Uric acid and nocturnal nondipping in hypertensive patients with normal renal function.

Background: The effect of uric acid on nocturnal dipping in hypertensive patients is unknown. We analyzed the specific relationship between uric acid and nocturnal dipping status in newly diagnosed essential hypertensive patients with normal renal function.

Methods: Two hundred fifteen patients with newly diagnosed essential hypertension underwent 24-hour ambulatory blood pressure monitoring, biochemistry analysis and 24-hour urine testing.

Results: Patients were classified as either dippers (157 patients) or nondippers (58 patients). Uric acid levels were higher in nondippers than in dippers (345.0 +/- 65.4 mmol/L vs. 270.6 +/- 59.5 mmol/L, p<0.0001) and positively correlated with the following blood pressure (BP) values: average nighttime ambulatory systolic BP (r=0.325, p<0.0001), average nighttime ambulatory diastolic BP (r=0.203, p=0.003), nighttime mean arterial BP (r=0.285, p<0.0001) and mean 24-hour arterial BP (r=0.197, p=0.004). Uric acid was also positively correlated with nighttime heart rate (r=0.293, p=0.001). Univariate logistic regression analysis showed that a high serum uric acid level (odds ratio [OR] = 3.566; 95% confidence interval [95% CI], 2.397-5.303; p<0.0001) and smoking (OR=2.294; 95% CI, 1.155-4.498; p=0.018) increased the risk of nocturnal nondipping. The results of multivariate analysis showed that serum uric acid levels (OR=3.453; 95% CI, 1.466-8.134; p=0.005) together with fasting blood glucose (OR=1.148; 95% CI, 1.028-1.281; p=0.014) were associated with the nondipping pattern.

Conclusions: This study is the first to demonstrate that increased serum uric acid levels are associated with nondipping blood pressure patterns in patients with essential hypertension.