Search PubMed⌕ Search

Biomedical subjects

F Halberg

Publications and source records attributed to F Halberg.

At least 91 records · Page 5Linked to original sources
PubMed1997

About-half-weekly (circasemiseptan) component of the endothelin-1 (ET-1) chronome and vascular disease risk.

Plasma ET-1 was measured around the clock on different calendar dates in healthy subjects and in subjects with diabetes and/or with high blood pressure and/or a history of vascular complications (HVDR). A transverse approach, with each subject contributing a single 24-h mean, assessed any about-weekly or half-weekly variation in ET-1. A circasemiseptan component resolved by single cosinor for nondiabetic (but not for diabetic) HVDR subjects (p = 0.010) differs in its timing of overall high values (p < 0.050) from that found in healthy subjects (p = 0.006). The results are aligned with circasemiseptan patterns in other circulatory variables and morbidity/mortality statistics.

Adult↗
PubMed1997

Computer analysis of environmental temperature, light and noise in intensive care: chaos or chronome nurseries?

Lighting, noise and temperature were monitored in two perinatal nurseries. Rhythms of several frequencies were found, including prominent 24-hour rhythms with acrophases around 13:00 (light intensity) and 16:00 (noise). For light and noise, the ratio formed by dividing the amplitude of a 1-week (circaseptan) or half-week (circasemiseptan) fitted cosine curve by the amplitude of a 24-hour fitted cosine curve is smaller than unity, since 24-hour rhythms are prominent for these variables. The amplitude ratios are larger than unity for temperature in the newborns' unit but not in the infants' unit. Earlier, the origin of the about-7-day rhythms of neonatal physiologic variables was demonstrated to have, in addition to a major endogenous, also a minor exogenous component. Hence, the possibility of optimizing maturation by manipulating environmental changes can be considered, using, as gauges of development, previously mapped chronomes (time structures of biologic multifrequency rhythms, trends and noise).

Circadian Rhythm↗
PubMed1997

Age, gender and fractal scaling in heart rate variability.

1. The fractal scaling of heart rate variability, gauged by the correlation dimension (CD), is hypothesized to be characterized by a time structure (chronome), which in health shows differences as a function of gender and age. 2. From 24 h Holter records of 44 clinically healthy male subjects in four age groups (5-10, 20-25, 40-45 and 60-65 years; n = 11 in each group), 500 s sections at 4 h intervals for 24 h were analysed for smoothed R-R intervals sampled at 4 Hz. Using an algorithm modified from Grassberger and Procaccia (Physica D 1983; 9: 189-208), the correlation integral was estimated for embedding dimensions from 1 to 20 with a 1.0 s time lag for each section. Nightly (02.00 hours-06.00 hours) ECG records were similarly analysed in 72 additional clinically healthy subjects of both genders, 5-70 years of age. The single cosinor assessed the circadian characteristics; one- and two-way analyses of variance and linear regression were used to examine changes as a function of gender and age. 3. The 24 h average of CD is largest in the 20-25-year-old men and decreases with age there-after (P < 0.05). These changes apply in particular to the nightly CD values, which are higher in female than in male subjects (P < 0.001). Increasing age is associated with a decrease in the amplitude and an advance in the phase of the circadian rhythm in CD (P < 0.05). 4. A chaotic end-point from fractal scaling, yielding a non-linear index, such as the correlation integral, undergoes a circadian rhythm and changes with gender and age. This assessment in the chronome represents an added diagnostic tool in cardiology, and provides new end-points for the study of coherence among internal variables of autonomic mechanisms and of influences by external environmental variables upon them.

Adolescent↗
PubMed1997

Meta-analyzed heart rate variability, exposure to geomagnetic storms, and the risk of ischemic heart disease.

The aim was to examine how heart rate variability (HRV) relates to the risk of ischemic heart disease (IHD) and may provide a means to assess effects of exposure to geomagnetic storms. In Stockholm, the 24-hour SD of hourly estimates of heart rate (HR) were obtained by Holter monitoring from 50 men who had had an acute myocardial infarction or had angina pectoris and compared to that of 50 clinically healthy men of similar age. In Tokyo, the HR 121 normotensives and 176 treated hypertensives was monitored. The incidence of IHD was recorded prospectively for 6 years. These results are aligned with those of a retrospective analysis of archived data on all crews of the Soyuz spacecraft for 1990-1994 focused on ECG from cosmonauts (47 male and 2 female) at times corresponding to geomagnetic storms. The results clearly indicate a decrease in HRV in association with IHD (20.5%, p=0.002 in Stockholm, 20.0%, p=0.04 in Tokyo). By comparison, the about 30% decrease (p=0.041) in rms SD of HR in cosmonauts studied during a geomagnetic storm as compared to cosmonauts monitored on quiet days adds supportive evidence to the proposition that exposure to geomagnetic disturbances increases cardiovascular disease risk.

Adult↗
PubMed1996

Clinical relevance of about-yearly changes in blood pressure and the environment.

