The 25-Year Early Warning: How a Blood Biomarker Is Changing What We Know About Dementia in Women
Last Updated on September 10, 2026
A Simple Blood Test Could Predict Dementia in Women Decades Before It Starts
What if a routine blood test could tell you, right now, whether you are at elevated risk for dementia 25 years down the track? That is no longer a hypothetical. Researchers from the University of California San Diego have published findings that bring that possibility closer to reality than ever before, and the implications for women’s health are genuinely significant.
The study, published in JAMA Network Open on March 10, 2026, examined data from 2,766 women who participated in the Women’s Health Initiative Memory Study. All women were cognitively healthy when they entered the study in the late 1990s, with blood samples collected at baseline and participants followed for up to 25 years. ucsd Researchers measured levels of a protein called phosphorylated tau 217, or p-tau217, in those stored blood samples. What they found was striking.
Higher levels of p-tau217 were strongly associated with a much greater chance of developing dementia later in life, and as levels of this biomarker increased, so did dementia risk. ucsd In the most telling finding, women in the highest quartile of p-tau217 faced a seven-fold higher hazard of developing dementia compared with those in the lowest quartile. jamanetwork That is a remarkable signal from a single blood test taken up to a quarter of a century before any symptoms appeared.
What makes this research especially noteworthy is the test itself. Blood-based biomarkers like p-tau217 are far less invasive and potentially more accessible than brain imaging or spinal fluid tests ucsd, which are the current methods used to detect Alzheimer’s-related changes. A blood draw is something most women already do as part of routine healthcare. The idea that it could one day screen for dementia risk decades in advance represents a meaningful leap forward.
The study also revealed important nuances. Risk was not uniform across all women. Higher p-tau217 levels were more strongly associated with poorer cognitive outcomes among women over age 70, and among those with the APOE ε4 genetic risk factor for Alzheimer’s disease. ucsd The research also found differences between racial groups, and flagged a potentially important interaction with hormone therapy, with p-tau217 being more predictive of dementia among women who had been randomised to estrogen plus progestin. These are areas researchers say require further investigation.
The lead researcher, Dr Aladdin Shadyab, put the significance plainly: “Our study suggests we may be able to identify women at elevated risk for dementia decades before symptoms emerge. 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.” ucsd
It is worth noting that p-tau217 blood tests are not yet recommended for routine clinical use in people without symptoms. More research is needed before this becomes standard practice. But the direction of travel is clear, and for women who carry genuine concerns about their long-term brain health, this research offers both a reason for hope and a compelling reason to stay informed.
Read the full research article at JAMA Network Open: https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2846152
And the accessible summary from UC San Diego: https://today.ucsd.edu/story/blood-test-predicts-dementia-in-women-as-many-as-25-years-before-symptoms-begin
