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.