CT-derived body composition: Differential association with disease, age and inflammation in a retrospective cohort study

Background Low skeletal muscle mass and density, as assessed by CT-body composition (CT-BC), are recognised to have prognostic value in non-cancer and cancer patients. The aim of the present study was to compare CT-BC parameters between non-cancer (abdominal aortic aneurysm, AAA) and cancer (colorectal cancer, CRC) patients. Methods Two retrospective multicentre cohorts were compared. Thresholds of visceral fat area (VFA, Doyle), skeletal fat index (SFI, Ebadi), skeletal muscle index (SMI, Martin), and skeletal muscle density (SMD, Martin) were applied to these cohorts and compared. The systemic inflammatory response (SIR) was measured by the systemic inflammatory grade (SIG). Results 1695 patients were included; 759 patients with AAA and 936 patients with CRC. Low SMD (33% vs. 66%, p <0.001) was more prevalent in the CRC cohort. Low SMI prevalence was similar in both cohorts (51% vs. 51%, p = 0.80). Compared with the AAA cohort, the CRC cohort had a higher prevalence of raised SIG (p <0.001). Increasing age (OR 1.54, 95% CI 1.38-1.72, p < 0.001) and elevated SIG (OR 1.23, 95% CI 1.09-1.40, p = 0.001) were independently associated with increased odds of low SMI. Increasing age (OR 1.90, 95% CI 1.66-2.17, p < 0.001) CRC diagnosis (OR 5.89, 95% CI 4.55-7.62, p < 0.001), ASA > 2 (OR 1.37, 95% CI 1.08-1.73, p = 0.01), and elevated SIG (OR 1.19, 95% CI 1.03-1.37, p = 0.02) were independently associated with increased odds of low SMD. Conclusions Increasing age and systemic inflammation appear to be important determinants of loss of skeletal muscle mass and quality irrespective of disease.