Assessment of 25-Hydroxyvitamin D Levels in Patients with Resistant Hypertension

OBJECTIVE To investigate the possible correlation between serum 25-hydroxyvitamin D levels and resistant hypertension (RH). SUBJECTS AND METHODS Patients who had undergone ambulatory blood pressure measurements (ABPM) during outpatient controls were enrolled. Fifty subjects with RH, 50 with controlled hypertension (CHT) and 50 normotensive subjects (NT) were included in the study. RH was defined as 'suboptimal blood pressure control despite using 3 antihypertensive agents including a diuretic or need for 4 or more drugs to control blood pressure'. The 25-hydroxyvitamin D and parathormone levels were compared between the groups. Pearson's correlation coefficient test was applied to assess the correlation between 25-hydroxyvitamin D levels and office blood pressure (BP) and ABPM. Logistic regression analysis was used to determine the independent correlates of RH. RESULTS The 25-hydroxyvitamin D level was significantly lower in the RH group (17.02 ± 5.4 ng/ml) compared to the CHT (24.9 ± 4.8 ng/ml) and NT groups (28.0 ± 5.7 ng/ml, p < 0.001). In univariate correlation analysis, 25-hydroxyvitamin D levels had a significant negative correlation with office systolic BP (r = -0.329, p < 0.001), office diastolic BP (r = -0.395, p < 0.001), systolic ambulatory BP (r = -0.844, p = 0.004), and diastolic ambulatory BP (r = -0.567, p = 0.005). ROC analysis revealed that 25-hydroxyvitamin D levels <21.50 ng/ml predicted the presence of RH with a sensitivity of 78% and a specificity of 79% (AUC = 0.89, 95% CI 0.83-0.94). In the multivariate logistic regression analysis, 25-hydroxyvitamin D level was independently correlated with the presence of RH (β 0.660, 95% CI 0.572-0.760, p < 0.001). CONCLUSION There was an independent correlation between lower 25-hydroxyvitamin D levels and presence of RH.