Changes identified by inferential statistics from summer to winter of high to low arterial blood pressures (BP) have been quantified as a large predictable about-yearly BP swing. This condition of a large annual BP amplitude (LABPA) raises concern about hypotension as well as hypertension and raises new questions regarding appropriate guidelines for diagnosis and treatment. Recommendations made in the fall on the basis of data collected in the summer may be totally inadequate in dealing with the patient's condition in the winter. In order to avoid such mistakes, it is imperative to implement a systematic surveillance of BP in the light of current chronobiological limits. Patients with a large circannual BP amplitude are particularly suited for a study of the underlying hormonal mechanisms. The longitudinal monitoring of their BP is also amenable to the study of environmental influences from near and far.

Aldosterone↗
PubMed1996

Changes in human blood pressure with season, age and solar cycles: a 26 year record.

The record was studied of a 71-year-old, diurnally active (0700-2200 hours) male psychiatrist (G.N.) who self-measured systolic and diastolic blood pressure (BPS and BPD) mostly but not exclusively on Sunday mornings, from 1969 to 1994. A large about-yearly change was revealed which increased with age and was accompanied by a decreasing trend in the yearly rhythm-adjusted mean (MESOR; P < 0.01). According to conventional criteria that specify only upper limits of acceptability, G.N. was hypertensive in summer and normotensive in other seasons. Since changes in both MESOR and circannual amplitude occurred, a systematic surveillance of BP is the chronobiological recommendation.

Age Factors↗
PubMed1996

The circadian rhythm of cortisol in the saliva of young pigs.

Single and population-mean cosinor analyses document a circadian rhythm in salivary cortisol of pigs (p < 0.001). The midline estimated statistic of rhythm, the MESOR (M), is 1.50 +/- 0.07 ng/ml. For the group of 14 pigs studied there was a predictable variation of 64% around this mean in salivary cortisol within a day: the double circadian amplitude, 2A, was 0.96 ng/ml, with a 95% confidence interval ranging from 0.60 to 1.32 ng/ml. A measure of timing, the acrophase, phi, was 10 h 52 min from the phase reference (0030, the middle of the daily dark span of the 24-h light-dark cycle in which the pigs were kept). The 95% confidence interval of phi extended from 9 h 48 min to 12 h 12 min from the reference time. The chronobiologic approach provides indispensable quantitive characteristics as reference standards for future basic or applied work.

Animals↗
PubMed1996

Chronobiometric assessment of autogenic training effects upon blood pressure and heart rate.

Autogenic training, a method of self-hypnosis, lowers the extent of within-day variation of systolic blood pressure assessed by the circadian double amplitude. The blood pressure and heart rate of ten patients, conventionally diagnosed as having hypertension or white-coat hypertension, were automatically monitored at 30-min intervals for 7 days before autogenic training and again for 7 days, at 1 or 2 months after the start of autogenic training (practiced three times daily). The circadian double amplitude of systolic blood pressure of the patients investigated was 3 to 17 mm Hg lower on autogenic training. In 5 patients, reductions by 7 to 17 mm Hg were statistically significant. These results are regarded as provisional statistics, the utility of which depends on replication. By contrast, the over-all group reduction of the circadian double amplitude of systolic blood pressure by 8 mm Hg on the average can be taken at face value. Autogenic training also lowered the circadian double amplitude of diastolic blood pressure, but the effect was small as was the effect of autogenic training upon the MESOR (a rhythm adjusted mean) and acrophase (a measure of the timing of over-all high values recurring each day). The effect of autogenic training upon the circadian double amplitude of systolic blood pressure suggests its trial as first-line treatment of patients with an excessive circadian blood pressure amplitude, a condition which, even in the absence of an elevated 24-hr, average of blood pressure, is associated with a large increase in the risk of developing ischemic stroke or nephropathy.

Aged↗
PubMed1996

Resonance of about-weekly human heart rate rhythm with solar activity change.

In several human adults, certain solar activity rhythms may influence an about 7-day rhythm in heart rate. When no about-weekly feature was found in the rate of change in sunspot area, a measure of solar activity, the double amplitude of a circadian heart rate rhythm, approximated by the fit of a 7-day cosine curve, was lower, as was heart rate corresponds to about-weekly features in solar activity and/or relates to a sunspot cycle.

Adult↗
PubMed1996

Evidence from a chronobiometric approach that chronic smokers, although normotensive, show an increase in diurnal blood pressure.

OBJECTIVE: To investigate the effects of chronic smoking on the 24 h blood pressure and heart rate pattern in normotensive subjects. METHODS: Twenty-five smokers and 25 age-, weight- and height-matched non-smokers, who were all clinically healthy young men, gave their informed consent to undergo non-invasive, automated, ambulatory blood pressure monitoring for 24 h. The smokers in this study consumed on average 25.4 cigarettes per day. The lifestyle of the two groups was comparable because they worked as clerks at the same company. The 24 h blood pressure and heart rate data were analysed according to chronobiological methods. RESULTS: Smokers were found to show a statistically significantly higher blood pressure versus non-smokers by day but not by night. Furthermore, smokers showed a slight increase in the mean level of circadian blood pressure rhythm versus non-smokers, accompanied by an amplification of one cyclic component of this periodicity. CONCLUSIONS: The increase in diumal blood pressure in smokers might be regarded as the haemodynamic effect of chronic smoking in normotensive subjects. Such an effect seems to be substantiated pathophysiologically by an amplitude overmodulation of one of the harmonic components which confer the circadian blood pressure rhythmicity. Because the diumal increase in blood pressure persists for two-thirds of the day-night period, one can argue that this phenomenon in normotensive smokers might be a premonitory sign of future hypertension. Apart from this, one can hypothesize that the diumal increase in blood pressure might itself be a cause of target organ damage, given its consistent within-day duration and daily repetition.

