Systemic inflammation and insulin resistance (IR) are linked, yet the determinants of IR and its impact on atherosclerosis in rheumatoid arthritis (RA) are incompletely understood. The aim of this study was to explore the prevalence of IR in RA and non-RA populations and investigate whether the associations of IR with measures of atherosclerosis differ between these groups.
IR was quantified using the homeostatic model assessment of IR (HOMA-IR), and was compared between RA patients and demographically matched non-RA controls. Differences in the associations between the HOMA-IR index and the Agatston coronary artery calcium (CAC) score, ultrasound-determined intima-media thickness (IMT) of the common carotid artery (CCA) and internal carotid artery (ICA), and focal plaque in the ICA/carotid bulb were compared according to RA status.
Among the 195 RA patients and 198 controls studied, average HOMA-IR levels were higher in the RA group by 31%, and were consistently higher in the RA group regardless of stratification by demographic or cardiometabolic risk factors. While the HOMA-IR index was strongly and significantly associated with C-reactive protein (CRP) and interleukin-6 (IL-6) levels in the control group, the association was weaker in the RA group. Among RA patients, higher HOMA-IR levels were associated with rheumatoid factor (RF) seropositivity in men and women, and prednisone use in women only. Before adjustment, higher HOMA-IR levels were associated with all assessed measures of subclinical atherosclerosis in the control group only; associations were diminished and lost statistical significance after adjustment for cardiovascular risk factors. Among the RA patients, neither baseline nor average HOMA-IR levels were significantly associated with change in any of the atherosclerosis measures over an average of 3.2 years of followup.
Although IR was higher in RA patients than in non-RA controls, higher levels may not independently impart additional risk of atherosclerosis.