Washington University researchers developed clock models based on plasma p‑tau217 to estimate the timing of symptomatic Alzheimer’s disease onset with a margin of error of roughly three to four years. The Nature Medicine study analyzed cohorts from the WashU Knight ADRC and the Alzheimer’s Disease Neuroimaging Initiative, using assays including the PrecivityAD2 test. Investigators likened amyloid/tau accumulation to tree rings and noted that younger brains showed greater resilience, with longer intervals between biomarker positivity and symptom emergence. The models could refine trial enrollment and timing for early interventions, but authors cautioned limited clinical utility for asymptomatic individuals outside research settings today.