Circadian variation in stroke - a prospective hospital-based study

Molecular circadian clock disruption in the leukocytes of individuals with type 2 diabetes and overweight, and its relationship with leukocyte-endothelial interactions

AIMS/HYPOTHESIS

Alterations in circadian rhythms increase the likelihood of developing type 2 diabetes and CVD. Circadian rhythms are controlled by several core clock genes, which are expressed in nearly every cell, including immune cells. Immune cells are key players in the pathophysiology of type 2 diabetes, and participate in the atherosclerotic process that underlies cardiovascular risk in these patients. The role of the core clock in the leukocytes of people with type 2 diabetes and the inflammatory process associated with it are unknown. We aimed to evaluate whether the molecular clock system is impaired in the leukocytes of type 2 diabetes patients and to explore the mechanism by which this alteration leads to an increased cardiovascular risk in this population.

METHODS

This is an observational cross-sectional study performed in 25 participants with type 2 diabetes and 28 healthy control participants. Clinical and biochemical parameters were obtained. Peripheral blood leukocytes were isolated using magnetic bead technology. RNA and protein lysates were obtained to assess clock-related gene transcript and protein levels using real-time PCR and western blot, respectively. Luminex XMAP technology was used to assess levels of inflammatory markers. Leukocyte-endothelial interaction assays were performed by perfusing participants' leukocytes or THP-1 cells (with/without CLK8) over a HUVEC monolayer in a parallel flow chamber using a dynamic adhesion system.

RESULTS

Participants with type 2 diabetes showed increased BMAL1 and NR1D1 mRNA levels and decreased protein levels of circadian locomotor output cycles kaput (CLOCK), cryptochrome 1 (CRY1), phosphorylated basic helix-loop-helix ARNT like 1 (p-BMAL1) and period circadian protein homologue 2 (PER2). Correlation studies revealed that these alterations in clock proteins were negatively associated with glucose, HbA1c, insulin and HOMA-IR levels and leukocyte cell counts. The leukocyte rolling velocity was reduced and rolling flux and adhesion were enhanced in individuals with type 2 diabetes compared with healthy participants. Interestingly, inhibition of CLOCK/BMAL1 activity in leukocytes using the CLOCK inhibitor CLK8 mimicked the effects of type 2 diabetes on leukocyte-endothelial interactions.

CONCLUSIONS/INTERPRETATION

Our study demonstrates alterations in the molecular clock system in leukocytes of individuals with type 2 diabetes, manifested in increased mRNA levels and decreased protein levels of the core clock machinery. These alterations correlated with the impaired metabolic and proinflammatory profile of the participants with type 2 diabetes. Our findings support a causal role for decreased CLOCK/BMAL1 activity in the increased level of leukocyte-endothelial interactions. Overall, our data suggest that alterations in core clock proteins accelerate the inflammatory process, which may ultimately precipitate the onset of CVD in patients with type 2 diabetes.

Elevated Hypoperfusion Intensity Ratio (HIR) observed in patients with a large vessel occlusion (LVO) presenting in the evening

BACKGROUND

Circadian variability has been implicated in timing of stroke onset, yet the full impact of underlying biological rhythms on acute stroke perfusion patterns is not known. We aimed to describe the relationship between time of stroke onset and perfusion profiles in patients with large vessel occlusion (LVO).

METHODS

A retrospective observational study was conducted using prospective registries of four stroke centers across North America and Europe with systematic use of perfusion imaging in clinical care. Included patients had stroke due to ICA, M1 or M2 occlusion and baseline perfusion imaging performed within 24h from last-seen-well (LSW). Stroke onset was divided into eight hour intervals: (1) Night: 23:00-6:59, (2) Day: 7:00-14:59, (3) Evening: 15:00-22:59. Core volume was estimated on CT perfusion (rCBF <30%) or DWI-MRI (ADC <620) and the collateral circulation was estimated with the Hypoperfusion Intensity Ratio (HIR = [Tmax>10s]/[Tmax>6s]). Non-parametric testing was conducted using SPSS to account for the non-normalized dependent variables.

