Smaller medial temporal lobe volumes in individuals with subjective cognitive decline and biomarker evidence of Alzheimer's disease-Data from three memory clinic studies

Introduction: Previous studies showed associations of brain volume differences and biomarker evidence for Alzheimer's disease (AD) in subjective cognitive decline (SCD). The consistency of this finding across SCD studies has not been investigated. Methods: We studied gray matter volume differences between SCD subjects with and without cerebrospinal fluid biomarker evidence for AD across three European memory clinic samples (German Center for Neurodegenerative Diseases Longitudinal Cognitive Impairment and Dementia study, Amsterdam, Barcelona). Analysis of covariance models with samples and cerebrospinal fluid biomarkers as between-subject factors were calculated. Results: A significant main effect for AD biomarker (Aβ42- > Aβ42+) in the left medial temporal lobe (MTL) was found, with the absence of main effects for sample or interaction effects between AD biomarker and sample. This indicates consistent lower left MTL volume across three samples in SCD subjects with abnormal Aβ42 levels. Discussion: Our results support the model that in the presence of AD pathology, SCD corresponds to the late preclinical stage (stage 2 of AD) with smaller MTL volumes.