Circaseptan Research Articles

Correcting for Plasma Aldosterone Improves the Accuracy of Repeated Timed Urine Sampling for Estimation of Dietary Sodium Intake.

Long-term sodium balance studies show that sodium can be temporarily stored and released in tissues, mediated by circaseptan rhythms of aldosterone and cortisol. This complicates the reliability of a single 24-h urine collection to estimate individual sodium intake. We investigated whether repeated timed urine collection with and without correction for plasma aldosterone is a more accurate alternative for estimating daily sodium intake. We conducted a post hoc analysis of a metabolic ward study in which 16 healthy male adults consumed a diet with a fixed sodium content (50 or 200 mmol/day) for 7 days. Each day, urine was collected in 4 intervals (7:00-13:00 h, 13:00-19:00 h, 19:00-23:00 h, and 23:00-07:00 h). Plasma aldosterone was measured at 6:30 h, 12:30 h, and 18:30 h. Sodium intakes were estimated by various formulas using 3 timed urines of day 5-7. During a 200-mmol daily sodium intake, sodium intake estimates based on three repeated timed urine samples and the Toft equation differed 10 [IQR: 3-14], 8 [6-19], 36 [16-49], and 20 [10-43] mmol from the actual intake for intervals 7:00-13:00 h, 13:00-19:00 h, 19:00-23:00 h, 23:00-7:00 h, respectively. These measurements did not significantly differ from a single 24-h urine (20 [12-55] mmol). During a 50-mmol daily sodium intake, repeated timed urine collection performed worse than a single 24-h urine collection. On both diets, correction for plasma aldosterone increased accuracy and sodium intake estimates were significantly more accurate than a single 24-h urine. In a controlled environment, repeated timed urine collection corrected for plasma aldosterone is more accurate than a single 24-h urine collection.

The menstrual cycle is influenced by weekly and lunar rhythms

To study whether the menstrual cycle has a circaseptan (7 days) rhythm and whether it is associated with the lunar cycle (also defined as the synodic month, it is the cycle of the phases of the Moon as seen from Earth, averaging 29.5 days in length). Cross-sectional study. A total of 35,940 European and North American women aged 18-40 years. Data were collected in real-life conditions. No intervention was performed. The onset of menstruation was assessed in prospectively measured menstrual cycles (311,064 cycles) over 3 full years (2019-2021). Associations were calculated between the onset of menstruation and the day of the week, and between the onset of menstruation and the lunar phase. In this large data set, a circaseptan (7-day) rhythmicity of menstruation was observed, with a peak (acrophase) of menstrual onset on Thursdays and Fridays. This circaseptan rhythm was observed in every age group, in every phase of the lunar cycle, and in all seasons. This feature was most pronounced for cycle durations between 27 and 29 days. In winter, the circaseptan rhythm was found in cycles of 27-29 days, but not in other cycle lengths. A circalunar rhythm was also statistically significant, but not as clearly defined as the circaseptan rhythm. The peak (acrophase) of the circalunar rhythm of menstrual onset varied according to the season. In addition, there was a small but statistically significant interaction between the circaseptan rhythm and the lunar cycle. Although relatively small in amplitude, the weekly rhythm of menstruation was statistically significant. Menstruation occurs more often on Thursdays and Fridays than on other days of the week. This is particularly true for women whose cycles last between 27 and 29 days. Circalunar rhythmicity was also statistically significant. However, it is less pronounced than the weekly rhythm.

Ultradian, circadian, and circaseptan rhythms in the patterns of usage of Facebook messenger

ABSTRACT The Facebook Messenger (FBM) is one of the most popular instant messaging social apps, launched by Facebook in 2010. As of October 2019, there were about 1.3 billion FBM users worldwide. In this study, we analyzed periodicities in the online activity patterns of users in FBM. We did not recruit any subjects in this study; rather four of us used our own FBM accounts to reveal the presence of any rhythms with τ = 12 h or τ = 24 h or τ = 168 h in the patterns FBM usage among our FB friends. We log-transformed the time series data and subjected those to Cosinor rhythmometry. The peaks in the daily pattern of FBM usages, revealed from Cosinor analyses, and harmonics curve fittings validated the presence of multi-frequency rhythms in the longitudinal time-series data captured over a period of 16 days. The underlying basis of the observed multi-frequency rhythms could be attributed to the phenomenon of social synchronization. The current findings might bear commercial applications with special reference to targeted content advertising (TCA).

