FRI0557 The Association between Body Mass Index and MRI-Detected Inflammation; Paradoxical Effects in Rheumatoid Arthritis, Other Arthritides and Symptom-Free Controls
Authors: L. Mangnus, W.P. Nieuwenhuis, H.W. van Steenbergen, M. Reijnierse, A.H.M. van der Helm-van Mil
Journal: Annals of the Rheumatic Diseases (2016)

<h3>Background</h3> Generally, an increased body mass index (BMI) is associated with higher inflammatory markers. Within rheumatoid arthritis (RA) it has been observed that a high BMI is associated with less severe radiographic joint damage.[1–4] The biologic mechanism underlying this association is unidentified. <h3>Objectives</h3> As joint damage is the consequence of inflammation, and because MRI is sensitive in detecting local inflammation, this study aimed to explore the association between BMI and MRI-detected inflammation in patients with RA, other arthritides and symptom-free persons recruited from the general population. <h3>Methods</h3> We studied 202 RA patients, 170 patients with other inflammatory arthritides from the Leiden Early Arthritis Clinic cohort and 193 symptom-free persons from the general population.[5] At baseline, all participants underwent a contrast-enhanced 1.5T MRI of the dominant or most painful MCP, wrist and MTP joints. Each MRI-scan was scored by two readers on synovitis, BME and tenosynovitis. The sum of the scores yielded the total MRI- inflammation score. Linear regression models (on log transformed MRI-data) were used for associations with the total MRI-inflammation score and Spearman9s correlations for correlations with separate inflammatory features as they were non-normally distributed. <h3>Results</h3> A higher BMI was associated with higher MRI-inflammation scores in symptom-free persons (β=1.029, p=0.040) and arthritides other than RA (β=1.082, p&lt;0.001). These β9s indicate an 1.029 fold and an 1.082 fold increase in MRI-inflammation with every point increase in BMI (Figure). However, in RA patients a higher BMI was associated with lower MRI-inflammation score (β=0.969, p=0.005). Similar results were seen when correcting for age and gender. Evaluating the different inflammatory features separately showed that BMI was correlated with higher synovitis and tenosynovitis scores in symptom-free persons (respectively ρ=0.17, p=0.016 and ρ=0.16, p=0.027) and in arthritides other than RA (respectively ρ=0.40, p&lt;0.001 and ρ=0.26, p&lt;0.001). This is in contrast to RA where a higher BMI was correlated with lower synovitis scores (ρ=-0.18, p=0.010) and was not correlated with tenosynovitis (ρ=-0.10, p=0.15). Similarly, BMI was positively correlated with BME in other arthritides (ρ=0.16, p=0.048)) and negatively correlated with BME in RA (ρ=-0.23, p=0.001). <h3>Conclusions</h3> The association between BMI and MRI-detected inflammation differs in patients with RA compared to patients with other arthritides and symptom-free controls. Within RA a higher BMI is associated with less MRI-detected synovitis and BME; this might explain the previously observed association of BMI with less radiographic damage. <h3>References</h3> Kaufmann J, et al. J Rheumatol 2003;30:2350–5. Mil AHM van der H, et al. Ann Rheum Dis 2008;67:769–74. Westhoff G, et al. Arthritis Rheum 2007;56:3575–82. Baker JF, et al. Ann Rheum Dis 2014;73:1923–8. Mangnus L, et al. Ann Rheum Dis 2015;74(Suppl2):153–153. <h3>Disclosure of Interest</h3> None declared