Obesity, weight change and disease activity measures in patients with rheumatoid arthritis

BACKGROUND: Rheumatoid arthritis (RA) is an autoimmune disease that causes inflammatory polyarthritis, typically of the small joints. Obesity, a serious global epidemic, has been shown to increase systemic inflammatory biomarkers, several of which are related to RA pathophysiology. Associations have been observed between obesity and worsened RA disease activity outcomes in crosssectional studies. Limited longitudinal studies investigated the effects of weight change on RA disease activity measures. Surgical interventions for weight loss in RA patients showed marked improvement in RA disease activity measures and outcomes but typical weight change in a clinical setting has not been investigated. OBJECTIVE: To investigate the impact of typical weight change on RA disease activity measures. METHODS: We conducted a retrospective cohort study on 178 RA patients seen in typical clinical practice that met the inclusion criteria for the study, which included patients with a minimum of two clinical disease activity assessments (CDAI) with corresponding body mass index (BMI) measures. Medical record review was conducted for each clinic visit where CDAI and BMI were measured, and at each of these visits, sociodemographic, lifestyle, medication usage, questionnaire data, RA characteristics, laboratory values, and comorbidities were collected. Linear regression was used to analyze the association between ΔBMI and ΔCDAI, defined at the dates of minimum and maximum BMI for each subject, adjusting for confounders including sex, age, disease duration, smoking status, serologic status, and steroid usage. Logistic regression was performed to evaluate whether ΔBMI was associated with low/remission RA disease activity according to accepted CDAI cutoffs. RESULTS: Unadjusted linear regression was performed on all 178 subjects to analyze the overall trend within the sample population. For every 1 kg/m2 increase in BMI, CDAI increased by 0.49 points, but these results were not statistically significant (p=0.155, 95%CI -0.176, 1.097). Subjects were stratified into BMI gain, stable, and loss groups. Within the BMI loss group (defined as those whose BMI decreased by more than 1 kg/m2), a significant association was found with ΔCDAI (β= -2.61 [p=0.028, 95%CI -4.91, -0.298]). Unadjusted linear regression on the BMI gain and stable groups was found to be not statistically significant. This association remained significant after adjusting for sex, age, disease duration, smoking status, serologic status, and steroid usage (β=-2.499 [p=0.044, 95%CI -4.94, -0.061]). There was no association between ΔBMI and low/remission RA disease activity (OR 0.990, (95%CI 0.855, 1.146). When stratified by BMI gain, stable, and loss groups there was no significant association with low/remission RA disease activity. CONCLUSION: These results suggest that weight loss may be associated with improved disease activity among patients with RA seen in a typical clinical setting. Weight loss has the potential to be a non-pharmacologic intervention to improve RA disease activity. Prospective studies of weight loss and RA disease activity are necessary to replicate these results