Circadian and circaseptan rhythms in human epilepsy: a retrospective cohort study

Epilepsy has long been suspected to be governed by cyclic rhythms, with seizure rates rising and falling periodically over weeks, months, or even years. The very long scales of seizure patterns seem to defy natural explanation and have sometimes been attributed to hormonal cycles or environmental factors. This study aimed to quantify the strength and prevalence of seizure cycles at multiple temporal scales across a large cohort of people with epilepsy. This retrospective cohort study used the two most comprehensive databases of human seizures (SeizureTracker [USA] and NeuroVista [Melbourne, VIC, Australia]) and analytic techniques from circular statistics to analyse patients with epilepsy for the presence and frequency of multitemporal cycles of seizure activity. NeuroVista patients were selected on the basis of having intractable focal epilepsy; data from patients with at least 30 clinical seizures were used. SeizureTracker participants are self selected and data do not adhere to any specific criteria; we used patients with a minimum of 100 seizures. The presence of seizure cycles over multiple time scales was measured using the mean resultant length (R value). The Rayleigh test and Hodges-Ajne test were used to test for circular uniformity. Monte-Carlo simulations were used to confirm the results of the Rayleigh test for seizure phase. We used data from 12 people from the NeuroVista study (data recorded from June 10, 2010, to Aug 22, 2012) and 1118 patients from the SeizureTracker database (data recorded from Jan 1, 2007, to Oct 19, 2015). At least 891 (80%) of 1118 patients in the SeizureTracker cohort and 11 (92%) of 12 patients in the NeuroVista cohort showed circadian (24 h) modulation of their seizure rates. In the NeuroVista cohort, patient 8 had a significant cycle at precisely 1 week. Two others (patients 1 and 7) also had approximately 1-week cycles. Patients 1 and 4 had 2-week cycles. In the SeizureTracker cohort, between 77 (7%) and 233 (21%) of the 1118 patients showed strong circaseptan (weekly) rhythms, with a clear 7-day period. Between 151 (14%) and 247 (22%) patients had significant seizure cycles that were longer than 3 weeks. Seizure cycles were equally prevalent in men and women, and peak seizure rates were evenly distributed across all days of the week. Our results suggest that seizure cycles are robust, patient specific, and more widespread than previously understood. They align with the accepted consensus that most epilepsies have some diurnal influence. Variations in seizure rate have important clinical implications. Detection and tracking of seizure cycles on a patient-specific basis should be standard in epilepsy management practices. Australian National Health and Medical Research Council.

Weekly enrollment and usage patterns in an Internet smoking cessation intervention

BackgroundPrevious analyses of Google search queries identified circaseptan (weekly) rhythms in smoking cessation information seeking, with Google searches for “quit” and “smoking” peaking early in the week. Similar patterns were observed for smoking cessation treatment seeking, such as calls to quitlines. These findings suggest that smoking cessation behaviors may have a weekly rhythm that could be leveraged to improve smoking cessation efforts. AimsTo assess whether weekly enrollment and usage patterns exist for an Internet smoking cessation intervention. MethodsWe used process data from a large, longstanding Internet smoking cessation intervention (www.becomeanex.org). Pearson's chi-squared tests were performed to identify day-of-the week differences in enrollment, first visit to site community pages, and quit date. Differences were considered statistically significant at the 1% level if p<0.00167 due to multiple comparisons. Regression analysis was used to examine differences in engagement activity based on the day of the week a user enrolled. ResultsWebsite users (n=69,237) were more likely to enroll on the site at the beginning of the week (Mondays and Tuesdays) (p<0.0001). Current smokers who selected quit dates (n=5574) preferred quit dates that came early in the week (Sundays and Mondays) compared to other weekdays (p<0.0001). Generally, there were no significant differences in overall website utilization metrics by day of enrollment, but there were some exceptions. Use of interactive features to select quit dates, track cigarette use, and record coping strategies was generally lower for Friday/Saturday enrollees. ConclusionsConsistent with prior research, the beginning of the week appears to be a time when individuals are more likely to enroll in an Internet smoking cessation intervention and engage with its core features. Emphasizing marketing and promotional efforts during the beginning of the week could result in greater reach of Internet smoking cessation interventions.

