A new study found that a simple blood test could predict a woman’s risk of dementia up to 25 years before symptoms appear.
The test measures a protein linked to early brain changes associated with Alzheimer’s disease. The findings were published March 10 in the journal JAMA Network Open.
The study focused on a protein known as phosphorylated tau 217, or p-tau217. Higher levels of this biomarker were strongly associated with future dementia and mild cognitive impairment.
Scientists examined blood samples from 2,766 women who participated in the Women’s Health Initiative Memory Study. The women were aged 65 to 79 in the late 1990s and had no signs of cognitive decline at the start of the study.
Researchers followed the participants for up to 25 years. During that time, some women developed memory or thinking problems, including dementia. The analysis showed that women who had higher levels of p-tau217 in their blood at the start of the study were far more likely to develop dementia later in life.
“Our study suggests we may be able to identify women at elevated risk for dementia decades before symptoms emerge,” said Dr. Aladdin H. Shadyab, associate professor of public health and medicine at UC San Diego and the study’s first author.
“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,” he said.
The study also found that the link between the biomarker and dementia risk was stronger in certain groups.
Women aged 70 and older with elevated p-tau217 levels were more likely to experience poorer cognitive outcomes than younger women at the start of the study. Risk was also higher for women who carried the APOE ε4 gene, which is known to increase the risk of Alzheimer’s disease.
Researchers also observed that the biomarker appeared to be a stronger predictor of dementia among women who had received estrogen plus progestin hormone therapy compared with those who received a placebo during the study.
In addition, the strength of the association varied between white and Black participants. However, researchers found that combining p-tau217 levels with age improved dementia risk prediction for both groups.
Scientists say blood-based biomarkers such as p-tau217 could help detect dementia earlier in the future.
“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 Dr. Linda K. McEvoy, 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,” she said.
Despite the promising results, the researchers caution that blood tests for Alzheimer’s disease are still under investigation. They are not currently recommended for routine screening in people without symptoms.
Shadyab said additional research is needed before the test could be used in everyday clinical care.
“The goal is not just prediction,” he said, “but using that knowledge to delay or prevent dementia altogether.”
The researchers also noted that the study examined only older women. That means the findings may not necessarily apply to men or younger people. Future studies will look at how genetics, hormone therapy, and other health factors interact with the p-tau217 biomarker over time.