to develop symptoms of Alzheimer’s disease,” explained lead author Kellen K. Petersen, PhD, instructor of neurology at Washington University in St. Louis.

The team developed a model that uses a patient’s age and protein levels to estimate symptom onset, with a margin of error of three to four years. Their findings revealed a significant age-related pattern: individuals who first showed abnormal p-tau217 levels around age 60 typically didn’t develop Alzheimer’s symptoms for about 20 years, while those with abnormal levels appearing around age 80 developed symptoms much faster — in about 10 years.

“This suggests that age and disease-related changes in the brain can influence how quickly Alzheimer’s symptoms become apparent,” Petersen noted.

The potential impact on Alzheimer’s research and treatment could be substantial. Traditional methods of detecting tau protein tangles involve complex and expensive brain imaging tests, making them impractical for widespread screening. A blood test would provide a more accessible and cost-effective alternative.

“This could transform how researchers design clinical trials and, eventually, how clinicians identify people at highest risk for cognitive decline associated with Alzheimer’s years before decline begins,” said Rebecca M. Edelmayer, PhD, vice president of scientific engagement at the Alzheimer’s Association, who was not involved in the study.

Despite the promising results, researchers caution that the test is not yet ready for clinical use. The study had several limitations that need to be addressed in future research.

“We were only able to make predictions for individuals whose p-tau217 levels fell within a certain range, although it was a fairly wide range,” Petersen said. “The models were developed in relatively healthy and well-educated research cohorts that were not diverse, so the results may not apply well to the broader population.”

Dr. Suzanne Schindler, a neurologist at Washington University and co-author of the study, emphasized that the test is not yet recommended for use by the general public. “At this point, we do not recommend that any cognitively unimpaired individuals have any Alzheimer’s disease biomarker test,” she stated.

The research comes at a significant time in Alzheimer’s treatment development. Two large clinical trials are currently underway to determine whether people with high levels of this protein can benefit from early treatment with recently approved Alzheimer’s drugs — lecanemab and donanemab. These medications are designed to reduce levels of brain plaques associated with Alzheimer’s disease, and researchers hope that earlier intervention may enhance their effectiveness.

Looking ahead, the Washington University team plans to refine the test by studying other Alzheimer’s-linked proteins to narrow the margin of error. They also aim to include more diverse participants in future studies to ensure the results apply broadly across different populations.

“There are many other blood and imaging biomarkers, as well as cognitive tests, that we can combine with plasma p-tau217 to improve the accuracy of predicting symptom onset,” Petersen said. “We hope this work will lead to even better models that will be useful to individuals.”

This research represents a significant step forward in the early detection and potentially the treatment of Alzheimer’s disease, which affects millions of people worldwide and places tremendous burdens on patients, caregivers, and healthcare systems.