Multifrequency Infradian Variation of Blood Pressure During and After Human Pregnancy

We used a chronobiologic approach to explore the possibility that there may be -7-day (circaseptan) and -30-day (circatrigintan) components in blood pressure during a healthy human pregnancy, the amenorrhea of this status notwithstanding. The results were compared with those obtained from data longitudinally monitored on the same subject at a time when she was not pregnant. The woman under study used an ABPM-630 Colin (Komaki, Japan) device to monitor her blood pressures and heart rates at half to 1-h intervals, with few interruptions. During pregnancy, starting during the first gestational week, she monitored herself for 2 of each 6-day span for the entire duration of pregnancy (a total of 76 days of monitoring). Additionally, with a monitoring protocol similar to that during pregnancy, the subject used the same blood pressure monitor for a total of 78 days during 9.6 months and starting 1 year after delivery. The data obtained oscillometrically for both longitudinal profiles were analyzed separately by multiple-component linear least-squares rhythmometry, a procedure used to describe the periodic waveform of nonsinusoidal rhythms. The analysis of blood pressure variability during pregnancy allows the identification not only of the circadian (with a period of 24 h), but also of other statistically significant components with periods of 156 (6.5 days, apparently free-running from the social week) and of 720 h (30 days) for both systolic and diastolic blood pressure. This multiharmonic time structure is somewhat different during menstruation in the same woman and during a similar time span, with statistically significant components of 96 h (4 days), 192 h (8 days), and 960 h (40 days) for both systolic and diastolic blood pressure. Moreover, the ratio between the amplitudes of the infradian components identified during pregnancy in clinical health is reversed from that obtained in women with preeclampsia. The complex time-structure of blood pressure during pregnancy offers new endpoints to be taken into account for an early identification of gestational hypertension or even preeclampsia.     

Multifrequency Infradian Variation of Blood Pressure During and After Human Pregnancy

We used a chronobiologic approach to explore the possibility that there may be -7-day (circaseptan) and -30-day (circatrigintan) components in blood pressure during a healthy human pregnancy, the amenorrhea of this status notwithstanding. The results were compared with those obtained from data longitudinally monitored on the same subject at a time when she was not pregnant. The woman under study used an ABPM-630 Colin (Komaki, Japan) device to monitor her blood pressures and heart rates at half to 1-h intervals, with few interruptions. During pregnancy, starting during the first gestational week, she monitored herself for 2 of each 6-day span for the entire duration of pregnancy (a total of 76 days of monitoring). Additionally, with a monitoring protocol similar to that during pregnancy, the subject used the same blood pressure monitor for a total of 78 days during 9.6 months and starting 1 year after delivery. The data obtained oscillometrically for both longitudinal profiles were analyzed separately by multiple-component linear least-squares rhythmometry, a procedure used to describe the periodic waveform of nonsinusoidal rhythms. The analysis of blood pressure variability during pregnancy allows the identification not only of the circadian (with a period of 24 h), but also of other statistically significant components with periods of 156 (6.5 days, apparently free-running from the social week) and of 720 h (30 days) for both systolic and diastolic blood pressure. This multiharmonic time structure is somewhat different during menstruation in the same woman and during a similar time span, with statistically significant components of 96 h (4 days), 192 h (8 days), and 960 h (40 days) for both systolic and diastolic blood pressure. Moreover, the ratio between the amplitudes of the infradian components identified during pregnancy in clinical health is reversed from that obtained in women with preeclampsia. The complex time-structure of blood pressure during pregnancy offers new endpoints to be taken into account for an early identification of gestational hypertension or even preeclampsia.     

