Association of temporal and masseter muscle thickness with cognitive function and clinical severity in Alzheimer's disease: a retrospective study.

Background: Temporal muscle thickness (TMT) has emerged as an imaging marker of skeletal muscle status and may be associated with cognitive decline in Alzheimer's disease (AD). However, its relationship with AD severity remains unclear, and the clinical relevance of masseter muscle thickness (MMT) is unknown. Objective: To evaluate the associations of TMT and MMT with cognitive function and disease severity in AD. Methods: This retrospective study included 242 patients with AD between December 2023 and April 2025. TMT and MMT were measured on axial T1-weighted MRI, cognitive function was assessed using standardized neuropsychological tests, and disease severity was determined by Clinical Dementia Rating (CDR). Results: The intraclass correlation coefficients (ICC) for the mean TMT and MMT were 0.868 and 0.896, respectively, indicating good consistency. As the severity of AD progresses, TMT tends to be thinner in severe AD than in mild AD. Spearman's correlation analysis revealed that both TMT and MMT were correlated with the Mini-Mental State Examination (MMSE) and CDR. After adjusting for various confounding factors using ordered logistic regression and multiple linear regression, TMT was found to be independently associated with AD severity (OR: 0.424, 95% CI: 0.290-0.618, Conclusion: Temporal muscle thickness is associated with cognitive impairment and clinical severity in patients with AD and may serve as a simple, noninvasive imaging marker; in contrast, the independent associations of MMT with disease severity were weak and sex-specific, suggesting that its clinical utility may be limited and requires further validation.