Baseline body mass index and early functional recovery after first recorded advanced therapy in rheumatoid arthritis: a real-world cohort study

Obesity is common in rheumatoid arthritis (RA), but its prognostic value at first recorded advanced-therapy initiation is incompletely defined. We examined whether baseline body mass index (BMI) was associated with early DAS28-ESR remission and Health Assessment Questionnaire Disability Index (HAQ-DI)-based functional recovery after first recorded advanced therapy. Adults with clinician-diagnosed RA initiating first recorded advanced therapy between 2013 and 2020 were studied retrospectively. BMI was analyzed continuously and categorically. Outcomes were assessed at the eligible visit closest to 9 months within 6-12 months. Complete-case multivariable logistic regression was supplemented by robust Poisson and sensitivity analyses. Of 581 screened patients, 574 had baseline BMI data, including 235 (40.9%) with obesity. DAS28-ESR remission was evaluable in 258 patients and occurred in 125 (48.4%); remission was less frequent with obesity than with BMI < 25.0 or 25.0-29.9 kg/m² (38.7% vs. 55.8% and 54.7%). In the primary adjusted remission model (n = 208), BMI was not conventionally significant (OR 1.048 per 1 kg/m², 95% CI 0.999-1.100; P = 0.056). HAQ-DI response was evaluable in 228 patients; 226 entered the primary adjusted model. Higher BMI was associated with poor HAQ-DI response (OR 1.056, 95% CI 1.006-1.110; P = 0.029), attenuating after hypertension/diabetes adjustment. Higher BMI showed its most consistent adjusted association with less complete early HAQ-DI-based functional recovery, whereas the DAS28-ESR remission signal was weaker and model-sensitive. Findings are associative and prognostic rather than causal.