Pressor reactions to psychological stress and prediction of future blood pressure: data from the Whitehall II Study.

OBJECTIVE--To examine whether reactions of blood pressure to psychological stress predict future blood pressure. DESIGN--Blood pressure was recorded at a medical screening examination after which pressor reactions to a psychological stress task were determined. Follow up measurement of blood pressure was undertaken, on average, 4.9 years later. SETTING--20 civil service departments in London. SUBJECTS--1003 male civil servants aged between 35 and 55 years at entry to the study. MAIN OUTCOME MEASURE--Blood pressure at follow up screening. RESULTS--Reactions of systolic blood pressure to stress correlated positively with systolic blood pressure at follow up screening (r = 0.22, P < 0.01). The dominant correlate of follow up blood pressure was blood pressure at initial screening (r = 0.60; P < 0.01 between initial and follow up systolic blood pressure; r = 0.59, P < 0.01 between initial and follow up diastolic blood pressure). Stepwise multiple regression analysis indicated that reactions to the stressor provided minimal prediction of follow up blood pressure over and above that afforded by blood pressure at initial screening. In the case of follow up systolic blood pressure, systolic reactions to stress accounted for only 1% of follow up variance; systolic blood pressure at initial screening accounted for 34%. With regard to diastolic blood pressure at follow up, the independent contribution from diastolic reactions to stress was less than 1%. CONCLUSION--Pressor reactions to psychological stress provide minimal independent prediction of blood pressure at follow up. Measurement of reactivity is not a useful clinical index of the course of future blood pressure.     

Intersalt: an international study of electrolyte excretion and blood pressure. Results for 24 hour urinary sodium and potassium excretion. Intersalt Cooperative Research Group.

The relations between 24 hour urinary electrolyte excretion and blood pressure were studied in 10,079 men and women aged 20-59 sampled from 52 centres around the world based on a highly standardised protocol with central training of observers, a central laboratory, and extensive quality control. Relations between electrolyte excretion and blood pressure were studied in individual subjects within each centre and the results of these regression analyses pooled for all 52 centres. Relations between population median electrolyte values and population blood pressure values were also analysed across the 52 centres. Sodium excretion ranged from 0.2 mmol/24 h (Yanomamo Indians, Brazil) to 242 mmol/24 h (north China). In individual subjects (within centres) it was significantly related to blood pressure. Four centres found very low sodium excretion, low blood pressure, and little or no upward slope of blood pressure with age. Across the other 48 centres sodium was significantly related to the slope of blood pressure with age but not to median blood pressure or prevalence of high blood pressure. Potassium excretion was negatively correlated with blood pressure in individual subjects after adjustment for confounding variables. Across centres there was no consistent association. The relation of sodium to potassium ratio to blood pressure followed a pattern similar to that of sodium. Body mass index and heavy alcohol intake had strong, significant independent relations with blood pressure in individual subjects.     

Pharmacological effect of beta toxin of Clostridium perfringens type C on rats

The biological effect of purified beta toxin of Clostridium perfringens type C in vivo was investigated. After intravenous injection of the purified beta toxin into rats, a rise in blood pressure and a simultaneous fall in heart rate were observed. After the blood pressure reached a maximum, the heart rate recovered gradually, and electrocardiographic and respiratory changes began. The rise in blood pressure induced by beta toxin tended to be proportional to the amount of toxin. The latent period between the injection of toxin and the onset of the increase, and also the time between the injection and the maximum pressure induced by the toxin decreased with increasing concentration of the toxin. A good correlation was found between the factor producing the rise in blood pressure and beta toxin. Alpha adrenergic and ganglionic blocking agents reduced blood pressure levels elevated by beta toxin. The data suggest that the toxin causes a release of catecholamines, and that the increase in blood pressure was induced by released catecholamines.     

