Excessive circadian amplitude of blood pressure increases risk of ischaemic stroke and nephropathy

Appropriate Circadian-Circasemidian Coupling Protects Blood Pressure from Morning Surge and Promotes Human Resilience and Wellbeing

Background

Blood pressure (BP) variability is involved in the appraisal of threat and safety, and can serve as a potential marker of psychological resilience against stress. The relationship between biological rhythms of BP and resilience was cross-sectionally assessed by 7-day/24-hour chronobiologic screening in a rural Japanese community (Tosa), with focus on the 12-hour component and the "circadian-circasemidian coupling" of systolic (S) BP.

Subjects and Methods

Tosa residents (N = 239, 147 women, 23-74 years), free of anti-hypertensive medication, completed 7-day/24-hour ambulatory BP monitoring. The circadian-circasemidian coupling was determined individually by computing the difference between the circadian phase and the circasemidian morning-phase of SBP. Participants were classified into three groups: those with a short coupling interval of about 4.5 hours (Group A), those with an intermediate coupling interval of about 6.0 hours (Group B), and those with a long coupling interval of about 8.0 hours (Group C).

Results

Residents of Group B who showed optimal circadian-circasemidian coordination had less pronounced morning and evening SBP surges, as compared to residents of Group A (10.82 vs 14.29 mmHg, P < 0.0001) and Group C (11.86 vs 15.21 mmHg, P < 0.0001), respectively. The incidence of morning or evening SBP surge was less in Group B than in Group A (P < 0.0001) or Group C (P < 0.0001). Group B residents showed highest measures of wellbeing and psychological resilience, assessed by good relation with friends (P < 0.05), life satisfaction (P < 0.05), and subjective happiness (P < 0.05). A disturbed circadian-circasemidian coupling was associated with elevated BP, dyslipidemia, arteriosclerosis and a depressive mood.

Conclusion

The circadian-circasemidian coupling of SBP could serve as a new biomarker in clinical practice to guide precision medicine interventions aimed at achieving properly timed rhythms, and thereby resilience and wellbeing.

Circadian Blood Pressure Rhythm in Cardiovascular and Renal Health and Disease

Blood pressure (BP) follows a circadian rhythm, it increases on waking in the morning and decreases during sleeping at night. Disruption of the circadian BP rhythm has been reported to be associated with worsened cardiovascular and renal outcomes, however the underlying molecular mechanisms are still not clear. In this review, we briefly summarized the current understanding of the circadian BP regulation and provided therapeutic overview of the relationship between circadian BP rhythm and cardiovascular and renal health and disease.

Applications of cosinor rhythmometry in pharmacology

Study design and data analysis are two important aspects relevant to chronopharmacometrics. Blunders can be avoided by recognizing that most physiological variables are circadian periodic. Both ill health and treatment can affect the amplitude, phase, and/or period of circadian (and other) rhythms, in addition to their mean. The involvement of clock genes in molecular pathways related to important physiological systems underlies the bidirectional relationship often seen between circadian rhythm disruption and disease risk. Circadian rhythm characteristics of marker rhythms interpreted in the light of chronobiologic reference values represent important diagnostic tools. A set of cosinor-related programs is presented. They include the least squares fit of multiple-frequency cosine functions to model the time structure of individual records; a cosinor-based spectral analysis to detect periodic signals; the population-mean cosinor to generalize inferences; the chronobiologic serial section to follow the time course of changing rhythm parameters over time; and parameter tests to assess differences among populations. Relative merits of other available cosinor and non-parametric algorithms are reviewed. Parameter tests to compare individual records and a self-starting cumulative sum (CUSUM) make personalized chronotherapy possible, where the treatment of each patient relies on an N-of-1 design. Methods are illustrated in a few examples relevant to endocrinology, cancer and cardiology. New sensing technology yielding large personal data sets is likely to change the healthcare system. Chronobiologic concepts and methods should become an integral part of these evolving systems.

Chronobiologic assessment of the effect of the DASH diet on blood pressure

This study compares the effect of three diets on the circadian rhythm of blood pressure (BP). Hypertension and abnormal BP variability (BPV) are major risk factors leading to morbidity and mortality from cardiovascular disease. When detected early, a dietary approach may be preferred to medication. Data stemming from ambulatory BP monitoring (ABPM) from the Dietary Approaches to Stop Hypertension (DASH) study were re-analyzed from a chronobiologic perspective. Compared to the control diet (N = 112) that had no effect on BP (from 131.2/83.5 to 131.0/83.6 mmHg), both the Fruit and Vegetable (FV; N = 113) diet and the DASH (N = 113) diet were associated with a decrease in BP (FV: from 132.6/84.4 to 129.0/82.1 mmHg; DASH: from 131.9/83.6 to 127.2/80.9 mmHg). The decrease in BP was found to be circadian stage-dependent, and to differ between men and women. Nighttime BP was decreased to a larger extent with the DASH than with the FV diet, a difference observed in women but not in men. Study participants who had a higher BP during the reference stage were more likely to decrease their BP to a larger extent after the 8-week dietary intervention. The FV and DASH diets had different effects on BPV. In view of the relatively large day-to-day variability in BP in both normotensive and hypertensive people, it is recommended to monitor BP around the clock for longer than 24 h, and to individualize the optimization of dietary or other intervention.

Regulation of vascular function and blood pressure by circadian variation in redox signalling

There is accumulating evidence that makes the link between the circadian variation in blood pressure and circadian variations in vascular contraction. The importance of vascular endothelium-derived redox-active and redox-derived species in the signalling pathways involved in controlling vascular smooth muscle contraction are well known, and when linked to the circadian variations in the processes involved in generating these species, suggests a cellular mechanism for the circadian variations in blood pressure that links directly to the peripheral circadian clock. Relaxation of vascular smooth muscle cells involves endothelial-derived relaxing factor (EDRF) which is nitric oxide (NO) produced by endothelial NO synthase (eNOS), and endothelial-derived hyperpolarising factor (EDHF) which includes hydrogen peroxide (H₂O₂) produced by NADPH oxidase (Nox). Both of these enzymes appear to be under the direct control of the circadian clock mechanism in the endothelial cells, and disruption to the clock results in endothelial and vascular dysfunction. In this review, we focus on EDRF and EDHF and summarise the recent findings on the influence of the peripheral circadian clock mechanism on processes involved in generating the redox species involved and how this influences vascular contractility, which may account for some of the circadian variations in blood pressure and peripheral resistance. Moreover, the direct link between the peripheral circadian clock and redox-signalling pathways in the vasculature, has a bearing on vascular endothelial dysfunction in disease and aging, which are both known to lead to dysfunction of the circadian clock.

