Circadian control of the sleep–wake cycle

Determination of Natural Blood Plasma Melatonin Concentration of Tsigai Ewes Characteristic for Gestation and Early Postpartum Period Between Autumnal Equinox and Winter Solstice

The aim of this investigation was to measure the natural nocturnal plasma melatonin concentration in gestating and fresh ewes. Studies in humans showed that maternal melatonin had a significant increase as pregnancy progressed and then decreased after birth. Two studies conducted in sheep so far, considering the entire gestation, have led to conflicting results. The breed of 16 pregnant ewes selected for the research was the Tsigai. Blood samples were taken into EDTA vacutainers predetermined times a night at different stages of their gestation. The RIA method was used to determine the melatonin concentrations. For estimation of its variations during gestation, population genetic statistics was applied. It was found that the average plasma melatonin concentration of 134 pg mL-1 is characteristic for the investigated period, and that it rises between the autumnal equinox and the winter solstice. Secondly, it was revealed that the average melatonin concentration adjusted for midnight is 162.4 pg mL-1, and its moderate variation is characteristic for the night. The investigation showed that there is no connection between the plasma melatonin concentration of the ewes and their gestational age in the Tsigai breed in Middle Europe. Our result is consistent with the results of single studies in sheep and donkey, in contrast to human observations. With regard to the nocturnal plasma melatonin, the concentration is reduced at the same level (30 pg mL-1) in ewes and lambs during the early postpartum period without nightly fluctuation. The expelled placenta, the constant vigilance between the mother and her lamb, and the opposition between melatonin and prolactin may provide a plausible explanation for this.

Evolution of canonical circadian clock genes underlies unique sleep strategies of marine mammals for secondary aquatic adaptation

To satisfy the needs of sleeping underwater, marine mammals, including cetaceans, sirenians, and pinnipeds, have evolved an unusual form of sleep, known as unihemispheric slow-wave sleep (USWS), in which one brain hemisphere is asleep while the other is awake. All aquatic cetaceans have only evolved USWS without rapid eye movement (REM) sleep, whereas aquatic sirenians and amphibious pinnipeds display both bihemispheric slow-wave sleep (BSWS) and USWS, as well as REM sleep. However, the molecular genetic changes underlying USWS remain unknown. The present study investigated the evolution of eight canonical circadian genes and found that positive selection occurred mainly within cetacean lineages. Furthermore, convergent evolution was observed in lineages with USWS at three circadian clock genes. Remarkably, in vitro assays showed that cetacean-specific mutations increased the nuclear localization of zebrafish clocka, and enhanced the transcriptional activation activity of Clocka and Bmal1a. In vivo, transcriptome analysis showed that the overexpression of the cetacean-specific mutant clocka (clocka-mut) caused the upregulation of the wakefulness-promoting glutamatergic genes and the differential expression of multiple genes associated with sleep regulation. In contrast, the GABAergic and cholinergic pathways, which play important roles in promoting sleep, were downregulated in the bmal1a-mut-overexpressing zebrafish. Concordantly, sleep time of zebrafish overexpressing clocka-mut and bmal1a-mut were significantly less than the zebrafish overexpressing the wild-type genes, respectively. These findings support our hypothesis that canonical circadian clock genes may have evolved adaptively to enhance circadian regulation ability relating to sleep in cetaceans and, in turn, contribute to the formation of USWS.

Recent Advances in Pineoblastoma Research: Molecular Classification, Modelling and Targetable Vulnerabilities

Pineoblastoma (PB) is a rare yet lethal pediatric brain cancer of the pineal gland, a small endocrine organ that secretes melatonin to regulate the circadian rhythm. For PB patients ≤5 years of age, the overall survival rate is approximately 15%; metastatic PB is incurable. Standard treatment, including surgical resection, radiation, and systemic chemotherapy, improves survival but compromises neurocognitive function. A better understanding of the disease and the generation of preclinical models may enable re-evaluation of previous clinical trials, development of precision therapeutic strategies and improve patient outcome. Over the past 5 years, PB has been recognized to include several major subtypes driven by (i) loss of microRNA processing factors DICER and DROSHA characterized by a relatively good prognosis; (ii) loss of the retinoblastoma tumor suppressor RB1; and (iii) amplification or induction of the cMYC protooncogene, with the latter two subtypes exhibiting exceedingly poor prognosis. Recently, mouse models for the major PB subtypes (RB1-, DICER1- and DROSHA-) except MYC- have been established. This progress, including better understanding of the disease, cell of origin, tumor progression, role of autophagy, and targetable vulnerabilities, holds promise for novel therapeutic strategies to combat each subtype of this lethal childhood malignancy.