RESULTS

A total of 1506 cases were included (median age 74.9 years, IQR 63.0-84.0). Median NIHSS, core volumes, and HIR were 14.0 (IQR 8.0-20.0), 13.0mL (IQR 0.0-42.0), and 0.4 (IQR 0.2-0.6) respectively. Most strokes occurred during the Day (n = 666, 44.2%), compared to Night (n = 360, 23.9%), and Evening (n = 480, 31.9%). HIR was highest, indicating worse collaterals, in the Evening compared to the other timepoints (p = 0.006). Controlling for age and time to imaging, Evening strokes had significantly higher HIR compared to Day (p = 0.013).

CONCLUSION

Our retrospective analysis suggests that HIR is significantly higher in the evening, indicating poorer collateral activation which may lead to larger core volumes in these patients.

The Potential Roles of Dec1 and Dec2 in Periodontal Inflammation

Periodontal inflammation is a common inflammatory disease associated with chronic inflammation that can ultimately lead to alveolar attachment loss and bone destruction. Understanding autophagy and pyroptosis has suggested their significant roles in inflammation. In recent years, studies of differentiated embryo-chondrocyte expressed genes 1 and 2 (Dec1 and Dec2) have shown that they play important functions in autophagy and in pyroptosis, which contribute to the onset of periodontal inflammation. In this review, we summarize recent studies on the roles of clock genes, including Dec1 and Dec2, that are related to periodontal inflammation and other diseases.

Circadian immune circuits

Immune responses are gated to protect the host against specific antigens and microbes, a task that is achieved through antigen- and pattern-specific receptors. Less appreciated is that in order to optimize responses and to avoid collateral damage to the host, immune responses must be additionally gated in intensity and time. An evolutionary solution to this challenge is provided by the circadian clock, an ancient time-keeping mechanism that anticipates environmental changes and represents a fundamental property of immunity. Immune responses, however, are not exclusive to immune cells and demand the coordinated action of nonhematopoietic cells interspersed within the architecture of tissues. Here, we review the circadian features of innate immunity as they encompass effector immune cells as well as structural cells that orchestrate their responses in space and time. We finally propose models in which the central clock, structural elements, and immune cells establish multidirectional circadian circuits that may shape the efficacy and strength of immune responses and other physiological processes.

Implications of Circadian Rhythm in Stroke Occurrence: Certainties and Possibilities

Stroke occurrence is not randomly distributed over time but has circadian rhythmicity with the highest frequency of onset in the morning hours. This specific temporal pattern is valid for all subtypes of cerebral infarction and intracerebral hemorrhage. It also correlates with the circadian variation of some exogenous factors such as orthostatic changes, physical activity, sleep-awake cycle, as well as with endogenous factors including dipping patterns of blood pressure, or morning prothrombotic and hypofibrinolytic states with underlying cyclic changes in the autonomous system and humoral activity. Since the internal clock is responsible for these circadian biological changes, its disruption may increase the risk of stroke occurrence and influence neuronal susceptibility to injury and neurorehabilitation. This review aims to summarize the literature data on the circadian variation of cerebrovascular events according to physiological, cellular, and molecular circadian changes, to survey the available information on the chronotherapy and chronoprophylaxis of stroke and its risk factors, as well as to discuss the less reviewed impact of the circadian rhythm in stroke onset on patient outcome and functional status after stroke.

The influence of circadian variation in ischemic stroke onset on the evolution of cognitive status

Introduction. It is already known and accepted that cerebrovascular disease onset has a temporal variation pattern, the best documented being the circadian variation pattern, with a frequency peak in the morning and a second lower peak during afternoon. The impact of this circadian variation on post-stroke cognitive status has been little studied. Materials and method. The study included a cohort of 63 patients with ischemic stroke, admitted to the Neurology Departments I and II of the Rehabilitation Hospital in Cluj-Napoca between 1 June 2008 and 1 June 2009, who were evaluated for their cognitive status over 2 years, during 5 successive visits. The onset time of ischemic stroke was assigned to one of the six-hour intervals: 00.01-06.00 (night), 06.01-12.00 (morning), 12.01-18.00 (afternoon), and 18.01-24.00 (evening). Statistical analysis was performed using Excel Microsoft, descriptive and ANOVA test. Results and conclusions. The circadian variation pattern of stroke onset is confirming in our study the known incidence pattern of ischemic stroke, with the morning peak. There are differences in the evolution during dynamics of the MMSE score depending on the time of the day when stroke occurs. Patients with stroke onset during the night have seems to have a less favorable cognitive evolution in the second year after ischemic stroke compared to patients with stroke onset during the other intervals of the day.