Chronomes, time structures, for chronobioengineering for "a full life"

Week-long or longer monitoring of blood pressure and heart rate, coupled to time-structure analyses, can help detect disease-risk elevations, as a warning of the need for a preventive prehabilitation. Within the normal range of physiologic variation, computer methods quantify time structures, or chronomes, that can serve as reference values. The major applied purpose for mapping chronomes is the detection of disease-risk syndromes such as blood pressure "overswinging" and heart rate "underswinging." Too much blood pressure variability (circadian hyperamplitude tension; CHAT), is a risk factor for vascular disease. Other risk syndromes are chronome alterations of heart rate variability (CAHRVs), consisting of a loss of "jitter", i.e., a reduced standard deviation of heart rate or of alterations in the spectral element of the heart-rate-variability chronome, such as in the correlation dimension, an endpoint of deterministic chaos. These alterations can again serve for prehabilitation. On the basic side, the spectral element of the heart-rate-variability chronomes extends from focus on the heartbeat's period of about 1 second to periods in heart rate and its standard deviation that are numerical equivalents of about 10.5- and about 21-year cycles of solar activity. A seemingly unnatural physiologic rhythm or pattern (such as one of 81.6 hours) may correspond numerically to a purely physical environmental rhythm. For example, interplanetary magnetic storms, with their cycles as external chronome components, trigger myocardial infarctions, strokes, and traffic accidents. The systematic monitoring of external rhythms along with physiologic ones for the concurrent analysis of rhythms with longer and longer periods could detect alterations anywhere in and between the 1 cycle/sec and the 1 cycle/10.5- or 21-years regions of the spectrum. Chronobiomimetic engineering for discovering both instantaneous and long-term chronorisk alterations can provide warnings of increased risk. If risk-lowering therapy is then instituted automatically, instrumented health care will be extended beyond the pacemaker-cardioverter-defibrillator, which focuses on the frequency of 1 cycle/sec. Instrumentation that automatically detects blood pressure that varies too much and heart rate that varies too little is needed for prompting prophylactic CHAT and CAHRV treatment. A database of reference values that can be used for chronodiagnosis is now accumulating.     

Chronobiology in the diagnosis and treatment of mesor-hypertension.

An elevation of systolic and diastolic bloodpressure to values regarded as abnormal ones on the basis of conventional criteria was recognized by self-measurement. For both systolic and diastolic blood pressure, the overall means adjusted for rhythms, the so-called mesors, also were elevated in the light of their response to treatment: these mesors were found to be lowered with statistical significance when values during treatment were compared by an objective test with values measured before treatment. Individualized rhythmometry quantitatively characterizes a predictalbe portion of the variability in human blood pressure and tests for the statistical significance of changes in blood pressure as a function of the treatment and also as a function of the circadian timing of such treatment. The case report thus illustrates an individualized chronotherapy of systolic and diastolic mesor-hypertension, diagnosed retrospectively from the tested effect of hydrochlorothiazide. In the case reported, and perhaps routinely, computer-analyzed self-measurements can serve 1) to prescribe the right kind and amount with the right timing, for a given therapy, and 2) for diagnosis and prevention as well (Meyer et al.; Halberg et al.).     

Chronobiology in 1975.

A spectrum of rhythms with several frequencies importantly characterizes not only the central nervous system but also the neuroendocrines and endocrines, other structures and organs, beyond the level of the cell to subcellular structures; it has a wide bearing since chronobiologic methods and facts relate to both basic research and its bearing on major problems of our day. Perhaps most important, computer analysis of data series allows study of temporal structure, progressive and rhythmic variations in life processes and in their responses to environment and drugs. By such methods coupled to modern data collection and/or self-measurement, chronobiology is particularly promising in the following areas, cited as illustrative rather than comprehensive examples: 1. Work hygiene: optimization of work schedules by adjustment of regular schedules and in particular of shift-work to the individuals' physical and mental rhythms. Experimentally, differences in manner of schedule change can account for the difference between the life span shortening and lengthening. 2. Population control: improved methods for detecting the neural as well as neurohormonal regulation of ovulatory cycles should aid efficient family planning by the recognition of a spectrum of rhythms and its synchronization with socio-ecologic factors acting, perhaps, via olfactory and/or other sensory modalities; 3. Nutrition: optimizing the utilization of ever scarcer food supplies and also the benefit from both oral and parenteral medications by meal timing; 4. Education: providing a do-it-yourself system for monitoring individual health in the context of secondary and adult education and as the basis for preventive health care; and, in another context, taking individual mental rhythms as well as morningness-eveningness into account in teaching and learning; 5. Health care: Any risk, e.g., from blood pressure rhythm alteration (perhaps preceding by years intermittent labile elevation) will be detected earlier and more efficiently by multiple measurements readily obtained by autorhythmometry. Results of such an endeavor provide at any one time indices that can be compared with an individualized rhythmometric reference standard as well as peer group rhythm parameters. The rhythm-determined average is more reliable than the single measurement. Other individualized characteristics of a rhythm, such as measures of extent of change or timing of change, may constitute an early warning signal and could be monitored by self-measured or preferably automatically-collected data. Timely and timed treatment can then be sought to prevent, in the case of blood pressure, elevation and consequent debilitating disease such as coronary infarction and stroke. 6. Therapy: One can strive toward the more specific correction of any pathogenic rhythm alteration when such can be recognized by modern methods of data collection and data analysis...     

