A simple blood test might help predict a woman’s risk of dementia up to 25 years before any symptoms start, a new study suggests.
The blood test looks for elevated levels of a protein known as phosphorylated tau 217 (p-tau217) that can reveal brain plaques tied to Alzheimer’s disease, the most common cause of dementia.
For the study, researchers tested for this protein in blood samples provided by about 2,800 cognitively healthy women ages 65 to 79. Over a follow-up period of up to 25 years, just over 1,300 of the women developed dementia or mild cognitive impairment, a potential precursor to dementia.
“Our study suggests we may be able to identify women at elevated risk for dementia decades before symptoms emerge,” says the lead study author, Aladdin Shadyab, PhD, MPH, an associate professor of public health and medicine at the University of California in San Diego.
“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,” Dr. Shadyab says.
Blood Tests Were Better Predictors of Risk for Certain People
The study suggests that not all women have the same risk of mild cognitive impairment or dementia based on elevated levels of p-tau217 in their blood.
Higher levels of this protein were more strongly linked to poorer cognitive outcomes in women over 70 years old than in younger study participants. Elevated protein levels were also a better predictor of dementia risk in women who had a genetic predisposition for Alzheimer’s than in women without a genetic risk factor.
In addition, higher protein levels in the blood were a stronger predictor of dementia risk in women who took hormone therapy for menopause combining both estrogen and progestin than in women who didn’t use hormones.
But the study wasn’t designed to determine whether or how hormone therapy use might directly impact levels of p-tau217 in the blood or dementia risk, Shadyab says. More research is needed in this area.
Risk With Hormone Therapy
It’s important to note that the higher risk of cognitive decline associated with hormone therapy in this study was found in women who started hormones after age 65, says JoAnn Manson, MD, MPH, DrPH, a professor at Harvard Medical School and the chief of preventive medicine at Brigham and Women’s Hospital in Boston.
“This risk would not be expected among women starting estrogen therapy early in menopause,” Dr. Manson says. “Prior research suggests a neutral or beneficial effect of hormone therapy on cognition in younger women.”
Blood Test Could Be ‘Game-Changing’ in Predicting Dementia Risk
Shadyab says blood-based biomarker tests are less invasive and more precise than other ways of identifying dementia risk, such as spinal taps or brain scans. While they’re not ready to be used for screening just yet — they aren’t approved or recommended for younger people or individuals who are symptom-free — Manson says the latest results are promising.
“This is one of the largest studies to demonstrate that p-tau217 blood levels can successfully predict future risk of cognitive impairment and dementia,” Manson says. “The availability and accessibility of this simple blood test will be game-changing in this field.”