Pulmonary Function and Abdominal Adiposity: Associations based on Whole-Body MR Imaging in a Population-based Cohort

Zielsetzung To explore the association between MR-based measures of pulmonary function in obstructive and restrictive lung diseases and hepatic fat content, visceral (VAT), and subcutaneous (SAT) adipose tissue in a population-based cohort.

Material und Methoden Our study subjects underwent whole-body MRI and pulmonary function test as part of the KORA FF4 cohort study. Based on MRI, VAT was derived semi-automatically from T1-DIXON through an in-house algorithm, while hepatic fat content was determined as proton density fat fraction (PDFF; log transformed for all analysis). Using multivariate linear regression (adjusted for age, sex, BSA, smoking, diabetes, hypertension, pack-years, obesity [BMI ≥30]), fat parameters were associated with spirometrically-measured parameters of forced vital capacity (FVC) as a measure for restrictive lung disease and forced expiratory volume in 1 second (FEV1) for obstructive lung disease.

Ergebnisse A total of 203 subjects presented a mean FVC of 4.2±1.0L and FEV1 of 3.1±0.8L/s, as well as a mean VAT of 4.8±2.7L, mean SAT of 8.1±3.4L and a median hepatic fat content of 4.7% [IQR 2.9, 13.1]. VAT (ݽ-0.13, p=0.03) and SAT (ݽ-0.26, p<0.001), but not hepatic fat content (p=0.52) were inversely associated with FEV1. In contrast, FVC was inverse associated with VAT (ݽ 0.27, p<0.001), SAT (ݽ 0.41, p<0.001) and hepatic fat content (ݽ 0.17, p=0.002). Interestingly, the Tiffeneau index (FEV1/FVC) demonstrated a positive association (e.g. ݽ2.46, p<0.001), which was driven by a stronger effect on FVC than on FEV1.

Schlußfolgerungen There was an inverse association between VAT and SAT compared to both FEV1 and FVC, possibly related to the mechanical impact of abdominal fat on diaphragmatic mobility. Hepatic fat content was inversely associated with FVC, but unrelated to diaphragmatic mechanics. Utilizing the Tiffeneau index alone, could therefore be misleading.