Association of Presynaptic Loss with Alzheimer's Disease and Cognitive Decline

Objective Increased presynaptic dysfunction measured by cerebrospinal fluid (CSF) growth-associated protein-43 (GAP43) may be observed in Alzheimer's disease (AD), but how CSF GAP43 increases relate to AD-core pathologies, neurodegeneration, and cognitive decline in AD requires further investigation. Methods We analyzed 731 older adults with baseline beta-amyloid (A beta) positron emission tomography (PET), CSF GAP43, CSF phosphorylated tau181 (p-Tau(181)), and F-18-fluorodeoxyglucose PET, and longitudinal residual hippocampal volume and cognitive assessments. Among them, 377 individuals had longitudinal F-18-fluorodeoxyglucose PET, and 326 individuals had simultaneous longitudinal CSF GAP43, A beta PET, and CSF p-Tau(181) data. We compared baseline and slopes of CSF GAP43 among different stages of AD, as well as their associations with A beta PET, CSF p-Tau(181), residual hippocampal volume, F-18-fluorodeoxyglucose PET, and cognition cross-sectionally and longitudinally. Results Regardless of A beta positivity and clinical diagnosis, CSF p-Tau(181)-positive individuals showed higher CSF GAP43 concentrations (p < 0.001) and faster rates of CSF GAP43 increases (p < 0.001) compared with the CSF p-Tau(181)-negative individuals. Moreover, higher CSF GAP43 concentrations and faster rates of CSF GAP43 increases were strongly related to CSF p-Tau(181) independent of A beta PET. They were related to more rapid hippocampal atrophy, hypometabolism, and cognitive decline (p < 0.001), and predicted the progression from MCI to dementia (area under the curve for baseline 0.704; area under the curve for slope 0.717) over a median 4 years of follow up. Interpretation Tau aggregations rather than A beta plaques primarily drive presynaptic dysfunction measured by CSF GAP43, which may lead to sequential neurodegeneration and cognitive impairment in AD or neurodegenerative diseases. ANN NEUROL 2022