The effect of sleep and shift work on the primary immune response to messenger RNA-based COVID-19 vaccination

Shift work can cause circadian misalignment, which often results in sleeping problems and has been associated with immune dysfunction. To better understand the impact of shift work on a primary immune response to vaccination, we compared severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-specific humoral and cellular immune responses after one injection of the messenger RNA (mRNA)-1273 vaccine between day workers (n = 24) and night shift workers (n = 21). In addition, duration and quality of sleep were assessed for a period of 7 days around the time of vaccination using actigraphy and daily sleep diaries, and their relationship with immunogenicity of mRNA-1273 vaccination was studied. We found that median total sleep time on the 2 days immediately after vaccination, which coincided with the days that night shift workers worked night shifts, was significantly lower in night shift workers (342 and 318 min) than day workers (431 and 415 min) (both p < 0.001). There was no difference in sleep quality between day workers and night shift workers. Furthermore, no difference in the antibody response between the two groups was observed, yet night shift workers had a significantly higher virus-specific T-cell response than day workers 28 days after immunisation (p = 0.013). Multivariate regression analysis showed no association between sleep duration, sleep quality and SARS-CoV-2-specific humoral or cellular immune responses. Collectively, these findings indicate that shift work-induced sleep loss and night shift work have little to no effect on the primary immune response to mRNA-based COVID-19 vaccination.

Circadian Rhythm Disruption in Cancer Survivors: From Oncogenesis to Quality of Life

BACKGROUND

Circadian rhythms are approximately 24-hour cycles in physiological and behavioral processes. They are entrained to the external solar day via blue wavelength light. Disruptions in these intrinsic rhythms can lead to circadian dysfunction, which has several negative implications on human health, including cancer development and progression.

AIMS

Here we review the molecular mechanisms of circadian disruption and their impact on tumor development and progression, discuss the interplay between circadian dysfunction and cancer in basic scientific studies and clinical data, and propose the potential clinical implications of these data that may be used to improve patient outcomes and reduce cost of treatment.

MATERIALS & METHODS

Using scientific literature databases, relevant studies were analyzed to draw overarching conclusions of the relationship between circadian rhythm dysruption and cancer.

CONCLUSIONS

Circadian disruption can be mediated by a number of environmental factors such as exposure to light at night, shift work, jetlag, and social jetlag which drive oncogenesis. Tumor growth and progression, as well as treatment, can lead to long-term alterations in circadian rhythms that negatively affect quality of life in cancer survivors.

The lifestyle of new middle-aged and older adults in Taiwan described by wearable device: age and gender differences

Studies of lifestyle through comprehensive objective and subjective measurements of health outcomes are lacking. An examination of lifestyle factors in middle-aged and older adults in terms of age, gender, and the interaction effect of age and gender from physiological and psychological perspectives are imperative. Recent advances in technology such as actigraphy have facilitated objective measurements. This exploratory study contributes to research on age and gender interactions on circadian rhythm, physical activity, sleep, and psychological variables by employing wrist accelerometers to measure behavioral circadian rhythm objectively and by using questionnaires to assess psychological status subjectively. The data were drawn from 218 participants aged 50 and older from the "Middle-aged and older adults Chinese Health and Actigraphy in Taiwan (MOCHA-T)". The results: (1) older adult group is associated with declined physical activity (MVPA time 79.9 min VS. 107.9 min, p = .002), worse sleep efficiency (78.1% VS. 81.9%, p = .008), and earlier lifestyle (Acrophase 14.19 h VS. 14.69 h, p = .01) comparing to middle-aged group. (2) Women have a more regular lifestyle (Interdaily stability 0.6 VS. 051, p < 0.001), higher physical activity (MVPA time 105.7 min VS. 79.3 min, p = .004), and better sleep efficiency (81.6% VS. 77.8%, p = .011) than men. (3) Significant age-by-gender interactions existed in life satisfaction (p = .025), relative amplitude (p = .016), and total wake time (p = .038). Furthermore, aging was associated with significant increases in life satisfaction among men as well as significant decreases in relative amplitude and reductions in the total wake time among women. In conclusion, aging exerted differential effects on life satisfaction in men as well as relative amplitude and the total wake time in women. This result highlights disparities in lifestyle arising from interconnected social and biological challenges.

