A study of 1,350 adults in their 50s and 60s found that people with elevated Alzheimer’s blood biomarkers had already shown much steeper cognitive decline over the previous five years — with the risk of a rapid drop reaching roughly four times higher, depending on which cognitive skill was measured. The findings, published in The Lancet and summarized by the NIH, come from researchers at UC San Francisco studying a long-running health cohort. None of the participants had been diagnosed with dementia.
What the Researchers Measured
Researchers drew on the NIH-funded CARDIA study, which has followed the same group of adults since the 1980s. Between 2020 and 2022 — the study’s Year 35 exam — the team drew blood from 1,350 CARDIA participants, all between ages 53 and 69, and compared the results with each person’s cognitive test scores from that same visit, as well as from the Year 30 exam roughly five years earlier.
The blood tests measured tau and amyloid-beta, the same two proteins that form tangles and plaques in the brains of people with Alzheimer’s disease. Detecting them through a blood draw is far less invasive than a spinal tap or a PET brain scan, the two methods typically used to confirm these changes today.
How Common Are High Alzheimer’s Blood Biomarkers?
It’s worth separating two numbers that easily get blurred together. Looking at the three biomarkers individually, NIH’s summary reported that between 4% and 15% of participants had levels high enough in at least one marker to suggest Alzheimer’s-related changes in the brain. UCSF, meanwhile, focused on participants who had high levels of amyloid and tau together — the specific combination considered a clearer hallmark of Alzheimer’s pathology — and found that applied to about 6% of the group. Both figures come from the same dataset; they’re just measuring different things, so neither one alone tells the full story.
Current Scores vs. the Five Years Before the Blood Draw
Two different kinds of results came out of this study, and they shouldn’t be conflated. At the time of the blood draw, participants with high biomarker levels already scored lower on tests of processing speed — how quickly the brain reacts to new information — and executive function, which covers planning, organizing, and staying on task.
Separately, when researchers looked back at the same participants’ cognitive scores from the Year 30 exam roughly five years earlier, the high-biomarker group had already gone through a distinctly steeper decline over that stretch: up to about 4.3 times the risk of a rapid drop in verbal memory, and up to about 4 times the risk of a rapid drop in processing speed, compared with participants whose biomarker levels were normal. That’s decline that had already happened by the time of the blood draw — not a forecast of what’s still ahead.
What This Does — and Doesn’t — Mean
A high biomarker result is a flag, not a diagnosis. Since 2025, the FDA has cleared a small number of blood tests — most recently one from Roche in August 2026 — to help diagnose Alzheimer’s in adults 55 and older who already have symptoms or signs of cognitive decline. None of them are cleared as a screening test for people who feel fine. Senior researcher Kristine Yaffe, MD, of UCSF has also cautioned that false positives are possible, and that these tests catch only Alzheimer’s-related pathology, not the many other conditions responsible for an estimated 60% to 70% of all dementia cases.
“Alzheimer’s disease pathology begins years before symptoms emerge,” Yaffe said.
The Takeaway for Midlife Women
A test that flags Alzheimer’s blood biomarkers years before symptoms start could eventually reshape brain-health checkups — but it isn’t there yet, and even once it is, a single result won’t function as a stand-alone forecast. What’s already well established is that a meaningful share of dementia risk is modifiable. Yaffe’s separate research has estimated that addressing factors like physical inactivity, poor sleep, depression, smoking, and cardiovascular health could delay or prevent as much as 40% of dementia cases.
For women navigating their 40s, 50s, and 60s, that’s the more actionable message for now: cardiovascular health, blood sugar, sleep quality, and staying physically and mentally active remain the levers within reach, regardless of what a future biomarker test might eventually show.
Common Questions
Can I get this blood test today?
A few blood tests for amyloid and tau are FDA-cleared, but only to help diagnose adults 55 and older who already have symptoms of cognitive decline. They aren’t cleared to screen people without symptoms, which is the population this study focused on.
Does having high biomarker levels mean I’ll develop Alzheimer’s?
Not necessarily. A high biomarker level reflects biological changes associated with Alzheimer’s, but genetics, cardiovascular health, and lifestyle factors all continue to shape whether — and how — someone experiences cognitive decline.
Why study people who don’t have any symptoms yet?
Because Alzheimer’s-related brain changes appear to begin decades before diagnosis. Researchers want to know whether catching those changes early creates a window for intervention.
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This article is for informational purposes only and is not a substitute for professional medical advice. Talk to your doctor about any concerns regarding your cognitive or brain health.