Objectives To study whether there is an association between body mass index (BMI) category and survival of various tumour necrosis factor inhibitors (TNFi) in rheumatoid arthritis (RA) patients in a real-life longitudinal international registry.
Methods Data from 5230 patients with RA starting treatment with any TNFi were selected from the METEOR registry. Patients were divided into six BMI categories: 3.7% underweight, BMI<18.5 kg/m2; 46% normal weight, BMI 18.5–25 kg/m2; 32% pre-obesity, BMI 25–30 kg/m2; 13% obesity class I, BMI 30–35 kg/m2; 3.4% obesity class II, BMI 35–40 kg/m2; and 1.6% obesity class III, BMI >40 kg/m2. Time on treatment in the different BMI categories was compared for all TNFi combined and for the infliximab, adalimumab and etanercept separately, using Kaplan–Meier curves and Cox regression analyses. Cox regression analyses were adjusted for potential confounders, with follow-up censored at 5000 days.
Results Patients in obesity class II (HR 1.28, 95% CI 1.06 to 1.54) and III (HR 1.67, 95% CI 1.29 to 2.18) and underweight patients (HR 1.30, 95% CI 1.07 to 1.58) showed statistically significantly shorter TNFi survival than normal weight patients. The effect in underweight patients was strongest for infliximab (HR 1.82, 95% CI 1.20 to 2.76), the effect in overweight patients was strongest for infliximab (category II (HR 1.49, 95% CI 0.98 to 2.26); category III (HR 1.46, 95% CI 0.79 to 2.71)) and etanercept (category II (HR 1.27 95% CI 0.98 to 1.65); category III (HR 1.79, 95% CI 1.25 to 2.55)). No significant effect modification from reported pain was found.
Conclusion Both underweight and overweight patients discontinued TNFi treatment earlier than normal weight patients, without evidence of reported pain as the main determinant. It remains uncertain what determines TNFi survival in individual patients.
- Rheumatoid arthritis
- DMARDs (synthetic)
- Disease activity
- DMARDs (biologic)
- Autoimmune diseases
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Contributors SAB and CFA involved in the concept and design of the study, analysis and interpretation of data, and drafting the manuscript. CFA, DVM, MB, EM, KSE and TWJH involved in the acquisition of data. CFA, DVM, MB, EM, KSE and TWJH revised the manuscript critically. All authors read and approved the final manuscript.
Funding This work was supported by a research grant from Bristol-Myers Squibb.
Competing interests Dr Vega-Morales is a speaker for Roche and Bristol-Myers Squibb. The other authors reported no conflicts of interest.
Patient consent for publication Not required.
Ethics approval All data were fully anonymised, and treatment and measurements were performed without any change to daily practice. Therefore, medical ethics approval or consent to participate were not required.
Data sharing statement Data are available upon reasonable request.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement The data sets used and/or analysed during the current study are available from the corresponding author on reasonable request.
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