Relationship between serum bilirubin concentration and nondipper hypertension

Although nondipper hypertension has been associated with increased cardiovascular morbidity and mortality, the relationship between bilirubin levels and nondipper hypertension remains unclear. Several studies have demonstrated that higher serum bilirubin levels inhibit inflammation and the proliferation of vascular smooth muscle cells, which may suggest a relationship between serum bilirubin levels and cardiovascular disease. The aim of this study was to compare serum bilirubin levels between dipper and nondipper hypertensive patients.

The present study included 80 hypertensive patients who were stratified into two groups: 50 dipper patients (mean [± SD] age 51.5 ± 8 years; 29 male) and 30 nondipper patients (mean age 50.6 ± 5.4 years; 17 male). All patients underwent 24 h ambulatory blood pressure monitoring.

No statistically significant differences were found between the two groups in terms of basic characteristics. Total, direct and indirect serum bilirubin levels were significantly lower among individuals with nondipper hypertension compared with patients with dipper hypertension (0.78 ± 0.6 mg/dL versus 0.42 ± 0.32 mg/dL; and 0.29 ± 0.1 mg/dL versus 0.18 ± 0.05 mg/dL; and 0.48 ± 0.52 mg/dL versus 0.25 ± 0.22 mg/dL, respectively; all P<0.001). Additionally, leukocyte counts were higher in patients with nondipper hypertension.

The present study revealed a potential relationship between lower serum bilirubin levels and a nondipping pattern in hypertensive patients.