Blue Light and Temperature Actigraphy Measures Predicting Metabolic Health Are Linked to Melatonin Receptor Polymorphism

This study explores the relationship between the light features of the Arctic spring equinox and circadian rhythms, sleep and metabolic health. Residents (N = 62) provided week-long actigraphy measures, including light exposure, which were related to body mass index (BMI), leptin and cortisol. Lower wrist temperature (wT) and higher evening blue light exposure (BLE), expressed as a novel index, the nocturnal excess index (NEIbl), were the most sensitive actigraphy measures associated with BMI. A higher BMI was linked to nocturnal BLE within distinct time windows. These associations were present specifically in carriers of the MTNR1B rs10830963 G-allele. A larger wake-after-sleep onset (WASO), smaller 24 h amplitude and earlier phase of the activity rhythm were associated with higher leptin. Higher cortisol was associated with an earlier M10 onset of BLE and with our other novel index, the Daylight Deficit Index of blue light, DDIbl. We also found sex-, age- and population-dependent differences in the parametric and non-parametric indices of BLE, wT and physical activity, while there were no differences in any sleep characteristics. Overall, this study determined sensitive actigraphy markers of light exposure and wT predictive of metabolic health and showed that these markers are linked to melatonin receptor polymorphism.

Chronotype and lipid metabolism in Arctic Sojourn Workers

This study relates answers to the Munich Chronotype Questionnaire (MCTQ) and Pittsburgh Sleep Quality Index (PSQI) from Arctic Sojourn Workers (ASW) of Yamburg Settlement, 68° Latitude North, 75° Longitude East (n = 180; mean age ± SD; range: 49.2 ± 7.8; 25-66 y; 45% women) to Arctic Sojourn Work Experience (ASWE), age and health status. Chronotype, Mid Sleep on Free Days sleep corrected (MSFsc) and sleep characteristics of ASW were compared to those of age-matched Tyumen Residents (TR, n = 270; mean age ± SD; range: 48.4 ± 8.4; 25-69 y; 48% women), 57° Latitude North, 65° Longitude East. ASW have earlier MSFsc than TR (70 min in men, p < 0.0001, and 45 min in women, p < 0.0001). Unlike TR, their MSFsc was not associated with age (r = 0.037; p = 0.627) and was linked to a larger Social Jet Lag (+21 min in men; p = 0.003, and +18 min in women; p = 0.003). These differences were not due to outdoor light exposure (OLE): OLE on work (OLEw) or free (OLEf) days was not significantly different between ASW and TR in men and was significantly less in ASW than in TR women (OLEw: -31 min; p < 0.001; OLEf: -24 min; p = 0.036). ASWE, but not age, was associated with compromised lipid metabolism in men. After accounting for multiple testing, when corrected for age and sex, higher triglycerides to high-density lipoprotein ratio, TG/HDL correlated with ASWE (r = 0.271, p < 0.05). In men, greater SJL was associated with lower HDL (r = -0.204; p = 0.043). Worse proxies of metabolic health were related to unfavorable components of the Pittsburgh Sleep Quality Index in ASW. Higher OLE on free days was associated with lower systolic (b = -0.210; p < 0.05) and diastolic (b = -0.240; p < 0.05) blood pressure.

Depression scores are associated with retinal ganglion cells loss

BACKGROUND

Light is a known factor affecting mood and the circadian system. Light deficit is linked to deteriorated transduction of photic information to the brain, and reduced amplitude of the perceived circadian light signaling. Retinal ganglion cells (RGCs) loss due to advanced glaucoma can be a factor compromising light perception, with consequences for circadian rhythms, sleep and mood. This study aimed to estimate associations of RGCs loss with a depression score by multiple regression, accounting for other features of glaucoma.

METHODS

One hundred and fifteen patients diagnosed with primary open-angle glaucoma completed the Beck Depression Inventory II questionnaire. The damage to their RGCs was assessed by high-definition optical coherence tomography (HD-OCT) and their function by pattern electroretinogram (PERG). On fifteen of these patients, 24-h salivary melatonin patterns were determined under light-controlled laboratory conditions, and analysis of eight clock related gene polymorphisms was performed.

RESULTS

Backward stepwise multiple regression revealed that the BDI score was the strongest factor that was most closely associated with the HD-OCT-based percentage of global RGCs loss (standardized coefficient, b* = 0.784, p < 0.001), surpassing other related factors, including age, intraocular pressure, visual field loss, and PERG amplitude. A high BDI score was associated with the GNβ3 825C > T polymorphism (dbSNP rs5443).