Accuracy of Consumer Wearable Heart Rate Measurement During an Ecologically Valid 24-Hour Period: Intraindividual Validation Study

Background

Wrist-worn smart watches and fitness monitors (ie, wearables) have become widely adopted by consumers and are gaining increased attention from researchers for their potential contribution to naturalistic digital measurement of health in a scalable, mobile, and unobtrusive way. Various studies have examined the accuracy of these devices in controlled laboratory settings (eg, treadmill and stationary bike); however, no studies have investigated the heart rate accuracy of wearables during a continuous and ecologically valid 24-hour period of actual consumer device use conditions.

Objective

The aim of this study was to determine the heart rate accuracy of 2 popular wearable devices, the Apple Watch 3 and Fitbit Charge 2, as compared with the gold standard reference method, an ambulatory electrocardiogram (ECG), during consumer device use conditions in an individual. Data were collected across 5 daily conditions, including sitting, walking, running, activities of daily living (ADL; eg, chores, brushing teeth), and sleeping.

Methods

One participant, (first author; 29-year-old Caucasian male) completed a 24-hour ecologically valid protocol by wearing 2 popular wrist wearable devices (Apple Watch 3 and Fitbit Charge 2). In addition, an ambulatory ECG (Vrije Universiteit Ambulatory Monitoring System) was used as the gold standard reference method, which resulted in the collection of 102,740 individual heartbeats. A single-subject design was used to keep all variables constant except for wearable devices while providing a rapid response design to provide initial assessment of wearable accuracy for allowing the research cycle to keep pace with technological advancements. Accuracy of these devices compared with the gold standard ECG was assessed using mean error, mean absolute error, and mean absolute percent error. These data were supplemented with Bland-Altman analyses and concordance class correlation to assess agreement between devices.

Results

The Apple Watch 3 and Fitbit Charge 2 were generally highly accurate across the 24-hour condition. Specifically, the Apple Watch 3 had a mean difference of −1.80 beats per minute (bpm), a mean absolute error percent of 5.86%, and a mean agreement of 95% when compared with the ECG across 24 hours. The Fitbit Charge 2 had a mean difference of −3.47 bpm, a mean absolute error of 5.96%, and a mean agreement of 91% when compared with the ECG across 24 hours. These findings varied by condition.

Conclusions

The Apple Watch 3 and the Fitbit Charge 2 provided acceptable heart rate accuracy (<±10%) across the 24 hour and during each activity, except for the Apple Watch 3 during the daily activities condition. Overall, these findings provide preliminary support that these devices appear to be useful for implementing ambulatory measurement of cardiac activity in research studies, especially those where the specific advantages of these methods (eg, scalability, low participant burden) are particularly suited to the population or research question.

Interplay between Microbes and the Circadian Clock

Circadian rhythms influence virtually all life forms on our planet, a notion that opens the question on how the circadian cycles of individual organisms may interplay with each other. In mammals, a potentially dangerous environmental stress is represented by encounters with infectious agents. Microbial attack is a major risk for organismal homeostasis and therefore needs to be efficiently counteracted by mechanisms implemented by the host immune system. Accumulating evidence shows that the immune system may anticipate an emerging pathogenic exposure through an enhanced inflammatory state. Notably, the circadian clock orchestrates these anticipatory responses to fluctuating conditions in the external world. In this article, we review the current knowledge about the relationship between the circadian clock and pathogenic infections. We discuss the role of the circadian clock against infection and specific pathogens, the core clock proteins involved in the defense mechanisms, and the specific tissue or cell type in which they function to counteract the infection. Finally, circadian oscillations in the gut microbiome composition and its possible role in protecting against foodborne pathogen colonization are presented.

Circadian Coordination of Antimicrobial Responses

Microbial infection poses a threat to organismal homeostasis and therefore must be efficiently counteracted by host defense mechanisms. It has been recently demonstrated that the immune system may anticipate an emerging pathogenic exposure through a heightened inflammatory state. Such anticipatory responses to fluctuating environmental conditions are typically orchestrated by the circadian clock, an intrinsic time-keeping system that adapts tissue physiology to diurnal variations in external influences. Here, we review current knowledge about the interplay between the circadian clock and antimicrobial responses. We summarize the molecular strategies employed by the circadian system against specific pathogens, the core-clock proteins as well as cells in which they are expressed that mediate host defense, and the consequences of circadian variations on immune function. Furthermore, we highlight the possible implications of such circadian gating in immune reactions against pathogenic infections for the chronopharmacology of antibacterial and antiviral therapies.