Circadian rhythm sleep loss impairs motor inhibition more than motor execution in continuous action

Under total sleep deprivation, both inhibitory and motor control are impaired. However, how circadian rhythm sleep loss caused by irregular sleep pattern affects motor inhibition and execution in continuous actions remains unknown. This study utilized a pointing task to investigate the question over 30 days. During regular trials, participants were instructed to tap on a specified location, while in countermanding trials, they were required to countermand their current action. Additionally, there was a control group performed the same task following a normal 24-h rhythm. The results indicated that the decrease in accuracy and the increase in movement time in countermanding trials were more prominent in the shift work group. In contrast, there was no significant difference in reaction time between the two groups. Notably, the shift work group outperformed the control group in terms of movement time in regular trials and radial displacement in countermanding trials. Overall, these results show that circadian rhythm sleep loss predominantly affects inhibitory control, rather than motor control, underscoring the nuanced impacts of sleep disruption on differential aspects of cognitive and motor functions.

Waking Up to the Issue! Research Inattention and Sex-Related Differences Warrant More Sleep Studies in Female Athletes

Understanding sleep patterns and behaviors of athletes is essential for developing targeted sleep-based interventions for implementation in practice. However, more than double the number of sleep studies have examined male athletes compared with female athletes, making the current understanding of sleep patterns, behaviors, and interventions among athletes disproportionately indicative of men. Consequently, this review demonstrates the need for more female-specific sleep data among athlete populations due to research inattention and sex-related differences. Specifically, this review identifies variations in sleep patterns and behaviors between male and female athletes, as well as physiological and lifestyle factors that potentially affect sleep patterns and behaviors across the lifespan, specifically in female athletes. In this regard, evidence suggests some female athletes experience longer sleep durations and better objective sleep quality, but similar or worse subjective sleep quality compared with male athletes. Additionally, scheduling training in the morning or throughout the day may benefit sleep in some female athletes. Considering sleep disorders, women may be at greater risk for insomnia and restless legs syndrome compared with men, which may be attributed to pregnancy, as well as a higher prevalence of anxiety and depressive symptoms, iron deficiency without anemia, and use of psychotropic medication among women. Finally, the menstrual cycle, menstrual disorders, oral contraceptive use, and the postpartum period have been shown to exert detrimental effects on sleep patterns and behaviors and should theoretically be considered when monitoring and managing sleep in female athletes.

Circadian Regulation of the Neuroimmune Environment Across the Lifespan: From Brain Development to Aging

Circadian clocks confer 24-h periodicity to biological systems, to ultimately maximize energy efficiency and promote survival in a world with regular environmental light cycles. In mammals, circadian rhythms regulate myriad physiological functions, including the immune, endocrine, and central nervous systems. Within the central nervous system, specialized glial cells such as astrocytes and microglia survey and maintain the neuroimmune environment. The contributions of these neuroimmune cells to both homeostatic and pathogenic demands vary greatly across the day. Moreover, the function of these cells changes across the lifespan. In this review, we discuss circadian regulation of the neuroimmune environment across the lifespan, with a focus on microglia and astrocytes. Circadian rhythms emerge in early life concurrent with neuroimmune sculpting of brain circuits and wane late in life alongside increasing immunosenescence and neurodegeneration. Importantly, circadian dysregulation can alter immune function, which may contribute to susceptibility to neurodevelopmental and neurodegenerative diseases. In this review, we highlight circadian neuroimmune interactions across the lifespan and share evidence that circadian dysregulation within the neuroimmune system may be a critical component in human neurodevelopmental and neurodegenerative diseases.