Repeated psychosocial stress at night, but not day, affects the central molecular clock

We have recently demonstrated that the outcome of repeated social defeat (SD) on behavior, physiology and immunology is more negative when applied during the dark/active phase as compared with the light/inactive phase of male C57BL/6 mice. Here, we investigated the effects of the same stress paradigm, which combines a psychosocial and novelty stressor, on the circadian clock in transgenic PERIOD2::LUCIFERASE (PER2::LUC) and wildtype (WT) mice by subjecting them to repeated SD, either in the early light phase (social defeat light = SDL) or in the early dark phase (social defeat dark = SDD) across 19 days. The PER2::LUC rhythms and clock gene mRNA expression were analyzed in the suprachiasmatic nucleus (SCN) and the adrenal gland, and PER2 protein expression in the SCN was assessed. SDD mice showed increased PER2::LUC rhythm amplitude in the SCN, reduced Per2 and Cryptochrome1 mRNA expression in the adrenal gland, and increased PER2 protein expression in the posterior part of the SCN compared with single-housed control (SHC) and SDL mice. In contrast, PER2::LUC rhythms in the SCN of SDL mice were not affected. However, SDL mice exhibited a 2-hour phase advance of the PER2::LUC rhythm in the adrenal gland compared to SHC mice. Furthermore, plasma levels of brain-derived neurotrophic factor (BDNF) and BDNF mRNA in the SCN were elevated in SDL mice. Taken together, these results show that the SCN molecular rhythmicity is affected by repeated SDD, but not SDL, while the adrenal peripheral clock is influenced mainly by SDL. The observed increase in BDNF in the SDL group may act to protect against the negative consequences of repeated psychosocial stress.

Cosinor-based rhythmometry

A brief overview is provided of cosinor-based techniques for the analysis of time series in chronobiology. Conceived as a regression problem, the method is applicable to non-equidistant data, a major advantage. Another dividend is the feasibility of deriving confidence intervals for parameters of rhythmic components of known periods, readily drawn from the least squares procedure, stressing the importance of prior (external) information. Originally developed for the analysis of short and sparse data series, the extended cosinor has been further developed for the analysis of long time series, focusing both on rhythm detection and parameter estimation. Attention is given to the assumptions underlying the use of the cosinor and ways to determine whether they are satisfied. In particular, ways of dealing with non-stationary data are presented. Examples illustrate the use of the different cosinor-based methods, extending their application from the study of circadian rhythms to the mapping of broad time structures (chronomes).

Diagnosing vascular variability anomalies, not only MESOR-hypertension

Chronobiology is the study of biological rhythms. Chronomics investigates interactions with environmental cycles in a genetically coded autoresonance of the biosphere with wrangling space and terrestrial weather. Analytical global and local methods applied to human blood pressure records of around-the-clock measurements covering decades detect physiological-physical interactions, a small yet measurable response to solar and terrestrial magnetism. The chronobiological and chronomic interpretation of ambulatory blood pressure monitoring (C-ABPM) records in the light of time-specified reference values derived from healthy peers matched by sex and age identify vascular variability anomalies (VVAs) for an assessment of cardio-, cerebro-, and renovascular disease risk. Even within the conventionally accepted normal range, VVAs have been associated with a statistically significant increase in risk. Long-term C-ABPM records help to "know ourselves," serving for relief of psychological and other strain once transient VVAs are linked to the source of a load, prompting adjustment of one's lifestyle for strain reduction. Persistent circadian VVAs can be treated, sometimes by no more than a change in timing of the daily administration of antihypertensive medication. Circadian VVA assessment is an emergency worldwide, prompted in the United States by 1,000 deaths per day every day from problems related to blood pressure. While some heads of state met under United Nation and World Health Organization sponsorship to declare that noncommunicable diseases are a slow-motion disaster, a resolution has been drafted to propose C-ABPM as an added tool complementing purely physical environmental monitoring to contribute also to the understanding of social and natural as well as personal cataclysms.

Toward a personalized chronotherapy of high blood pressure and a circadian overswing

Timing can greatly affect the response to a stimulus, including antihypertensive medications. Herein, we assess the response of 30 patients to losartan/hydrochlorothiazide (L/H), administered for at least 1 month at a given circadian stage to each patient, this stage being changed during consecutive spans to cover six treatment times from awakening to bedtime at approximately 3-hour intervals. At the end of each stage, each patient underwent a 7-day around-the-clock ambulatory blood pressure (BP) profile, analyzed chronobiologically. A larger reduction of the midline estimating statistic of rhythm (MESOR; a rhythm-adjusted mean) of diastolic BP was achieved by L/H administration in the early morning for more patients (P < .05), while treatment upon awakening was the best choice for most patients to reduce the circadian amplitude of BP the most (P < .01). The optimal treatment time varied considerably among patients, however. Special attention should be given to the effect on the circadian amplitude since treatment can increase it above a threshold, beyond which there is a marked increase in cardiovascular disease risk. The results indicate the desirability to individualize the optimization of the antihypertensive effect of L/H by timing along the circadian scale.

Nighttime blood pressure dipping in young adults and coronary artery calcium 10-15 years later: the coronary artery risk development in young adults study

Nighttime blood pressure (BP) dipping can be quantified as the ratio of mean nighttime (sleep) BP to mean daytime (awake) BP. People whose dipping ratio is ≥ 0.90 have been referred to as nondippers, and nondipping is associated with cardiovascular disease events. We examined the relationship between systolic nighttime BP dipping in young adults and the presence of coronary artery calcium (CAC) 10 to 15 years later using data from the ambulatory BP monitoring substudy of the Coronary Artery Risk Development in Young Adults Study. Among 239 participants with adequate measures of both nighttime and daytime readings and coronary artery calcium, the systolic BP dipping ratio ranged from 0.72 to 1.24 (mean, 0.88; SD, 0.06), and CAC was present 10 to 15 years later in 54 participants (22.6%). Compared with those whose systolic BP dipping ratio ranged from 0.88 to 0.92 (quartile 3), the 57 participants (23.9%) with less pronounced or absent dipping (ratio, 0.92-1.24; quartile 4) had an unadjusted odds ratio of 4.08 (95% CI, 1.48-11.2) for the presence of CAC. The 60 participants (25.1%) with a more pronounced dipping (ratio, 0.72-0.85; quartile 1) also had greater odds for presence of CAC (odds ratio, 4.76 [95% CI, 1.76-12.9]). When modeled as a continuous predictor, a U-shaped relationship between systolic BP dipping ratio and future CAC was apparent and persisted after adjustment for multiple potential confounders (P<0.001 for quadratic term). Both failure of systolic BP to dip sufficiently and "overdipping" during nighttime may be associated with future subclinical coronary atherosclerosis.

Abnormalities in circadian blood pressure variability and endothelial function: pragmatic markers for adverse cardiometabolic profiles in asymptomatic obese adults

Background

Cardiovascular disease (CVD) risk, although perceived to be high, is often difficult to demonstrate in disease free (healthy) obese adults.

Hypothesis

Changes in circadian blood pressure variability (CBPV) and endothelial function (EF) may be early correlates of cardiometabolic disorders.

Methods

Asymptomatic men and women in 3 groups: normal weight (n = 10), overweight (n = 10) and obese (n = 15) were evaluated. Blood pressure and heart rate were recorded over 7 days: every 30 minutes during the day and every 60 minutes during the night, by automatic ambulatory monitoring. Resting EF was assessed in a fasting state between 8-10 AM by brachial ultrasound. Anthropometric and cardiometabolic indicators were measured and correlations with CBPV and EF were investigated.