Endogenous melatonin promotes rhythmic recruitment of neutrophils toward an injury in zebrafish

Neutrophil recruitment to injured tissue appears to be an evolutionarily conserved strategy for organisms to fight against exogenous insults. Recent studies have shown rhythmic migration of neutrophils and several factors, including melatonin, have been implicated in regulating this rhythmic migration. The mechanisms underlying how endogenous melatonin regulates rhythmic neutrophils migration, however, are unclear. Here we generated a zebrafish annat2 mutant that lacks endogenous melatonin and, subsequently, a Tg(lyz:EGFP);aanat2^−/− transgenic line that allows for monitoring neutrophils migration visually in live zebrafish. We observed that migrating neutrophils are significantly reduced in aanat2^−/− mutant zebrafish under a light/dark condition, and the disrupted migrating rhythmicity of neutrophils in aanat2^−/− zebrafish is independent of the circadian clock. Further, we also found that endogenous melatonin enhances neutrophils migration likely by inducing the expression of cytokines such as interleukin-8 and interleukin-1β. Together, our findings provide evidence that endogenous melatonin promotes rhythmic migration of neutrophils through cytokines in zebrafish.

Antigen exposure in the late light period induces severe symptoms of food allergy in an OVA-allergic mouse model

The mammalian circadian clock controls many physiological processes that include immune responses and allergic reactions. Several studies have investigated the circadian regulation of intestinal permeability and tight junctions known to be affected by cytokines. However, the contribution of circadian clock to food allergy symptoms remains unclear. Therefore, we investigated the role of the circadian clock in determining the severity of food allergies. We prepared an ovalbumin food allergy mouse model, and orally administered ovalbumin either late in the light or late in the dark period under light-dark cycle. The light period group showed higher allergic diarrhea and weight loss than the dark period group. The production of type 2 cytokines, IL-13 and IL-5, from the mesenteric lymph nodes and ovalbumin absorption was higher in the light period group than in the dark period group. Compared to the dark period group, the mRNA expression levels of the tight junction proteins were lower in the light period group. We have demonstrated that increased production of type 2 cytokines and intestinal permeability in the light period induced severe food allergy symptoms. Our results suggest that the time of food antigen intake might affect the determination of the severity of food allergy symptoms.

Melatonin regulates the rhythmic migration of neutrophils in live zebrafish

The circadian clock plays a vital role in physiology and behavior such as the sleep-wake cycle and blood pressure and hormone levels. Immune responses also display circadian rhythmicity and particularly pineal melatonin contributes to immunological processes. Little attention, however, is given to mechanisms underlying rhythmic neutrophil responses to the injury. Here, we used a transgenic Tg(lyz:EGFP) zebrafish tail fin transection model to investigate whether the recruitment of neutrophils toward the injured site is regulated by the circadian clock. We found that migrating neutrophils display robust rhythmicity, peaking at darkness. Melatonin positively regulates rhythmic neutrophil migration, as evidenced that treatment with melatonin at low dosage can significantly enhance neutrophil recruitment toward the injured site, which is attenuated by luzindole treatment and in pinealectomized fish. Furthermore, using a transgenic zebrafish eyeball model, we observed that melatonin enhances secretion of two cytokines, TNF-α and IL-8, both of which markedly enhance neutrophil migration. Taken together, these results highlight a positive role of melatonin in rhythmic neutrophil migration and help obtain a better understanding of circadian regulation in immunology.

Circadian Variation of Stroke Onset: A Hospital-Based Study

Aims and background.

The circadian pattern of stroke occurrence variation has been recognized with certain differences between authors and stroke types. The underlying reason may be related to exogenous factors (cyclic physical activity, including sleep–awake cycles and assuming the up-right posture) and endogenous factors, with their diurnal variation (blood pressure, hemostatic balance, autonomic system activity). The aims of the present study are to investigate the existence of a circadian variation of stroke and the possible differences between stroke subtypes in the Cluj Napoca area.

