Objective Obesity is a traditional cardiovascular risk factor that affects one third of rheumatoid arthritis (RA) patients. Presently, the importance of obesity in RA activity remains unclear. This study aims to determine the influence of obesity on treatment response to biologic therapy evaluated by DAS28 at six months, in patients with RA, regardless of the targeted cytokine or cell, by analyzing a cohort of patients treated with anti-IL-6, TNFinhibitors (TNFi) or anti-CD20 therapies.
Methods We conducted a retrospective longitudinal cohort study using the Rheumatic Diseases Portuguese Register (Reuma.pt). RA patients refractory to DMARD therapy, with at least 6 months of follow up after starting their first biologic therapy, with available data on weight and height at baseline were included. A DMARD naïve patients group was used as control
Information was obtained on patient demographics, education, body mass index (BMI), present smoking status, disease duration, therapy, baseline disease activity score in 28 joints (DAS28), erosive disease, rheumatoid factor and anti-citrullinated protein antibodies, health assessment questionnaire (HAQ), type of biologic therapy (TNFi vs non-TNFi). BMI was categorised in two classes: non-obese (BMI <30) and obese (BMI > = 30 Kg/m2). Multivariate analysis was performed in order to evaluate the association between obesity and DAS 28 at 6 month and remission state (DAS28 <2.6).
Results 317 patients treated for the first time with a biologic agent were included in this study. 23% were obese. We found a significant association between obesity and DAS28 at 6 months (β = 0.412 (0.045–0.779); p = 0.028). Other factors also showed a significant association namely baseline DAS28 (β = 0.514 (0.393–0.636); p < 0.001) and the use of a TNFi (β = 1.22 (0.787–1.653; p < 0.001). Considering disease remission the analysis did not show a significant association between obesity and DAS28 remission at 6 months for all biologic agents as a group (OR = 0.391 (0.132–1.161; p = 0.091). Baseline DAS28 (OR = 0.384 (0.264–0.597); p < 0.001) and the use of TNFi as a biologic therapy did show a significant association with achieving remission in these patients (OR = 0.037 (0.012–0.111); p < 0.001). In the 35 DMARD naïve patients evaluated we also found a significantly association of obesity and DAS28 at 6 months (β = 1.048 (0.227–1.829); p-value = 0.009) but not with remission (OR = 0.24 (0.006–1.938); p = 0.24).
Conclusion Obesity predicts worse treatment response in rheumatoid arthritis. These results suggest that obese RA patients should be encouraged to reduce weight in order to improve disease control.