LIMITATIONS

This study did not specifically address damage to intrinsically photoreceptive RGCs. The gene study is based on a limited number of volunteers.

CONCLUSIONS

Depression scores are strongly associated with RGCs loss, increasing abruptly above a threshold of 15 %, supporting the hypothesis that RGCs loss in advanced glaucoma may affect non-visual photic transduction and lead to mood disturbances.

Outdoor daylight exposure and longer sleep promote wellbeing under COVID-19 mandated restrictions

Light is an important regulator of daily human physiology in providing time‐of‐day information for the circadian clock to stay synchronised with the 24‐hr day. The coronavirus disease 2019 (COVID‐19) pandemic led to social restrictions in many countries to prevent virus spreading, restrictions that dramatically altered daily routines and limited outdoor daylight exposure. We previously reported that sleep duration increased, social jetlag decreased, and mid‐sleep times delayed during social restrictions (Global Chrono Corona Survey, N = 7,517). In the present study, we investigated in the same dataset changes in wellbeing and their link to outdoor daylight exposure, and sleep–wake behaviour. In social restrictions, median values of sleep quality, quality of life, physical activity and productivity deteriorated, while screen time increased, and outdoor daylight exposure was reduced by ~58%. Yet, many survey participants also reported no changes or even improvements. Larger reductions in outdoor daylight exposure were linked to deteriorations in wellbeing and delayed mid‐sleep times. Notably, sleep duration was not associated with outdoor daylight exposure loss. Longer sleep and decreased alarm‐clock use dose‐dependently correlated with changes in sleep quality and quality of life. Regression analysis for each wellbeing aspect showed that a model with six predictors including both levels and their deltas of outdoor daylight exposure, sleep duration and mid‐sleep timing explained 5%–10% of the variance in changes of wellbeing scores (except for productivity). As exposure to daylight may extenuate the negative effects of social restriction and prevent sleep disruption, public strategies during pandemics should actively foster spending more daytime outdoors.

Melatonin mitigates disrupted circadian rhythms, lowers intraocular pressure, and improves retinal ganglion cells function in glaucoma

Glaucoma is a progressive optic neuropathy associated with damage to retinal ganglion cells (RGCs) and disrupted circadian rhythms. Melatonin is a promising substance to ameliorate glaucoma-associated compromised circadian rhythms, sleep, mood, and retinal cells function. However, studies estimating melatonin effects in glaucoma are currently lacking. Therefore, In this study, we investigated the effect of long-term (daily at 10:30 pm for 90 days) oral melatonin administration on systemic (Tb) and local to the organ of vision (IOP) circadian rhythms, pattern electroretinogram (PERG), sleep, and mood, depending on glaucoma stage in patients diagnosed with stable or advanced primary open-angle glaucoma. In a laboratory study in 15 of them, 24-hour records of salivary melatonin were obtained and MTNR1B receptor gene polymorphism was assessed. Melatonin increased the stability of the Tb circadian rhythm by improving its phase alignment and alignment with IOP. Melatonin time-dependently decreased IOP and IOP standard deviation (SD). IOP 24-hour mean and IOP SD decreases were more pronounced in individuals with the higher initial 24-hour IOP mean. Melatonin improved RGCs function in advanced glaucoma; N95 amplitude increase correlated positively with RGCs loss. The beneficial effects of melatonin on sleep and mood were greater in advanced glaucoma. Finally, delayed salivary melatonin and Tb phases were observed in MTNR1B G-allele carriers with advanced glaucoma. Combined, these results provide evidence for melatonin efficiency in restoring disrupted circadian rhythms in glaucoma with different effects of melatonin on systemic vs. local circadian rhythms, indicating that a personalized strategy of melatonin administration may further refine its treatment benefits.