Ambulatory blood pressure monitoring: assessing the diurnal variation of blood pressure

The purposes of this paper are to examine the effects of activity, situation of measurement, mood, and occupation on the daily variation of blood pressure and to discuss the potential utility of ambulatory blood pressure monitoring in physical anthropological studies. The subjects of the blood pressure variability study are 125 men who were referred to the Hypertension Center at New York Hospital--Cornell Medical Center for evaluation of hypertension. There were 1,386 blood pressure measurements from these subjects available for study, which were taken using noninvasive ambulatory blood pressure monitoring techniques. Pressures were transformed to z scores using the subject's daily mean pressure and standard deviation to assess the relative elevation during the experience of the various factors. The results show that activity and mood are the most significant sources of blood pressure variation (P less than .005) and are additive. Occupation, which may be an indicator of social class in this population, also modified the mood effects. Because ambulatory blood pressure monitors obtain many readings over a day under a variety of circumstances, their use can improve epidemiological and human biological studies of the inheritance and variability of blood pressure. Ambulatory blood pressure monitoring is an important new tool in the study of human biological variation.     

Mesor-hypertension: hints by chronobiologists

Circadian systems are intermodulated by networks of specialized neural, hormonal and cellular functions, with time structures that are interdependent. In cardiovascular pathophysiology, circadian and ultradian rhythms of clinical interest have been demonstrated. Cardiac output, heart rate, arterial pressure and blood volume are the best known. Systolic and diastolic blood pressure and heart rate have circadian patterns in health and therefore arterial pressure cannot be evaluated by a single measurement during a 24-h span. With correct monitoring for at least 48-h it is possible to detect the mesor-hypertension and the possible amplitude-hypertension that precedes the mesor-hypertension. Prolonged elevation of blood pressure can cause irreparable harm to sensitive tissues. To quantify the damage, the concept of hyperbaric impact has been introduced. This is a measure of the excess load exerted upon the arterial walls. Studies of the beta-blocker penbutolol with correct automatic monitoring have shown the persistence of the physiological circadian variation in the cardiovascular parameters during penbutolol administration. The so-called elimination of the circadian rhythm in blood pressure, which would not really be desirable, was not seen in any of our patients, whose cardiovascular parameters were monitored continuously, day and night, while taking penbutolol. The amplitudes of the rhythms were always prominent. A phase shift, a delay of about 100 degrees, was demonstrated in the heart rate of one 63-year-old mesor-normotensive woman.     

Circadian Time Structure of Cardiovascular Characteristics in Human Pregnancy

Conventional time-unspecified single measurements of blood pressure and heart rate may be misleading because they may be influenced, among other factors, by the patient's emotional state, position, diet, and external stimuli. All of these effects depend on the stages of a (mathematical) spectrum of rhythms and trends with age. The evaluation of predictable variability in blood pressure and heart rate by (a) the use of fully ambulatory devices, and (b) chronobiologic data processing, assesses early cardiovascular disease risk, e.g., in pregnancy. We have used this approach to quantify changes in 24-h synchronized (circadian) characteristics of cardiovascular variables in two consecutive pregnancies of a clinically healthy woman. Blood pressure and heart rate were automatically monitored, with few interruptions, at I-h intervals, each time for at least 48 consecutive h, and for a total of 76 days of monitoring in each pregnancy. Circadian parameters of those circulatory variables were computed for each single day of measurement by the least-squares fit of a 24-h cosine curve. Regression analysis of parameters thus obtained revealed patterns of variation of circadian-rhythm-adjusted means and amplitudes with gestational age. In both pregnancies, the predictable variability of the circadian-rhythm-adjusted mean of blood pressure can be approximated by a second-order polynomial model on gestational age: a steady linear decrease in systolic, diastolic, and mean arterial blood pressure up to the 22nd week of pregnancy is followed by an increase in blood pressure up to the day of delivery. This longitudinal study confirms and extends to ambulatory everyday life conditions the predictable pregnancy-associated variability in blood pressure and heart rate and also allows the establishment of prediction and confidence limits for cardiovascular parameters in a healthy pregnancy.     

