Researchers are working to identify methods for detecting the risk of dementia as early as possible. A new study suggests a blood biomarker could indicate a future risk of cognitive decline in women years before symptoms appear.
A blood test measuring levels of a protein linked to brain changes in Alzheimer’s disease may predict dementia risk in women up to 25 years before symptoms begin, according to research from the University of California San Diego (UCSD) published on Tuesday, March 12, 2026, in JAMA Network Open. Early detection of dementia risk is a critical step toward improving patient outcomes and developing preventative strategies.
The study showed that elevated levels of the p-tau217 biomarker (phosphorylated tau 217), a form of the tau protein associated with brain changes seen in Alzheimer’s disease, were strongly correlated with the later development of mild cognitive impairment and dementia in older women who initially had no cognitive issues.
“The results suggest we may be able to identify women at increased risk for dementia decades before symptoms emerge,” said study lead author Aladdin H. Shadyab, associate professor of public health and medicine at the Herbert Wertheim School of Public Health and Human Longevity Science and the School of Medicine at UCSD.
Researchers say this extended timeframe between risk identification and symptom onset could allow for earlier implementation of preventative strategies and closer monitoring of at-risk individuals, rather than interventions starting only after memory problems appear.
The findings are based on an analysis of data from 2,766 participants in the Women’s Health Initiative Memory Study, a large national study that included women aged 65 to 79 at the end of the 1990s and followed them for up to 25 years.
At the start of the study, all participants had normal cognitive function. Blood samples collected at the beginning of the research were later analyzed to determine the level of the p-tau217 biomarker, a form of the tau protein that reflects early brain changes associated with Alzheimer’s disease.
Over the follow-up period, researchers identified participants who subsequently developed memory or thinking problems, including dementia.
Women with higher levels of p-tau217 in their blood at the beginning of the study were significantly more likely to develop dementia later in life. The higher the biomarker level, the greater the risk of dementia, with women exhibiting the highest values having the greatest likelihood of developing the disease long-term.
The analysis also revealed that the association between high p-tau217 levels and cognitive decline risk wasn’t uniform across all participants. For example, the link between the biomarker and unfavorable cognitive outcomes was stronger in women over 70 at the study’s start compared to younger women, and in those with the APOE ε4 genetic risk factor for Alzheimer’s disease.
p-tau217 was more predictive of dementia in women assigned to hormone therapy with estrogen and progestin in the study, compared to those receiving a placebo.
Researchers also observed differences between white and Black women regarding the strength of the association between the biomarker and dementia. However, combining p-tau217 level with age improved dementia risk prediction similarly in both groups.
Study authors emphasize that blood-based biomarkers like p-tau217 are promising because they are less invasive and easier to use than methods relying on brain imaging or cerebrospinal fluid analysis. “This is important for accelerating research into factors influencing dementia risk and for evaluating strategies that could reduce that risk,” said Linda K. McEvoy, principal investigator at Kaiser Permanente Washington Health Research Institute and senior author of the study, in a statement.
Currently, blood biomarker tests are not recommended for clinical use in people without symptoms of cognitive impairment. The researchers stress that further studies are needed to determine how p-tau217 testing could be integrated into medical practice and whether early risk identification can alter the course of the disease.
Future research will also examine how factors such as hormone therapy, genetic profile, and age-related health conditions interact with plasma p-tau217 levels throughout life and influence dementia risk.
