🧠 A Blood-Based Clock for Alzheimer's Symptom Onset

🧠 Can a simple blood test tell us when Alzheimer's symptoms will begin?   A new Nature Medicine study introduces a plasma p-tau217 "molecular clock" that estimates time to symptom onset with an error margin of ~3–4 years. By modeling the rise of phosphorylated tau in cognitively unimpaired individuals, investigators move from predicting if to predicting when.   ⏳ Implication: smarter prevention trials, earlier intervention windows, and biologically timed enrollment.   ⚠️ Not ready for routine screening—but a compelling proof of concept.   The era of temporal precision in neurodegeneration may have begun.