Chronobiologically interpreted ambulatory blood pressure monitoring: past,present, and future

Research at the Halberg Chronobiology Center focused to a large extent on the monitoring of blood pressure (BP) and heart rate (HR). Self-measurements and later ambulatory BP monitoring yielded new knowledge of interest to basic science and clinical practice. After a brief review of BP measurement, we outline developments in methods of data analysis that paralleled technological advances in the measurement of BP. We review work done in cooperation with colleagues worldwide to illustrate how a chronobiological approach led to the mapping of spontaneous circadian and other rhythms for the derivation of refined reference values and to the assessment of response rhythms underlying chronotherapy. BIOCOS members work in different fields, spanning from cardiology and nutrition to obesity, diabetes, exercise physiology and rehabilitation, but all strive for “pre-habilitation”. The early recognition of increased risk can prompt the timely institution of prophylactic intervention. As technology continues to improve, studies on groups are complemented by longitudinal self-surveillance for health maintenance. Longitudinal records serve for the investigation of environmental influences on human physiology, the topic of chronomics. As current advances in technology and wireless communication will likely impact the future of healthcare, chronobiological methods and concepts should be an integral part of this seachange.     

Circadian Time Structure of Cardiovascular Characteristics in Human Pregnancy

Conventional time-unspecified single measurements of blood pressure and heart rate may be misleading because they may be influenced, among other factors, by the patient's emotional state, position, diet, and external stimuli. All of these effects depend on the stages of a (mathematical) spectrum of rhythms and trends with age. The evaluation of predictable variability in blood pressure and heart rate by (a) the use of fully ambulatory devices, and (b) chronobiologic data processing, assesses early cardiovascular disease risk, e.g., in pregnancy. We have used this approach to quantify changes in 24-h synchronized (circadian) characteristics of cardiovascular variables in two consecutive pregnancies of a clinically healthy woman. Blood pressure and heart rate were automatically monitored, with few interruptions, at I-h intervals, each time for at least 48 consecutive h, and for a total of 76 days of monitoring in each pregnancy. Circadian parameters of those circulatory variables were computed for each single day of measurement by the least-squares fit of a 24-h cosine curve. Regression analysis of parameters thus obtained revealed patterns of variation of circadian-rhythm-adjusted means and amplitudes with gestational age. In both pregnancies, the predictable variability of the circadian-rhythm-adjusted mean of blood pressure can be approximated by a second-order polynomial model on gestational age: a steady linear decrease in systolic, diastolic, and mean arterial blood pressure up to the 22nd week of pregnancy is followed by an increase in blood pressure up to the day of delivery. This longitudinal study confirms and extends to ambulatory everyday life conditions the predictable pregnancy-associated variability in blood pressure and heart rate and also allows the establishment of prediction and confidence limits for cardiovascular parameters in a healthy pregnancy.     

Chronobiology of human blood pressure in the light of static (room-restricted) automatic monitoring

