Exploring the Relationship Between Body Composition and Brain Morphology in Aging: A Focus on Thigh Muscle Mass and Subcutaneous Fat as Predictors of Cortical Thickness in Healthy Older Adults

Abstract

Purpose: Subcutaneous fat accumulation has been linked to adverse brain health outcomes. This study examines the relationship between thigh muscle mass, subcutaneous fat distribution, and brain structure in elderly adults. It explores how body composition affects cortical thickness in brain regions linked to cognitive function. Methods or Background: Fifty-four healthy elderly individuals underwent imaging of the right thigh and brain using a 3T Siemens Avanto MRI system. Muscle and subcutaneous fat cross-sectional areas (CSA) were measured at 50% and 20% of thigh length, with the muscle-to-fat ratio calculated at the 50% mark. Cortical thickness was assessed through brain volumetric analysis using Freesurfer 7.4.1 software. Results or Findings: Significant positive correlations (r ≥ 0.2, p ≤ 0.05) were found between the muscle-to-fat ratio and cortical thickness in the left cerebellum, cuneus, and transverse temporal cortex, in the right entorhinal cortex, inferior temporal cortex, postcentral gyrus, superior temporal cortex, and the banks of the superior temporal sulcus (BANKSSTS). Additionally, significant negative correlations (r ≤ -0.2, p ≤ 0.05) were observed between subcutaneous fat CSA at 50% of thigh length and cortical thickness in the left cuneus and entorhinal cortex, in the right BANKSSTS, postcentral gyrus, and superior temporal cortex. Additionally, subcutaneous fat CSA at 20% of thigh length was inversely correlated with cortical thickness in the left cuneus and right BANKSSTS (r ≤ -0.2, p ≤ 0.05). Conclusion: Our findings demonstrate that increased thigh muscle mass correlates with greater cortical thickness in cognitive regions, while elevated subcutaneous fat is linked to reduced thickness. These results highlight the role of body composition in maintaining brain health in the elderly and underscore the importance of muscle mass in mitigating age-related cortical decline. Limitations: With only 54 participants, the study's findings may lack generalizability.