Radiographically-Measured Sarcopenia Predicts Hospitalization in Patients With Crohn's Disease

Introduction: Sarcopenia (SP) is a measure of body composition. It is increasingly recognized as a poor prognostic factor in clinical outcomes, predicting the need for surgery in patients with Crohn's disease (CD). However, the role of SP in other CD-related outcomes remains unclear. Methods: We retrospectively identified adult patients (≥18 years) with CD who were evaluated at our outpatient tertiary care center between 2017-2020 and underwent CT scan within 3 months of their visit. Using CT cross-sectional measurements at the L3 vertebral level, we quantified visceral, subcutaneous, and intermuscular adipose tissue area as well as skeletal muscle area (SMA; the sum of psoas, quadratus lumborum, erector spinae, and abdominal wall muscle areas, Figure 1). SMA was indexed to height as skeletal muscle index (SMI) and SP was defined as SMI < 25th percentile of the study population of men and women. Sarcopenic obesity (SO) was concomitant SP and body mass index (BMI) >30. We collected data on patient demographics, comorbidities, CD phenotype, and outcomes including hospitalization at 1 year. Categorical variables were compared using Chi-squared and Fisher's exact test and continuous variables using independent t-tests. Multivariate logistic regression was used to determine odds ratios (ORs) with 95% confidence intervals (CIs). Results: Fifty-nine patients with CD were included, mean age of 54.5 years ±16.8. Overall 54.2% (32/59) of patients were women with average SMI of 42.1±7.1 cm2/m2 vs 51.0±9.4 for men. Overall, 25.4% (15/59) of patients had SP and of these 13.3% (2/15) had SO. In univarate analysis, patients with SP were more likely to require inpatient antibiotics at 1 year (50.0% vs 10.0% for non-SP patients, P< 0.05) and have penetrating CD phenotype (20.0% vs 2.3% for non-SP, P< 0.05). On multivariate regression, higher BMI (OR 1.23 [95% CI 1.00-1.51], P=0.05) and lower SMI were associated with increased odds of hospitalization, with each 1 unit increase in SMI conferring 0.80 lower odds of hospitalization (OR 0.80 [95%CI 0.68-0.93], P< 0.01). CD onset at >17 years old was associated with lower odds of hospitalization (age-of-onset 17-40 years OR 0.05 [95%CI 0.003-0.85, P< 0.05] and > 40 years OR 0.04 [95%CI 0.001-0.95, P< 0.05]). Conclusion: In patients with CD, radiographically-measured SP and higher BMI were independently associated with increased odds of hospitalization at 1 year. These body composition metrics may serve as important markers of disease status and prognosis.Figure 1.: Visualization of CT image segmentation at L3 vertebral level used to perform quantification of body composition.