Results

The 3 groups had (Mean(SD)) BMI: 22.6(1.6), 27(3) and 34(5) kg/m², respectively, weight: 64(16), 79(14), 95(16) kg and waist circumference: 79(9), 93(10), 107(13) cm. None in normal-weight or overweight groups had abnormal CBPV, while 8 of 15 obese adults had one or more CBPV abnormities (p < 0.05). Obese adults with CBPV abnormalities had elevated hs-CRP (15.3(9.3) mg/L), fibrinogen (593(97) mg/dl), fasting serum glucose (102(16) mg/dL), and cardiac risk ratios (Total-C/HDL-C: 5.2(1.9), LDL-C/HDL-C: 3.1(1.4)). Adults in the 3 respective groups who did not have CBPV abnormalities had flow-mediated brachial artery dilatation (FMD) of 0.22(0.06); 0.20(0.04), 0.23(0.02) mm over resting diameter. Obese participants with CBPV abnormalities (Mesor-hypotension, circadian hyper amplitude tension, elevated pulse pressure), had attenuated FMD at 78, 52, and 56% of resting reference diameter (means 0.18(0.07), 0.12(0.08), and 0.13(0.05) mm; p < 0.05), respectively.

Conclusions

Asymptomatic obese adults with abnormal CBPV and EF exhibit unfavorable cardiometabolic profiles.

Circadian rhythmic fractal scaling of heart rate variability in health and coronary artery disease

BACKGROUND

In clinical cardiology, heart rate variability is a putative index of autonomic cardiovascular function. Signs of reduced vagal activity are not only associated with an enhanced risk of sudden cardiac death, but such impaired heart rate variability became a new predictor of sudden cardiac death and other mortality in patients with a variety of diseased states.

HYPOTHESIS

It is postulated (1) that the time structure (chronome) of heart rate variability in clinical health includes a circadian rhythm and deterministic chaos, the latter gauged by the correlation dimensions of RR intervals; and (2) that this chronome is altered in patients with coronary artery disease (CAD).

METHODS

From 24-h Holter records of 11 healthy controls and 10 patients with CAD, 500-s sections around 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 hours were analyzed for smoothed RR intervals sampled at 4 Hz. Correlation integrals were estimated for embedding dimensions from 1 to 20 with a 1.0-s time lag, using an algorithm modified from Grassberger and Procaccia. The Wilcoxon signed-rank test compares circadian end points assessed by cosinor between the CAD patients and age-matched controls.

RESULTS

A circadian rhythm characterizes the correlation dimension of healthy subjects peaking during the night (p < 0.005). Patients with CAD have a lowered correlation dimension (p < 0.05) and an altered circadian variation which requires the consideration of an approximately 12-h (circasemidian) component.

CONCLUSION

The results demonstrate the sensitivity of circadian rhythms for the detection of disease. A partial 24- to 12-h (circadian-to-circasemidian) frequency multiplication (or partial variance transposition) in CAD of the correlation dimension, apart from being a potential clue to the etiology of the disease, adds a new feature to a chronocardiology combining, with the fractal scaling, an assessment of circadian and circasemidian components as measures of predictable variability to be tested for use in diagnosis, prognosis, and as putative guides to treatment timing.

Circadian rhythm of maternal blood pressure and fetal growth

This study aimed at examining any relation between the circadian variation in blood pressure (BP) in human pregnancy and fetal growth. A prospective study included 52 pregnant women monitored during the third trimester of pregnancy. There were 33 uncomplicated pregnancies with normal fetal growth (Group 1) and 19 pregnancies complicated by intrauterine growth retardation (IUGR), confirmed at birth (Group 2). Ten women (five in each group) had pregnancy-induced hypertension. All women were hospitalized and followed a similar daily routine. BP was recorded with an automatic wearable device. Measurements were obtained every 20 min for 24 +/- 1 h. BP profiles were analyzed by conventional statistical methods and by cosinor, involving the least squares fit of cosine curves with an anticipated period (24 h) to the data. BP parameters, fetal outcome, demographic and obstetric characteristics were compared between the two groups. Logistic regression and multivariate analyses were used to assess factors putatively associated with fetal outcome. The circadian amplitude of diastolic BP was found to be larger in normotensive women with IUGR. As gauged by odds ratios (OR), the circadian amplitude of diastolic BP (OR = 1.7, 95% CI: 1.1-2.8; P = 0.03) and hematocrit (OR = 1.4, 95% CI: 1.0-1.9; P = 0.04) were the only variables positively and independently associated with IUGR. In the presence of maternal hypertension, the circadian amplitude of systolic BP was negatively associated with IUGR (OR = 0.7, 95% CI: 0.5-1.0; P = 0.03). A larger circadian variation in diastolic BP, rather than a difference in the mean value of systolic or diastolic BP, was found to be statistically significantly associated with IUGR. This study adds another condition in which the circadian BP amplitude constitutes a harbinger of elevated risk, apart from an association with a shortened lifespan in the absence or presence of malignant hypertension and with an increased risk of stroke and nephropathy reported earlier.

Circadian and circaseptan (about-weekly) aspects of immigrant Indians' blood pressure and heart rate in California, USA

Time structurally (chronomically) interpreted half-hourly monitoring of blood pressure (BP) and heart rate (HR) for at least 7 days and preferably for 17 days is recommended, separately for a diagnosis of BP disorders and when necessary again for the same or longer spans for treatment, whenever a positive diagnosis of a disorder is made. In this study, 30 clinically healthy subjects underwent 7-day monitoring and provided a series of findings, including the detection of Circadian Hyper-Amplitude-Tension (CHAT), that is blood pressure overswinging, which carries a high risk of hard cardiovascular events. The results specifically bear upon south-east Asian-Indian immigrants. They show that cardiovascular disease risk increases with age, with a positive family history of hypertension and/or other cardiovascular diseases and even with the duration of stay in the USA. A relation to body mass index is also shown. Such monitoring for prehabilitation may eventually reduce the need for rehabilitation.

Plasma catecholamines: follow-up on 10-year study in health and cardiovascular disease

The predictive value of blood pressure (BP), heart rate (HR), and catecholamines in terms of any subsequent development of cardiovascular disease was investigated. Systolic (S) and diastolic (D) BP, HR, epinephrine (E) and norepinephrine (NE) were measured three times a year in 1980, 1984, and 1989 on 20 clinically healthy subjects, 18 patients with 'essential hypertension', and 22 patients with angina pectoris. Of the 22 patients in the latter group, 15 died during a 2-year follow-up (1990-1991). Each individual data series was analyzed by single cosinor to assess the circannual variation. Results were summarized by population-mean cosinor for each group. Parameter tests were used to compare the circannual rhythm characteristics among the different patient groups. A circannual rhythm was invariably demonstrated on a group basis (P < 0.05). Differences in MESOR and/or circannual amplitude were found among the different groups. In particular, patients with angina pectoris who will die within the 2-year follow-up differ in terms of their E and NE from all other patient groups, a difference already detected at the beginning of the study, more than 10 years before they die. A similar separation is not achieved in terms of BP or HR.

