Time between milestone events in the Alzheimer's disease amyloid cascade.

Abstract Objective Estimate the time-course of the spread of key pathological markers and the onset of cognitive dysfunction in Alzheimer's disease. Methods In a cohort of 335 older adults, ranging in cognitive functioning, we estimated the time of initial changes of Aβ, tau, and decreases in cognition with respect to the time of Aβ-positivity. Results Small effect sizes of change in CSF Aβ42 and regional Aβ PET were estimated to occur several decades before Aβ-positivity. Increases in CSF tau occurred 7–8 years before Aβ-positivity. Temporoparietal tau PET showed increases 4–5 years before Aβ-positivity. Subtle cognitive dysfunction was observed 4–6 years before Aβ-positivity. Conclusions: Increases in tau and cognitive dysfunction occur years before commonly used thresholds for Aβ-positivity. Explicit estimates of the time for these events provide a clearer picture of the time-course of the amyloid cascade and identify potential windows for specific treatments.