Uric acid is a product of the activity of xanthine oxidase, an enzyme linked to oxidative stress, endothelial dysfunction, and heart failure. It is unclear whether adding uric acid levels to the assessment of cardiovascular risk might contribute to the improved ability to stratify cardiovascular risk. The purpose of this study was to evaluate the prognostic value of serum uric acid levels in a large cohort of men and women at high risk of cardiovascular disease.
Serum uric acid levels were determined in all patients seen for primary/secondary cardiovascular disease prevention at the Cleveland Clinic Section of Preventive Cardiology and Rehabilitation between 1998 and 2004, and all data were entered into the Preventive Cardiology Information System (PreCIS) database. Vital status of the patients was determined through the Social Security Death Index. Death from all causes was summarized across quartiles of uric acid values.
A total of 3,098 patients (age range 18–87 years) were identified in the database, among whom 43% had cardiovascular disease. There were 156 deaths (5%) during the 14,262 person-years of followup. For each 1-mg/dl increase in the serum uric acid level, there was a 39% increase in the risk of death (by Cox regression analysis). After adjusting for age, sex, smoking status, alcohol consumption, weight, body mass index, waist circumference, blood pressure, history of cardiovascular disease, estimated glomerular filtration rate, levels of cholesterol fractions, and plasma glucose levels, the serum uric acid level continued to predict the risk of death (hazard ratio = 1.26 [95% confidence interval 1.15–1.38], P < 0.001). This association was present regardless of diuretic use. Concordance index (C statistic) analyses showed that uric acid significantly improved the predictive accuracy of a model that included Framingham Heart Study score factors, metabolic syndrome components, and fibrinogen levels.
Serum uric acid levels are an independent predictor of death in patients at high risk of cardiovascular disease. Further studies are warranted to evaluate its prognostic implications and potential utility in the monitoring of therapy.