Opportunity of detecting pre-hypertension: worldwide data on blood pressure overswinging

Overswinging or CHAT (brief for Circadian Hyper-Amplitude-Tension), that is an excessive circadian variation in blood pressure (BP), has been associated with a large increase in cardiovascular disease risk, present even in the absence of an elevated BP itself. This usually asymptomatic condition is usually overlooked by current practice based on spot-checks, because to be diagnosed, measurements need to be taken around-the-clock, preferably for 7 days at the outset. Once diagnosed, however, a usual circadian BP pattern can be restored by means of certain non-pharmacologic or pharmacologic interventions timed appropriately. Thereby, it is possible to reduce the risk of cardiovascular morbidity and mortality, cerebral ischemic events and nephropathy in particular. For the preparation of guidelines regarding the diagnosis of BP disorders and for the institution of primary as well as secondary preventive measures, it is important to know what the incidence of CHAT is on a global basis. We found 191 cases of CHAT among 1602 mostly 7-day/24-h BP profiles, obtained from several centers in different countries participating in an ongoing project on the BIOsphere and the COSmos (BIOCOS). CHAT incidence is about the same between men and women, but it is diagnosed more often among patients with borderline hypertension or with glucose intolerance. It is also more common among MESOR-hypertensive than among MESOR-normotensive individuals. Priority should be given to the development of an unobtrusive and affordable device to automatically monitor BP and to analyze the data as-one-goes, so that cardiovascular disease risk can be prevented.

100 or 30 years after Janeway or Bartter, Healthwatch helps avoid 'flying blind'

Longitudinal records of blood pressure (BP) and heart rate (HR) around the clock for days, weeks, months, years, and even decades obtained by manual self-measurements (during waking) and/or automatically by ambulatory monitoring reveal, in addition to well-known large within-day variation, also considerable day-to-day variability in most people, whether normotensive or hypertensive. As a first step, the circadian rhythm is considered along with gender differences and changes as a function of age to derive time-specified reference values (chronodesms), while reference values accumulate to also account for the circaseptan variation. Chronodesms serve for the interpretation of single measurements and of circadian and other rhythm parameters. Refined diagnoses can thus be obtained, namely MESOR-hypertension when the chronome-adjusted mean value (MESOR) of BP is above the upper limit of acceptability, excessive pulse pressure (EPP) when the difference in MESOR between the systolic (S) and diastolic (D) BP is too large, CHAT (circadian hyper-amplitude tension) when the circadian BP amplitude is excessive, DHRV (decreased heart rate variability) when the standard deviation (SD) of HR is below the acceptable range, and/or ecphasia when the overall high values recurring each day occur at an odd time (a condition also contributing to the risk associated with 'non-dipping'). A non-parametric approach consisting of a computer comparison of the subject's profile with the time-varying limits of acceptability further serves as a guide to optimize the efficacy of any needed treatment by timing its administration (chronotherapy) and selecting a treatment schedule best suited to normalize abnormal patterns in BP and/or HR. The merit of the proposed chronobiological approach to BP screening, diagnosis and therapy (chronotheranostics) is assessed in the light of outcome studies. Elevated risk associated with abnormal patterns of BP and/or HR variability, even when most if not all measurements lie within the range of acceptable values, becomes amenable to treatment as a critical step toward prevention (prehabilitation) to reduce the need for rehabilitation (the latter often after costly surgical intervention).

Chronobiologically explored effects of Telmisartan

Effects of Micardis (Telmisartan), alone or with low-dose aspirin, on blood pressure and other cardiovascular endpoints are examined in 20 patients with MESOR-hypertension in a crossover, double-blind, randomized study consisting of three stages, each lasting 7 days: I-placebo, II-Micardis, and III-Micardis with low-dose aspirin. Treatment was administered each day at a different circadian stage, upon awakening, and 3, 6, 9, 12, 15 and 18 hr after awakening. During each stage, the following variables were measured at 3-hr intervals during waking: systolic and diastolic blood pressure, heart rate, ejection fraction, intrarenal resistive index, acceleration time, and serum creatinine. Each data series was analyzed by single cosinor. Results were summarized by population-mean least squares spectra. At matched treatment times, the MESOR and circadian amplitude of each variable were compared among the three treatments by paired t-tests. A prominent circadian rhythm characterizes all variables. Micardis was associated not only with a lowering of blood pressure, but also with a reduction of the circadian blood pressure amplitude. The ejection fraction was increased, and the resistive index and acceleration time were decreased, the effect being more pronounced when low-dose aspirin was added to Micardis. Any circadian-stage dependent effect of Micardis, with or without low-dose aspirin, will require monitoring over spans longer than a single day for a given treatment administration time.

About 7-day (circaseptan) and circadian changes in cold pressor test (CPT)

We assess circadian (CD) and circaseptan (CS) changes in the blood pressure (BP) response to a 1-min immersion of the hand into ice water, the cold pressor test (CPT). An about 8 mmHg BP increase in the CPT reported by others for health and an elevation >25 mmHg for patients with "hypertension" have been viewed as predisease, but variables related to the vascular system exhibit prominent CD, CS and circannuals, among other components of their genetically anchored time structure or chronome, and may also have to be considered. Hence, a 16-year-old adolescent (ML) immersed her hand into ice water every 2-4 h for 2 days and once daily in the morning thereafter for 1 week (N = 25), as did, only for <2 days (> or =24 h), four adults 20-66 years of age. BP and heart rate (HR) were monitored automatically around the clock at 15-min intervals and at 1-min intervals before and immediately after the CPT. Data were analyzed by cosinor. The difference between the first post-CPT BP value and the mean of the last seven values prior to the CPT was a measure of CPT response (at 1-min). Overall, ML's systolic (S) BP increased by 8.2 +/- 1.4 mmHg and her diastolic (D) BP by 6.2 +/- 0.9 mmHg (P < 0.001). Increases were found in 96% of the tests for SBP, 92% for DBP and 20% for HR. There was only one tie for HR (4%), resulting in a HR decrease in 76% of CPTs. The BP response to CPT at 1 min was CS-dependent. The CS double amplitudes are 12.5 +/- 4.1 for SBP (P = 0.019) and 7.8 +/- 2.8 mmHg for DBP (P = 0.030), with acrophases occurring on late Sunday, early Monday (at -50 degrees and -67 degrees from 00:00 h from Saturday to Sunday for SBP and DBP, respectively, with 360 degrees identical with 1 week). The response of HR did not allow the detection of a CS rhythm (P = 0.969). The CD response peaked in the early morning hours; with 24 h identical with 360 degrees and 0 degrees = local midnight, the acrophase (phi) for SBP is at -80 degrees and for DBP at -113 degrees, in keeping with earlier results from four adult subjects (SBP: -37 degrees; DBP: -42 degrees ), individual differences notwithstanding. The average timing of the largest overall response of BP to CPT coincides with the timing of the response to other stimuli. The CS acrophases coincide with the times of increased morbidity/mortality from vascular diseases. Chronomes, time structures broader than circadian, notably their about-weekly components, should be considered, not only at the extremes of life when the CS and about-half-weekly rhythms are particularly prominent in BP and HR but also in interpreting BP responses as a gauge of vascular disease status in adolescents.