Blood pressure control by home monitoring: meta-analysis of randomised trials

Objective To determine the effect of home blood pressure monitoring on blood pressure levels and proportion of people with essential hypertension achieving targets.Design Meta-analysis of 18 randomised controlled trials.Participants 1359 people with essential hypertension allocated to home blood pressure monitoring and 1355 allocated to the “control” group seen in the healthcare system for 2-36 months.Main outcome measures Differences in systolic (13 studies), diastolic (16 studies), or mean (3 studies) blood pressures, and proportion of patients achieving targets (6 studies), between intervention and control groups.Results Systolic blood pressure was lower in people with hypertension who had home blood pressure monitoring than in those who had standard blood pressure monitoring in the healthcare system (standardised mean difference 4.2 (95% confidence interval 1.5 to 6.9) mm Hg), diastolic blood pressure was lower by 2.4 (1.2 to 3.5) mm Hg, and mean blood pressure was lower by 4.4 (2.0 to 6.8) mm Hg. The relative risk of blood pressure above predetermined targets was lower in people with home blood pressure monitoring (risk ratio 0.90, 0.80 to 1.00). When publication bias was allowed for, the differences were attenuated: 2.2 (-0.9 to 5.3) mm Hg for systolic blood pressure and 1.9 (0.6 to 3.2) mm Hg for diastolic blood pressure.Conclusions Blood pressure control in people with hypertension (assessed in the clinic) and the proportion achieving targets are increased when home blood pressure monitoring is used rather than standard blood pressure monitoring in the healthcare system. The reasons for this are not clear. The difference in blood pressure control between the two methods is small but likely to contribute to an important reduction in vascular complications in the hypertensive population.     

Phenotypic variability and correlation between skinfold thickness and arterial pressure level]

Contribution of genetic and environmental factors in phenotypic variability of blood pressure level and skinfold thickness, and phenotypic correlation between these characters was calculated on the basis of familial correlations. It was shown that genetic determinant explains considerable portion of blood pressure level and skinfold thickness variability. Among common environmental effects, the factors affecting one generation are important with regard to variability of these characters. Maternal effect is expressed in the variability of systolic and diastolic blood pressure. Correlation between blood pressure level and triceps skinfold thickness is determined by genetic factors, whereas that between blood pressure level and subscapular skinfold thickness is mediated by environmental factors. The results obtained may be applied in populational prevention of cardiovascular disease.     

The role of genetic and environmental factors in phenotypic variability of arterial pressure and body weight and their interconnection (a family study)

Contribution of genetic and environmental factors into phenotypic variability of blood pressure and body mass as well as into phenotypic correlation between these traits was defined. It was shown that additive genetic determinant is responsible for considerable level of blood pressure and body mass variability. Those common environmental factors are of importance which operate within the limits of one generation. Maternal effect of systolic and diastolic blood pressure variability is negligible. The correlation between systolic and diastolic blood pressure is determined both by environmental and genetic factors, whereas that between blood pressure and body mass is mediated by only environmental factors. The contribution of environmental factors into correlation between blood pressure and body mass lessens with age. The results obtained may be applied in development of population and individual programmes for preventing cardiovascular diseases.     

Caffeine restriction: effect on mild hypertension.

OBJECTIVE--To determine the effects on blood pressure of modifying dietary caffeine intake in patients with mild and borderline hypertension by monitoring ambulatory and clinic blood pressure. DESIGN--Four way, randomised, crossover trial of four consecutive two week dietary regimens: normal diet, caffeine free diet alone, caffeine free diet with decaffeinated instant coffee, caffeine free diet with caffeinated instant coffee (instant coffee phases conducted double blind). SETTING--Hospital hypertension clinic, Scotland. PATIENTS--52 patients (23 men; aged 26-67 years) with untreated borderline or mild hypertension (diastolic blood pressure 90-105 mm Hg) who normally drank a minimum of three cups of coffee daily. MAIN OUTCOME MEASURES--Mean ambulatory blood pressure over 24 hours; mean morning, daytime, and night time ambulatory blood pressure; sitting clinic blood pressure at 1700; plasma caffeine concentration at 1700 on the last day of each regimen. RESULTS--Mean 24 hour ambulatory blood pressure was not different between regimens. There was no difference in blood pressure variability between regimens. During the caffeine free diet alone morning ambulatory diastolic blood pressure was higher (2.8 mm Hg) than during the caffeine free diet with caffeinated coffee. Mean sitting clinic systolic blood pressure was higher at 1700 (4.7 mm Hg) with a caffeine free diet than with the caffeine free diet with caffeinated coffee (p less than 0.05). Dietary compliance as assessed by plasma caffeine concentration was excellent. There was no significant correlation between plasma caffeine concentration and blood pressure. CONCLUSIONS--Drinking caffeinated instant coffee over a two week period does not adversely influence blood pressure in patients with borderline or mild hypertension; abstinence is of no benefit.     

Arterial Blood Pressure and Modernization in Brazil

The relationship between individual modernization and elevated arterial blood pressure was examined in a study in urban Brazil. We hypothesized that elevated blood pressure would result from the discrepancy between an individual's style of life and his or her economic resources; specifically, we suggested that when modern life-style acquisition exceeded economic resources, a circumstance referred to as "life-style stress," blood pressure would be elevated. This factor was related to diastolic, but not systolic, blood pressure, independently of a variety of biologic, dietary, and sociocultural confounding factors. The perceived change associated with life events also predicted diastolic, but not systolic, blood pressure. Other predictors of diastolic blood pressure were calcium intake, fat intake, race, age, and the body mass index. We argue that sociocultural risk factors emerge in the modernization process as a result of social structural imbalances generated by economic development and represent independent risk factors for elevated arterial blood pressure.     

