To better understand the evolution of AD in its earliest stages, we explored CSF characteristics in patients with symptomatic AD and a cohort of 1149 CN middle-aged individuals (50-75 years) in the Emory Healthy Brain Study (EHBS)22, including a subset of 134 individuals with CSF levels of Aβ42, total Tau (tTau), and phospho181-Tau (pTau) indicative of underlying AD pathology based on a locally-determined cutoff ratio of tTau to Aβ42. Here, MAPT is linked to Alzheimer disease.