Community‐living persons volunteered for participation in longitudinal studies at the Knight Alzheimer Disease Research Center (Knight ADRC) at Washington University. Both cognitively unimpaired and cognitively impaired participants were eligible for and agreed in principle to undergo amyloid positron emission tomography (PET) and lumbar puncture (LP) to obtain cerebrospinal fluid (CSF) for assays of amyloid beta (Aβ) and tau proteins, among other analytes. All participants underwent clinical and cognitive assessments using the Uniform Data Set (UDS), 21 which includes interviews with a study partner who knows the participant well (generally the spouse or other relative) to enable scoring of the CDR and the determination of the likely etiological diagnosis of the cognitive impairment, if present, in accordance with standard criteria. 21 Exclusion criteria for Knight ADRC participants include the inability to speak English and medical or psychiatric disorders that preclude longitudinal participation (e.g., dialysis for end‐stage renal disease). For this study, we selected participants who met criteria similar to those enrolled in recent clinical trials of anti‐amyloid antibodies 1 , 2 : participants had a clinical diagnosis of AD dementia in
