By Naveen Athrappully
Contributing Writer
A simple blood test opens the possibility of helping to predict dementia in women by up to 25 years before the onset of symptoms, according to a March 10 peer-reviewed study published in the JAMA Network Open journal.
Researchers analyzed health data of 2,766 older women recruited into the Women’s Health Initiative Memory Study between 1996 and 1999. The participants were 65-79 years old and cognitively unimpaired at the time of recruitment.
These women were assessed for up to 25 years through 2021. Their fasting blood was collected during recruitment and stored. Blood samples were then analyzed in 2024 for plasma p-tau217, a type of protein that indicates early brain changes associated with Alzheimer’s.
Among the 2,766 participants, 1,311 women were found to have eventually developed mild cognitive impairment or dementia. Alzheimer’s is the most common form of dementia.
“Higher plasma p-tau217 was associated with incident MCI or dementia for up to 25 years of follow-up,” according to the study. “We observed a threefold higher hazard of all-cause dementia with higher baseline p-tau217 levels.”
“We found that the association of p-tau217 with MCI or dementia was greater among women older than 70 years and among APOE ε4 carriers.” APOE ε4 is a gene allele that is the strongest genetic risk factor for late-onset Alzheimer’s.
The association between p-tau217 and dementia was identified to be larger in magnitude among women who took estrogen plus progestin hormone replacement therapy compared with a placebo group, the researchers wrote.
P-tau217 was discovered to have a stronger association with MCI or dementia among white women compared with Black women.
“These findings suggest that age, race, APOE ε4, and HT [hormone therapy] use should be considered when examining associations of p-tau217 with cognitive outcomes,” the study said. “Our results support the value of plasma p-tau217 as an easily measured biomarker for future MCI or dementia.”
The study was funded by the National Institute on Aging and, in part, by the Intramural Research Program of the National Institutes of Health. One researcher revealed conflicts of interest, including receiving personal fees from biotech company Biogen, pharmaceutical giant Merck, and health care company Roche. Three other researchers also disclosed conflicts of interest.
Currently, blood-based biomarkers are not recommended for clinical use among individuals with no symptoms of cognitive impairment, according to a March 10 post from the University of California San Diego, whose researchers were part of the study.
“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, senior author of the study. “This is important for accelerating research into the factors that affect risk of dementia and for evaluating strategies that may reduce risk.”
Aladdin H. Shadyab, first author of the study, said the ability to identify women who are at risk of dementia decades before symptoms emerge “opens the door to earlier prevention strategies and more targeted monitoring, rather than waiting until memory problems are already affecting daily life.”
‘Not a Prediction’ of Future Dementia
In a comment on the study submitted to the Science Media Center, a charity that seeks to provide accurate and evidence-based information about science and engineering, Richard Unwin, professor of disease proteomics at the University of Manchester, criticized the study for claiming that it can predict dementia.
“The blood test does not ‘predict’ dementia early as one would commonly understand it; if you get a result above a certain level, it does not tell you if you are, or not, going to develop dementia with any degree of accuracy,” Unwin wrote.
The researchers show that “if you have substantially above-average levels of pTau217 then you are more likely to develop dementia than someone with lower levels,” the professor said. While this is useful information, it is “not a prediction of a future dementia diagnosis.”
Dr. Ivan Koychev, clinical associate professor in neuropsychiatry at Imperial College London, called the study a “well conducted” one that adds to the growing body of evidence of p-tau217 being linked to future Alzheimer’s disease.
However, “it is also important to note that mild cognitive impairment is not dementia, and many people with MCI do not go on to develop dementia. In studies like this, combining MCI and dementia as a single outcome can make the association appear stronger,” Koychev wrote.
“MCI represents a risk state rather than established disease, so interpreting results as prediction of dementia needs caution, particularly when considering how such biomarkers might be used in real world clinical decision making.”
According to the Alzheimer’s Association, more than 7 million Americans are living with the illness, a number that is projected to jump to almost 13 million by 2050.
In 2025, health and long-term care costs associated with people living with dementia was estimated to be $384 billion. By mid-century, this is expected to climb to nearly $1 trillion.
In an August 2024 report, the Centers for Disease Control and Prevention said that the early symptoms of Alzheimer’s tend to appear after the age of 60, with the risk increasing with age. While younger people can also get Alzheimer’s, this is less common.
Symptoms of Alzheimer’s include memory loss that disrupts daily life, misplacing things and being unable to retrace steps to find these items, difficulty completing tasks, poor judgment, and trouble handling money or paying bills, according to the CDC.
While the actual causes of Alzheimer’s are not fully understood, some key factors may include genes, lifestyle behaviors and family history.
