Incremental effects of serum uric acid levels, autonomic dysfunction, and low-grade inflammation on nocturnal blood pressure in untreated hypertensive patients and normotensive individuals

OBJECTIVES: We aimed to evaluate the associations between nocturnal blood pressure (BP) and serum uric acid (SUA) level, low-grade inflammation, and cardiac autonomic function in untreated dipper and nondipper hypertensive patients and normotensive individuals. STUDY DESIGN: The study included 92 consecutive patients (44 men, 48 women; mean age 51.6 ± 9.7 years) who presented for initial evaluation of hypertension. All patients underwent 24-hour Holter monitoring to assess heart rate variability (HRV) and ambulatory BP. Serum high-sensitivity C-reactive protein (hs-CRP) and SUA levels were measured. Due to the non-normal distribution of hs-CRP and microalbuminuria (MAU), they were normalized by logarithmic transformation. RESULTS: Of the study group, 60 patients (65.2%) were diagnosed as hypertensive (50% nondippers). In univariate correlation analysis, log(MAU) showed a significant correlation with nocturnal BP (r=0.560, p<0.001). Among HRV parameters, SDNN, SDANN, and triangular index were inversely correlated with log(hs-CRP) (r=-0.356, p=0.001; r=-0.350, p=0.001; r=-0.314, p=0.002, respectively) and nighttime BP (r=-0.286, p=0.006; r=-0.251, p=0.02; r=-0.294, p=0.004, respectively). Log(hs-CRP) was positively correlated with nighttime BP (r=0.302, p=0.003). Serum UA levels were correlated with only nocturnal BP; i.e., nocturnal mean (r=0.260, p=0.01), systolic (r=0.249, p=0.016), and diastolic BP (r=0.249, p=0.017). In multiple linear regression analysis, log(hs-CRP) and age were independent predictors of cardiac autonomic dysfunction, and log(hs-CRP), SUA, and HRV parameters were independent predictors of nocturnal BP measurements. CONCLUSION: Our findings suggest the role of low-grade inflammation, uric acid levels, and autonomic dysfunction even in the early stages of hypertension.