Disruption of 24-Hour Rhythm in Intraocular Pressure Correlates with Retinal Ganglion Cell Loss in Glaucoma

Parameters of 24-h rhythm in intraocular pressure (IOP) were assessed in patients with stable or advanced primary open-angle glaucoma (S-POAG/A-POAG) and referenced to the phase of “marker” circadian temperature rhythm of each patient. Body temperature and IOP were measured over a 72-h span in 115 participants (65 S-POAG and 50 A-POAG). Retinal Ganglion Cell (RGC) damage was assessed by high-definition optical coherence tomography. The 24-h IOP rhythm in A-POAG patients peaked during the night, opposite to the daytime phase position in S-POAG patients (p < 0.0001). The 24-h IOP phase correlated with RGC loss (p < 0.0001). The internal phase shift between IOP and body temperature gradually increased with POAG progression (p < 0.001). Angiotensin converting enzyme Alu-repeat deletion/insertion (ACE I/D) emerged as a candidate gene polymorphism, which may play a role in the alteration of the circadian IOP variability in advanced glaucoma. To conclude, a reliable estimation of the 24-h rhythm in IOP requires the degree of RGC damage to be assessed. In advanced POAG, the 24-h phase of IOP tended to occur during the night and correlated with RGC loss, being progressively delayed relative to the phase of temperature.

COVID-19-mandated social restrictions unveil the impact of social time pressure on sleep and body clock

In humans, sleep regulation is tightly linked to social times that assign local time to events, such as school, work, or meals. The impact of these social times, collectively—social time pressure, on sleep has been studied epidemiologically via quantification of the discrepancy between sleep times on workdays and those on work-free days. This discrepancy is known as the social jetlag (SJL). COVID-19-mandated social restrictions (SR) constituted a global intervention by affecting social times worldwide. We launched a Global Chrono Corona Survey (GCCS) that queried sleep–wake times before and during SR (preSR and inSR). 11,431 adults from 40 countries responded between April 4 and May 6, 2020. The final sample consisted of 7517 respondents (68.2% females), who had been 32.7 ± 9.1 (mean ± sd) days under SR. SR led to robust changes: mid-sleep time on workdays and free days was delayed by 50 and 22 min, respectively; sleep duration increased on workdays by 26 min but shortened by 9 min on free days; SJL decreased by ~ 30 min. On workdays inSR, sleep–wake times in most people approached those of their preSR free days. Changes in sleep duration and SJL correlated with inSR-use of alarm clocks and were larger in young adults. The data indicate a massive sleep deficit under pre-pandemic social time pressure, provide insights to the actual sleep need of different age-groups and suggest that tolerable SJL is about 20 min. Relaxed social time pressure promotes more sleep, smaller SJL and reduced use of alarm clocks.

Some Near- and Far-Environmental Effects on Human Health and Disease with a Focus on the Cardiovascular System

Environmental effects on human physiopathology are revisited herein from a chronobiologic viewpoint, with a focus on the cardiovascular system. Physiological variables undergo recurring changes that are predictable in a statistical, albeit not deterministic way. Biological rhythms cover a broad range of frequencies, which are usually shared by the environment as “co-periodisms”. Some of these photic and non-photic periodicities shared by the environment and physiopathology are reviewed herein, together with their possible underlying mechanisms. A plausible cascade of events from the long-period cycles found in the cosmic environment to those affecting the Earth’s atmosphere and weather conditions is presented, which may shed light on how they may shape the cycles characterizing human health. Maps of important cycles shared between the environment and physiopathology are being catalogued in an atlas of chronomes with the goal of distinguishing between strong and weak associations and providing an estimate of the lag that can be anticipated before observing physiological changes.

Circasemiannual chronomics: half-yearly biospheric changes in their own right and as a circannual waveform

Geomagnetic activity has a strong half-yearly but no precise yearly component in its spectrum, as Armin Grafe suggested nearly half a century ago. We have postulated elsewhere that non-photic cycles such as those in geomagnetics may have signatures in the biosphere and vice versa that biological rhythms have likely counterparts in the physical environment. Accordingly, we document phenomena characterized by a prominent about half-yearly variation, re-analyzed to constitute the start of a transdisciplinary chronomic (time structural) map, aligning these conditions with a half-yearly cycle in the geomagnetic index Kp. At least some biospheric phenomena fitted concomitantly with 1- and 0.5-year cosine curves exhibit an amplitude (A) ratio of A(0.5-year)/A(1-year) larger than unity. Methodologically, it is pertinent that even if data were read off published graphs, the resulting analyses were practically the same as those in the original data received subsequently. The main point is a circasemiannual pattern in status epilepticus, in several morbid oral conditions, in the cell density of vasopressin-containing neurons in the human suprachiasmatic nuclei (SCN), in circulating melatonin at middle latitudes at night during years of minimal solar activity or around noon at high latitudes, and in an unusual circasemiannual aspect of a birth-month-dependence of human longevity. Others have asked whether annual rhythms in human reproduction are biological, sociological or both. We show some other possibilities herein, involving the physical environment, hardly to be neglected in the case of open systems. As to almost certainly multifactorial circasemiannual rhythms, geomagnetics may also be a signal, a proxy or a putative, at least partial mechanism. Geomagnetic activity is related in its turn to solar and galactic activity, and may be a marker for other cyclic events that affect the biosphere. The similarity of cycle lengths in itself can only be a hint prompting the search for causal relations.