Exogeneity of the circaseptan mood rhythm and its relation to the working week

Previous longitudinal studies of mood showed that mood displays a circaseptan (weekly) rhythm, reaching its peaks during weekends and falling during the working week. These studies stirred numerous debates about whether the circaseptan nature of the mood is determined culturally or biologically. The goal of the present study was to determine how the division of the week on the working week and the weekend impacts mood. A sample of students completed the shortened version of the PANAS-X questionnaire each day throughout July (working week and the weekend not separated) and November (working week and the weekend separated). Cosinor rhythmometry was used to analyze the data. As in previous research, a circaseptan mood rhythm was detected in November. However, a circaseptan rhythm was not detected in July - a circasemilunar rhythm was detected instead. These results suggest that the division of the week on the working week and the weekend has a great impact on mood and that more longitudinal studies of this type are needed to better understand this relationship.

Circasepran rhytyms of motion activity

In this study the circaseptan rhythms of the motion activity of practically healthy people with an average level of locomotor activity were analyzed, engaged in mental work, of different ages and sex. We compared data of peoples, who have usual working week (5 working days per week) and a person who worked seven days per week, at the same pace, to determine the influence of the social factor. The statistically significant circaseptan rhythms with period between 6.4 and 7.0 days were found, with the internal, endogenous rhythm being in most cases more significant in relation to the external rhythm, which should be taken into account, for example, in the formulation of optimal individual schedule.

Prospective Measurement of Daily Health Behaviors: Modeling Temporal Patterns in Missing Data, Sexual Behavior, and Substance Use in an Online Daily Diary Study of Gay and Bisexual Men.

Daily diary and other intensive longitudinal methods are increasingly being used to investigate fluctuations in psychological and behavioral processes. To inform the development of this methodology, we sought to explore predictors of and patterns in diary compliance and behavioral reports. We used multilevel modeling to analyze data from an online daily diary study of 371 gay and bisexual men focused on sexual behavior and substance use. We found that greater education and olderage as well as lower frequency of substance use were associated with higher compliance. Using polynomial and trigonometric functions, we found evidence for circaseptan patterns in compliance, sexual behavior, and substance use, as well as linear declines in compliance and behavior over time. The results suggest potential sources of non-random patterns of missing data and suggest that trigonometric terms provide a similar but more parsimonious investigation of circaseptan rhythms than do third-order polynomial terms.

Circadian and circaseptan rhythms in implant-based thoracic impedance

Thoracic impedance (TI) denotes the electrical resistance that is measured between the right ventricular lead and the can of an implantable cardioverter-defibrillator. It is used in medical diagnostics for fluid load monitoring in heart failure patients. We analysed TI for diurnal and weekly components that go along with the recurrent patterns of daily life.TI was measured in 53 patients over 280 d each with a resolution of 1 h. Information about the patients’ professional occupation and typical sleeping rhythm was sought. Periodic signal components were identified in the amplitude spectrum, and their main characteristics were derived by cosinor analysis. The typical daily and weekly pattern were reconstructed by Fourier filtering.The Fourier spectrum indicates a strong circadian and a weaker circaseptan component in TI. The latter is significantly elevated in patients who regularly go to work, on error level . Cosinor analysis states a significant circadian rhythm in all patients (), with MESOR 61.8 , amplitude 1.9 , and acrophase 17.5 h. A significant weekly rhythm is found in 25 patients (), with amplitude 0.31 and acrophase typically on Wednesday. Both rhythms typically obtain their maximum during the ‘active’ phase of the period in daily life, i.e. in the afternoon and on working days, respectively, while the minimum is reached in the ‘recreative’ phase.Circadian and circaseptan variation are hence prevalent components of TI, which can induce impedance changes of several Ohms and thus be an error source for daily TI measurements.

Chronobiological studies of chicken IgY: Monitoring of infradian, circadian and ultradian rhythms of IgY in blood and yolk of chickens

IgY is the functional equivalent of mammalian IgG found in birds, reptiles and amphibians. Many of its biological aspects have been explored with different approaches. In order to evaluate the rhythmicity of serum and yolk IgY, four chickens were examined and reared under the same conditions. To monitor biological oscillations of IgY in yolk and serum, the eggs and blood samples were collected over a 60 day period and the rhythm of yolk and serum IgY was determined by direct-ELISA. Results indicated that, there is a significant circaseptan rhythm in yolk IgY and circaquattran rhythm in serum IgY. The serum IgY concentration reached a peak in the morning, decreased to a minimum during the daytime and increased again at night revealing a significant circadian rhythm was superimposed by an ultradian rhythm. These data are suited to address the controversies concerning the IgY concentration in egg yolk and blood of laying hens. In addition, this study raised new questions, if the different rhythms in yolk and serum are concerned.

