Researchers from the University of California San Diego reported on Mar. 10 that a blood-based biomarker, phosphorylated tau 217 (p-tau217), can predict a woman's risk of developing dementia up to 25 years before symptoms appear. The study, published in JAMA Network Open, found that higher levels of p-tau217 were strongly associated with future mild cognitive impairment and dementia among older women who were cognitively healthy at the start of the study.
This research is significant because it suggests that early detection of dementia risk may be possible through a simple blood test, potentially allowing for earlier intervention or monitoring. The findings are based on data from 2,766 participants in the Women's Health Initiative Memory Study, which enrolled women ages 65 to 79 in the late 1990s and followed them for up to 25 years.
Blood samples collected at baseline were analyzed years later to measure p-tau217. Over time, researchers identified women who developed memory or thinking problems, including dementia. Those with higher baseline levels of p-tau217 faced a greater likelihood of developing dementia as they aged. The association between elevated p-tau217 and increased dementia risk was particularly strong among women over age 70 at baseline and those carrying the APOE ε4 genetic risk factor for Alzheimer's disease. Additionally, p-tau217 was more predictive among women who had received estrogen plus progestin hormone therapy compared to placebo.
The study also observed differences in how well p-tau217 predicted dementia between white and Black women; however, combining this biomarker with age improved prediction similarly across both groups.
"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, PhD, senior author of the study, senior investigator at Kaiser Permanente Washington Health Research Institute and professor emeritus at the Herbert Wertheim School of Public Health. "This is important for accelerating research into the factors that affect risk of dementia and for evaluating strategies that may reduce risk."
Currently, blood-based biomarkers are not recommended for clinical use in people without symptoms of cognitive impairment. The authors emphasize that further studies are needed to determine how p-tau217 testing might be used routinely and whether early identification can change outcomes meaningfully. Future research will examine how hormone therapy, genetics, and age-related health conditions interact with plasma p-tau217 over time.
"Ultimately, the goal is not just prediction," Shadyab added, "but using that knowledge to delay or prevent dementia altogether."
