A simple blood test detecting a specific protein linked to Alzheimer’s disease may help predict future cognitive decline in older adults up to a decade before any noticeable symptoms appear, according to a new study.

The Harvard-led research, presented at the Alzheimer’s Association International Conference in London and simultaneously published in The Journal of the American Medical Association, could transform how doctors assess dementia risk and help patients prepare for the disease.

By measuring a blood biomarker called p-tau217, which tracks the build-up of damaging proteins in the brain, clinicians may soon be able to assess Alzheimer’s risk much like they use cholesterol tests to estimate heart disease risk, researchers say.

ALZHEIMER’S BLOOD TESTS MAY PREDICT SYMPTOMS YEARS IN ADVANCE, BUT EXPERTS URGE CAUTION

In one of the largest analyses of its kind, researchers tracked nearly 2,700 cognitively healthy adults averaging 70 years of age for up to a decade.

They found that symptom-free individuals with very high levels of p-tau217 had an estimated 78% chance of developing cognitive impairment within 10 years, and a roughly one in three chance within five years. Even those with moderately elevated levels faced a 45% risk over a decade.

The p-tau217 protein is a modified form of tau, which forms tangles in the brain and is associated with memory loss. The blood test provided information beyond what standard brain scans and genetic testing can offer, according to the researchers.

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Rachel Buckley, the study’s lead author and an associate professor of neurology at Harvard Medical School, said the findings provide some of the clearest evidence yet that dementia risk can be detected years before memory problems begin.

Even individuals with only moderately elevated levels of the biomarker face a significant 45% risk of cognitive decline over 10 years. (iStock)

“Once verified, these blood tests could be used to recruit patients for clinical trials of treatments to prevent cognitive decline and dementia,” she said in a press release.

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“In the future, when treatments are approved for use early in the disease process, these tests could help guide monitoring, treatment decisions and counseling for patients and families,” Buckley added.

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The researchers cautioned that p-tau217 cannot fully predict an individual’s future on its own. Other factors like age, genetics, kidney function and racial background can also influence biomarker levels and dementia risk.

Researchers found identical, consistent risk patterns across nearly 2,700 participants from six international research groups. (iStock)

The team emphasized the need for longer studies in more diverse groups to perfect these risk estimates.

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Maria Carrillo, chief science officer at the Alzheimer’s Association in Chicago, said that targeting the silent stage of the disease before memory issues arise is where future treatments could have the greatest impact.

“Identifying people at risk earlier could fundamentally change how we diagnose, treat and potentially prevent dementia,” she told Fox News Digital, noting that earlier detection could allow people to begin interventions before symptoms develop.