Translation and Validation of the Arabic Version of the Athlete Sleep Screening Questionnaire

Sleep improves the cognitive and physical performance of athletes. A detailed questionnaire that detects sleep disruptions is required to identify sleep-deprived athletes. This study evaluates the translated Athlete Sleep Screening Questionnaire (ASSQ), a tool suggested by the International Olympic Committee, among Arabic-speaking athletes. The ASSQ was translated into Arabic and examined for floor or ceiling effects, internal consistency, and validity among Arabic-speaking athletes. The Arabic Pittsburgh Sleep Quality Index (PSQI) was employed to assess convergent validity. Ninety athletes (28.9% women) participated and completed this study's questionnaires. The Cronbach's alpha for the ASSQ-Sleep Difficulty Score (SDS) was 0.435, and that of the ASSQ-chronotype was 0.632. The SDS and chronotype subset of the ASSQ demonstrated excellent test-retest reliability, with intraclass correlation coefficients of 0.84 and 0.938, respectively. The ASSQ-SDS correlated positively with the PSQI (0.734, p = 0.001). The ASSQ-chronotype was inversely associated with the PSQI (p = 0.001). This study's findings can assist clinicians in assessing sleep disorders in sports. The Arabic version of the ASSQ has satisfactory psychometric qualities and can identify clinically relevant sleep problems in athletes.

Potential effects of shift work on skin autoimmune diseases

Shift work is associated with systemic chronic inflammation, impaired host and tumor defense and dysregulated immune responses to harmless antigens such as allergens or auto-antigens. Thus, shift workers are at higher risk to develop a systemic autoimmune disease and circadian disruption with sleep impairment seem to be the key underlying mechanisms. Presumably, disturbances of the sleep-wake cycle also drive skin-specific autoimmune diseases, but epidemiological and experimental evidence so far is scarce. This review summarizes the effects of shift work, circadian misalignment, poor sleep, and the effect of potential hormonal mediators such as stress mediators or melatonin on skin barrier functions and on innate and adaptive skin immunity. Human studies as well as animal models were considered. We will also address advantages and potential pitfalls in animal models of shift work, and possible confounders that could drive skin autoimmune diseases in shift workers such as adverse lifestyle habits and psychosocial influences. Finally, we will outline feasible countermeasures that may reduce the risk of systemic and skin autoimmunity in shift workers, as well as treatment options and highlight outstanding questions that should be addressed in future studies.

Association of chronotype with eating habits and anthropometric measures in a sample of Iranian adults

There is a lack of consistency in the literature that shows a relationship between chronotype, habits of eating and obesity in Iranian adults. This cross-sectional study was conducted on 850 individuals aged ≥ 18 years, selected from health houses of Tehran, Iran. Chronotype was assessed by Horne and Ostberg morningness-eveningness questionnaire. Specific eating habits, including breakfast skipping, intakes of fruits and vegetables, fast food, processed meats, soft drinks, coffee and tea, were assessed by dietary recalls. Weight, height, BMI, waist circumference, waist to hip ratio, waist to height ratio, visceral adiposity index, body roundness index and body adiposity index were based on measured values. We used logistic regression to investigate the association between chronotypes and anthropometric measures as well as eating habits. Morning- and intermediate/evening-type chronotypes accounted for 51·4 and 48·6 % of the total individuals, respectively. Moreover, intermediate/evening-type chronotypes were shown to have a lower education of diploma (53 %), employed (49·9 %) and smokers (11·6 %) compared with morning types (both sexes). We found that intermediate/evening-type chronotypes might not be significantly related to higher anthropometric measures and following unhealthy eating habits after controlling for confounders in men and women (all P > 0·05). Overall, both anthropometric measures and specific eating habits were not related to chronotype among Iranian adults. Further studies are needed to clarify these relations and to consider sleep disturbances.

Sleep and Athletic Performance: Impacts on Physical Performance, Mental Performance, Injury Risk and Recovery, and Mental Health: An Update

Sleep health is an important consideration for athletic performance. Athletes are at high risk of insufficient sleep duration, poor sleep quality, daytime sleepiness and fatigue, suboptimal sleep schedules, irregular sleep schedules, and sleep and circadian disorders. These issues likely have an impact on athletic performance via several domains. Sleep loss and/or poor sleep quality can impair muscular strength, speed, and other aspects of physical performance. Sleep issues can also increase risk of concussions and other injuries and impair recovery after injury. Cognitive performance is also impacted in several domains, including vigilance, learning and memory, decision making, and creativity.