Effects of diaphragmatic breathing on ambulatory blood pressure and heart rate

Psychological procedures, such as self-hypnosis in the form of autogenic training, have been proposed for correcting a deviant, e.g., high blood pressure (BP). In view of the overwhelming evidence for the circadian (CD) stage dependence of any treatment effects, the CD stage dependence of the effects of diaphragmatic breathing (DB) on BP and heart rate (HR) was explored in data from a clinically healthy normotensive subject who, following 3 weeks of ambulatory monitoring as a reference standard, measured BP and HR with a manual monitor at 1-min intervals for 5 min before and after DB (three deep diaphragmatic breaths) and who performed DB for about 2 weeks at about 2-h intervals while awake. The 3-week data series were analyzed by cosinor, involving the least-squares fit of cosine curves with periods of 24, 12 and 168 h. A CD rhythm was detected for BP and HR (P < 0.001 in each case), peaking in the afternoon. Some about-weekly (circaseptan; CS) BP rhythms and 12-h (circasemidian) components were also statistically significant. DB was found to reduce systolic (S) BP. Overall, SBP decreased by 5.9 +/- 0.8 mmHg (P < 0.001) and diastolic (D) BP by 1.4 +/- 0.8 mmHg (P < 0.005), while HR remained at about the same average. The effect of DB on BP was CD-dependent, the largest response occurring in the afternoon, 2-3 h before the peaks in SBP and DBP found in the reference data of the same subject. There was also a 5-10% decrease in SBP around the weekend (Friday, Saturday and Sunday). The results on a single subject suggest the need to collect similar data on others for optimizing by clock-hour, day of the week, and eventually by the marker rhythms BP and/or HR the best times for DB and other procedures. The personalized best time for people on different work/rest schedules for relaxation may be several hours before their BP has reached its highest point in the 24-h span. HR may serve as a marker for DB timing, but the effect on HR of DB was only of borderline statistical significance in the subject investigated.

Chronomics for chronoastrobiology with immediate spin-offs for life quality and longevity

Effects of geomagnetic disturbance on heart rate variability (HRV), the 1/f fractal scaling in particular, are being assessed in adults living at high latitude, where magnetic storms are more frequent and more intense than at lower latitudes. The latter may constitute a signal or a proxy, and possibly a mechanism underlying both undesirable and desirable effects, depending upon circumstances yet to be elucidated. Any circadecadal stage-dependence of morbidity and/or mortality from certain conditions such as myocardial infarctions remains to be studied in both adult and pediatric populations. Further work could thus examine whether any associations of geomagnetic disturbances may account, at least in part, through effects upon the circulation, for long-term infra-annual changes, possibly anchored in the population's gene pool, observed in a number of anthropologic measurements at birth as well as in other population statistics. In order to assess the development of several chronome components of the electrocardiogram (ECG), around-the-clock ambulatory ECG were recorded from 19 infants (25 days-3 months of age), 22 children (3-9 years of age), 18 boys and girls (10-14 years of age), pubertal boys (15-20 years of age), and 10 young men (21-29 years of age). Time- and frequency-domain measures of HRV were obtained by spectral analysis, using the maximal entropy method (MEM). The frequency of detection of the circadian, circasemidian and circaoctohoran components, with periods of about 24, 12 and 8 h, respectively, was compared among the five groups for several HRV endpoints, notably 1/f fractal scaling, total spectral power within a 5-min span, and its distribution into several frequency regions. A circadian component is already detectable in a sizeable proportion of infants and children for most of the HRV indices considered. The incidence of detection of the circadian component increases with age for the spectral power in different frequency regions, notably around 10.5 s ("LF") and around 3.6 s ("HF"); it peaks around puberty for 1/f in our data; and it did not detectably change with age for the total spectral power. Similar changes with age are not observed for the circasemidian or circaoctohoran components. The latter characterizes primarily 1/f and less so the about 3.6 s power ("HF"). Several aspects of the HRV chronome may thus develop differently as a function of age. In 2000, we began a community-based study named "Longitudinal Investigation of Longevity and Aging in Hokkaido County (LILAC study)". The ambulatory blood pressure (BP) of middle-aged subjects, aged 40-74 years, was monitored 7-day/24-h, and the cardiovascular and neurobehavioral functions of elderly people above 75 years were evaluated. Our goal was the prevention of stroke and myocardial infarction and the decline in cognitive function of the elderly in a community. Of 115 elderly people recruited in a longitudinal community-based study in 2000, 72 completed yearly follow-ups in 2002. A cardiovascular score based on BP, pulse wave velocity, and 1-h ECG-based HRV endpoints served to distinguish between normal, mildly disordered, or disordered participants. A comparison of cognitive function in 2002 vs. 2000, assessed with the MMSE, HDSR, the Up & Go and Functional Reach tests, gauged any effect of social intervention. Cognitive function was maintained or improved, especially for people suffering from hypertension, tachycardia, or a decreased HRV, suggesting that cardiovascular function is a major factor affecting cognitive function.

Can brain dysfunction be a predisposing factor for metabolic syndrome?

The various mechanisms that may explain the association between brain dysfunction and the pathogenesis of metabolic syndrome (MS) leading to cardiovascular disease and type 2 diabetes have been reviewed. A Medline search was conducted until September 2003, and articles published in various national and international journals were reviewed. Experts working in the field were also consulted. Compelling evidence was found that saturated and total fat and low dietary n-3 fatty acids and other long-chain polyunsaturated fatty acids (PUFAs) in conjunction with sedentary behavior and mental stress combined with various personality traits can enhance sympathetic activity and increase the secretion of catecholamine, cortisol and serotonin, all of which appear to be underlying mechanisms involved in MS. Excess secretion of these neurotransmitters in conjunction with underlying long-chain PUFA deficiency may damage the neurons in the ventromedial hypothalamus and insulin receptors in the brain, in particular during fetal life, infancy and childhood, and lead to their dysfunction. Since 30-50% of the fatty acids in the brain are long-chain PUFAs, especially omega-3 fatty acids which are incorporated in the cell membrane phospholipids, it is possible that their supplementation may have a protective effect. Omega-3 fatty acids are also known to enhance parasympathetic activity and to increase the secretion of anti-inflammatory cytokines as well as acetylecholine in the hippocampus. It is possible that a marginal deficiency of long-chain PUFAs, especially n-3 fatty acids, due to poor dietary intake during the critical period of brain growth and development in the fetus, and later in the infant and also possibly in the child, adolescent and adult may enhance the release of tumor necrosis factor-alpha (TNF-alpha) interleukin (IL)-1, 2 and 6 and cause neuronal dysfunction. Experimental studies indicate that ventromedial hypothalamic lesions in rats induce hyperphagia, resulting in glucose intolerance and insulin resistance. Treatment with neuropeptide Y abolished hyperphagia and ob mRNA (leptin mRNA) in this animal model. Long-term infusion of norepinephrine and serotonin into the ventromedial hypothalamus impaired pancreatic islet function inasmuch as ventromedial hypothalamic norepinephrine and serotonin levels were elevated in hyperinsulinemic and insulin-resistant animals. Treatment with insulin was associated with restoration of hypothalamic neurotransmitter abnormalities, indicating that ventromedial hypothalamus dysfunction can impair pancreatic beta cells resulting in metabolic abnormalities consistent with MS. Treatment with omega-3 fatty acids, beta blockers, ACE inhibitors, estrogen, and meditation may have a beneficial effect on insulin receptors and ventromedial hypothalamic dysfunction. However, no definite or precise insight into the pathophysiological link between MS, brain function and nutrition is available. Despite this, epidemiological studies and intervention trials indicate that treatment with n-3 fatty acids may be adopted in clinical practice and used to direct therapy for prevention of type 2 diabetes, hypertension, coronary artery disease (CAD), and atherosclerosis, thereby indicating that MS may also respond to this treatment.

