Discovering the Physio-Pathological Mechanisms of Interaction between Bone Mineral Density, Muscle Mass, and Visceral Adipose Tissue in Female Older Adults through Structural Equation Modeling

This study aims to examine the relation between visceral adipose tissue (VAT), as a proxy for metabolically unhealthy obesity, muscle, as a proxy for muscle quality and sarcopenia, and bone, as a proxy for bone mineral density and osteoporosis. Other variables, such metabolic syndrome, nutritional status, number of diseases, kidney and liver function and inflammation were assessed as direct or indirect effects. This study used structural equation modeling (SEM) in a sample of 713 older women (mean age 82.1 ± 6.3). The results indicate a positive statistically significant association between bone and muscle mass (β = 0.195, <0.001) and nutritional status and muscle mass (β = 0.139 , p < 0.001), but negative association between age with muscle mass (β = −0.509, p < 0.001) and nutritional status (estimates: −2.264, p < 0.001). A negative association between VAT and muscle mass was also reported (β = −1.88, p < 0.001). A negative statistically significant association was reported between bone mineral density and functional status (β = −1.081, p < 0.001), and a positive association between functional status and muscle mass (β = 9.000, p < 0.001). In addition, functional status was positively statistically associated with cognitive performance (β = 0.032, p < 0.001). The SEM method demonstrates that the VAT, muscle mass and bone mineral density are associated, but the form of the relation is different in relation to different factors, such as nutritional status, mental and functional status, age, and number of pathologies, having different impacts on metabolic outcomes. SEM is a feasible technique for understanding the complex mechanisms of frailty in the elderly.