Systematic 24-h automatic physiologic monitoring has obvious merits, even without rhythmometry. It can lead more readily to the recognition of odd-hour blood pressure elevation (e.g., of 'evening' or 'morning' hypertension). Such a condition can constitute an initial diagnosis or it may be found under treatment that may seem to be satisfactory if its effects are assessed only on the basis of a conventional check at a casual, possibly 'wrong' time. The mere inspection of a 24-h record, however, does not necessarily allow one to make objective quantitative global statements as to a change in pattern, e.g., after a given intervention. This paper illustrates how by rhythmometry, some of the uncertainties of a subjective interpretation of a record may be removed by practitioners of medicine, as well as basic scientists interested in mechanisms of blood pressure variability. This is possible since a large part of blood pressure variability can be accounted for by its circadian periodic behavior. We herein present a methodology for data collection and analysis that allows the objective quantification of blood pressure rhythm parameters in health and disease and the derivation of reference standards for such parameters. The chronobiologic approach thus makes it possible to define 'hypertension' objectively, and to distinguish between 'mesor-' and 'amplitude-hypertension', i.e., between an elevation in overall mean and one in the predictable extent of variability. Moreover, chronobiology has shown that mesor-hypertension may be preceded by an elevation in circadian amplitude only (amplitude-hypertension). Parameter tests readily allow the assessment, in relation to an objective reference standard, of these conditions, with a defined probability. Similarly, response to drug or non-drug therapy can be established and a given intervention optimized by timing treatment. Using chronobiologic tools in cardiovascular research provides new insights into possible mechanisms underlying mesor- and amplitude-hypertension. The teaching of the chronobiology of blood pressure and autorhythmometry in schools has been proven to be feasible and has been recommended as a step toward self-help for health care.     

Chromosome aberrations (CA), sister-chromatid exchanges (SCE) and mitogen-induced blastogenesis in cultured peripheral lymphocytes from 48 control individuals sampled 8 times over 2 years

Confidence in the measurement of positive effects determined by monitoring of environmentally or occupationally exposed individuals can be enhanced by a knowledge of the normal variability in these endpoints in the general population. Confounding effects can be determined and study interpretation improved by correlation of this variability with various lifestyle factors such as sex and age of donor, smoking and drinking habits, viral infections, exposure to diagnostic X-rays, etc.

8 blood samples were taken from each of 24 male and 24 female volunteers over a period of 2 years. Questionnaires pertaining to lifestyle were completed at the time of each sampling. Whole blood was cultured and slides prepared for CA or SCE analysis. Separated mononuclear cells were cultured with a range of phytohaemagglutinin concentrations and the maximum level of mitogen-induced blastogenesis was determined by measurement of [³H]thymidine uptake.

There was a significant effect of both year and season of sampling for all 3 endpoints. No significant effects in any of the 3 endpoints were found with respect to sex or age of donor nor any of the other lifestyle factors, although SCE frequency and mitogen-induced blastogenesis were nearly always higher in females than males. These results point to the need for concurrent sampling of controls with exposed populations.     

Circadian rhythms in zebrafish (Danio rerio) behaviour and the sources of their variability

Over recent decades, changes in zebrafish (Danio rerio) behaviour have become popular quantitative indicators in biomedical studies. The circadian rhythms of behavioural processes in zebrafish are known to enable effective utilization of energy and resources, therefore attracting interest in zebrafish as a research model. This review covers a variety of circadian behaviours in this species, including diurnal rhythms of spawning, feeding, locomotor activity, shoaling, light/dark preference, and vertical position preference. Changes in circadian activity during zebrafish ontogeny are reviewed, including ageing-related alterations and chemically induced variations in rhythmicity patterns. Both exogenous and endogenous sources of inter-individual variability in zebrafish circadian behaviour are detailed. Additionally, we focus on different environmental factors with the potential to entrain circadian processes in zebrafish. This review describes two principal ways whereby diurnal behavioural rhythms can be entrained: (i) modulation of organismal physiological state, which can have masking or enhancing effects on behavioural endpoints related to endogenous circadian rhythms, and (ii) modulation of period and amplitude of the endogenous circadian rhythm due to competitive relationships between the primary and secondary zeitgebers. In addition, different peripheral oscillators in zebrafish can be entrained by diverse zeitgebers. This complicated orchestra of divergent influences may cause variability in zebrafish circadian behaviours, which should be given attention when planning behavioural studies.     