Materials and method.

The stroke event data were acquired from the Patient Records of a consecutive series of 1083 patients admitted through the Emergency Room at Neurology Departments I and II of the District Hospital of Cluj Napoca, between 1 January 2012 and 31 December 2012. The classifiable onset time was assigned to one of four six-hour intervals: 00.01–06.00 (night), 06.01–12.00 (morning), 12.01–18.00 (afternoon) and 18.01–24.00 (evening). Demographic data and vascular risk factors were recorded.

Results.

All three stroke types (ischemic stroke, hemorrhagic stroke and subarachnoid hemorrhage) have shown a circadian variation regarding their occurrence, with the peak of incidence in the morning and the nadir during nighttime. This circadian pattern is independent by demographic factors and vascular risk factors.

Conclusion.

Our study confirmed the circadian variation of onset occurrence for all stroke subtypes. Some triggering factors promote ischemic stroke and prevent hemorrhagic stroke. The diurnal pattern of variation with the higher incidence in the morning and the lower in the night may lead to chrono-therapeutic and preventive approach (chrono-therapy of the risk factors), which targets the period of the highest vulnerability after awaking.

Circadian influences on myocardial infarction

Components of circadian rhythm maintenance, or "clock genes," are endogenous entrainable oscillations of about 24 h that regulate biological processes and are found in the suprachaismatic nucleus (SCN) and many peripheral tissues, including the heart. They are influenced by external cues, or Zeitgebers, such as light and heat, and can influence such diverse phenomena as cytokine expression immune cells, metabolic activity of cardiac myocytes, and vasodilator regulation by vascular endothelial cells. While it is known that the central master clock in the SCN synchronizes peripheral physiologic rhythms, the mechanisms by which the information is transmitted are complex and may include hormonal, metabolic, and neuronal inputs. Whether circadian patterns are causally related to the observed periodicity of events, or whether they are simply epi-phenomena is not well established, but a few studies suggest that the circadian effects likely are real in their impact on myocardial infarct incidence. Cycle disturbances may be harbingers of predisposition and subsequent response to acute and chronic cardiac injury, and identifying the complex interactions of circadian rhythms and myocardial infarction may provide insights into possible preventative and therapeutic strategies for susceptible populations.

Circadian control of the immune system

Circadian rhythms, which have long been known to play crucial roles in physiology, are emerging as important regulators of specific immune functions. Circadian oscillations of immune mediators coincide with the activity of the immune system, possibly allowing the host to anticipate and handle microbial threats more efficiently. These oscillations may also help to promote tissue recovery and the clearance of potentially harmful cellular elements from the circulation. This Review summarizes the current knowledge of circadian rhythms in the immune system and provides an outlook on potential future implications.

Lesion size and behavioral deficits after endothelin-1-induced ischemia are not dependent on time of day

BACKGROUND

The occurrence of stroke exhibits a strong circadian pattern with a peak in the morning hours after waking. The factors that influence this pattern of stroke prevalence may confer varying degrees of neuroprotection and therefore influence stroke severity. This question is difficult to address in clinical cases because of the variability in the location and duration of the ischemic event.

METHODS

The purpose of this study was to determine if time of day affected the severity of stroke targeting the motor cortex in rats. Strokes were produced using topical application of the vasoconstrictor endothelin-1 to motor cortex of unanesthetized animals at 2 time points: early day and early night. Behavioral deficits were measured using reaching, cylinder, and horizontal ladder tasks, and the volume of the lesion was quantified.

RESULTS

Behavior on reaching and horizontal ladder tasks were both severely impaired by endothelin-1 treatment compared to vehicle-treated animals, but deficits did not differ according to time of treatment. Similarly, while endothelin-1 produced larger lesions of the motor cortex than did vehicle treatment, the size of the lesion did not differ according to time of treatment.

CONCLUSIONS

These results suggest that while many factors under circadian control can influence the prevalence of stroke, the magnitude of lesion and behavioral deficit resulting from an ischemic event may not be influenced by time of day.

