Correlation Between Serum 25-hydroxyvitamin D Levels And Blood Pressure Variability And Circadian Rhythm In Patients With Essential Hypertension

Objective Essential hypertension is a multifactorial disease, which is the result of interaction between genetic and acquired factors. In recent years, many large clinical studies showed that serum 25 hydroxyvitamin D [25(OH)D] levels were negatively related to arterial blood pressure. Vitamin D deficiency may be an acquired risk factor for vascular contraction, closely leaded to hypertension. The aim of this study is to investigate the correlation between serum 25(OH)D levels and blood pressure variability and circadian rhythm in essential hypertensive patients.Methods389 patients with untreated essential hypertension as the research object were selected from September 2014 to September 2015 in the Second Affiliated Hospital of Zhengzhou University Outpatient and Inpatient Department. Serum 25(OH) D concentration of patients with essential hypertension were detected by using electrochemical luminescence. According to the serum 25(OH)D levels, all patients were divided into normal(>30 nmol/L, n=89), mild deficiency(16-30 nmol/L, n=120)and severe deficiency(<16 nmol/L, n=180) groups. The 24-hour ambulatory blood pressure monitoring was performed in all patients. The average systolic blood pressure and diastolic blood pressure in 24-hour, daytime and nighttime periods and the corresponding standard deviation(as blood pressure variability) were analyzed.The relationship between the levels of 25(OH)D and blood pressure variability and circadian rhythm was compared. The circadian rhythm of blood pressure was indicated by the decrease of systolic blood pressure and diastolic blood pressure at night.Results Among patients with hypertension, those with 25(OH)D normal,mild deficiency,severe deficiency accounted for 22.9%, 30.8%, 46.3%, respectively. The mean concentration of 25(OH)D were lower in female than that in male [(15.20±8.23) vs(19.47±7.02) nmol/L,P<0.05]. Among the groups, there was statistical difference in24-hour systolic blood pressure(24h SBP), daytime systolic blood pressure(d SBP),nighttime systolic blood pressure(n SBP), 24 hour systolic blood pressure standard deviation(24h SSD), 24 hour diastolic blood pressure standard deviation(24h DSD),daytime systolic blood pressure standard deviation(d SSD), daytime diastolic blood pressure standard deviation(d DSD), nighttime systolic blood pressure standard deviation(n SSD), nighttime diastolic blood pressure standard deviation(n DSD) and the drop rate of nighttime systolic and diastolic blood pressure(all P<0.05).Compared with normal group and mild deficiency group, 24-hour diastolic blood pressure(24h DBP), daytime diastolic blood pressure(d DBP), nighttime diastolic blood pressure(n DBP) were higher in severe deficiency group(all P<0.05). While the difference between normal group and mild deficiency group was not significant(P>0.05). The serum 25(OH)D levels negatively correlated with 24 h SSD, 24 h DSD,d SSD, d DSD, n SSD, n DSD, 24 h SBP, 24 h DBP, d SBP, d DBP, n SBP, n DBP and positively correlated with nighttime systolic and diastolic blood pressure drop rate indicated by Person correlation analysis.(r=-0.583,-0.580,-0.520,-0.389,-0.463,-0.377,-0.599,-0.186,-0.577,-0.318,-0.573,-0.283, 0.308, 0.336 respectively, all P<0.05). At the same time, gender(male ratio) was negatively correlated with n DSD(r=-0159, P=0.046), BMI, Hb A1 c were positively correlated with n DSD(r=0.156,P=0.050; r=0.181, P=0.022); total cholesterol was positively correlated with d DBP(r=0.188, P=0.018). In order to describe the linear association between the dependent variables(24h SSD, 24 h DSD, d SSD, d DSD, n SSD, n DSD and night systolic pressure and diastolic pressure drop rate) and the independent variables [age, sex, BMI,Hb A1 c, fasting blood glucose, triglyceride, total cholesterol, HDL-C, LDL-C, serum calcium, 25(OH) D ]as independent variables, a multiple linear regression model was developed by stepwise method. The results indicated that 25(OH)D was the influencing factor for 24 h SSD(B=-0.227), 24 h DSD(B=-0.193), d SSD(B=-0.211),d DSD(B=-0.119), n SSD(B=-0.193), n DSD(B=-0.136)and nighttime systolic and diastolic blood pressure drop rate( B=0.273,0.329)(all P<0.01). Also, the response variable 24 h SSD was affected by age(B=-0.193; P=0.021). n SSD was affected by male ratio, BMI, Hb A1c(B=-0.794, P=0.050; B=0.188, P=0.010;B=-0.930, P<0.01, respectively).Conclusion1. Serum 25(OH) D deficiency in patients with essential hypertension is more common.2. Serum 25(OH) D level and arterial blood pressure are negative correlation,The correlation between 25(OH) D and systolic blood pressure was stronger than diastolic blood pressure.3. Serum 25(OH)D is the influence factors of blood pressure variability and circadian rhythm changes in patients with essential hypertension.