血压昼夜节律特征及其分子调控机制

正常血压具有典型的昼夜节律特征。血压昼夜节律异常与高血压靶器官损害和心血管事件发生呈明显相关关系,是独立于血压水平的重要致病因素。血压昼夜节律的产生和维持与时钟基因的周期性表达有关。时钟基因bmal1、per2是体内生物钟系统运行的关键基因,其表达水平和节律变化直接调节血压的昼夜节律。     

Blood pressure cosegregates with a microsatellite of angiotensin I converting enzyme (ACE) in F2 generation from a cross between original normotensive Wistar-Kyoto rat (WKY) and stroke-prone spontaneously hypertensive rat (SHRSP).

We investigated the linkage between high blood pressure and the ACE gene in the F2 generation between SHRSP/Izm and WKY/Izm. The male F2 rats were categorized into 3 genotypes according to a microsatellite polymorphism in the ACE gene. Significantly high blood pressure was observed in the SHRSP homozygotes when it was compared to the blood pressure of the heterozygotes. Further, after 2 or 3 months salt-loading, the blood pressure was significantly higher in the SHRSP homozygotes than in the heterozygotes and the WKY homozygotes. The heterozygotes had a blood pressure similar to that in the WKY homozygotes, indicating that the effect of the ACE gene genotype was recessive. Salt appetite was neither correlated with the salt-sensitivity nor cosegregated with the ACE genotype. The results indicate that the locus of ACE gene associates with the development of hypertension, especially salt-sensitive hypertension.     

Plasma vasopressin during increases and decreases in blood volume in anaesthetized dogs

In chloralose-anaesthetized dogs, plasma vasopressin concentration was measured by radioimmunoassay during step changes in blood volume of 4 mL/kg over a range of blood volume from +20 to -12 mL/kg. Blood volume was both increased and decreased over this range. There was a logarithmic relationship between blood volume and plasma vasopressin concentration over the range of blood volume examined. There was also a logarithmic relationship between blood volume and mean left atrial pressure. Linear regression between the natural logarithm of plasma vasopressin concentration and mean arterial pressure, heart rate, and mean left atrial pressure gave the highest correlation coefficient (r = 0.94) between vasopressin and mean arterial pressure. The results support the hypothesis that there are sensitive mechanisms controlling the release of vasopressin in response to changes in blood volume. Observations were also made of changes in atrial pressure and activity of left atrial receptors during changes in blood volume over the same range. The results suggest that changes in atrial receptor activity are unlikely to be the major cause of the large increases in plasma vasopressin concentration associated with hypovolemia.     

Relation of low diastolic blood pressure to coronary heart disease death in presence of myocardial infarction: the Framingham Study.

OBJECTIVE--To examine the hypothesis that a J curve relation between blood pressure and death from coronary heart disease is confined to high risk subjects with myocardial infarction. DESIGN--Cohort longitudinal epidemiological study with biennial examinations since 1950. SETTING--Framingham, Massachusetts, USA. SUBJECTS--5209 subjects in the Framingham study cohort followed up by a person examination approach. MAIN OUTCOME MEASURES--Coronary heart disease deaths and non-cardiovascular disease deaths in men and women with or without myocardial infarction relative to blood pressure. RESULTS--Among subjects without myocardial infarction non-cardiovascular disease deaths were twice to three times as common as coronary heart disease deaths. Furthermore, there was no significant relation between non-cardiovascular disease death and diastolic or systolic blood pressure. Also coronary heart disease deaths were linearly related to diastolic and systolic blood pressures. Among high risk patients (that is, people with myocardial infarction but free of congestive heart failure) death from coronary heart disease was more common than non-cardiovascular disease death. There was a significant U shaped relation between coronary heart disease death and diastolic blood pressure. Although there was an apparent U shaped relation between coronary heart disease death and systolic blood pressure, it did not attain statistical significance when controlling for age and change in systolic blood pressure from the pre-myocardial infarction level. None of the above conclusions changed when adjustments were made for risk factors such as serum cholesterol concentration, antihypertensive treatment, and left ventricular function. The U shaped relation between diastolic blood pressure and high risk subjects existed for both those given antihypertensive treatment and those not. CONCLUSIONS--These data suggest that an age and sex independent U curve relation exists for diastolic blood pressure and coronary heart disease deaths in patients with myocardial infarction but not for low risk subjects without myocardial infarction. The relation seems to be independent of left ventricular function and antihypertensive treatment.     