血压波动性对主动脉夹层发生发展影响的研究进展

高血压病是严重威胁人类健康的一类疾病。近年来研究表明,血压波动对于靶器官的损伤较高血压本身更大。主动脉夹层是一种与高血压密切相关的疾病。近年来,主动脉夹层的发生发展与血压波动的关系,越来越受到关注。血压波动性可造成内膜损伤和中膜层退行性变,从而在局部影响主动脉夹层的发生;还可通过免疫反应,炎性变化等全身因素造成主动脉夹层的发生。血压波动性在已发生主动脉夹层的患者中也是影响预后的重要因素。本文主要介绍血压波动性的分类和测量方法,以及对主动脉夹层发生发展影响的研究进展,旨在为临床医生进行主动脉夹层与血压波动性的关系研究提供参考。     

Effect of rosary prayer and yoga mantras on autonomic cardiovascular rhythms: comparative study

ObjectiveTo test whether rhythmic formulas such as the rosary and yoga mantras can synchronise and reinforce inherent cardiovascular rhythms and modify baroreflex sensitivity.DesignComparison of effects of recitation of the Ave Maria (in Latin) or of a mantra, during spontaneous and metronome controlled breathing, on breathing rate and on spontaneous oscillations in RR interval, and on blood pressure and cerebral circulation.SettingFlorence and Pavia, Italy.Participants23 healthy adults.ResultsBoth prayer and mantra caused striking, powerful, and synchronous increases in existing cardiovascular rhythms when recited six times a minute. Baroreflex sensitivity also increased significantly, from 9.5 (SD 4.6) to 11.5 (4.9) ms/mm Hg, P<0.05.ConclusionRhythm formulas that involve breathing at six breaths per minute induce favourable psychological and possibly physiological effects.

What is already known on this topic

Reduced heart rate variability and baroreflex sensitivity are powerful and independent predictors of poor prognosis in heart diseaseSlow breathing enhances heart rate variability and baroreflex sensitivity by synchronising inherent cardiovascular rhythms

What this study adds

Recitation of the rosary, and also of yoga mantras, slowed respiration to almost exactly 6/min, and enhanced heart rate variability and baroreflex sensitivityThe rosary might be viewed as a health practice as well as a religious practice     

Chronophysiology of the cardiovascular system

The development of ambulatory blood pressure monitoring devices and the beat-by-beat measurement of heart rate have enabled it to be established that there are circadian rhythms in heart rate and blood pressure in subjects living normally. Investigations of these variables have led to quantification of their fall at night, and rapid rise on awakening and becoming active in the morning. These changes are of particular interest insofar as abnormalities in them are associated with cardiovascular problems and morbidity in patients and also act as risk factors in otherwise healthy individuals. It has also been shown that there are many other variables of the cardiovascular system. The causes of the circadian rhythms in heart rate and blood pressure are outlined, with particular stress upon the role of the autonomic nervous system, as assessed from low- and high-frequency components of the variation in heart rate measured beat-by-beat. Activity increases blood pressure, but there is evidence that this “reactivity” varies with time of day, and this also might be related to cardiovascular morbidity. Based upon data from several sources, including night work, resting subjects and bed-ridden patients, it is concluded that the contribution of the “body clock” to producing the circadian rhythm in heart rate and blood pressure is relatively small. A bias towards an exogenous cause applies also to most other circadian rhythms in the cardiovascular system. Knowledge of circadian rhythmicity in cardiovascular system, together with an understanding of its causes, provides a rationale for advice to reduce cardiovascular risk and to assess the efficacy of therapies.     

Blunting of circadian rhythms and increased acrophase variability in sleep-time hypertensive subjects

24 h and ultradian rhythms of blood pressure (BP) have been previously shown to be disorganized in nocturnal hypertensive subjects. The present study was undertaken to further analyze the ultradian and circadian BP rhythm structure in sleep-time hypertensive subjects with normal or elevated awake-time BP levels. Fourier analysis was used to fit 24, 12, 8, and 6 h curves to mean BP as well as heart rate (HR) time series data derived from 24 h ambulatory blood pressure monitoring. Awake and sleep periods were defined according to individual sleep diaries. Awake-time hypertension was defined as diurnal systolic (SBP) and/or diastolic BP (DBP) means ≥135/85 mmHg. Sleep-time hypertension was defined as nocturnal SBP and/or DBP means ≥120/70 mmHg. The sample included 240 awake-time normotensive subjects (180 sleep-time normotensives and 60 sleep-time hypertensives) and 138 untreated awake-time hypertensive subjects (31 sleep-time normotensives and 107 sleep-time hypertensives). The amplitude and integrity (i.e., percent rhythm) of the 24 and 12 h BP rhythms were lower in the sleep-time hypertensive subjects and higher in the awake-time hypertensive subjects. However, no differences were detected when the integrity and amplitude of the 6 and 8 h mean BP rhythms were analyzed. The sleep-time hypertensive group showed significantly higher 24 h BP rhythm acrophase variability. No differences could be found in any of the HR rhythm parameters. Altogether, the findings suggest a disorganization of the BP circadian rhythm in sleep-time hypertensives that results in reduced 24 h rhythm amplitude and integrity that could be related to cardiovascular risk.     