Heart-rate variability in women during 40-hour prolonged wakefulness

Heart-rate variability patterns of 18 women during a 40-h constant routine of prolonged wakefulness under controlled laboratory conditions were analyzed. The authors tested the circadian timing of the autonomic nervous system and the relationship between the sympathetic and vagal branches in women with both a functional disorder of vascular regulation (main symptom: cold hands and feet) and prolonged sleep onset and controls without these symptoms. Spectral analysis of R-R intervals during paced breathing episodes revealed significantly lower power values in the high-frequency band (HF; 0.15-0.4 Hz) but not in the low-frequency band (LF; 0.04-0.15 Hz), leading to a significantly elevated LF/HF ratio in the former group. A significant circadian rhythm in LF power and heart rate occurred in both groups, and a significant correlation was found between sleepiness and sympathovagal balance (r = .53, p < .05). These findings indicate not only an autonomic imbalance in the first group compared with controls, but also two strategies of the autonomic nervous system to fight against fatigue in women. One implies circadian control and the other homeostatic control, and both are reflected by the LF/HF ratio.

Melatonin and circadian biology in human cardiovascular disease

Diurnal rhythms influence cardiovascular physiology, i.e. heart rate and blood pressure, and they appear to also modulate the incidence of serious adverse cardiac events. Diurnal variations occur also at the molecular level including changes in gene expression in the heart and blood vessels. Moreover, the risk/benefit ratio of some therapeutic strategies and the concentration of circulating cardiovascular system biomarkers may also vary across the 24-hr light/dark cycle. Synchrony between external and internal diurnal rhythms and harmony among molecular rhythms within the cell are essential for normal organ biology. Diurnal variations in the responsiveness of the cardiovascular system to environmental stimuli are mediated by a complex interplay between extracellular (i.e. neurohumoral factors) and intracellular (i.e. specific genes that are differentially light/dark regulated) mechanisms. Neurohormones, which are particularly relevant to the cardiovascular system, such as melatonin, exhibit a diurnal variation and may play a role in the synchronization of molecular circadian clocks in the peripheral tissue and the suprachiasmatic nucleus. Moreover, mounting evidence reveals that the blood melatonin rhythm has a crucial role in several cardiovascular functions, including daily variations in blood pressure. Melatonin has antioxidant, anti-inflammatory, chronobiotic and, possibly, epigenetic regulatory functions. This article reviews current knowledge related to the biological role of melatonin and its circadian rhythm in cardiovascular disease.

Circadian rhythm of stroke onset during the month of Ramadan

BACKGROUND AND PURPOSE

The onset of acute stroke exhibits a circadian pattern occurring more frequently in late morning hours. The objective of this study was to investigate the diurnal pattern of stroke during the month of Ramadan.

PATIENTS AND METHODS

We studied consecutive stroke patients 1 month before Ramadan (BR) and during Ramadan (DR) over two successive years 2007 and 2008. The age, gender, risk factor profiles were analyzed. The National Institute of Health and Stroke Scale Score (NIHSS) was used for clinical assessment at admission. The exact time of stroke onset in both groups was obtained.

RESULTS

A total of 507 patients were studied: 245 patients in the DR group and 262 patients in the BR group. The age distribution of patients was not significantly different between the two groups. There was no statistically significant difference in the sex ratio, risk factors, and NIHSS score between the two groups (P > 0.05). The higher frequency of stroke onset time in the BR group was in the time between 6:00 a.m. and noon; whereas the frequency was higher between noon and 6:00 p.m. in the DR group.

CONCLUSION

A significant shift of the circadian pattern of stroke onset time from the period between 6:00 a.m. and noon to that between noon and 6:00 pm has been found during the month of Ramadan.

Searching for prognostic variables for secondary worsening after ischaemic stroke