血压昼夜节律特征及其分子调控机制

正常血压具有典型的昼夜节律特征。血压昼夜节律异常与高血压靶器官损害和心血管事件发生呈明显相关关系,是独立于血压水平的重要致病因素。血压昼夜节律的产生和维持与时钟基因的周期性表达有关。时钟基因bmal1、per2是体内生物钟系统运行的关键基因,其表达水平和节律变化直接调节血压的昼夜节律。     

Association between Ambient Temperature and Blood Pressure and Blood Pressure Regulators: 1831 Hypertensive Patients Followed Up for Three Years

Several studies have suggested an association between ambient air temperature and blood pressure. However, this has not been reliably confirmed by longitudinal studies. Also, whether the reaction to temperature stimulation is modified by other factors such as antihypertensive medication is rarely investigated. The present study explores the relationship between ambient temperature and blood pressure, without and with antihypertensive medication, in a study of 1,831 hypertensive patients followed up for three years, in two or four weekly check ups, accumulating 62,452 follow-up records. Both baseline and follow-up blood pressure showed an inverse association with ambient temperature, which explained 32.4% and 65.6% of variation of systolic blood pressure and diastolic blood pressure (P<0.05) respectively. The amplitude of individual blood pressure fluctuation with temperature throughout a year (a 29 degrees centigrade range) was 9.4/7.3 mmHg. Medication with angiotensin converting enzyme inhibitor benazepril attenuated the blood pressure fluctuation by 2.4/1.3 mmHg each year, though the inverse association of temperature and blood pressure remained. Gender, drinking behavior and body mass index were also found to modify the association between temperature and diastolic blood pressure. The results indicate that ambient temperature may negatively regulate blood pressure. Hypertensive patients should monitor and treat blood pressure more carefully in cold days, and it could be especially important for the males, thinner people and drinkers.     

Blood pressure in first 10 years of life: the Brompton study.

OBJECTIVES--To determine the normal range of blood pressure and its pattern of change in the first 10 years of life. To estimate at what age (if any) children consistently appear in one part of the blood pressure distribution and at what age familial correlations in blood pressure become significant. DESIGN--Longitudinal cohort study. SETTING--South east England. SUBJECTS--2088 children of both sexes born consecutively in Farnborough Hospital, Kent, and their parents. MAIN OUTCOME MEASURE--Blood pressure measured by Doppler ultrasonography and sphygmomanometry. RESULTS--Systolic blood pressure rose from a mean of 88.5 mm Hg at age 6 months to 96.2 mm Hg at 8 years measured with a 8 cm cuff and from 89.1 mm Hg at age 5 years to 94.3 mm Hg at age 10 years measured with a 12 cm cuff. The larger cuff gave blood pressure readings about 6 mm Hg lower. This effect was independent of body weight and arm circumference. Diastolic blood pressure rose from 57.8 mm Hg at 5 years to 61.8 mm Hg at 10 years (12 cm cuff). There was only about 1 mm Hg difference between sexes. Blood pressure was correlated with weight, weight adjusted for height, height, and arm circumference at all ages studied. The correlation coefficient of repeated yearly measurements increased steadily with age from 0.28 at 2 years to 0.59 at 10 years. The correlation coefficients between child''s blood pressure and mother''s average blood pressure increased from 0.1 at age 1 year to 0.23 at age 10. CONCLUSIONS--Blood pressure changes relatively little between the ages of 6 months and 10 years. Yet because of the increasing strength of between occasion and family correlations, children are more consistently occupying a specific part of the blood pressure distribution as they grow older. Studies in children should help determine why some adults have hypertension and others do not.     

Comparison between perindopril and nifedipine in hypertensive and normotensive diabetic patients with microalbuminuria. Melbourne Diabetic Nephropathy Study Group.