Radiobiological investigations at tumor cell lines by exploiting aspects of chronological dose administration

Purpose: Using 31P-NMR spectroscopy the chronological behavior of the ATP-metabolism of the tumor spheroids C3H-MA, 9L-Gliome and the mono-layer L1210 has been analyzed via increase and decrease of the β-peak. The goal of this study is to elaborate an optimal fractionation scheme with regard to the irradiation of tumor spheroids and possibly to human tumors. Methods : The NMR-spectroscopy has been carried out by the FID technique (free induction decay), and the intensity of the β-peak provides a measure of the survival fraction S after radiation exposure with 30 kV X-rays. The linear-quadratic model has to be generalized in order to be valid for irradiation beyond the shoulder. Results and Conclusion: All three cell lines show characteristic periods, and a homeostatic control cannot be recognized. Essential components of these periods are circadian (i.e. one day), circa-semiseptan (i.e. 3.5 days) and circa-septan (i.e. one week). The determination of the survival fractions provides an optimum exploitation of radiation damages, when the ATP-concentration assumes a maximum value. This optimum is reached, when all three cycles exhibit an ATP maximum, which is only possible by accounting for the circa-septan rhythm. -------------------------------------- Cite this article as : Ulmer W. Radiobiological investigations at tumor cell lines by exploiting aspects of chronological dose administration. Int J Cancer Ther Oncol 2014; 2 (3):020312. DOI : 10.14319/ijcto.0203.12

What's the healthiest day?: Circaseptan (weekly) rhythms in healthy considerations.

Biological clocks govern numerous aspects of human health, including weekly clocks-called circaseptan rhythms-that typically include early-week spikes for many illnesses. To determine whether contemplations for healthy behaviors also follow circaseptan rhythms. We assessed healthy contemplations by monitoring Google search queries (2005-2012) in the U.S. that included the word healthy and were Google classified as health-related (e.g., healthy diet). A wavelet analysis was used in 2013 to isolate the circaseptan rhythm, with the resulting series compared by estimating ratios of relative query volume (healthy versus all queries) each day (e.g., (Monday-Wednesday)/Wednesday). Healthy searches peaked on Monday and Tuesday, thereafter declining until rebounding modestly on Sunday. Monday and Tuesday were statistically indistinguishable (t=1.22, p=0.22), but their combined mean had 30% (99% CI=29, 32) more healthy queries than the combined mean for Wednesday-Sunday. Monday and Tuesday query volume was 3% (99% CI=2, 5) greater than Wednesday, 15% (99% CI=13, 17) greater than Thursday, 49% (99% CI=46, 52) greater than Friday, 80% (99% CI=76, 84) greater than Saturday, and 29% (99% CI=27, 31) greater than Sunday. We explored media-based (priming) motivations for these patterns and they were consistently rejected. Just as many illnesses have a weekly clock, so do healthy considerations. Discovery of these rhythms opens the door for a new agenda in preventive medicine, including implications for hypothesis development, research strategies to further explore these rhythms, and interventions to exploit daily cycles in healthy considerations.

Circaseptan (Weekly) Rhythms in Smoking Cessation Considerations

Smokers’ rhythms in contemplating quitting or making quit attempts are poorly understood. Tobacco control has focused on annual events (e.g., New Year’s Day), but weekly “circaseptan” time-cycles may likewise exist. For example, many illnesses (e.g., strokes) are more common on Mondays.1 Do cessation behaviors also have weekly rhythms?

Characteristics of Infradian and Circadian Rhythms in the Persistent Vegetative State

This retrospective study investigated the circadian and infradian characteristics of blood pressure and heart rate in 26 patients with traumatic head injury in a persistent vegetative state (PVS). Systolic and diastolic blood pressures and heart rate were measured every hour for the first 240 h (10 days) following hospital admission. These data were analysed for the presence of circadian and infradian rhythms using the least-squares fit of the cosine function with the single cosinor method. Infradian rhythms were defined as biological rhythms with a period of approximately 7 days (circaseptan rhythms). All the patients studied had circadian and circaseptan rhythms of systolic and diastolic blood pressures and heart rate. The amplitudes of all the circaseptan rhythms were significantly greater than those of the corresponding circadian rhythms. It was concluded that there was an altered association between circadian and infradian blood pressure and heart rate rhythms in patients in a PVS. Circadian and infradian rhythms were present, but the infradian rhythm had a greater amplitude than the circadian rhythm.