Secondary worsening of stroke symptoms is described in 13-37% of stroke patients, but the exact mechanism of this phenomenon remains unclear. The aim of this study is to find prognostic variables in correlation to secondary worsening of stroke symptoms in patients with lacunar or cortical strokes. In this prospective observational study we included all patients with ischaemic stroke; patients with transient ischaemic attack were excluded. Patients undergoing thrombolysis and becoming symptom-free after 24 h were still included in our analyses. Secondary worsening of stroke symptoms was defined as an increase of two or more points on the NIH Stroke Scale (NIHSS). The NIHSS score was assessed on admission, at discharge, and when patients had symptoms that indicated worsening of stroke. Applying univariate and multivariable analysis, we studied the relation between symptoms indicating secondary worsening of stroke and prognostic variables such as extreme nocturnal blood pressure falls (>20% of the average blood pressure), infection, diabetes mellitus, hypertension, smoking, dyslipidaemia, a history of cardiovascular or cerebrovascular disease and thrombolysis. This study included 202 patients with a mean age of 72 years, 48.8% were men and 43% had a lacunar stroke. Secondary worsening of stroke symptoms occurred in 13.5% of all patients, more often but not significantly (NS) after lacunar than cortical strokes (16.8 and 11.4%, respectively), and in patients with extreme nocturnal blood pressure falls versus without (15.6 and 11.8%, respectively (NS)). There was no significant relation between the analysed prognostic variables and secondary worsening of stroke symptoms. This study did not show significant correlation between several variables and secondary worsening of stroke symptoms in patients with recent ischaemic stroke.

Effects of circadian disruption on the cardiometabolic system

The presence of day-night variations in cardiovascular and metabolic functioning is well known. However, only recently it has been shown that cardiovascular and metabolic processes are not only affected by the behavioral sleep/wake cycle but are partly under direct control of the master circadian pacemaker located in the suprachiasmatic nucleus (SCN). Heart rate, cardiac autonomic activity, glucose metabolism and leptin-involved in appetite control-all show circadian variation (i.e., under constant behavioral and environmental conditions). This knowledge of behavioral vs. circadian modulation of cardiometabolic function is of clinical relevance given the morning peak in adverse cardiovascular incidents observed in epidemiological studies and given the increased risk for the development of diabetes, obesity, and cardiovascular disease in shift workers. We will review the evidence for circadian control of cardiometabolic functioning, as well its sensitivity to light and melatonin, and discuss potential implication for therapy.

Robust circadian rhythm in heart rate and its variability: influence of exogenous melatonin and photoperiod

Heart rate (HR) and heart rate variability (HRV) undergo marked fluctuations over the 24-h day. Although controversial, this 24-h rhythm is thought to be driven by the sleep-wake/rest-activity cycle as well as by endogenous circadian rhythmicity. We quantified the endogenous circadian rhythm of HR and HRV and investigated whether this rhythm can be shifted by repeated melatonin administration while exposed to an altered photoperiod. Eight healthy males (age 24.4 +/- 4.4 years) participated in a double-blind cross-over design study. In both conditions, volunteers were scheduled to 16 h-8 h rest : wake and dark : light cycles for nine consecutive days preceded and followed by 29-h constant routines (CR) for assessment of endogenous circadian rhythmicity. Melatonin (1.5 mg) or placebo was administered at the beginning of the extended sleep opportunities. For all polysomnographically verified wakefulness periods of the CR, we calculated the high- (HF) and low- (LF) frequency bands of the power spectrum of the R-R interval, the standard deviation of the normal-to-normal (NN) intervals (SDNN) and the square root of the mean-squared difference of successive NN intervals (rMSSD). HR and HRV variables revealed robust endogenous circadian rhythms with fitted maxima, respectively, in the afternoon (16:36 hours) and in the early morning (between 05:00 and 06:59 hours). Melatonin treatment phase-advanced HR, HF, SDNN and rMSSD, and these shifts were significantly greater than after placebo treatment. We conclude that endogenous circadian rhythmicity influences autonomic control of HR and that the timing of these endogenous rhythms can be altered by extended sleep/rest episodes and associated changes in photoperiod as well as by melatonin treatment.

Fluctuations in coagulation activity among patients with atrial fibrillation who are stably anticoagulated

Atrial fibrillation is an important independent risk factor for stroke and increases the risk of systemic embolism. The individual risk depends on several clinical, environmental and biological factors. Additionally, a hypercoagulable state with abnormalities of hemostasia, thrombosis and platelet function have been observed in atrial fibrillation. This arrhythmia is also influenced by a disrupted circadian rhythm of hypercoagulable status implicated in the genesis of cardiovascular and cerebral diseases. The beneficial effect of oral anticoagulation therapy in atrial fibrillation has been confirmed by several studies. However, circadian variations in the degree of anticoagulation in these patients have also been described. In this review, the authors analyze the factors that might condition diurnal variations in thrombogenesis, hypercoagulability, and the extent of anticoagulation in patients with atrial fibrillation.