OBJECTIVE--To compare the efficacy of angiotensin converting enzyme inhibition with calcium antagonism in diabetic patients with microalbuminuria. DESIGN--Randomised study of diabetic patients with microalbuminuria treated with perindopril or nifedipine for 12 months and monitored for one or three months after stopping treatment depending on whether they were hypertensive or normotensive. Patients were randomised separately according to whether they were hypertensive or normotensive. SETTING--Diabetic clinics in three university teaching hospitals. PATIENTS--50 diabetic patients with persistent microalbuminuria. In all, 43 completed the study: 30 were normotensive and 13 hypertensive; 19 had type I diabetes and 24 had type II diabetes. INTERVENTIONS--For 12 months 20 patients were given perindopril 2-8 mg daily and 23 were given nifedipine 20-80 mg daily. MAIN OUTCOME MEASURES--Albumin excretion rate, blood pressure, and glomerular filtration rate. RESULTS--Both perindopril and nifedipine significantly reduced mean blood pressure. During treatment there was no significant difference between those treated with perindopril and those treated with nifedipine with respect to albuminuria or mean blood pressure. Stopping treatment with both drugs was associated with a sustained increase in albuminuria and mean blood pressure. There was a significant correlation between mean blood pressure and albuminuria and also between the reduction in mean blood pressure and the decrease in albuminuria during treatment with both drugs. In hypertensive patients both drugs caused significant decreases in mean blood pressure and albuminuria. In normotensive patients there was no significant reduction in albuminuria with either regimen. CONCLUSIONS--In diabetic patients with microalbuminuria blood pressure seems to be an important determinant of urinary albumin excretion. Perindopril and nifedipine have similar effects on urinary albumin excretion, both preventing increases in albuminuria in normotensive patients and decreasing albuminuria in hypertensive patients.     

The efflux rate of norepinephrine from platelets and its relation to blood pressure

The uptake and efflux rate of norepinephrine in platelets have been studied in 63 individuals, 48 men and 15 women. 40 of these had a diastolic blood pressure ?95 mm Hg. If the initial efflux rate, k, was correlated to the diastolic blood pressure a highly significant relationship (r = 0.748 p<0.001) was obtained, i.e. a high diastolic blood pressure is correlated to a rapid efflux of norepinephrine from platelets. No correlation was found between uptake values and diastolic blood pressure.     

脑内γ—氨基丁酸（GABA）在急性失血性低血压时对血压的影响

本实验通过大鼠和家兔侧脑室注射GABA受体阻断剂荷包牡丹碱(Bicuculline)研究正常血压和急性失血性低血压时,中枢GABA对血压的调节作用。结果表明:在两种情况下,荷包牡丹碱均有明显的升压作用,但后者显著大于前者,且这种升压效应不被去肾或去肾上腺所影响。同时发现:急性失血性低血压时,兔脑脊液中GABA含量明显增加,提示在急性失血性低血压时,中枢GABA具有阻止血压回升的作用,这种作用是通过对中枢交感神经系统的抑制引起的。     

Relationship between blood pressure and Alzheimer's disease in Linxian County,China

To investigate the relationship between hypertension and Alzheimer's disease(AD) and the change of Alzheimer's patients' blood pressure(BP) before and after the onset of AD, we conducted this epidemiological study. Subjects for this study were individuals who participated in a large scale, randomized controlled trial of nutritional intervention from 1984 to 1991. Participants were initially screened for dementia using Chinese Mini-Mental State Examination (CMMS) and Activities of Daily Living (ADL). Positive subjects were subsequently administered a detailed neuropsychological and neurobehavioral examination. The diagnosis of AD was made by a consensus conference of psychiatrists using Diagnostic And Statistical Manual Of Mental Disorders-Fourth Edition(DSM-IV) criteria. 16488 subjects were examined and 301 were diagnosed as AD. We compared the prevalence of AD in different populations that were stratified with 1984's systolic or diastolic blood pressure(those four stratifications being high blood pressure, borderline blood pressure, normal, low blood pressure), and compared the change of blood pressure of 301 AD patients between 1984 and 1999-2000, which is before and after the onset of AD respectively. Multiple Logistic Regression (1:1 nested case-control study) was used to assess if hypertension is an independent risk factor for AD, and Trend test was used to assess the relationship between blood pressure and AD. Here we demonstrate that there was a significant difference in AD prevalence among different populations stratified by systolic or diastolic blood pressure (P < 0.01).The prevalence is highest in hypertension group, and lowest in hypotension group. Multiple Logistic Regression identified high blood pressure as a risk factor for AD (OR = 1.97, 95%CI:1.09-3.54, P = 0.02). Trend test showed that there is a significant dose-response relationship between blood pressure and AD (P < 0.0002). For hypertensive AD patients, there was no significant difference in systolic blood pressure(SBP) before and after the onset of AD, but diastolic blood pressure(DBP) decreased dramatically after the onset of AD (P < 0.01); however, the result also showed that DBP decrease occurred in the non-demented group. Based on this, we think the DBP decrease is not related to AD. We further investigated whether BP values differed crossed-sectionally between the AD-patients and non-demented individuals. We found that regardless of SBP or DBP, the BP values of the AD group were all significantly higher than that of non-demented. In summary, these data suggest there is a strong relationship between hypertension and AD; however, the mechanism remains to be studied.