Monitoring of laying capacity, immunoglobulin Y concentration, and antibody titer development in chickens immunized with ricin and botulinum toxins over a two-year period

One of the key benefits in using chickens for immunization is the high yield of antibodies obtainable. It is known that egg production decreases over time, while animal maintenance costs remain stable. It would, however, be desirable to keep hens as long as possible to obtain maximal amounts of antibodies. To identify a suitable length of time that animals can be kept and to optimize the cost:yield ratio, we monitored the number of eggs laid, the total amount of chicken IgY, and the specific antibody titer from individually prepared eggs over a 2-yr period. The plant toxin ricin and the Clostridium botulinum neurotoxins type A and B were used to immunize 4 chickens. The number of eggs laid in 2 yr was approximately 600 per hen (about 80% of the maximum egg number), yielding about 20 to 40 g of total IgY per hen. A stable antibody titer of 1:100,000 to 1:1,000,000, as measured by ELISA, was obtained following up to 11 injections of 10 to 20 μg of immobilized native toxin. Laying capacities were found to decrease, on average, from 7 eggs/wk at the point of first immunization to 2 eggs/wk after more than 2 yr. In parallel, the yield of total and specific IgY increased over time, so that the antibody recovery remained high, even after prolonged immunization times. Using purified IgY preparations, classical immunological assays such as ELISA and Western blotting were performed. Furthermore, the IgY showed neutralizing capacity when used to block the functional activity of the toxins both in vitro and in vivo. Analysis of the total IgY content over time demonstrated a complex biological oscillation (and the antigen-specific titer), with a shorter time period of around 7 d (circaseptan rhythm). In summary, we successfully immunized chickens with ricin and botulinum neurotoxins and monitored laying capacity, IgY concentration, and specific antibody titer over an extended period of 2 yr.

Chronomic community screening reveals about 31% depression, elevated blood pressure and infradian vascular rhythm alteration

Depression, which is a risk factor for cardiac morbidity and mortality, is not an unusual occurrence among individuals with coronary heart disease (CHD), but evidence concerning its role in the pathogenesis of this condition is less clear. Ambulatory blood pressure monitoring (ABPM) has become an important tool in the diagnosis and management of hypertension. Several previous studies have indicated that various kinds of target organ damage and cardiovascular morbidity are more strongly associated with a diagnosis by ABPM than through spot-checks in a clinical setting. This study investigated whether depressive mood was associated with changes in the about-weekly (circaseptan) and half-weekly (circasemiseptan) variations in blood pressure (BP) and heart rate (HR), including a BP surge on Mondays, in community-dwelling subjects monitored chronomically for the time structure (chronome) of their BP and HR variabilities. From April 2001 to April 2003, 217 subjects (85 men and 132 women; mean age: 56.8±11.3 yr) from U town, Hokkaido (latitude: 43.45°N, longitude: 141.85°E), self-monitored their BP and HR for 7 days starting around 11 a.m. on Thursday, and took readings at 30-minute intervals between 7 a.m. and 10 p.m., then at 60-minute intervals between 10 p.m. and 7 a.m. The data were retrieved and analyzed on a PC with appropriate commercial software (TM-2430-15; A&D Co., Japan). Subjects were asked about 15 items on a depression rating scale through a self-administered questionnaire. When the score amounted to 5 or higher, subjects were considered to be depressive. Student's t-test, a one-way analysis of variance (ANOVA), and cosinor methods with parametric tests were also used. A p-value below 0.05 was considered to indicate statistical significance (below 0.10: borderline statistical significance). Depression rating scales were obtained for 192 out of the 217 subjects enrolled in this study. Depression scores were (>) 5 in 72 subjects. The average values of systolic (S) and diastolic (D) BP were statistically significantly higher in depressed subjects (SBP: 129.2 vs 124.5 mmHg; p=0.034; DBP: 79.0 vs 76.5 mmHg; p=0.041). The 7-day average for HR did not differ between subjects with depression scores of < 5 or > 5. DBP dipping was less in the depressed subjects (16.30 vs 18.22%; p=0.048). The dipping ratios of SBP and HR showed no statistically significant difference. In the group with depression scores of <5, HR variability (estimated by the SD of HR and HR dip) was higher during vacations and lower on Mondays. The 24-h BP measures showed a novelty effect and a surge on Mondays. In the depressed group, a prominent circaseptan rhythm appeared to replace the novelty effect, vacation dip, and Monday surge. The results of this investigation indicate the clinical importance of the monitoring of depressed subjects. Fewer than 7 days of monitoring means a greater risk of false diagnosis, and thus a therapeutic decision including potentially unnecessary or inappropriate long-term treatment. Records shorter than 7 days would not have detected circaseptan BP dysrhythmia associated with a depressive state. Prominent circaseptans can provide new indications on the mechanisms underlying the strong relation between depression and adverse cardiac events. Future studies should aim at determining whether the treatment of depression, especially from the standpoint of a chronodiagnosis and chronotherapy, can reduce the incidence of adverse cardiac events, and whether this depends upon restoring normal BP and HR variability, i.e. anormal BP and HR chronome.

