Background/Purpose: The prevalence of obesity among patients with psoriatic arthritis (PsA) is increased compared to the general population. Obese patients with PsA tend to respond less favorably to TNF alpha blockers compared to patients with normal weight. We aimed to investigate whether obesity is associated with higher risk of development of radiographic damage among patients with PsA.

Methods: A retrospective cohort analysis was performed among patients who have been followed in a large PsA clinic from 1998 to 2013. Patients were followed according to a standard protocol at 6-12 month intervals. Body Mass Index (BMI) was calculated and patients were categorized accordingly into the following groups: Normal (<25), Overweight (25-30) and Obese (>30). Radiographs of the hands, feet and spine were performed at 2 years intervals. Radiographic damage to 42 joints in the hands and feet was assessed according to a modification of the Steinbrocker method. Radiographic damage to the lumbar and cervical spine was scored using the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS). For each patient all available radiographic data were included. Patients who initiated treatment with TNFα blockers were censored. The outcome of interest was the annual rate of radiographic progression that was calculated as the difference in modified Steinbrocker score and mSASSS compared to the previous radiographic assessment divided by the interval of time between the assessments. Multivariate regression analysis using Generalized Estimating Equations (GEE) for repeated measures was used to compare progression in radiographic damage across the three BMI categories incorporating available information from all time points.

Results: 339 PsA patients were included in the study (28.6% with normal weight, 38.9% were overweight and 32.4% were obese). At first visit, patients who were overweight and obese had higher mean erythrocyte sedimentation rate (p=0.007) and trended for higher CRP levels (p=0.06). There was no difference in the number of tender or swollen joints, dactylitic digits or active entheseal sites.  At baseline, overweight and obesity were associated with the presence of radiographic damage (61.9% in normal weight, 65.2% in overweight and 75.5% in obese, p=0.03); however, no difference was observed in modified Steinbrocker score and mSASSS across the three groups. Regression analysis did not show an association between the rate of radiographic progression of modified Steinbrocker score and BMI category (p=0.85). In multivariate regression analysis only the use of disease modifying anti rheumatic drugs was associated with an increased rate of radiographic damage progression. Similarly, BMI category was not associated with rate of progression of mSASSS (p=0.9).

Conclusion:  Among patients with PsA, increased BMI was associated with the presence of radiographic damage at first assessment. However, no association was found between BMI and the rate of radiographic progression of damage in the peripheral joints and the spine.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-association-between-obesity-and-radiographic-progression-of-joint-damage-among-patients-with-psoriatic-arthritis/