Blood Test Predicts Dementia in Women 25 Years Early | Medical Xpress

A new blood test may offer a window into a woman’s future cognitive health, potentially predicting the onset of dementia up to 25 years before symptoms appear. Researchers at the University of California San Diego have identified a biomarker – phosphorylated tau 217, or p-tau217 – that shows a strong association with the development of mild cognitive impairment and, dementia in cognitively healthy older women. This discovery, published in JAMA Network Open, could reshape how we approach the prevention and early management of these debilitating conditions.

Understanding the Biomarker and the Study

Phosphorylated tau 217 is a protein linked to the brain changes characteristic of Alzheimer’s disease. The UC San Diego study analyzed data from 2,766 participants in the Women’s Health Initiative Memory Study, a long-term national study that began enrolling women aged 65 to 79 in the late 1990s. Blood samples collected at the study’s outset were later analyzed for p-tau217 levels. Over the following decades, researchers tracked which women developed memory or thinking problems, including dementia. The findings revealed a clear correlation: women with higher levels of p-tau217 at the beginning of the study were significantly more likely to develop dementia later in life. As p-tau217 levels increased, so did the risk of dementia.

“Our study suggests we may be able to identify women at elevated risk for dementia decades before symptoms emerge,” explained Aladdin H. Shadyab, Ph.D., MPH, the study’s first author and an associate professor at UC San Diego. “That kind of long lead time opens the door to earlier prevention strategies and more targeted monitoring, rather than waiting until memory problems are already affecting daily life.”

Nuances in Risk: Age, Genetics, and Hormone Therapy

Still, the relationship between p-tau217 levels and cognitive decline wasn’t uniform across all participants. The study revealed that the association was stronger in women over 70 at the study’s start compared to younger women. Similarly, women carrying the APOE ε4 genetic risk factor for Alzheimer’s disease experienced a more pronounced link between p-tau217 levels and poorer cognitive outcomes.

Interestingly, the study also found that p-tau217 was more predictive of dementia in women who had been randomly assigned to receive estrogen plus progestin hormone therapy compared to those who received a placebo. The researchers also noted differences in the association between p-tau217 and cognitive impairment between White and Black women, while combining p-tau217 levels with age improved dementia prediction similarly in both groups.

The Promise and Practicality of Blood-Based Biomarkers

The development of blood-based biomarkers like p-tau217 represents a significant step forward in dementia research. Currently, diagnosing Alzheimer’s disease often relies on more invasive and expensive methods, such as brain imaging and cerebrospinal fluid analysis. Blood-based biomarkers offer a less invasive and potentially more accessible alternative, which could accelerate research and broaden access to early detection.

“Blood-based biomarkers like p-tau217 are especially promising because they are far less invasive and potentially more accessible than brain imaging or spinal fluid tests,” said Linda K. McEvoy, Ph.D., senior author of the study and a senior investigator at Kaiser Permanente Washington Health Research Institute. “This is important for accelerating research into the factors that affect risk of dementia and for evaluating strategies that may reduce risk.”

Current Limitations and Future Directions

It’s important to note that blood-based biomarkers are not yet recommended for routine clinical use in individuals without cognitive symptoms. The authors emphasize the need for further research to determine how p-tau217 testing can be integrated into clinical practice and whether early identification can lead to meaningful improvements in patient outcomes. The study also highlights the complex interplay of factors – including hormone therapy, genetics, and age-related health conditions – that influence dementia risk.

Researchers are now focusing on understanding how these factors interact with p-tau217 levels over a person’s lifetime to affect their risk of developing dementia. The ultimate goal, as Shadyab notes, is not simply prediction, but the development of strategies to delay or even prevent dementia altogether.

Currently, the FDA has approved only one blood test, the Lumipulse G pTau217/Aβ42 plasma ratio, to assist in diagnosing Alzheimer’s disease, but it remains costly and is only available in specialized centers. This new research points toward the possibility of a more widely accessible and affordable screening tool.

What’s Next: Refining Risk Assessment and Prevention Strategies

The findings from this UC San Diego study will likely fuel further research into the use of p-tau217 as a risk assessment tool. Ongoing and future studies will aim to refine our understanding of the biomarker’s predictive power, identify individuals who would benefit most from early intervention, and evaluate the effectiveness of various prevention strategies. This includes exploring lifestyle modifications, such as diet and exercise, as well as potential pharmacological interventions. Public health surveillance will also be crucial in tracking trends in biomarker levels and dementia incidence, informing future guidance and resource allocation.

For individuals concerned about their risk of dementia, it’s important to discuss these concerns with a qualified healthcare professional. While a blood test for p-tau217 is not yet widely available, maintaining a healthy lifestyle, engaging in regular cognitive stimulation, and managing cardiovascular risk factors are all steps that can promote brain health and potentially reduce the risk of cognitive decline. You can identify more information about Alzheimer’s disease and related dementias from organizations like the Alzheimer’s Association and the National Institute on Aging.

Plasma Phosphorylated Tau 217 and Incident Mild Cognitive Impairment and Dementia in Older Women, JAMA Network Open (2026). DOI: 10.1001/jamanetworkopen.2026.1295