Computerized Tomography‐Derived Abdominal Body Fat Indices in a Healthy Young Midwestern US Population

Abstract

Objective We report body composition via Computerized Tomography (CT)-derived adipose metric values for a young healthy population in the Midwestern United States across age, sex, and Body Mass Index (BMI) including Subcutaneous Adipose Tissue (SAT), Visceral adipose tissue (VAT), Sketelal Muscle (SM), and waist circumference (WC). Background To improve upon current inaccurate clinical assessments of body composition, national guidelines have recommended expanding diagnostic CT reporting to include body composition metrics which are currently not part of standard reporting. SAT, VAT, SM, and WC are easily measured in an automated format, providing precise measurement and better identification of adipose tissue distribution over traditional methods. However, there exists a paucity of normal reference values for these metrics. Data collected from a young and healthy population has been requested to allow for disease state comparisons. Aside from importance in body composition, these adipose metrics are also clinically relevant to other disease states, especially VAT with cardiovascular health. Hypothesis Pre-existing diagnostic CT scans be re-analyzed to obtain clinically relevant population-based data on body composition. Methods Pre-existing abdominal non-contrast computerized tomography (CT) scans from a young Midwestern population (19-40 years) were analyzed using Aquarius iNtuition software with automated identification of waist circumference and adipose tissue and skeletal muscle cross-sectional areas and densities. Normal health status and lack of chronic medical conditions among participants and Body Mass Index (BMI) were confirmed by automated screening and manual medical record review prior to analysis. Any abnormal or acute findings on CT led to exclusion. Results From 193 (45 male, 148 female) CT scans, for males, VAT surface area (SA) was 186.0 cm2 (SD=95.4) with attenuation (ATT) -96.7 HU (SD=8.6) and SAT SA was 265.6 cm2 (SD=191.5) with ATT -102.4 HU (SD=7.8); for females, VAT SA was 116.2 cm2 (SD=63.6) with ATT -93.8 HU (SD=8.7) and SAT SA was 309.6 cm2 (SD=186.2) with ATT -103.9 HU (SD=6.4). SM SA for males was 193.3 cm2 (SD=30.6) with ATT 40.4 HU (SD=8.4). SM SA for females was 127.9 cm2 (SD=21.9) with ATT 38.0 HU (SD=6.6) (Table 1). Pearson's correlation revealed BMI was statistically significant to the 0.01 level for a positive correlation with VAT, SAT, and SM SAs and a negative correlation for VAT, SAT, and SM ATTs (Figure 1 - VAT and BMI). Percentiles for sex-specific adipose tissue indices in accordance with body mass index were generated. An Analysis of Variance (ANOVA) revealed males have statistically significantly higher VAT SA than females (p<0.001). Additionally, males have lower VAT ATT than Women (p=0.048). Males also have significantly higher SM SA than females and higher SM ATT than Women (p=0.045). Conclusions Adipose tissue indices are newly generated for a young healthy Midwestern United States population. This study provides novel data as our population is young, devoid of chronic disease states, and from a population with minimal existing data. Such information has the ability to provide a baseline for comparison across disease states and body weights.