New blood test accurately predicts dementia risk a decade early

In recent years, scientists have worked hard to find better ways to detect dementia, including Alzheimer's disease, long before it shows up through memory loss or confusion. A new study gives hope that simple blood tests might help predict these diseases many years before they begin. Instead of relying on more invasive procedures like brain scans or spinal taps, researchers now believe that blood could hold the key to early detection.

In a long-term study based in Sweden, researchers tracked over 2,100 adults aged 60 and older for up to 16 years. None of the participants had dementia when the study began. Scientists wanted to test whether certain proteins in their blood—known as biomarkers—could predict who would develop dementia, including Alzheimer’s disease, over the next decade.

These biomarkers included proteins linked to brain damage and disease. They measured levels of amyloid-β 42 and amyloid-β 40 (used as a ratio), phosphorylated tau proteins (p-tau181 and p-tau217), total tau (t-tau), neurofilament light chain (NfL), and glial fibrillary acidic protein (GFAP). These proteins are closely tied to Alzheimer’s pathology and brain changes.

By the end of the 10-year follow-up, 17% of the people had developed dementia. The most promising biomarkers—p-tau217, NfL, and GFAP—were able to predict future dementia with up to 83% accuracy. This high level of accuracy shows that blood-based testing could become a valuable tool in identifying people at risk years before symptoms start.

“This is an encouraging result, especially considering the 10-year predictive window between testing and diagnosis,” said Giulia Grande, assistant professor at Karolinska Institutet and first author of the study. “It shows that it is possible to reliably identify individuals who develop dementia and those who will remain healthy.”

Until now, most studies on dementia biomarkers focused on people who were already showing signs of cognitive decline. These individuals usually visited memory clinics because of memory loss or confusion. That means past studies might not fully represent how these biomarkers behave in the general population—people who are still healthy but could be at risk later.

This new Swedish study was different. It looked at adults living in the community, not just those already showing problems. This broader group gave researchers a better view of how these blood proteins work across a more typical population. With more than 2,000 participants, the study also had enough size to produce reliable data over a long follow-up.

Blood tests are far easier to perform than other methods like PET scans or spinal fluid collection. They cost less, cause less discomfort, and can be used in regular clinics or even at community centers. If proven effective, these tests could help more people find out about their brain health early, without needing a specialist referral.

Among the proteins studied, three stood out as especially useful: p-tau217, NfL, and GFAP.

Phosphorylated tau (p-tau217) is strongly linked to the tangles that form in the brains of people with Alzheimer's disease. These tangles, along with amyloid plaques, are among the key features of the disease.

Neurofilament light chain (NfL) is a marker of nerve damage. It rises in the blood when neurons in the brain are breaking down.

Glial fibrillary acidic protein (GFAP) signals inflammation and the activation of astrocytes—support cells in the brain that become active during damage.

Each of these biomarkers provides a different type of information about what might be happening inside the brain. When used together, they give a clearer picture of whether the brain is starting to change in ways that lead to dementia.

While the results are promising, the researchers warn against using these tests for widespread screening just yet. Although they can identify people who are likely to remain healthy when the biomarkers are low, high levels don't always mean that a person will get dementia.

“Our findings imply that if an individual has low levels of these biomarkers, their risk of developing dementia over the next decade is minimal,” said Davide Vetrano, senior author of the study and associate professor at Karolinska Institutet. “This information could offer reassurance to individuals worried about their cognitive health, as it potentially rules out the future development of dementia.”

Still, elevated levels of the biomarkers were not perfect at predicting who would definitely develop dementia. This means that a positive result does not guarantee a diagnosis, which could lead to unnecessary worry if the test were used too freely.

“These biomarkers are promising, but they are currently not suitable as standalone screening tests to identify dementia risk in the general population,” Vetrano added.

The team believes combining these biomarkers with other clinical data—like memory tests, genetics, or physical function—might improve prediction in the future. For now, the blood tests are best used in research settings or alongside other tools.

As more studies confirm these findings, blood-based testing for dementia risk may move from research labs into regular clinics. But more work is needed to make sure these tests are reliable, especially across different groups of people and in real-world settings.

“We need to move a step further and see whether the combination of these biomarkers with other clinical, biological or functional information could improve the possibility of these biomarkers to be used as screening tools for the general population,” said Grande.

The researchers point out that early detection doesn’t just give a name to a disease. It opens the door to earlier care, possible treatments, and better planning. If a person knows they are at higher risk, they may be more likely to take part in clinical trials or adjust their lifestyle to protect their brain health.

The study, published in Nature Medicine, was led by scientists from Karolinska Institutet’s Aging Research Center. It involved close partnerships with SciLifeLab and the Royal Institute of Technology in Stockholm. Funding came from the Swedish Research Council, the Swedish Brain Foundation, and other research organizations. The researchers reported no conflicts of interest.

As the science moves forward, these findings could one day change how dementia is diagnosed and treated—not just in hospitals, but also in communities around the world.

Note: The article above provided above by The Brighter Side of News.

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