Cardiovascular risk in rheumatoid arthritis versus osteoarthritis: acute phase response related decreased insulin sensitivity and high-density lipoprotein cholesterol as well as clustering of metabolic syndrome features in rheumatoid arthritis

Abstract

Rheumatoid arthritis (RA) patients experience a markedly increased frequency of cardiovascular disease. We evaluated cardiovascular risk profiles in 79 RA patients and in 39 age-matched and sex-matched osteoarthritis (OA) patients. Laboratory tests comprised ultrasensitive C-reactive protein (CRP) and fasting lipids. Insulin sensitivity (IS) was determined by the Quantitative Insulin Sensitivity Check Index (QUICKI) in all OA patients and in 39 of the RA patients. Ten RA patients were on glucocorticoids. RA patients exercised more frequently than OA patients (chi2 = 3.9, P < 0.05). Nine RA patients and one OA patient had diabetes (chi2 = 4.5, P < 0.05). The median CRP, the mean QUICKI and the mean high-density lipoprotein (HDL) cholesterol were 9 mg/l (range, 0.5-395 mg/l), 0.344 (95% confidence interval [CI], 0.332-0.355) and 1.40 mmol/l (95% CI, 1.30-1.49 mmol/l) in RA patients, respectively, as compared with 2.7 mg/l (range, 0.3-15.9 mg/l), 0.369 (95% CI, 0.356-0.383) and 1.68 mmol/l (95% CI, 1.50-1.85 mmol/l) in OA patients. Each of these differences was significant (P < 0.05). After controlling for the CRP, the QUICKI was similar in RA and OA patients (P = 0.07), while the differences in HDL cholesterol were attenuated but still significant (P = 0.03). The CRP correlated with IS, while IS was associated with high HDL cholesterol and low triglycerides in RA patients and not in OA patients. A high CRP (>/= 8 mg/l) was associated with hypertension (chi2 = 7.4, P < 0.05) in RA patients. RA glucocorticoid and nonglucocorticoid users did not differ in IS and lipids (P > 0.05). Excess cardiovascular risk in RA patients as compared with OA patients includes the presence of decreased IS and HDL cholesterol in RA patients. The latter is only partially attributable to the acute phase response. The CRP, IS, HDL cholesterol, triglycerides and hypertension are inter-related in RA patients, whereas none of these relationships were found in OA patients.

Figure 1

Relationships among waist circumference, C-reactive protein, Quantitative Insulin Sensitivity Check Index (QUICKI), high-density lipoprotein cholesterol (HDL chol) and triglycerides in osteoarthritis patients (n = 39) and rheumatoid arthritis patients (n = 39). Significant associations are printed in bold italic.