Plasma p-tau217 levels helped estimate 5- and 10-year cognitive impairment risk in older adults without memory or thinking symptoms.
A plasma phosphorylated tau 217 (p-tau217) test may help estimate the long-term risk of cognitive impairment among older adults without memory or thinking symptoms, according to a pooled analysis of nearly 2700 participants presented at the Alzheimer’s Association International Conference 2026 and published simultaneously in JAMA.1,2
Adults with p-tau217 concentrations more than twice the study average had an estimated 38% risk of cognitive impairment within 5 years and a 78% risk within 10 years. “Our findings provide some of the clearest evidence yet that elevated p-tau217 levels may help detect dementia risk years earlier—even in adults with no noticeable memory or thinking problems,” lead author Rachel F. Buckley, PhD, of Mass General Brigham and Harvard Medical School, said in a press release.
The investigators analyzed data from 6 Alzheimer disease research cohorts and clinical trials. Participants were cognitively unimpaired at blood collection, had an average age of 70 years, and were followed for a mean of nearly 5 years; some had more than 10 years of follow-up.1
Participants underwent longitudinal assessments of memory, cognition, daily functioning, and clinical status. The outcome was progression to cognitive impairment, defined as mild cognitive impairment, dementia, or consecutive Clinical Dementia Rating scores of 0.5. Statistical models estimated absolute risk at 2, 5, and 10 years.
Risk increased across p-tau217 levels. Participants with moderately elevated concentrations—described as slightly above the study average—had estimated risks of approximately 15% at 5 years and 45% at 10 years. The association between p-tau217 and cognitive decline was strongest among participants with elevated amyloid-β on positron emission tomography. Investigators also reported that the blood marker contributed prognostic information beyond imaging and genetic testing.1,2
P-tau217 measures a phosphorylated form of tau in blood or cerebrospinal fluid. Tau tangles are a defining pathologic feature of Alzheimer disease and are closely associated with cognitive deterioration; circulating p-tau217 also correlates with cerebral amyloid pathology. The current findings extend its potential role from identifying Alzheimer-associated brain changes to estimating when an asymptomatic person may develop impairment.
Clinically, however, the analysis does not establish p-tau217 as a stand-alone screening test. The reported categories were based on concentrations relative to the study average rather than a universally applicable clinical cutoff. The study also did not demonstrate that biomarker-guided treatment prevents cognitive decline in asymptomatic adults.
Several factors may affect both biomarker concentrations and dementia risk, including age, genetic background, kidney function, obesity, and race and ethnicity. Selection from research cohorts and trials may further limit generalizability to primary care populations. Longer follow-up and validation in more diverse cohorts will be needed before the risk estimates can be applied broadly.
For now, the clearest potential application may be enrichment of prevention trials with participants at higher near-term risk. Future studies must determine assay-specific thresholds, calibration across populations, and whether combining p-tau217 with clinical, genetic, or imaging measures improves decisions sufficiently to justify routine testing.
