Blood Test May Predict Dementia Risk Decades in Advance

Researchers at the University of California, San Diego, have identified a blood marker, phosphorylated tau 217 (p-tau217), that could predict the risk of developing dementia up to 25 years before symptoms manifest. Their study, published in JAMA Network Open, analyzed data from 2,766 participants in the Women’s Health Initiative Memory Study, which followed older women with normal cognitive function for as long as 25 years. The findings indicate that higher levels of p-tau217 correlate with an increased likelihood of developing mild cognitive impairment or dementia, particularly in women over the age of 70 and those carrying the APOE ?4 genetic variant.

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The study suggests that p-tau217 reflects early Alzheimer’s-related changes in the brain. As noted by Aladdin H. Shadyab, the first author of the study, this long lead time for risk identification could facilitate earlier prevention strategies and more targeted monitoring. Linda K. McEvoy, the senior author, emphasized the advantages of blood-based biomarkers like p-tau217, stating they are less invasive and potentially more accessible than traditional diagnostic methods such as brain imaging or spinal fluid tests. However, the researchers caution that blood-based biomarkers are not yet recommended for clinical use in asymptomatic individuals, highlighting the need for further studies to evaluate their effectiveness in routine care.

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The study also revealed differences in p-tau217 levels between white and Black women, although combining these levels with age improved prediction accuracy across both demographics. This nuance underscores the importance of considering genetic and demographic factors in dementia risk assessments.

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The potential of blood tests for early dementia detection aligns with broader efforts to diagnose Alzheimer’s disease at its earliest stages. Recent advancements include the approval of two biomarker tests by the Food and Drug Administration for diagnosing Alzheimer’s in symptomatic individuals. Research is ongoing to determine if these tests can identify at-risk individuals before cognitive decline occurs. Dr. Eric Reiman, chief executive of the Banner Alzheimer’s Institute, noted that while amyloid plaques can appear up to 20 years prior to symptoms, tau tangles, which are more damaging, typically emerge closer to the onset of cognitive impairment.

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The goal of ongoing research is not only to predict dementia but also to explore how early detection can lead to interventions that delay or prevent the disease. Future studies will investigate the interactions between hormone therapy, genetics, and age-related health conditions with plasma p-tau217 levels over time.

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The researchers stress the importance of further investigation into the clinical applications of p-tau217 testing. Shadyab stated, “Ultimately, the goal is not just prediction, but using that knowledge to delay or prevent dementia altogether.”

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While the study presents promising findings regarding p-tau217, it is important to note that blood-based biomarkers are still under evaluation, and their clinical utility remains to be fully established. There are also ongoing discussions about the accuracy and reliability of existing tests, as highlighted by varying perspectives on their effectiveness in predicting dementia risk.

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• “Our study suggests we may be able to identify women at elevated risk for dementia decades before symptoms emerge,” — Aladdin H. Shadyab, PhD, MPH

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• “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,” — Linda K. McEvoy, PhD

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• “We think of tau tangles and neurodegeneration as the raging fire that does the most damage in people with Alzheimer’s disease,” — Dr. Eric Reiman, Chief Executive, Banner Alzheimer’s Institute

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