Association of High Body Mass Index with Decreased Treatment Response to Combination Therapy in Recent-onset Rheumatoid Arthritis Patients

Objective: To assess the association between high body mass index (BMI) and treatment response in recent-onset rheumatoid arthritis.

Methods: In the Behandelstrategieën voor Reumatoide Artritis (Treatment Strategies for Rheumatoid Arthritis) study, 508 patients were randomized to initial monotherapy or combination therapy with prednisone or infliximab (IFX). The response to Disease Activity Score (DAS) ≤2.4-steered treatment (first dose and after 1 year) was compared between patients with a BMI <25 kg/m(2) and ≥25 kg/m(2) , using relative risk (RR) regression analyses. DAS, components of DAS, and functional ability during the first year were compared using linear mixed models.

Results: High BMI was independently associated with failure to achieve a DAS ≤2.4 on initial therapy (RR 1.20 [95% confidence interval (95% CI) 1.05, 1.37]). The effect for combination therapy with prednisone was RR 1.55 (95% CI 1.06, 2.28) and for combination therapy with IFX 1.42 (95% CI 0.98, 2.06). The RRs for failure after 1 year were 1.46 (95% CI 0.75, 2.83) and 2.20 (95% CI 0.99, 4.92), respectively. High BMI was also associated with failure on delayed combination therapy with IFX, after adjustment for selection bias related to previous failure on disease-modifying antirheumatic drugs. No significant association was observed in the initial monotherapy groups. In the first year, patients with a high BMI had higher DAS and worse functional ability, with more tender joints and a higher visual analog scale global health, but not more swollen joints and similar systemic inflammation.

Conclusion: High BMI was independently associated with failure to achieve low DAS on initial combination therapy with prednisone and on initial and delayed treatment with IFX. Patients with a high BMI experienced more pain, but not more swelling or systemic inflammation.