The Influence of Abdominal Obesity on the Accuracy of Cardiovascular Risk Prediction in Rheumatoid Arthritis

Abstract

Objectives. Underweight patients with rheumatoid arthritis incur greater total and cardiovascular mortality compared to overweight or obese. We explored whether obesity confounded cardiovascular risk estimates and the potential utility of noninvasive coronary atherosclerosis assessment and cardiac damage biomarkers in optimizing risk prediction in obese patients with rheumatoid arthritis. Methods. We evaluated 150 participants undergoing screening atherosclerosis evaluation with coronary computed tomography angiography and follow-up over 6.0±2.4 years. Framingham 2008 modified general cardiovascular risk score was computed at baseline. Obesity was defined as waist circumference >88 cm in females and >102 cm in males. Serum highly-sensitive cardiac troponin I (hs-cTnI) and leptin were measured at baseline. Results. An interaction between the Framingham risk score and obesity on cardiovascular risk was observed (p=0.032); lower estimates were seen in obese (area under the curve-AUC 0.660, 95% CI 0.487-0.832) vs. non-obese patients (AUC 0.952, 95% CI 0.897-1.007, p=0.002). Likewise, risk estimates were inferior in patients with high (>22.1 ng/ml) vs. low leptin (AUC 0.618, 95% CI 0.393-0.842 vs. 0.874, 95% CI 0.772-0.976, p=0.042). In obese patients, sequential addition of the top highly-sensitive cardiac troponin I tertile values and extensive atherosclerotic plaque (>5 segments) information to a base model including the Framingham risk score alone significantly improved risk estimates, based on changes in net reclassification index (1.093 95% CI 0.517-1.574), integrated discrimination improvement (0.188, 95% CI 0.060-0.526), and AUC (0.179, 95% CI 0.058-0.378, p=0.02). The final, combined model accurately predicted 83.9% of incident cardiovascular events. Conclusion. Obesity attenuated cardiovascular risk estimate accuracy in patients with rheumatoid arthritis. Risk optimization employing non-invasive assessment of coronary atherosclerosis burden and serum cardiac damage biomarkers may warrant further study.