Adult↗
PubMed1996

Suprachiasmatic nuclei lesions eliminate the group circadian rhythm of systolic arterial pressure but not of heart rate in rats.

The aim of this study was to evaluate the participation of the suprachiasmatic nuclei (SCN) in the generation and synchronization of cardiovascular rhythms. Seven sham-operated and 11 SCN-lesioned animals maintained under 12/12 hr light/dark cycle were used. Systolic arterial pressure (SAP) and heart rate (HR) were measured indirectly during 24-hour periods at 3-4 hour intervals. The data were analyzed using individual and group cosinor rhythmometry and Fourier analysis. A circadian rhythm of water intake was not detected in animals with successful SCN lesions. A reduction of the double amplitude/MESOR ratio for the 24-hour component of drinking rhythm in the SCN-lesioned rats was observed. After SCN lesions the group 24-hour rhythm of SAP was eliminated while a significant group circadian rhythm for HR was detected. The individual amplitude/MESOR ratios for the 24-, 12-, 8- and 6-hour periodic components of SAP and HR in the lesioned rats showed no marked differences as compared with controls. The generation and entrainment of circadian variations in HR is probably not dependent on the integrity of SCN in rats. The SCN may participate in the entrainment of the circadian rhythm of SAP. The combination of completely abolished (water intake) and persisting (heart rate) rhythms further supports that the circadian regulatory system consists of a network of multiple oscillators.

Animals↗
PubMed1996

[From Pavlov's recording of time and conditioned reflexes to the chronophysiology of human nutrition].

That I. P. Pavlov understood how important to record the time factor allowed him to anticipate the chronobiological approach in physiology. As compared to the conditioned reflexes, the body's biological rhythms appeared to have a deeper basis - chronomes coded in the genes. The authors comparatively characterize the homeostatic approach used by I. P. Pavlov and the chronobiological approach proposed by F. Halberg both for biology and medicine.

Animals↗
PubMed1994

Chronopharmacologic issues in space.

Times of heightened susceptibility are expressed by nonrandom patterns in the incidence of various diseases, not only along the scale of a day but also of a week and a year. Whereas these rhythms can be synchronized by the environment, their endogenicity is revealed by their persistence in the absence of time cues with a period slightly but statistically significantly different from the environmental match. In the case of some circadians, the gene involved has been identified and heritabiliy in humans determined by studies on twins. Vital signs are now amenable to automatic monitoring around the clock. When analyzed by chronobiologic software, the data provide information regarding the given individual's time structure (chronome). Such physiologic monitoring serves the multiple purposes of deriving time-specified reference norms on the basis of which rhythm alteration can detect an elevated risk early, thus prompting timely preventive action and timed treatment whenever warranted. For long journeys in space, the design of a multi-disease prophylactic pill poses a chronopharmacologic challenge. Drugs such as aspirin and carnitine, used for the prevention of strokes, myocardial infarctions and depression, all show striking chronome-dependent effects which can determine not only the presence or the absence of a desired effect, but even yield effects in opposite directions.

Animals↗
PubMed1994

Telehygiene system for preventive chronopharmacology in space.

A remote computerized health care (telehygiene) system for space travel includes monitoring devices and pharmaceuticals aimed at the optimization of health and the environment. Early risk indicators are provided by dynamic characteristics of rhythms of several frequencies describing variation inside the physiologic range. These rhythm characteristics, assessed as one goes, can be updated and compacted as data accumulate by the use of chronobiologic software that resolves anticipated components of lower and lower frequency, thus providing summaries of data at intervals of differing length. At any time, harbingers of risk, including characteristics of circannual rhythms, can be retrieved in an instant. On their basis, early preventive action can be instituted for risk lowering and for delivery of timed treatment when needed. Preventive or curative health care in space and terrestrial spin-offs are the more effective the more of the chronome (time-structure) is resolved.

Aerospace Medicine↗
PubMed1994

Three-field breast irradiation technique using tangential quarter fields.

We have developed and implemented in clinical practice an isocentric three-field breast irradiation technique using tangential quarter fields. In this technique, the same isocenter is used for the supraclavicular and the tangential breast fields. The superior-posterior corner of the tangential breast fields is placed at the central axis by asymmetric collimation of both the length and the width of the field. Consequently, the beam divergence at both the superior and posterior edges is eliminated, allowing a perfect geometric match between the posterior borders of both tangential breast fields and the supraclavicular field without table rotation. Compared to conventional techniques requiring table rotations, the present method produces a more uniform dose distribution in the target volume and requires significantly less simulation time.

Breast↗