Circadian Time-Qualified Tolerance Intervals for Ambulatory Blood Pressure Monitoring in the Diagnosis of Hypertension

The large-amplitude circadian pattern in blood pressure of healthy subjects of both genders suggests that the constant threshold currently used to diagnose hypertension should be replaced by a time-specified reference limit reflecting the mostly predictable blood pressure variability during the 24 h. Accordingly, we derived circadian time-specified reference standards for blood pressure as a function of gender. We studied 743 normotensive Caucasian volunteers (400 men and 343 women), 45.7 ± 16.5 (mean ± SD) years of age. Blood pressure was measured by ambulatory monitoring at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours. Data from each blood pressure series were synchronized according to the rest-activity cycle of each individual in order to avoid differences among subjects in actual times of daily activity. Data were then used to compute 90% circadian tolerance intervals for each gender separately. The method, derived on the basis of bootstrap techniques, does not need to assume normality or symmetry in the data and, therefore, it is highly appropriate to describe the circadian pattern of blood pressure variability. Results reflect expected changes in the tolerance limits as a function of gender and circadian sampling time, as well as upper blood pressure limits below the thresholds currently used for diagnosing hypertension, especially for women. The use of these time-dependent tolerance limits for the computation of a hyperbaric index as a measure of blood pressure excess has already been shown to provide a reproducible and high-sensitivity test for the diagnosis of hypertension, which can also be used to evaluate treatment efficacy.     

Circadian time-qualified tolerance intervals for ambulatory blood pressure monitoring in the diagnosis of hypertension

The large-amplitude circadian pattern in blood pressure of healthy subjects of both genders suggests that the constant threshold currently used to diagnose hypertension should be replaced by a time-specified reference limit reflecting the mostly predictable blood pressure variability during the 24 h. Accordingly, we derived circadian time-specified reference standards for blood pressure as a function of gender. We studied 743 normotensive Caucasian volunteers (400 men and 343 women), 45.7 ± 16.5 (mean ± SD) years of age. Blood pressure was measured by ambulatory monitoring at 20-min intervals during the day and at 30-min intervals at night for 48 consecutive hours. Data from each blood pressure series were synchronized according to the rest-activity cycle of each individual in order to avoid differences among subjects in actual times of daily activity. Data were then used to compute 90% circadian tolerance intervals for each gender separately. The method, derived on the basis of bootstrap techniques, does not need to assume normality or symmetry in the data and, therefore, it is highly appropriate to describe the circadian pattern of blood pressure variability. Results reflect expected changes in the tolerance limits as a function of gender and circadian sampling time, as well as upper blood pressure limits below the thresholds currently used for diagnosing hypertension, especially for women. The use of these time-dependent tolerance limits for the computation of a hyperbaric index as a measure of blood pressure excess has already been shown to provide a reproducible and high-sensitivity test for the diagnosis of hypertension, which can also be used to evaluate treatment efficacy.     

Campodimele Study: Blood Pressure and Heart Rate Pattern in Clinically Healthy Elderly Subjects

Noninvasive ambulatory blood pressure (BP) monitoring is a developing method in clinical practice. Its interpretation needs reference standards stratified by age and gender. This study addresses ambulatory BP monitoring in elderly people with the purpose of quantifying the discrete and periodic variability of BP pattern over a 24-h period. The ABPM was performed in 92 clinically healthy subjects (45 men and 47 women) ranging in age from 76 to 102 years. The results refer to the time-qualified mean values with their dispersion, to the circadian rhythm with its parameters, and to the daily baric impact (BI) with its variability. The conclusion is drawn that BP preserves its nychtohemeral variability and circadian rhythmicity despite old age. The daily BP mean level and BI in older people in good health are comparable with those of young subjects, suggesting that humans surviving into old age are characterized by a eugenic control of their pressure regimen.