Background/Purpose : Obesity has been associated with worsened RA outcomes and increased disease activity. However, few longitudinal studies have investigated whether weight loss might improve RA disease activity. We hypothesized that weight loss improves RA disease activity in routine clinical care.

Methods : We conducted a retrospective cohort study among RA patients that met 1987/2010 ACR criteria at a single academic medical center from 2012 to 2015. We included patients with at least two Clinical Disease Activity Index (CDAI) measures and corresponding body mass index (BMI) measures at routine clinic visits. We collected data on sociodemographic, lifestyle, medications, laboratory values, and RA characteristics at each clinic visit. We identified the maximum and minimum weight for each individual to calculate Δweight, as well as corresponding CDAI measures at these visits to calculate ΔCDAI. We defined significant weight loss as losing ≥5 kg, and a significant improvement in disease activity as ≥5 point improvement in CDAI (validated as the minimally clinically important difference, MCID). We used logistic regression to estimate the odds ratio (OR) for improved disease activity according to significant weight loss and baseline BMI category. We used linear regression to evaluate the association between Δweight and ΔCDAI among those who were overweight/obese and lost at least 1 kg.

Results : We identified 178 RA patients to include in the study. There were a total of 854 clinic visits, with a median of 5 visits per patient (range 2-11) in 1.8 years (IQR 1.3-2.4) of follow-up. Mean age at baseline was 60.2 years (SD 13.5) and median time for Δweight was 1.1 years (IQR 0.6-1.5). At baseline, 66% were overweight/obese, mean RA duration was 11.9 years (SD 9.5), 78% were seropositive, and mean CDAI was 11.6 (SD 9.2) with 42% in high/moderate disease activity by CDAI. Patients who were overweight or obese and lost >5 kg had three-fold increased odds of disease activity improvement by MCID compared to those who did not lose 5 kg (OR 3.03, 95%CI 1.18-7.83, Table). Among those who were obese/overweight at baseline, for each kg of weight lost, CDAI decreased by 1.15 (95% CI -1.88, -0.42; p=0.0026, Figure), adjusted for age, sex, RA duration, smoking, steroid use, serostatus, and time for weight loss.

Conclusion : These results suggest that weight loss may be associated with improved disease activity in patients with RA in a routine clinical setting. Weight loss has the potential to be a non-pharmacologic intervention to improve RA disease activity. Further studies of weight loss interventions and RA disease activity are necessary to confirm these results in other populations.