Cumulative inflammatory burden and obesity as determinants of insulin resistance in patients with established rheumatoid arthritis: cross-sectional study

Objectives To describe the prevalence of insulin resistance (IR) in patients with established rheumatoid arthritis (RA) and to analyse the contribution of cumulative inflammatory burden and other factors to its development. Design Observational cross-sectional study. Participants Patients with RA and controls matched for age, sex and Body Mass Index. We excluded patients with diabetes. Settings Patients from an RA inception cohort at Hospital Regional Universitario de Malaga, Spain, were recruited between September 2016 and May 2018. Primary and secondary outcome measures IR was evaluated using the homeostasis model assessment for IR and beta-cell function and the quantitative insulin sensitivity check index. Other variables included the cumulative 28-Joint Disease Activity Score (DAS28) with C reactive protein (CRP) body composition and cytokines. Two logistic regression models were constructed to identify factors associated with IR in patients with RA. Results Eighty-nine patients with RA and 80 controls were included. The prevalence of IR was similar in both cases and controls. Inflammatory activity was controlled appropriately in patients during follow-up (mean DAS28 3.1 (0.8)). The presence of IR in patients with RA was associated with obesity (OR 6.01, 95% CI 1.9 to 8.7), higher cumulative DAS28-CRP values during follow-up (OR 2.8, 95% CI 1.3 to 6.0), and higher interleukin-1 beta levels (OR 1.6, 95% CI 1.1 to 2.4). The second model showed that the risk of IR increased by 10% for each kilogram of excess body fat. Conclusion In patients with well-controlled, established RA, IR is associated mainly with poorer control of inflammation from diagnosis and with obesity, specifically total fat mass.