Anthem recently announced coverage of FDA approved Tau217 for Alzheimer diagnostic work-ups.
A new study Buckley et al in JAMA (7/14/26) finds that Tau217 levels map out dementia risk in healthy elders. Here's an AI summary.
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Yes—you will be seeing news stories this week. This is the paper, published online in JAMA on July 14, 2026, alongside its presentation at AAIC 2026 in London:
Buckley RF, Townsend DL, Birkenbihl CJ, et al. “Prognostic Value of Blood-Based P-Tau217 Levels for Progression to Cognitive Impairment.” JAMA. Published online July 14, 2026. doi:10.1001/jama.2026.12556. (JAMA Network)
The biomarker is p-tau217.
The important numerical clarification
Your concern about relative-risk news reporting is exactly right in general—but the 38% and 78% figures in this paper are absolute risks, not relative increases:
| Baseline p-tau217 | 5-year absolute risk | 10-year absolute risk |
|---|---|---|
| Low | 12% | 40% |
| Intermediate | 15% | 45% |
| High | 24% | 62% |
| Very high | 38% | 78% |
Thus, in this study, a “38%” does not mean that a baseline 10% risk becomes 13.8%. (A journalist might have misreported that).
It means that the model estimated roughly 38 of 100 people in the very-high p-tau217 category would reach the study’s cognitive-impairment endpoint within five years. The corresponding low-p-tau217 estimate was 12 of 100. (JAMA Network)
The paper also reported the relative-type statistic you were thinking of: each 1-SD increase in p-tau217 was associated with a hazard ratio of 1.38. But that HR is separate from the 38% absolute five-year risk. (JAMA Network)
Important qualifications
“Healthy elders” here means cognitively unimpaired at baseline, not necessarily a representative sample of ordinary community-dwelling elders. The pooled analysis included 2,684 participants from six research cohorts, with a median age of 69.6; 43% were amyloid-positive, partly because the A4 cohort deliberately enrolled amyloid-positive people. (JAMA Network)
Also, the endpoint was broader than dementia alone. It included:
diagnosed MCI,
dementia, or
two consecutive global CDR scores of at least 0.5.
So the headline is more accurately “risk of developing cognitive impairment” rather than “risk of dementia.” (JAMA Network)
The ten-year figure deserves particular caution: only about 5% of participants had more than ten years of follow-up, and most of those came from one cohort. The 78% estimate had a 95% CI of 69%–84%, but data sparsity and failure to model death as a competing risk make it less secure than the five-year result. (JAMA Network)
So the blood-pressure analogy is reasonable conceptually, but the study’s “very high” p-tau217 category appears more like a marker of substantially advanced preclinical Alzheimer pathology than a modest independent risk factor such as slightly elevated blood pressure. The authors expressly say that the result is currently most useful for prevention-trial enrichment—not for giving an individual cognitively healthy person a clinical ten-year forecast. (JAMA Network)
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The table shows low-Tau risk was 12%, higheset-tau risk was 38%. That's 3X. But were the risk tiers based on quartiles of population or some other distribution?
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They were not quartiles. The four categories were quite unequal because the cut points were anchored to biologically meaningful amyloid-PET Centiloid ranges, rather than chosen to divide the sample into four equal parts.
| Baseline p-tau217 group | Approximate amyloid-PET correspondence | N | Share of 2,684 | 5-year risk | 10-year risk |
|---|---|---|---|---|---|
| Low: <−0.5 SD | <10 Centiloids | 516 | 19.2% | 12% | 40% |
| Intermediate: −0.5 to <1.1 SD | 10–24 Centiloids | 1,087 | 40.5% | 15% | 45% |
| High: 1.1 to <2.5 SD | 25–60 Centiloids | 598 | 22.3% | 24% | 62% |
| Very high: ≥2.5 SD | >60 Centiloids | 483 | 18.0% | 38% | 78% |
Thus, the “very high” result was not based on a tiny extreme tail: it included 483 participants, about one in six. The intermediate group was by far the largest. (JAMA Network)
The thresholds were intended to correspond approximately to:
10 Centiloids: a low amyloid level already associated with measurable cognitive change;
25 Centiloids: a conventional amyloid-positive threshold;
60 Centiloids: a heavier amyloid burden associated with the emergence of neocortical tau pathology. (JAMA Network)
One major qualification: these proportions should not be interpreted as the prevalence of the four categories among ordinary healthy older Americans. This was a pooled collection of selected research cohorts, including the 952-person A4 prevention trial, which specifically required amyloid positivity; overall, 43% of the pooled sample was amyloid-positive. The study therefore had deliberate enrichment for Alzheimer pathology. (JAMA Network)
Also, the endpoint was incident cognitive impairment, not dementia alone. And while the very-high group began with 483 people, only 11 remained under observation and event-free at the 10-year risk-set point, which helps explain why the ten-year estimates deserve much more caution than the five-year numbers.
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Cognitively healthy older adults with high levels of a biomarker called p-tau217 in their blood had an estimated 38% greater chance of developing early signs of dementia over five years, a new study found. S. Lamotte.
Press from MGH
JAMA Network
https://jamanetwork.com/journals/jama/fullarticle/2851720
