The role of obesity on inflammation and damage in spondyloarthritis: a systematic literature review on body mass index and imaging.

The objective of this systematic literature review was to evaluate the effect of obesity and/or body mass index (BMI) on radiographic findings of spondyloarthritis (SpA) for both axial and peripheral inflammation and damage.Medline, Embase and Cochrane databases were screened on February 13, 2017. The titles and the abstracts were independently screened by two investigators. Articles that have evaluated the link between BMI and plain radiography, ultrasound (US) and magnetic resonance imaging (MRI) in SpA were investigated.The literature search resulted in 613 articles, 5 of which met the inclusion criteria for the final analysis. Studies mostly investigated the effect of BMI on axial disease and mostly in ankylosing spondylitis. The major finding was that a higher BMI was closely related with new bone formation including syndesmophytes, enthesophytes and also a higher modified Stoke Ankylosing Spondylitis Spinal Score. Fewer studies looked at the effect of BMI on the peripheral enthesis which found a moderately positive correlation between the Madrid Sonographic Enthesitis Index for enthesitis on US and BMI. Gender was a significant factor to influence this link with one study correlated US enthesophyte scores with BMI in males but not in females. No studies on MRI met the inclusion criteria to be included.BMI is linked to both axial and peripheral new bone formation and entheseal inflammation by imaging, as supported by the limited number of studies in the literature. Its effect on the sacroiliac joint and spinal inflammation is not clear as MRI studies are lacking.