Night shift work characteristics are associated with several elevated metabolic risk factors and immune cell counts in a cross-sectional study

Night shift work is associated with increased health risks. Here we examined the association of metabolic risk factors and immune cell counts, with both night shift work and particular characteristics thereof: frequency, duration and consecutive night shifts. We performed a cross-sectional study using data from 10,201 non-shift workers and 1062 night shift workers of the Lifelines Cohort study. Linear regression analyses, adjusted for demographic, lifestyle and occupational factors, were used to study associations of night shift work characteristics with metabolic risk factors and immune cell counts. Night shift workers had an increased BMI, waist circumference and immune cell counts compared to non-shift workers. This was especially seen in night shift workers who had a higher frequency of night shifts per month (≥ 5: BMI: B = 0.81 kg/m² (95%-CI = 0.43–1.10); waist circumference: B = 1.58 cm (95%-Cl = 0.34–1.71; leukocytes: B = 0.19 × 10⁹ cells/L (95%-CI = 0.04–0.34 × 10⁹)) and worked more consecutive night shifts (> 3: BMI: B = 0.92 kg/m² (95%-CI = 0.41–1.43); waist circumference: B = 1.85 cm (95%-Cl = 0.45–3.24); leukocytes: B = 0.32 × 10⁹ cells/L (95%-CI = 0.09–0.55 × 10⁹)). This association was less pronounced in long-term night shift workers (≥ 20 years). Our findings provide evidence for the association between night shift work characteristics and BMI, waist circumference and leukocytes (including, monocytes, lymphocytes, and basophil granulocytes).

Circadian influence on intrusive re-experiencing in trauma survivors' daily lives

BACKGROUND

The core clinical feature of posttraumatic stress disorder (PTSD) is recurrent re-experiencing in form of intrusive memories. While a great number of biological processes are regulated by sleep and internal biological clocks, the effect of 24-hour biological cycles, named circadian rhythm, has not been investigated in the context of intrusive memories.

OBJECTIVE

Here we examined effects of time of day on frequency and characteristics of intrusive re-experiencing.

METHODS

Fifty trauma survivors reported intrusive memories for 7 consecutive days using ecological momentary assessment in their daily life. We investigated (i) time-of-day dependent effects on frequency and distribution of intrusive re-experiencing in the overall sample as well as in PTSD versus non-PTSD and (ii) time-of-day dependent effects on the memory characteristics intrusiveness, vividness, nowness and fear.

RESULTS

Intrusive memories showed a curvilinear pattern that peaked at 2pm. Intrusive memories in the PTSD group showed a constant level of intrusive re-experiencing in the afternoon and evening, whereas a descending slope was present in the non-PTSD group. In PTSD, intrusive memories might thus be experienced in a more time-scattered fashion throughout the day, indicating chronodisruption. Intrusion characteristics did not follow this pattern.

CONCLUSION

Although preliminary and based on a small sample size, these findings contribute to a better understanding of the everyday occurrence and characteristics of intrusive memories, and point to the added value of examining time-dependent effects, which can directly inform prevention and intervention science.

Revisiting nocturnal heart rate and heart rate variability in insomnia: A polysomnography-based comparison of young self-reported good and poor sleepers

Primary insomnia is often considered a disorder of 24-hr hyperarousal. Numerous attempts have been made to investigate nocturnal heart rate (HR) and its variability (HRV) as potential pathophysiological hallmarks of altered arousal levels in insomnia, with mixed results. We have aimed to overcome some of the pitfalls of previous studies by using a young, medication-free, age- and gender-matched population consisting of 43 students aged 18-30 years half with a subthreshold insomnia complaint. We employed at-home ambulatory polysomnography and compared this attenuated insomnia group to a good sleeping group. The poor sleepers had significantly higher wake after sleep onset, arousal count, mean HR in all sleep stages (with the exception of Stage 1) and lower sleep efficiency. Consistent with previous research, we also found a significant group-by-sleep stage interaction in the prediction of nocturnal HR, highlighting the insomnia group to have a lower wake-sleep HR reduction compared to good sleepers. When restricting our analyses to insomnia with objectively determined short sleep duration, we found significantly lower standard deviation of RR intervals (SDNN; a measure of HRV) compared to good sleepers. Taken together, this lends credence to the hyperarousal model of insomnia and may at least partially explain the increased prevalence of cardiovascular morbidity and mortality observed in patients with insomnia.

