Body composition’s effect on the bone–vascular axis of osteoporosis discovered in AI-based CT analysis of COPD patients

Objectives This study aimed to investigate the effect of body composition on the inverse relationship between vertebral bone density (T12 BMD) and total thoracic vascular calcification (TTVC) in patients with chronic obstructive pulmonary disease (COPD). Moreover, we aimed to assess whether intermuscular adipose tissue (IMAT) affects the bone-vascular axis. Materials and methods Chest CT scans of 539 COPD patients from the multicentric prospective COSYCONET study were retrospectively analyzed using AI-based tools for T12 BMD, TTVC, and volumetric body composition. Multivariable linear regression models were built to investigate the effect of conventional body phenotypes (normal, sarcopenic, non-sarcopenic obesity, and sarcopenic obesity). Stepwise interaction model building included T12 BMD, IMAT, their interaction, adding BMI, clinical and metabolic covariates, lung function, physical performance, and age. Results The T12 BMD showed a consistent inverse association with TTVC in all phenotypes, with β = −0.38 ( p < 0.01) in normal nutritional status, β = −0.36 ( p < 0.01) in sarcopenia, and β = −0.24 ( p < 0.01) in non-sarcopenic obesity. However, the phenotype’s significant effect was not confirmed in the interaction model. Age and pack-years were associated with calcification, but IMAT remained independently associated (β = 0.15, 95% CI 0.015–0.28, p = 0.029), while the interaction between T12 BMD and IMAT lost significance once age was included. Conclusion IMAT index was independently associated with TTVC in COPD. The modifying effect of IMAT on the bone-vascular axis was most evident in models without age adjustment, suggesting that the observed interaction may be influenced by age. Key Points Question The interactions between body composition, sarcopenia, arteriosclerosis, and osteoporosis are not fully understood. AI-based CT analysis provides a more holistic picture of multimorbidity in COPD. Findings Intermuscular adipose tissue (IMAT) was independently associated with vascular calcification in stepwise-adjusted models. The interaction of IMAT and bone density is demonstrated but showed age-dependence. Clinical relevance Increased IMAT can capture a vulnerable COPD patient group with metabolic dysregulation and physical frailty, besides vascular aging. Muscle fat infiltration may indicate impaired musculoskeletal health and serve as a marker of arteriosclerosis beyond possible effects of age or BMI.