PROJECT SUMMARY Dementia due to Alzheimer’s disease is a global health crisis that is intensified by the absence of disease modifying treatments. The failure of past clinical trials in Alzheimer’s disease has been due in part to late initiation of treatment and inaccurate screening for study inclusion. In clinical settings, there are numerous causes of cognitive decline in aging and treatment and prognosis vary depending on the underlying etiology. Current methods of screening for Alzheimer’s pathology include cerebrospinal fluid analysis and positron emission tomography, both of which are not widely accessible. For both the research lab and the clinic, development of an accessible and accurate early marker of Alzheimer’s pathology is essential. Recent technological advances in highly sensitive single-molecule array techniques have created the opportunity to accurately measure phosphorylated tau (p-tau), a pathological hallmark of Alzheimer’s disease, in the blood. Plasma p-tau has emerged as a leading blood-based Alzheimer’s biomarker, showing strong correlations with other markers of Alzheimer’s pathology, distinguishing clinical Alzheimer’s disease from other dementia subtypes, and accurately predicting post-mortem Alzheimer’s pathology. Plasma p-tau has shown tremendous potential, yet existing research has largely focused on establishing the sensitivity and specificity of this biomarker for Alzheimer’s disease; its ability to predict more clinically meaningful longitudinal outcomes remains in question. The proposed research will examine baseline plasma p-tau in a longitudinal cohort study of aging as it relates to longitudinal neurodegeneration and clinical outcomes over a 9-year follow-up period. Highly clinically relevant outcomes were selected, including neurodegeneration, domain-based cognition, subjective cognitive decline, and functional abilities for activities of daily living, to maximize the potential of this biomarker being meaningfully integrated into clinical care. The proposed research will leverage the rich resources of the Vanderbilt Memory & Alzheimer’s Center, Vanderbilt University Institute of Imaging Science, and the Clinical Neurochemistry Laboratory of Sahlgrenska University Hospital, Sweden. The research will be guided by an interdisciplinary mentorship team, including experts in geriatric neuropsychology, Alzheimer’s disease, magnetic resonance imaging, subjective cognitive decline, fluid biomarkers, clinical management of abnormal cognitive aging, and statistical analysis. The parallel training plan will facilitate the candidate’s acquisition of the necessary knowledge and skills to study blood-based Alzheimer’s biomarkers and propel him into a successful career as an independent clinician-scientist. Understanding the predictive validity of plasma p-tau for clinically relevant outcomes would provide essential information that is necessary for the further development of this biomarker as a tool for clinical trial enroll...