Chronobiological features of dream production.

A review of the scientific literature clarifies several chronobiological features of dreaming. The literature supports the conclusions that dreaming 'intensity' and, to a lesser extent dream-like quality, is modulated by (1) a sinusoidal, 90-min ultradian oscillation, (2) a 'switch-like' circadian oscillation, (3) a 12-h circasemidian rhythm, and (4) a 28-day circatrigintan rhythm (for women). Further, access to dream memory sources appears to be modulated by (5) a 7-day circaseptan rhythm. Further study of these rhythmic influences on dreaming may help to explain diverse and often contradictory findings in the dream research literature, to clarify relationships between dreaming and waking cognitive processes, to explain relationships between disturbed phase relationships and dream disturbances and to shed new light on the problems of dreaming's functions and biological markers. Further chronobiological studies of dreaming will likely enable the development of theoretical models that explain how interactions between and within major levels of oscillation determine the variable characteristics of dreaming.

Feeble Weekly Rhythmicity in Hematological, Cardiovascular, and Thermal Parameters in the Horse

The homeostatic control of physiological processes is affected by a variety of temporal programs, such as circadian rhythms, estrous cycles, and circannual rhythms. The existence of circaseptan rhythms (endogenous rhythms with the duration of a week) has been postulated but not properly verified. In this study, we compared plasma concentration of lactic acid, systolic and diastolic blood pressure, and rectal temperature in athletic horses (maintained under a weekly training schedule) with those in sedentary horses (maintained under a constant schedule throughout the week). Although exercise had robust acute effects on the measured parameters, measurements conducted early in the morning or in the evening showed significant weekly rhythmicity only in one of the parameters (plasma concentration of lactic acid) in a few animals. This rhythmicity was feeble, was present only in athletic horses, and vanished if rigorous statistical criteria were applied. In contrast, 24 h rhythmicity was significant in all parameters in all horses. We conclude that the overall 7-day pattern in physiological parameters of the horse is feeble and is caused by the weekly schedule of activity. The available evidence does not support the notion of endogenous, circaseptan rhythms.

Analysis of rhythmic variance - ANORVA. A new simple method for detecting rhythms in biological time series

Cyclic variations of variables are ubiquitous in biomedical science. A number of methods for detecting rhythms have been developed, but they are often difficult to interpret. A simple procedure for detecting cyclic variations in biological time series and quantification of their probability is presented here. Analysis of rhythmic variance (ANORVA) is based on the premise that the variance in groups of data from rhythmic variables is low when a time distance of one period exists between the data entries. A detailed stepwise calculation is presented including data entry and preparation, variance calculating, and difference testing. An example for the application of the procedure is provided, and a real dataset of the number of papers published per day in January 2003 using selected keywords is compared to randomized datasets. Randomized datasets show no cyclic variations. The number of papers published daily, however, shows a clear and significant (p < 0.03) circaseptan (period of 7 days) rhythm, probably of social origin.

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 (≥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° and –67° from 00:00 h from Saturday to Sunday for SBP and DBP, respectively, with 360° ≡ 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 ≡ 360° and 0° = local midnight, the acrophase ( φ) for SBP is at –80° and for DBP at –113°, in keeping with earlier results from four adult subjects (SBP: –37°; DBP: –42°), 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.