Chronoastrobiology: proposal, nine conferences, heliogeomagnetics, transyears, near-weeks, near-decades, phylogenetic and ontogenetic memories

"Chronoastrobiology: are we at the threshold of a new science? Is there a critical mass for scientific research?" A simple photograph of the planet earth from outer space was one of the greatest contributions of space exploration. It drove home in a glance that human survival depends upon the wobbly dynamics in a thin and fragile skin of water and gas that covers a small globe in a mostly cold and vast universe. This image raised the stakes in understanding our place in that universe, in finding out where we came from and in choosing a path for survival. Since that landmark photograph was taken, new astronomical and biomedical information and growing computer power have been revealing that organic life, including human life, is and has been connected to invisible (non-photic) forces, in that vast universe in some surprising ways. Every cell in our body is bathed in an external and internal environment of fluctuating magnetism. It is becoming clear that the fluctuations are primarily caused by an intimate and systematic interplay between forces within the bowels of the earth--which the great physician and father of magnetism William Gilbert called a 'small magnet'--and the thermonuclear turbulence within the sun, an enormously larger magnet than the earth, acting upon organisms, which are minuscule magnets. It follows and is also increasingly apparent that these external fluctuations in magnetic fields can affect virtually every circuit in the biological machinery to a lesser or greater degree, depending both on the particular biological system and on the particular properties of the magnetic fluctuations. The development of high technology instruments and computer power, already used to visualize the human heart and brain, is furthermore making it obvious that there is a statistically predictable time structure to the fluctuations in the sun's thermonuclear turbulence and thus to its magnetic interactions with the earth's own magnetic field and hence a time structure to the magnetic fields in organisms. Likewise in humans, and in at least those other species that have been studied, computer power has enabled us to discover statistically defined endogenous physiological rhythms and further direct effects that are associated with these invisible geo- and heliomagnetic cycles. Thus, what once might have been dismissed as noise in both magnetic and physiological data does in fact have structure. And we may be at the threshold of understanding the biological and medical meaning and consequences of these patterns and biological-astronomical linkages as well. Structures in time are called chronomes; their mapping in us and around us is called chronomics. The scientific study of chronomes is chronobiology. And the scientific study of all aspects of biology related to the cosmos has been called astrobiology. Hence we may dub the new study of time structures in biology with regard to influences from cosmo- helio- and geomagnetic rhythms chronoastrobiology. It has, of course, been understood for centuries that the movements of the earth in relation to the sun produce seasonal and daily cycles in light energy and that these have had profound effects on the evolution of life. It is now emerging that rhythmic events generated from within the sun itself, as a large turbulent magnet in its own right, can have direct effects upon life on earth. Moreover, comparative studies of diverse species indicate that there have also been ancient evolutionary effects shaping the endogenous chronomic physiological characteristics of life. Thus the rhythms of the sun can affect us not only directly, but also indirectly through the chronomic patterns that solar magnetic rhythms have created within our physiology in the remote past. For example, we can document the direct exogenous effects of given specific solar wind events upon human blood pressure and heart rate. We also have evidence of endogenous internal rhythms in blood pressure and heart rate that are close to but not identical to the period length of rhythms in the solar wind. These were installed genetically by natural selection at some time in the distant geological past. This