Body Composition and Disease Activity Correlate in Crohn Disease

Visceral and subcutaneous fat increases while muscle mass decreases over time among patients with Crohn disease (CD), according to study findings published in Diagnostics (Basel).

Researchers in Seoul, South Korea, conducted a retrospective study of 71 patients diagnosed with CD between January 2000 and December 2009 with follow-up through August of 2020 to assess changes in body composition in relation to disease activity levels. They collected data on patient demographics, anthropometric characteristics such as body mass index (BMI), and from at least 2 computed tomography (CT) scans at baseline and at follow-up examinations performed at the following time intervals: 2 to 5 years, 5 to 8 years, and after 8 years. The Simple Endoscopic Score for Crohn Disease (SES-CD) was used to assess disease severity.

In addition to SES-CD, CT scan parameters assessed elements of CD activity, including bowel wall thickness, lesion length, comb sign, intensity of bowel wall enhancement, and pattern of bowel wall enhancement and each parameter was scored between 0 (less severe) to 3 (most severe).

The researchers used these same CT scans to analyze each patient’s body composition including visceral fat area, subcutaneous fat area, and skeletal muscle area. Changes in skeletal muscle area from baseline to follow-up were used to determine onset of sarcopenia based on normative gender measurements (<38.5 cm²/m² for women and <52.4 cm²/m² for men).

At baseline, 95.65% of the patients exhibited active disease inflammation on endoscopy, which decreased with treatment during the respective follow-up time periods (62.96%, 56.82%, and 37.21%, respectively). The CT scan scores started at moderate to severe in 88.7% of patients at baseline and gradually decreased with treatment.

Skeletal muscle index decreased over time (β, -1.8; 95% CI, -2.6 to -1.0; P <.001), while visceral (β, 7.2; 95% CI, 4.9-9.4; P <.001) and subcutaneous (β, 6.5; 95% CI, 4.6-8.5; P <.001) fat areas increased over time. Overall BMI among the study patients decreased slightly from baseline through the follow-up periods (β, -0.8; 95% CI, -1.2 to -0.4; P <.001). Approximately 53.5% of patients developed sarcopenia, and this was more likely to occur in women compared with men (55.3% vs. 6.5%; P <.001).

When analyzing body composition changes in relation to disease activity using both the CT imaging scores and the SES-CD, the researchers observed that the skeletal muscle index and the subcutaneous fat area decreased as disease activity increased (P <.05). Visceral fat area did not correlate with either of the disease activity scores.

Regardless of remission status, visceral and subcutaneous fat areas increased over time. Skeletal muscle index at time of the last follow-up was the sole significant predictor of remission (odds ratio, 1.21; 95% CI, 1.03-1.42; P =.021), with skeletal muscle mass being slightly higher among those who achieved remission (P =.61).

Limitations of the study include the retrospective design, incomplete data, and heterogeneity and inconsistency of CT imaging studies.

The study authors conclude, “Patients with CD showed a gradual increase in fat and a decrease in muscle mass…during the follow-up after treatment. Sarcopenia was associated with higher disease activity, and SMI inversely correlated with disease activity.”