Background/Purpose: Disease activity measurement is a cornerstone to treat to target strategy. The impact of body mass index (BMI) on disease activity in rheumatoid arthritis (RA) is not clear. We studied the impact of body mass index on various patient and physician variables in RA patients.

Methods: A retrospective observational study was done in a community based rheumatology clinic. Random visits from 155 patients with a diagnosis of RA who had documented DAS28-(ESR) (Disease Activity Score) and BMIs were studied. Baseline patient demographics, DAS28, RAPID3, CDAI, SDAI, tender count, swollen count, physician global, pain scale, patient global, function, ESR, CRP, and BMI were collected. Obese was defined as: BMI < 29.9 (NON-OBESE) and BMI ≥ 30.0 (OBESE). A multiple regression analysis was done using a random set of patients. We used BMI and Obese as independent variables to determine the impact of BMI or Obesity on RA disease activity.

Results: Study population consisted of 155 patients of which 46% of the patients were obese with a mean BMI of 30. Patients had a mean DAS28 of 2.40, RAPID3 of 9.08, CDAI of 11.26, SDAI of 11.94. After controlling for age, sex, and duration of disease, higher BMIs were found to have a significantly increased ESR; obese patients had elevated ESR and DAS28, without changes in any other patient or physician reported measure. Additional results show that for every 10-point increase in BMI, ESR increases by 4.3mm/hour which leads to an increase in 1.02 points in the DAS28.

Table 1: Multiple regression for impact of Obesity on RA disease activity measures, controlling for age, sex, disease duration

Conclusion: In this cohort, BMI was shown to significantly affect ESR, but no other objective or subjective measures of RA disease activity, suggesting that obesity in itself may increase the levels of inflammatory markers rather than the actual disease process. Using ESR may erroneously elevate DAS28 leading to misclassification of RA. This could lead to potential overtreatment in obese patients with RA. Further studies comparing the treatment groups and using larger number of patients are required to substantiate the results of this study.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/obesity-impacts-esr-and-not-other-measures-of-rheumatoid-arthritis-disease-activity/