interpretive model of the data makes the prediction that the internal and external influences on heart rate and blood pressure can reinforce or cancel each other out at different times. A study of extensive clinical and physiological data shows that the interpretive model is robust and that internal and external effects are indeed augmentative at a statistically significant level. Chronoastrobiological studies are contributing to basic science--that is, our understanding is being expanded as we recognize heretofore unelaborated linkages of life to the complex dynamics of the sun, and even to heretofore unelaborated evolutionary phenomena. Once, one might have thought of solar storms as mere transient 'perturbations' to biology, with no lasting importance. Now we are on the brink of understanding that solar turbulences have played a role in shaping endogenous physiological chronomes. There is even documentation for correlations between solar magnetic cycles and psychological swings, eras of belligerence and of certain expressions of sacred or religious feelings. Chronoastrobiology can surely contribute to practical applications as well as to basic science. It can help develop refinements in our ability to live safely in outer space, where for example at the distance of the moon the magnetic influences of the sun will have an effect upon humans unshielded by the earth's native magnetic field. We should be better able to understand these influences as physiological and mechanical challenges, and to improve our estimations of the effects of exposure. Chronoastrobiology moreover holds great promise in broadening our perspectives and powers in medicine and public health right here upon the surface of the earth. Even the potential relevance of chronoastrobiology for practical environmental and agricultural challenges cannot be ruled out at this early stage in our understanding of the apparently ubiquitous effects of magnetism and hence perhaps of solar magnetism on life. The evidence already mentioned that fluctuations in solar magnetism can influence gross clinical phenomena such as rates of strokes and heart attacks, and related cardiovascular variables such as blood pressure and heart rate, should illustrate the point that the door is open to broad studies of clinical implications. The medical value of better understanding magnetic fluctuations as sources of variability in human physiology falls into several categories: 1) The design of improved analytical and experimental controls in medical research. Epidemiological analyses require that the multiple sources causing variability in physiological functions and clinical phenomena be identified and understood as thoroughly as possible, in order to estimate systematic alterations of any one variable. 2) Preventive medicine and the individual patients'care. There are no flat 'baselines', only reference chronomes. Magnetic fluctuations can be shown statistically to exacerbate health problems in some cases. The next step should be to determine whether vulnerable individuals can be identified by individual monitoring. Such vulnerable patients may then discover that they have the option to avoid circumstances associated with anxiety during solar storms, and/or pay special attention to their medication or other treatments. Prehabilitation by self-help can hopefully complement and eventually replace much costly rehabilitation. 3) Basic understanding of human physiological mechanisms. The chronomic organization of physiology implies a much more subtle dynamic integration of functions than is generally appreciated. All three categories of medical value in turn pertain to the challenges for space science of exploring and colonizing the solar system. The earth's native magnetic field acts like an enormous umbrella that offers considerable protection on the surface from harsh solar winds of charged particles and magnetic fluxes. The umbrella becomes weaker with distance from the earth and will offer little protection for humans, other animals, and plants in colonies on the surface of the moon or beyond. Thus it is important before more distant colonization is planned or implemented to better understand those magnetism-related biological- solar interactions that now can be studied conveniently on earth. (ABSTRACT TRUNCATED)

