Relationship Between Circadian Rhythm And Ankle Brachial Index In Patients With Essential Hypertension

Blood pressure fluctuates with the rhythm of 24 hours in healthy people. When people wake up, blood pressure rises from 6:00 a.m. and reaches its first peak from 8:00 to 10:00 a.m. Then it declines gradually and reaches the second peak from 16:00 to 20:00. Its trough appears from 0:00 to 2:00. During the day the blood pressure is at a relatively high level for 16 hours and during the night at a relatively low level for about 8 hours. The curve shape of blood pressure is formed with two peaks and one trough looking like a ladle. During the past decades 24-hour ambulatory blood pressure monitoring (ABPM) has been extensively applied by which we can observe circadian rhythm more easily. According to characters of the fluctuation blood pressure rhythms can be divided into four types:1. Dipper, which defined as a 10%-20% fall in nocturnal blood pressure; 2. Non-dipper, with a nocturnal fall less than 10%; 3.Extreme-dipper, which with a nocturnal fall greater than 20%; 4. Reverse-dipper, as less than 0 at most fall in nocturnal blood pressure. Dipper is the normal circadian rhythm while the others are abnormal ones. In recent years many studies showed that abnormal circadian rhythm could aggravate the degree of arteriosclerosis and was related to the progressive damage of target organs. The ankle brachial index is a classical non-invasive indicator for detecting the degree of atherosclerosis which is associated with atherosclerosis in early stage. It is closely associated with cardiac and cerebrovascular events in the later stage. In this study we investigated the impact of circadian rhythm on the ankle brachial index and aimed at analyzing the relationship between circadian rhythm and the degree of atherosclerosis. We should pay more attention to maintaining and restoring the circadian rhythm in addition to lowering blood pressure up to standard. That has important clinical significance on preventing and treating atherosclerosis and target organs damage.Objective:It was to analyze the relationship between circadian rhythm and ankle brachial index (ABI) in patients with essential hypertension, as while as to investigate the impact of circadian rhythm on atherosclerosis.Method:1.759 cases were randomly selected from Department of Geriatrics of the Affiliated Hospital of Chengde Medical College during the period from July 2010 to June 2011. All patients with essential hypertension were classified into 4 groups according to circadian rhythm:Dippers, with 190 cases; Non-dippers, with 204 cases; Extreme-dippers, with 186 cases; Reverse-dippers, with 179 cases.2. The values of blood pressure were monitored by Japanese AND TM-2430 ambulatory blood pressure monitoring system. All observed parameters contained 24hSBP,24hDBP,24hMAP, dSBP, dDBP, dMAP, nSBP, nDBP,nMAP, △MAP% and HR.3. Method of evaluating circadian rhythm and grouping.△MAP%=(dMAP-nMAP)/dMAP×100%. Dipper, which defined as a 10%-20% fall in nocturnal blood pressure; Non-dipper, with a nocturnal fall less than 10%; Extreme-dipper, which with a nocturnal fall greater than 20%; Reverse-dipper, as less than 0 at most fall in nocturnal blood pressure.4. Professional medical staff examined ABI with the Huntleigh Dopplex RD2 Bi-Directional Doppler and PPG System produced in Britain. ABI values were calculated and the lower values were chosen as the final results.5. The subjects’basic situation, such as name, sex, age, course of hypertension, smoking, height, weight, BMI, SBP and DBP were selected and recorded.6. Laboratory tests:GLU, TG, TC, LDL-C, HDL-C, Cr and BUN were examined.7. SPSS 17.0 was used in all statistical analyses, one-way analysis of variance (ANOVA) and LSD-t test were used to analyze measurement data, Chi-square test was used to analyze enumeration data, multivariate Logistic was used to analyze the relationship of ABI with risk factors. There was statistical significance if P<0.05.Results:1. There were no significant differences in sex, age, course of hypertension, smoking, BMI, SBP and DBP in Dippers, Non-dippers, Extreme-dippers and Reverse-dippers(P>0.05).2. Index of 24-hour blood pressure monitoring.2.1 nSBP Dippers:133.52±12.81 mmHg, Non-dippers:151.61±10.85 mmHg, Extreme-dippers:121.27±14.80 mmHg, Reverse-dippers:158.96± 10.76 mmHg, mean of all subjects:143.10±12.16 mmHg, F=18.54, P=0.000, there were significant differences in Dippers, Non-dippers, Extreme-dippers and Reverse-dippers.2.2 nDBP Dippers:76.42±7.17 mmHg, Non-dippers:87.00±11.91 mmHg, Extreme-dippers:77.72±10.12 mmHg, Reverse-dippers:91.72±8.12 mmHg, mean of all subjects:83.98±9.36 mmHg, F=9.502, P=0.000, there were significant differences in Dippers, Non-dippers, Extreme-dippers and Reverse-dippers.2.3 nMAP Dippers:93.25±8.85 mmHg, Non-dippers:110.42±11.55 mmHg, Extreme-dippers:88.12±10.68 mmHg, Reverse-dippers:116.23± 8.90 mmHg, mean of all subjects:103.98±9.86 mmHg, F=10.482,P=0.000 there were significant differences in Dippers, Non-dippers, Extreme-dippers and Reverse-dippers.2.4 △MAP% Dippers:14.39±3.04%, Non-dippers:4.39±2.55%, Extreme-dippers:22.70±3.46%, Reverse-dippers:-6.5±4.44%, mean of all subjects:7.36±7.66%, F=274.74, P=0.000, there were significant differences in Dippers, Non-dippers, Extreme-dippers and Reverse-dippers.2.5 There were no significant differences on 24hSBP,24hDBP,24hMAP, dSBP, dDBP, dMAP and HR in Dippers, Non-dippers, Extreme-dippers and Reverse-dippers (P>0.05).3. There were no significant differences on GLU, TG, TC, LDL-C, HDL-C, Cr and BUN in Dippers, Non-dippers, Extreme-dippers and Reverse-dippers (P>0.05).4. The levels of ABI in Dippers, Non-dippers, Extreme-dippers and Reverse-dippers.4.1 The levels of ABI in Non-dippers(0.84±0.18) and Reverse-dippers (0.72±0.16)were lower than Dippers(1.06±0.22), the levels in Reverse-dippers were lower than those in Non-dippers, the differences were significant (P<0.05).4.2 There were no significant differences on ABI between Extreme-dippers(1.00±0.23) and Dippers(1.06±0.22) (P>0.05).5. The result of Multivariate Logistic Regression showed that abnormal circadian rhythm, age and smoking were risk factors on declining of ABI.Conclusion:1. There were no significant differences on 24 hour mean systolic blood pressure, mean diastolic blood pressure, mean artery pressure, day mean systolic blood pressure, mean diastolic blood pressure, and mean artery pressure, but there were obvious differences on night mean systolic blood pressure, mean diastolic blood pressure and mean artery pressure among patients of essential hypertension with different circadian rhythm.2. Different circadian rhythm of patients with essential hypertension had effects on ABI differently:Reverse-dippers>Non-dippers> Extreme-dippers= Dippers.3. There were different effects on the degree of atherosclerosis for different circadian rhythm.4. Circadian rhythm, age and smoking were risk factors of ABI.