Systems and Circuits Linking Chronic Pain and Circadian Rhythms

Research over the last 20 years regarding the link between circadian rhythms and chronic pain pathology has suggested interconnected mechanisms that are not fully understood. Strong evidence for a bidirectional relationship between circadian function and pain has been revealed through inflammatory and immune studies as well as neuropathic ones. However, one limitation of many of these studies is a focus on only a few molecules or cell types, often within only one region of the brain or spinal cord, rather than systems-level interactions. To address this, our review will examine the circadian system as a whole, from the intracellular genetic machinery that controls its timing mechanism to its input and output circuits, and how chronic pain, whether inflammatory or neuropathic, may mediate or be driven by changes in these processes. We will investigate how rhythms of circadian clock gene expression and behavior, immune cells, cytokines, chemokines, intracellular signaling, and glial cells affect and are affected by chronic pain in animal models and human pathologies. We will also discuss key areas in both circadian rhythms and chronic pain that are sexually dimorphic. Understanding the overlapping mechanisms and complex interplay between pain and circadian mediators, the various nuclei they affect, and how they differ between sexes, will be crucial to move forward in developing treatments for chronic pain and for determining how and when they will achieve their maximum efficacy.

In vivo flow cytometry reveals a circadian rhythm of circulating tumor cells

Circulating tumor cells (CTCs) is an established biomarker of cancer metastasis. The circulation dynamics of CTCs are important for understanding the mechanisms underlying tumor cell dissemination. Although studies have revealed that the circadian rhythm may disrupt the growth of tumors, it is generally unclear whether the circadian rhythm controls the release of CTCs. In clinical examinations, the current in vitro methods for detecting CTCs in blood samples are based on a fundamental assumption that CTC counts in the peripheral blood do not change significantly over time, which is being challenged by recent studies. Since it is not practical to draw blood from patients repeatedly, a feasible strategy to investigate the circadian rhythm of CTCs is to monitor them by in vivo detection methods. Fluorescence in vivo flow cytometry (IVFC) is a powerful optical technique that is able to detect fluorescent circulating cells directly in living animals in a noninvasive manner over a long period of time. In this study, we applied fluorescence IVFC to monitor CTCs noninvasively in an orthotopic mouse model of human prostate cancer. We observed that CTCs exhibited stochastic bursts over cancer progression. The probability of the bursting activity was higher at early stages than at late stages. We longitudinally monitored CTCs over a 24-h period, and our results revealed striking daily oscillations in CTC counts that peaked at the onset of the night (active phase for rodents), suggesting that the release of CTCs might be regulated by the circadian rhythm.

Can a tDCS treatment enhance subjective and objective sleep among student-athletes?

INTRODUCTION

Previous studies have shown that student-athletes suffer from sleep difficulties. This study explored the impact of tDCS on sleep parameters among student-athletes.

METHOD

Thirty student-athletes (15 females, 15 males, age 21.1 ± 2.1 years) were recruited. All participants underwent a series of questions to rule out depressive and anxiety disorders or any specific tDCS exclusion criteria. All participants were advised to maintain their usual sleep schedule.

RESULTS

Compared polysomnographic and Psychomotor Vigilance Task data analyses did not show any improvement after experimental tDCS. Regardless of groups, PVT mean reaction time was decreased. Regarding the questionnaires, data analyses showed improvement on the PSQI (p < .001), ISI (p < .001) and ASSQ (p < .007) scores after tDCS.

DISCUSSION

tDCS appears to increase total sleep time and should be further explored. Improvements in subjective sleep suggest that tDCS bears interesting possibilities into the enhancement of sleep among student-athletes.

Environmental chemicals affect circadian rhythms: An underexplored effect influencing health and fitness in animals and humans

Circadian rhythms control the life of virtually all organisms. They regulate numerous aspects ranging from cellular processes to reproduction and behavior. Besides the light-dark cycle, there are additional environmental factors that regulate the circadian rhythms in animals as well as humans. Here, we outline the circadian rhythm system and considers zebrafish (Danio rerio) as a representative vertebrate organism. We characterize multiple physiological processes, which are affected by circadian rhythm disrupting compounds (circadian disrupters). We focus on and summarize 40 natural and anthropogenic environmental circadian disrupters in fish. They can be divided into six major categories: steroid hormones, metals, pesticides and biocides, polychlorinated biphenyls, neuroactive drugs and other compounds such as cyanobacterial toxins and bisphenol A. Steroid hormones as well as metals are most studied. Especially for progestins and glucocorticoids, circadian dysregulation was demonstrated in zebrafish on the molecular and physiological level, which comprise mainly behavioral alterations. Our review summarizes the current state of knowledge on circadian disrupters, highlights their risks to fish and identifies knowledge gaps in animals and humans. While most studies focus on transcriptional and behavioral alterations, additional effects and consequences are underexplored. Forthcoming studies should explore, which additional environmental circadian disrupters exist. They should clarify the underlying molecular mechanisms and aim to better understand the consequences for physiological processes.

