The impact of APOE ε4 in Alzheimer's disease: a meta-analysis of voxel-based morphometry studies.

Background: Alzheimer's disease (AD) is the most prevalent form of dementia, exerting substantial personal and societal impacts. The apolipoprotein E (APOE) ε4 allele is a known genetic factor that increases the risk of AD, contributing to more severe brain atrophy and exacerbated symptoms. Purpose: We aim to provide a comprehensive review of the impacts of the APOE ε4 allele on brain atrophy in AD and mild cognitive impairment (MCI) as a transitional stage of AD. Methods: We performed a coordinate-based meta-analysis of voxel-based morphometry (VBM) studies to identify the patterns of grey matter atrophy in APOE ε4 carriers vs. non-carriers. We obtained coordinate-based structural magnetic resonance imaging (MRI) data for 1135 individuals from 12 studies on PubMed and Google Scholar that met our inclusion criteria. Results: We found significant atrophy in the hippocampus and parahippocampus of APOE ε4 carriers compared to non-carriers, especially within the AD and MCI groups, while healthy controls showed no significant atrophy in these regions. Conclusion: Our meta-analysis sheds light on the significant link between the APOE ε4 allele and hippocampal atrophy in both AD and MCI, emphasizing the allele's critical influence on neurodegeneration, especially in the hippocampus. Our findings contribute to the understanding of the disease's pathology, potentially facilitating progress in early detection, targeted interventions, and personalized care strategies for individuals with the APOE ε4 allele who are at risk for Alzheimer's Disease.