Blood pressure self-surveillance for health also reflects 1.3-year Richardson solar wind variation: spin-off from chronomics

Self-experimentation concerns not only scientists, but also each individual for the sake of his/her chronobiologic health and science literacy, eventually to be acquired in primary and secondary education. Public education ensures that everybody who knows how to read or write can dispense with the service of a costly scribe. At all ages, public education can teach equally well how to find out whether one's blood pressure (BP) and heart rate (HR) responds to an increase in sodium intake with a rise, with no change or with a decrease in BP. This task and many others could become a matter of informed self-surveillance. Whenever there are inter-individual, sometimes opposite differences in response, government-sponsored trials on groups that do not consider such differences cannot solve what only the individual can do, at first by help from schools. Eventually special institutions may be designed for chronomics, the monitoring, interpretation and archivization of chronomes (time structures; from chronos = time and nomos = rule) of biological variables, also charged with a demographic analyzing and reporting system. Each individual's properly coded record, to guard confidentiality, becomes part of a promptly accessible database for one's own needs and for society's requirements. What individuals and small groups started as chronobiology, what is immediately available on back burners, as a service by an international project on the biosphere and the cosmos (BIOCOS) (corne001@umn.edu) could become a public system of planned surveillance archivization of one's rhythms from womb to tomb. Alterations of a rhythm's amplitude or acrophase or of a deterministic or other chaotic endpoint, such as a correlation dimension and approximate entropy, or of a standard deviation, among a multitude of other endpoints, can signal (in the otherwise neglected normal range) reversible risk elevations. If these elevated risks are detected and prompt the institution of countermeasures, such prehabilitation can save the cost of rehabilitation or of long-term care after morbid events; suffering also can be prevented such as that by those who are unlucky enough to helplessly survive a massive brain, heart or societal "stroke". As an equally important dividend, science gains in basic and applied terms, as illustrated herein by the demonstration of a trans-year, an approximately 1.3 to 1.6-year, heretofore unknown component of the human BP and HR spectrum, beating with the circannual component and characterizing the same data. Chronomically interpreted self-monitoring is a civic duty for both one's health and everybody's science.

Circadian heart rate and blood pressure variability considered for research and patient care

OBJECTIVES

To review mechanisms of circadian variations in heart rate variability (HRV) and blood pressure variability (BPV) and mortality and morbidity due to cardiovascular diseases (CVD).

METHODS

Results from 7-day/24-h HRV and BPV are interpreted by gender and age-specified reference values in the context of a Medline search.

RESULTS

Abnormal HRV and BPV measured around the clock for 7 days provides information on the risk of subsequent morbid events in subjects without obvious heart disease and without abnormality outside the conventional (in the sense of chronobiologically unquantified) physiological range. Meditation, beta-blockers, ACE inhibitors, n-3 fatty acids and estrogens may have a beneficial influence on HRV, but there is no definitive outcome-validated therapy. Low HRV has been associated with a risk of arrhythmias and arrhythmic death, unstable angina, myocardial infarction, progression of heart failure and atherosclerosis. BPV may be characterized by treatable circadian-hyper-amplitude-tension (CHAT), which can be transient '24-h CHAT' or '7-day-CHAT', MESOR-hypertension and/or an unusually-timed (odd) circadian acrophase (ecphasia), all associated with an increased risk of stroke, stroke death, myocardial infarction, and kidney disease.

CONCLUSIONS

Precise insight into the patho-physiology in time of HRV and BPV is needed with development of a consensus on best measures of HRV for clinical purposes and to determine when a 7-day record interpreted chronobiologically suffices and when it does not, for detection within as well as outside the conventional normal range, for diagnostic clinical practice and to direct therapy of risk greater than that associated with hypertension, smoking or any other risk factor.

Impact of circadian amplitude and chronotherapy: relevance to prevention and treatment of stroke

The long-acting calcium antagonist nifedipine reduces the incidence of stroke in Eastern Asia, as shown by the Shanghai Trial Of Nifedipine in the Elderly (STONE) and the Systolic Hypertension in China (Syst-China) trials. Recent trials in Japan have shown that benidipine may be more efficient than the former drug in preventing strokes in the elderly. Benidipine, commonly prescribed in Japan for a definite depressor effect, reportedly without causing remarkable fluctuations in blood pressure (BP), is investigated herein from a chronobiological viewpoint. Eighteen subjects (nine women and nine men, 39 to 87 years of age) with essential hypertension (office and ambulatory systolic, S/diastolic, D BP values above 160/95 mm Hg and 130/80 mm Hg, respectively) were enrolled in this investigation. Ambulatory BP was monitored at 30-min intervals for at least 24 h (ABPM-630, Colin Medical) before and after 4 weeks of crossover treatment with nifedipine tablets (twice daily, 20 mg/d) and benidipine (once daily, 4 mg/d, in the morning). The results indicate that: 1) benidipine and nifedipine reduce 24-h daytime (10:00-20:00) and nighttime (00:00-06:00) averages of SBP and DBP (P < 0.001); 2) the circadian double amplitude of BP is decreased after treatment with benidipine (from 28.6 to 21.1 mm Hg SBP and from 19.7 to 15.2 mm Hg DBP; P< 0.05), while the day-night difference in SBP is increased after treatment with nifedipine (18.6 vs 27.9 mm Hg, P< 0.01); and 3) the increase in the day-night difference of heart rate (HR) is significant after treatment with benidipine (13.6 vs 18.8 beats per minute, bpm; P< 0.05), but not with nifedipine. We have previously evaluated the usefulness of the circadian amplitude of BP as a prognostic tool of cardiovascular outcome, and found that an excessive circadian SBP or DBP amplitude was associated with an increased risk of vascular disease. The fact that benidipine reduces the circadian BP amplitude may be one reason for the superiority of this treatment over nifedipine in preventing an adverse outcome. A reduced heart rate variability (HRV) also predicts adverse cardiovascular outcomes in patients with overt cardiovascular disease and in hypertensive subjects. The fact that benidipine increases the day-night difference in HR may be another reason for the positive effects of this treatment.

Can nutrition influence circadian rhythm and heart rate variability?

