Visceral adiposity is negatively associated with bone density and muscle attenuation

Abstract

Background: The storage of adipose tissue in ectopic compartments is a hallmark attribute linking greater body mass index (BMI) with cardiometabolic diseases. Despite ample evidence to confirm that increased visceral adipose tissue (VAT) deposition occurs with obesity, the interrelations between altered fat partitioning and regional muscle and bone quality are less well understood.

Objective: We examined the association between adiposity and spinal muscle and bone quality across a large, heterogeneous cohort of adults.

Design: We identified 8833 thoracic or abdominal computed tomography scans from patients in the University of Michigan Health System who were aged 18-64.9 y. We measured trabecular bone densities, cortical bone densities, VAT areas, and subcutaneous adipose tissue (SAT) areas at vertebral levels T7 to L5. Psoas muscle attenuation (an indicator of fat infiltration in muscle) was measured at the L4 level.

Results: Muscle attenuation as well as trabecular and cortical bone densities revealed negative correlations with BMI, SAT, and VAT. The correlation between BMI and psoas attenuation was -0.321, between BMI and the density of cortical bone was -0.250, and between BMI and trabecular bone was -0.143 (all P < 0.001). However, correlations between VAT and lower muscle attenuation were stronger as were those between VAT and lower bone densities. Inverse correlations between VAT and densities of psoas muscle and cortical and trabecular bone were -0.460, -0.407, and -0.434, respectively (P < 0.001). Even after adjustment for age, sex, and BMI, partial correlations between VAT, muscle attenuation, and bone densities remained significant at -0.250, -0.119, and -0.216, respectively (P < 0.001).

Conclusions: Contrary to previous reports that high body mass is associated with increased bone quality, our data show a significant negative association between BMI and muscle and bone densities, suggesting fat infiltration into these tissues. More importantly, correlations between VAT and decreased bone and muscle densities remained statistically significant even after adjustment for age, sex, and BMI.

Keywords: analytic morphomics; bone density; computed tomography; muscle attenuation; visceral adiposity.

FIGURE 1

Analytic morphomic processing.

FIGURE 2

Scatter plot of bone and muscle densities compared with visceral adiposity area (the y axis is plotted in the log scale).

FIGURE 3

Medians of muscle attenuation and bone densities for different BMI categories and VAT area tertiles (we divided subjects into 5 groups according to standard BMI cutoffs as follows (in kg/m²): <18.5, 18.5–24.9, 25–29.9, 30–39.9, and ≥40). Within each BMI category, we further divided subjects into 3 groups according to tertiles of VAT areas. In each of these 15 subgroups, we presented median Hounsfield units of psoas muscle attenuation, cortical BMD, and trabecular BMD and respective 95% CIs. Low, median, and high represent 3 VAT-area tertile groups. BMD, bone mineral density; VAT, visceral adipose tissue.