Engineering and governmental challenge: 7-day/24-hour chronobiologic blood pressure and heart rate screening: Part I

This review provides evidence that the bioengineering community needs to develop cost-effective, fully unobtrusive, truly ambulatory instrumentation for the surveillance of blood pressure and heart rate. With available instrumentation, we document a disease risk syndrome, circadian blood pressure overswinging (CHAT, short for circadian hyper-amplitude-tension). Circadian hyper-amplitude-tension is defined as a week-long overall increase in the circadian amplitude or otherwise-measured circadian variability of blood pressure above a mapped threshold, corresponding to the upper 95% prediction limit of clinically healthy peers of the corresponding gender and age. A consistently reduced heart rate variability, gauged by a circadian standard deviation below the lower 5% prediction limit of peers of the corresponding gender and age, is an index of a separate yet additive major risk, a deficient heart rate variability (DHRV). The circadian amplitude, a measure of the extent of reproducible variability within a day, is obtained by linear curve-fitting, which yields added parameters: a midline-estimating statistic of rhythm, the MESOR (a time structure or chronome-adjusted mean), the circadian acrophase, a measure of timing of overall high values recurring in each cycle, and the amplitudes and acrophases of the 12-hour (and higher order) harmonic(s) of the circadian variation that, with the characteristics of the fundamental 24-hour component, describe the circadian waveform. The MESOR is a more precise and more accurate estimate of location than the arithmetic mean. The major risks associated with CHAT and/or DHRV have been documented by measurements of blood pressure and heart rate at 1-hour or shorter intervals for 48 hours on populations of several hundred people, but these risks are to be assessed in a 7-day/24-hour record in individuals before a physical examination, for the following reasons. (1) The average derived from an around-the-clock series of blood pressure measurements, computed as its MESOR, the proven etiopathogenetic factor of catastrophic vascular disease, can be above chronobiologic as well as World Health Organization limits for 5 days or longer and can be satisfactory for months thereafter, as validated by continued automatic monitoring. The MESOR can be interpreted in light of clock-hour-, gender-, and age-specified reference limits and thus can be more reliably estimated with a systematic account of major sources of variability than by casual time-unspecified spot checks (that conventionally are interpreted by a fixed and, thus, rhythm, gender-, and age-ignoring limit). With spot checks, in a diagnostically critical range of "borderline" blood pressures, an inference can depend on the clock-hour of the measurement, usually providing a diagnosis of normotension in the morning and of hypertension in the afternoon (for the same diurnally active, nocturnally resting patient!). Long-term treatment must not be based upon the possibility of an afternoon vs a morning appointment. Moreover, the conventional approach will necessarily miss cases of CHAT that are not accompanied by MESOR hypertension. (2) Circadian hyper-amplitude-tension indicates a greater risk for stroke than does an increase in the around-the-clock average blood pressure (above 130/80 mm Hg) or old age, whereas (3) CHAT can be asymptomatic, as can MESOR hyptertension. (4) Deficient heart rate variability, the fall below a threshold of the circadian standard deviation of heart rate, an entity in its own right, is also a chronome alteration of heart rate variability (CAHRV). Deficient heart rate variability can be present together with CHAT, doubling the relative risk of morbid events. In each case--either combined with CHAT or as an isolated CAHRV--a DHRV constitutes an independent diagnostic assessment provided as a dividend by current blood pressure monitors that should be kept in future instrumentation designs. CHAT and DHRV can be screened by systematic focus on variability, preferably by the use of automatic instrumentation and analyses, which are both available (affordably) for research in actual practice, in conjunction with the Halberg Chronobiology Center at the University of Minnesota.

Spin-offs from blood pressure and heart rate studies for health care and space research

Evidence here cited underlies resolutions at international meetings to initiate a chronobiology project for health improvement. This project demonstrates expeditiously the feasibility and the health benefits of incorporating chronomedical considerations in the diagnosis, treatment, and prevention of one (or a few closely related) vascular (and oncological) diseases, that have high awareness and importance in the public perspective. Thereby, chronomedicine should become a mainstream basic and applied speciality leading to continual improvement in national/international health status. Reference data obtained for health care can also serve to give a better understanding of the relationship between the terrestrial biosphere and cosmoi near and far.

Chronomedical aspects of oncology and geriatrics

Extensive laboratory evidence on the merits of cancer chronotherapy is validated by the doubling of 2-year disease-free survival rate obtained by the chronoradiotherapy of patients with very advanced perioral cancers and by the quadrupling of the 5-year survival achieved by the chronochemotherapy of patients with advanced ovarian and bladder cancer. Miniaturized monitors for marker rhythmometry of tumor and core temperature recorded over long spans should facilitate the optimization of treatment by timing, while also serving the purpose of earliest intervention. The likelihood of a cure should be increased by focusing upon the now extensively documented tumor marker rhythms that may show time structure (chronome) alterations before exceeding the physiological range (that is otherwise neglected as one of random variation), and before overt symptoms appear.

The human blood pressure chronome: a biological gauge of aging

OBJECTIVE

This study examines changes in the broad time structure (chronome) of blood pressure (BP) as a function of age.

DESIGN

This is an observational study.

SETTING

The study was conducted at the Chronobiology Laboratories of the University oi Minnesota, Minneapolis, Minnesota.

PARTICIPANTS

Seventy-two individuals 12 to 106 years of age provided a 7-day record of BP measured indirectly with an ambulatory monitor, mostly at 15-60-minute intervals.

MAIN OUTCOME MEASURES

Amplitudes in least squares spectra at frequencies of 1 to 7 cycles per week and 1 to 8 cycles per day were analyzed by linear regression as a function of age. A two-way analysis of variance for subjects classified in four age groups tested for any variance transposition from the circadian (about-daily) to the infradian (frequency lower than one cycle per day) and/or to the ultradian (frequency higher than one cycle per day) domain.

RESULTS

The decreasing circadian BP amplitude with age is accompanied by an increase in infradian and ultradian prominence. The day-to-day variability in circadian characteristics also increases with age.

CONCLUSION

A variance transposition from the circadian to the neighboring ultradian and infradian domains characterizes the elderly human BP chronome, as a new, technically implementable biological, rather than chronological, gauge of human aging.

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.