Recent studies indicate that there is an interaction between biorhythms, the biological clock and triggers, which may be important in the pathogenesis of altered heart rate variability (HRV) and blood pressure variability (BPV). Circadian rhythms are under the influence of, and physiological variables are mediated by the activation of the adrenals, sympathetic/parasympathetic, hypothalamic and pituitary activity. Emotional stress, physical exertion, sleep deprivation and large fatty meals are major triggers of myocardial ischemia, angina, infarction, sudden cardiac death (SCD) and stroke. These events have been reported to exhibit a circadian variation with increased frequency in the second quarter of the day, which has also been observed in our studies on Indians. Recent studies indicate that altered HRV and BPV are also important in the pathogenesis and progression of heart failure, atheroma and thrombosis. Mediation via beta-blockers, oestrogens, n-3 fatty acids, vitamin E and coenzyme Q10 and fasting appears to have a beneficial influence whereas progestins, nifedipine, stress and exercise may have an adverse effect on HRV and BPV. We have reported that plasma levels of vitamin E and C are lower in the second quarter of the day than at other times, indicating their role in the pathogenesis of variability and cardiac events. Prospective studies also indicate that HRV and BPV are important and independent risk factors for cardiovascular events. However, no study has yet been conducted in patients with abnormal HRV and BPV in a randomized, placebo-controlled intervention trial to find out whether improvement in variability can cause a significant reduction in cardiovascular events. There is a need to study the role of n-3 fatty acids, coenzyme Q10, the effect of regular physical training, medication and ACE inhibitors in patients with abnormal HRV and BPV to demonstrate that improving variability can modulate cardiovascular events.

Office blood pressure variability as a predictor of acute myocardial infarction in elderly patients receiving antihypertensive therapy

Larger variability of office blood pressure (BP) was reportedly associated with a higher risk of stroke or mortality from all causes. In the present study, we focused on the relationship of variability of office BP and occurrence of acute myocardial infarction (MI). We registered 139 patients receiving antihypertensive therapy for more than 1 year who experienced first-ever episode of MI at the age of 60 years or over. At least two sex- and age-matched (+/- 5 years) control patients were registered for every MI patient. Average systolic and diastolic BP during the 12-month period prior to the occurrence of MI, or the time of registration in the case of control patients, was similar in both patient groups. The office BP variability was evaluated by calculating the variation coefficient (VC) of BP. VC of diastolic BP was significantly higher in the MI patients (10.0 +/- 4.0%) compared with the control patients (8.8 +/- 3.4%). VC of systolic BP was not different between the MI and the control patients. Multiple logistic analysis revealed the relationship of the VC for office diastolic BP to the occurrence of MI was significant after adjustment for BP level, age, gender, body mass index, serum total cholesterol concentrations, diabetes mellitus, and current smoking. In conclusion, larger long-term variability of office diastolic BP during antihypertensive therapy is a predictor of MI.

Seven-day (24-h) ambulatory blood pressure monitoring, self-reported depression and quality of life scores

OBJECTIVE

Effects of environmental conditions on blood pressure (BP) and heart rate (HR) variations as putative factors underlying the onset of vascular events.

METHODS

BP and HR were monitored around the clock for 7 days on 54 residents from Urausu, Hokkaido, Japan. Daytime, night-time, and 24-h means served to identify dippers and non-dippers. Questionnaire-assessed depression and subjective quality of life were related to BP and HR by analyses of variance and linear regression. Statistical significance was at 5%.

RESULTS

A circaseptan (about 7-day) component characterizes the 24-h mean and standard deviation (SD) of HR, and the daytime and day-night ratio of systolic BP. The SD of HR is higher on weekends and lower on Mondays and Thursdays. When awake, systolic BP is lowest on Sundays and the day-night ratio is optimal on weekends (Saturdays: 15.7 +/- 9.4%; Sundays: 14.0 +/- 13.2%). Depression was detected in 15 subjects, who had higher mean systolic and diastolic BP values (systolic BP: P = 0.028 Fridays, P = 0.021 Tuesdays; diastolic BP: P = 0.022 Mondays, P = 0.006 daytime Mondays) and a lower day-night ratio of diastolic BP (P = 0.012 Tuesdays, P = 0.005 Wednesdays, and P = 0.038 Thursdays). A depressive mood correlated positively with 24-h averages of systolic (P = 0.037) and diastolic (P = 0.030) BP.

CONCLUSIONS

Depression (and subjective quality of life) can affect BP and HR variability. The results indicate the role that psychological factors may play in the pathogenesis of cardiovascular disease. Therapeutic implications are suggested for primary and secondary prevention.

Blood pressure outcomes of dental patients screened chronobiologically: a seven-year follow-up

BACKGROUND

This article is a follow-up on a 1998 article in JADA. The blood pressure, or BP, of 23 of 24 normotensive patients was monitored at 15-minute intervals for a total of nine days, in three consecutive sessions of four, two and three days, respectively, separated by a few weeks.

METHODS

Twelve patients were reached by phone seven years after the prior chronobiologically interpreted monitoring to ascertain their cardiovascular status since the initial monitoring.

RESULTS

Only two of the 12 patients reached in follow-up had abnormalities in all three sessions, and only these two patients reported having experienced an adverse vascular event (one a myocardial infarction, the other coronary artery bypass graft surgery). The difference in outcome between the patients with chronobiological abnormality in all three sessions vs. the pool of those with abnormality in only two, one or none of the sessions is statistically significant.

CONCLUSIONS

Even a five-day (and sometimes a longer) profile, while greatly preferred to single measurements, may not suffice for a definitive diagnosis of certain patients. Retrospectively, the 864 measurements, on the average, on each person in our study could have served for a recommendation to each person. Chronobiologically interpreted BP and heart rate monitoring for a week or longer as a start detects high-risk states that may be missed by conventional casual measurements that are rarely accompanied by one-day profiles.

CLINICAL IMPLICATIONS

The dentist has an important opportunity for conveying the importance of monitoring BP and heart rate for a week to detect an abnormal variability, and for implementing this monitoring. Dentists can educate patients regarding the need for screening and for interpreting the results for variability, and contribute to their overall health by referring them to their physicians when treatment is indicated.

Near 10-year and longer periods modulate circadians: intersecting anti-aging and chronoastrobiological research

Biological cycles with relatively long and some unusual periods in the range of the half-week, the half-year, years, or decades are being discovered. Their prior neglect constituted a confounder in aging and much other research, which then"flew blind" concerning the uncertainties associated with these cycles when they are not assessed. The resolution of more about 10-year and other cycles, some reported herein, replaces the admission of complete unpredictability, implied by using the label "secularity." Heretofore unaccounted-for variability becomes predictable insofar as it proves to be rhythmic and is mapped systematically to serve as a battery of useful reference values. About 10-year cycles in urinary 17-ketosteroid excretion and in heart rate and its variability, among others, are aligned with cycles of similar length in mortality from myocardial infarction. Associations accumulate between cycles of natural physical time structures, chronomes such as the 10.5-year (circadecennian) Schwabe and the 21-year (circavigintunennian) Hale cycles of solar activity, and chronomes in biota. There are about 50-year (circasemicentennian) cycles in mortality from stroke in Minnesota and in the Czech Republic and also in human morphology at birth, the latter result reducing the likelihood that these cycles are purely human made. Associations among large populations warrant long-term systematic coordinated sampling of natural physical and biological variables of interest for the design of countermeasures against already documented elevated risks of stroke, myocardial infarction, and other catastrophic diseases, notably in elderly adults. New findings will be introduced against the background of the documented value of mapping rhythms in medicine and gerontology. In both these fields, rhythms promise the seeming paradox of better care for less.

