Abstract
BACKGROUND: Biomarkers play an important role in the diagnosis of early-stage Alzheimer disease (AD), with the hippocampal emerging as the most reliable indicator of AD pathology. Elucidation of the patient's left and right hippocampal volumes warrants further consideration. Therefore, caution should be exercised regarding the constraints inherent in the measurement method. This meta-analysis aimed to determine the left and right hippocampal volume changes and the volume measurement method. METHODS: The PubMed, Web of Science, and Scopus databases were searched and published until September 2023. A total of 29 studies were included in this meta-analysis. RESULTS: The meta-analysis results indicate a significant reduction in total hippocampal volume in AD patients. The results for the hippocampal volume on the left and right sides of 3 classes, such as AD, mild cognitive impairment (MCI), and normal control (NC), showed a greater reduction on the left side. The results showed in AD: 95% confidence interval (CI) = -142 to 1.61, P = .04, I2 = 44%; MCI: 95% CI= -186 to -72, P = <.00001, I2 = 0%, and NC: 95% CI = -141 to 14, P = .11, I2 = 80%, respectively, with random effect. The left hippocampal in AD is smaller, while the right hippocampal is larger. The AD class significantly reduced hippocampal volume on both the left and right sides. CONCLUSION: Notably, automatic segmentation methods impact hippocampal volume measurements, with results potentially relying heavily on their correlation with the manual labeling process.