Associations between body mass, radiographic joint damage, adipokines and risk factors for bone loss in rheumatoid arthritis.

OBJECTIVE: To evaluate the association between BMI and radiographic joint damage (RJD) in RA.
METHODS: van der Heijde-Sharp (vdHS) erosion scores were determined in 499 participants with RA, ages 18-85 years, while enrolled in a clinical trial of golimumab (GO-BEFORE trial). Subjects were MTX and biologic therapy naïve. Multivariable logistic regressions determined the odds of prevalent RJD (defined as vdHS score >10) according to BMI category. Longitudinal analyses evaluated the association between BMI category and progression of vdHS score over 52 weeks. Analyses in a subset of 100 participants examined the association between adipokines and vdHS scores.
RESULTS: At enrolment and 52 weeks, 37.6 and 43.6% of participants had RJD. Compared with normal weight, obese subjects had lower odds of RJD [0.40 (95% CI 0.22, 0.74); P = 0.003], and underweight subjects had greater odds [3.86 (95% CI 1.66, 9.00); P = 0.002] at baseline, adjusted for demographic and disease characteristics. The baseline associations between BMI category and RJD were greater among participants with multiple risk factors for bone loss (female >50 years, smoking, glucocorticoid exposure and vitamin D deficiency); test for interaction P = 0.05. Adjustment for adiponectin levels did not attenuate the association between BMI and vdHS scores. Baseline BMI and change in weight did not independently predict radiographic progression (P > 0.1).
CONCLUSIONS: Higher BMI was independently associated with less RJD and was greatest in participants with risk factors for bone loss. Future studies are needed to examine the associations between RJD, obesity, weight loss and osteoporosis.