Feedsidewards: intermodulation (strictly) among time structures, chronomes, in and around us, and cosmo-vasculo-neuroimmunity. About ten-yearly changes: what Galileo missed and Schwabe found

The spectrum of biological rhythms is extended far beyond circadians, circannuals, and ultradians, such as 1.5-hourly melatonin and 8-hourly endothelin-1 (ET-1) rhythms by statistics of natality, growth, morbidity, and mortality, some covering decades or centuries on millions of individuals. These reveal infradian cycles to be aligned with half-weekly rhythms in ET-1, weekly and half-yearly ones in melatonin, and even longer--about 50-, about 20-, and about 10-year cycles found in birth statistics. About daily, weekly, yearly, and ten-yearly patterns are also found in mortality from myocardial infarctions; the 10-yearly ones are also in heart rate and its variability; in steroid excretion, an aspect of resistance, for example, to bacteria; and in the genetic changes of the bacteria themselves. Automatic physiological measurements cover years and, in one case, cover a decade; the latter reveal an about 10-year (circadecennial) cycle. ECGs, covering months beat-to-beat, reveal circaseptans, gaining prominence in response to magnetic storms or after coronary artery bypass grafting. A spectrum including cycles from fractions of 1 Hz to circasemicentennians is just one element in biological time structures, chronomes. Chaos, trends, and any unresolved variability are the second to fourth elements of chronomes. Intermodulations, feedsidewards, account for rhythmically and thus predictably recurring quantitive differences and even for opposite treatment effects of the same total dose(s) of (1) immunomodulators inhibiting or stimulating DNA labeling of bone in health or speeding up versus slowing down a malignant growth and thus shortening or lengthening survival time, or (2) raising or lowering blood pressure or heart rate in the vascular aspect of the body's defense. Latitude-dependent competing photic and nonphotic solar effects upon the pineal are gauged by alternating yearly (by daylight) and half-yearly (by night) signatures of circulating melatonin at middle latitudes and by half-yearly signatures at noon near the pole. These many (including novel near 10-yearly) changes, for example, in 17-ketosteroid excretion, heart rate, heart rate variability, and myocardial infarction in us and those galactic, solar, and geophysical ones around us have their own special signatures and contribute to a cosmo-vasculo-immunity and, if that fails, to a cosmo(immuno?) pathology.

The impact on dentistry of recent advances in the management of hypertension

Dentistry has played an important role in the detection of patients with hypertension. Patients found to have high blood pressure at or beyond defined levels should be referred for a medical diagnosis and indicated treatment. Once the hypertensive condition is under control, oral and dental evaluation and treatment can be initiated. Beginning in 1976, the percentage of the general population in the United States with undetected hypertension declined steadily. However, this decline reversed, beginning in 1994. In addition, fewer than 50% of the patients who are aware of their hypertension have it medically under control. Thus, a significant number of patients with undetected high blood pressure or uncontrolled hypertension today are seeking dental treatment. These patients are at high risk for significant complications such as stroke, heart disease, kidney disease, and retinal disease. Those with very high blood pressure are at great risk for acute medical problems when receiving dental treatment. For those reasons, dentistry must continue to place an emphasis on the detection and referral of patients with high blood pressure. In addition, increased numbers of medically compromised patients are seeking dental treatment who should have their blood pressure monitored during the more stressful dental procedures, such as oral surgery, periodontal surgery, and placement of dental implants. This article reviews the recent advances in the dental and medical management of hypertension. It is important for dentists to be aware of hypertension in relation to the practice of dentistry.

SHR Y chromosome enhances the nocturnal blood pressure in socially interacting rats

Our objective was to test the hypothesis that nocturnal mean arterial pressure (MAP), heart rate (HR), and activity would be increased in 1) colony over individually caged rats and 2) the spontaneously hypertensive rat (SHR) Y chromosome strain (SHR/y colony) compared with Wistar-Kyoto (WKY) rats. MAP, HR, and activity were monitored using radiotelemetry. The nocturnal MAP rise expressed as the percentage change in MAP from light to dark was increased (P < 0.05) in the SHR/y colony. The SHR Y chromosome increased MAP in both the colony and caged groups compared with WKY (P < 0.001). The SHR/y colony animals spent 23% of a 24-h period at a MAP >120 mmHg, whereas the WKY colony animals spent 2% of a 24-h period in this range. The MAP of the SHR/y colony on clonidine was reduced (P < 0.001) to WKY baseline values. Activity but not HR was increased (P < 0.01) in the WKY and SHR/y colonies compared with caged animals. In conclusion, colony housing and the SHR Y chromosome increased MAP compared with individually caged housing.

Blood pressure variability assessed by semiautomatic and ambulatorily functional devices for home use

As a basis for chronobiologic analyses and thereby for screening deviant blood pressure, measurements are advocated, preferably with ambulatorily functional instrumentation at half-hour intervals around-the-clock for an initial span of 7 days. When only manual instrumentation is available, 3-hourly measurements during waking and one measurement, preferably by a companion, around mid-sleep is recommended to detect a blood pressure disorder. Such screening is warranted for a reasonably reliable diagnosis, particularly in order to recognize circadian blood pressure overswinging (Circadian Hyper-Amplitude-Tension, CHAT) and to separate this new disease risk syndrome from an elevation of the time structure (chronome)-adjusted average (MESOR), that is MESOR-hypertension, and from the coexistence of the two foregoing conditions.

Rewards in practice from chrono-meta-analyses 'recycling' heart rate, ectopy, ischemia and blood pressure information

Previously published average curves of heart rate and duration of ischemia in patients with coronary artery disease, studied while on placebo or on treatment with either atenolol or diltiazem, are re-analysed for the assessment of about-daily (circadian) and about-weekly (circaseptan) changes in these variables and of any treatment effect on rhythm characteristics. In addition to circadians, a circaseptan pattern characterizes the duration of ischemia in all three aforementioned study stages. Both drugs decrease the duration of ischemia, atenolol, but not diltiazem, also affects the circadian amplitude and acrophase of this variable. A circaseptan pattern is also found for heart rate on placebo and on treatment with atenolol, but not with diltiazem. Both drugs lower heart rate and the circadian amplitude and 24-h standard deviation of heart rate, atenolol much more markedly than diltiazem. Circadian and circaseptan rhythm characteristics and their alterations with treatment serve to optimize treatment by timing its administration. Chronobiologic surveillance of variables that are being readily monitored as-one-goes by modern implantable devices can also serve for the validation of the effectiveness of drug and electrical therapy. Rhythm alterations, in turn, can provide the earliest warnings of an elevated disease risk and lead to an improved diagnosis.