Race Is Associated with Fat-free Body Mass but Not Exercise Fitness in a Tertiary Center IBD Cohort

Abstract

Purpose: Patients with inflammatory bowel disease (IBD) tend to have decreased muscle mass when compared to healthy controls. We performed a cross sectional study to determine anthropometric differences, by race, in a tertiary IBD cohort. Methods: Anthropometric testing included fat-free body mass, fat mass, total bone mineral density by dual energy x-ray absorptiometry (DXA), and measurement of body mass index (BMI) and waist-to-hip ratio. Laboratory testing included basic metabolic panel, complete blood count, albumin, lipid panel, and oral glucose tolerance test. Maximal aerobic capacity (VO2max) was measured using maximal effort treadmill testing. Disease activity was measured by the Harvey Bradshaw index (HBI) and the Simple Clinical Colitis Activity index (SCCAI) in participants with Crohn's disease and ulcerative colitis, respectively. Quality of life was assessed using the Short Inflammatory Bowel Disease questionnaire (SIBDQ). Physical activity level was measured by the Instrumental Activities of Daily Living (IADL) questionnaire. Results: Thirty-four participants were studied from June 2010 to July 2011. Fifty-nine percent were female, 24 participants (74%) had CD, and 22 participants (65%) self-identified as Caucasian. “Other” race category (n=12) included participants who self-identified as African-American (n=10), Asian (n=1), or other race (n=1). Mean disease duration was 18.2 (±19.8) years, SIBDQ score was 55.7 ±8.4, HBI score was 1.9 ±2.3, and SCCAI score was 2.1 ±1.9. There was no difference, by race, in IBD diagnosis, smoking status, disease duration, age at diagnosis (less than 40 or ≥40 years of age), HBI, SCCAI, or SIBDQ. Lipid panel, mean percent body fat (31.6%), BMI (mean 24 ±7), waist-to-hip ratio (mean 1.9), and level of physical activity (mean IADL score 7.8, mean VO2 max = 36 mL/kg/min) were similar between groups. Total bone mineral density did not differ between race categories (p = 0.16); there was also no significant difference in VO2max by race (p = 0.43) or DEXA total body fat by race (p= 0.54). Caucasians had greater fat-free body mass (57.4 ±15.2) by DXA compared to participants in the other race category (41.8 ±4.5) (p = 0.03). Mean fat-free mass did not differ by IBD diagnosis, age at diagnosis, or gender. Mean fat-free mass stratified by gender did not differ between race groups (p =0.20). Conclusion: Non-white (primarily African-American) patients have decreased fat-free mass compared to Caucasian patients, despite comparable levels of disease activity, physical activity, and maximal aerobic capacity. This would place them at greater risk for frailty and its comorbid consequences. Additional studies are needed to further elucidate the etiology of this difference.