Background There appears to be a paradoxical relationship between increasing body mass index (BMI) and outcome from rheumatoid arthritis (RA), with studies demonstrating less radiographic joint damage (RJD) for obese patients compared to those with lower BMI. However, increasing adiposity is associated with heightened production of proinflammatory adipokines and raised inflammatory markers. This systemic inflammation could inflate standard disease activity scores (DAS) and, if treat to target treatment protocols are adopted for management of RA, may result in obese patients being treated more aggressively.
Objectives To identify whether BMI is associated with RA disease activity in early and established RA, utilising data from a large international RA cohort.
Methods Using clinical data from the Meteor Foundation International RA database, an early RA cohort (eRA, disease duration <12 months) and an established RA cohort (disease duration ≥12 months) were identified. Patient demographics, DAS28 and BMI were collected from the first recorded visit on the database. The cohorts were stratified into 5 categories by BMI: 1) Underweight <18.5, 2) Normal 18.5-24.9, 3) Overweight 25-29.9, 4) Obese I 30-34.9 and 5) Obese II ≥35. Associations between RA disease variables and BMI category (using normal BMI as the reference group) were explored using logistic regression analysis for both the eRA and established RA cohorts, adjusting for age, gender and smoking status. Median values were used as cut offs for high DAS28 component levels.
Results 3,534 patients with complete data were identified. Mean age was 54.7 (SD 14.3) and 72.5% were female. The eRA cohort was comprised of 1,553 patients with <1 year of disease duration. In the established RA cohort (n=1981) the median disease duration was 7.2yrs [IQR 3.7, 13.6]. The distribution of BMI categories was similar in both the eRA and established RA cohorts (mean BMI 27.1 (SD 5.4) and 26.8 (SD 5.2) respectively).
When the analysis was repeated in the established RA cohort, similar significant associations between BMI categories and disease characteristics were seen (although high VAS did not reach significance).
When RA adjusted BMI categories1 were used, significant associations between obese patients (BMI ≥28) and DAS28 >5.1, elevated ESR, high TJC, and high VAS remained.
Conclusions Obese patients with RA have higher DAS28 scores, with significantly increased levels of ESR, TJC and VAS scores. These observations were similar for both eRA and established RA cohorts. These findings may provide an explanation for the inverse association observed between increasing BMI and RJD if DAS28 is used as a treatment target.
Stavropoulos-Kalinoglou et al. Redefining overweight and obesity in rheumatoid arthritis patients. Ann Rheum Dis 2007;66:1316-1321
Disclosure of Interest None declared
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