The Impact of Self-Reported Sleep Quantity on Perceived Decision-Making in Sports Officials During a Competitive Season

Objectives: While sleep research in athletes is extensive, no research has investigated sleep in sports officials during a competitive season. This study explored the (a) self-reported quantity and quality of sleep obtained by sports officials according to the time of competition (day or evening) and (b) impact of reduced sleep on perceived decision-making ability. Design: Sports officials (n = 371) from various sporting codes completed an online questionnaire that evaluated self-reported sleep quantity and quality on habitual nights, before competition, and after competition, as well as perceived decision-making constructs. Results: With sleep restriction defined as less than 7 h of sleep, mixed-effects logistic regression revealed that the estimated probability of reporting reduced sleep quantity increased (p< .05) on habitual nights (0.58), before competition (0.48), and after competition (0.56). The estimated probability of reporting poor sleep quality was 0.01-0.04 across all nights. When considering time of competition (day or evening), reduced sleep quantity was experienced after evening competition (odds ratio [OR] = 3.33, p < .05), while poorer sleep quality (p< .05) was experienced following day (OR = 2.1) and evening (OR = 12.46) competition compared to habitual nights. Furthermore, the impact of reduced sleep on perceived decision-making constructs was negative, with the estimated probability of reporting impaired perceived decision-making between 0.13 and 0.21. Conclusion: Overall, sports officials are vulnerable to reduced quantity and quality of sleep before and after competition, with impaired perceived decision-making ability following nights of less than average sleep.

Association between social jet lag, quality of diet and obesity by diurnal preference in Finnish adult population

The evening type has been associated with unhealthy behaviors and adverse health outcomes, such as unhealthy dietary habits and obesity. Misalignment between biological and social rhythms, referred to as social jet lag (SJL), has been considered to explain these outcomes, because evening types are more prone to SJL. However, the existing evidence has been inconsistent and SJL by diurnal preference has hardly been examined. We examined the associations between SJL, the quality of the diet, and the prevalence of obesity by diurnal preference. This dataset included 6779 Finns (55% women, aged 25-74 years) from the National FINRISK 2012 and DILGOM 2014 studies. Diurnal preference was assessed with a shortened version of the Morningness-Eveningness Questionnaire (MEQ). SJL was calculated with the sleep-corrected formula (SJL_sc). SJL was divided into three groups by the degree of SJL (<1h, ≥1h but <2h and ≥2h). The dietary intake was assessed with a validated food frequency questionnaire (FFQ) and the quality of the diet with the Baltic Sea Diet Score. Body weight, height, and waist circumference (WC) were measured, and the body mass index (BMI) was calculated (kg/m²). Analysis of covariance (ANCOVA) followed by Bonferroni multiple comparison post-hoc tests and logistic regression models were used to analyze the differences between the lowest and the highest SJL groups by diurnal preference. In the highest SJL group (≥2h), there were more evening types than morning types (7%-points, p < .001). Overall, those in the highest SJL_sc group were on average younger than those in the lowest SJL_sc group (p< .001). Also, those in the highest SJL_sc group tended to have lower adherence to the Baltic Sea Diet compared to the participants in the lowest SJL_sc group, but this difference reached significance only in morning types (p = .006). Furthermore, morning types in the highest SJL_sc group had higher BMI and WC compared to the morning types in the lowest SJL_sc group (BMI, p = .016; WC, p = .012). In conclusion, evening types had on average more SJL than morning types, but the degree of SJL was associated with the quality of the diet and obesity only in the morning types.

The effects of acute work stress and appraisal on psychobiological stress responses in a group office environment

BACKGROUND

The high prevalence of office stress and its detrimental health consequences are of concern to individuals, employers and society at large. Laboratory studies investigating office stress have mostly relied on data from participants that were tested individually on abstract tasks. In this study, we examined the effect of psychosocial office stress and work interruptions on the psychobiological stress response in a realistic but controlled group office environment. We also explored the role of cognitive stress appraisal as an underlying mechanism mediating the relationship between work stressors and the stress response.

METHODS AND MATERIALS

Ninety participants (44 female; mean age 23.11 ± 3.80) were randomly assigned to either a control condition or one of two experimental conditions in which they were exposed to psychosocial stress with or without prior work interruptions in a realistic multi-participant laboratory setting. To induce psychosocial stress, we adapted the Trier Social Stress Test for Groups to an office environment. Throughout the experiment, we continuously monitored heart rate and heart rate variability. Participants repeatedly reported on their current mood, calmness, wakefulness and perceived stress and gave saliva samples to assess changes in salivary cortisol and salivary alpha-amylase. Additionally, cognitive appraisal of the psychosocial stress test was evaluated.

RESULTS

Our analyses revealed significant group differences for most outcomes during or immediately after the stress test (i.e., mood, calmness, perceived stress, salivary cortisol, heart rate, heart rate variability) and during recovery (i.e., salivary cortisol and heart rate). Interestingly, the condition that experienced work interruptions showed a higher increase of cortisol levels but appraised the stress test as less threatening than individuals that experienced only psychosocial stress. Exploratory mediation analyses revealed a blunted response in subjective measures of stress, which was partially explained by the differences in threat appraisal.

DISCUSSION

The results showed that experimentally induced work stress led to significant responses of subjective measures of stress, the hypothalamic-pituitary-adrenal axis and the autonomic nervous system. However, there appears to be a discrepancy between the psychological and biological responses to preceding work interruptions. Appraising psychosocial stress as less threatening but still as challenging could be an adaptive way of coping and reflect a state of engagement and eustress.

Sleep and Athletic Performance: Impacts on Physical Performance, Mental Performance, Injury Risk and Recovery, and Mental Health

Research has characterized the sleep of elite athletes and attempted to identify factors associated with athletic performance, cognition, health, and mental well-being. Sleep is a fundamental component of performance optimization among elite athletes, yet only recently embraced by sport organizations as an important part of training and recovery. Sleep plays a crucial role in physical and cognitive performance and is an important factor in reducing risk of injury. This article aims to highlight the prevalence of poor sleep, describe its impacts, and address the issue of sport culture surrounding healthy sleep.

Reduced melatonin synthesis in pregnant night workers: Metabolic implications for offspring

Several novel animal studies have shown that intrauterine metabolic programming can be modified in the event of reduced melatonin synthesis during pregnancy, leading to glucose intolerance and insulin resistance in the offspring. It is therefore postulated that female night workers when pregnant may expose the offspring to unwanted health threats. This may be explained by the fact that melatonin is essential for regulating energy metabolism and can influence reproductive activity. Moreover, the circadian misalignment caused by shift work affects fertility and the fetus, increasing the risk of miscarriage, premature birth and low birth weight, phenomena observed in night workers. Thus, we hypothesize that light-induced melatonin suppression as a result of night work may alter intrauterine metabolic programming in pregnant women, potentially leading to metabolic disorders in their offspring.

The Effect of Structured Exercise on Sleep During the Corresponding Night Among Older Women in an Exercise Program

This study investigated the acute effect of exercise on sleep outcomes among healthy older women by comparing days with structured exercise versus days without structured exercise during 4 months of exercise training. Participants (n = 51) in this study had wrist-worn actigraphic sleep data available following at least 3 days with structured exercise and 3 days without structured exercise at mid-intervention and at the end of intervention. The exercise intervention was treadmill walking. Multilevel models were used to examine whether structured exercise impacted sleep outcomes during the corresponding night. Overall, 1,362 nights of data were included in the analyses. In unadjusted and adjusted models, bedtimes were significantly earlier on evenings following an acute bout of structured exercise than on evenings without structured exercise. No other sleep parameters differed between exercise and nonexercise days. Understanding the effects of exercise on sleep in this understudied population may help to improve their overall sleep quality.

Modulation of Motoneuronal Activity With Sleep-Wake States and Motoneuronal Gene Expression Vary With Circadian Rest-Activity Cycle

In both nocturnal and diurnal mammals, sleep and wake states differentially aggregate during the rest and active phases of circadian cycle. Closely associated with this rhythm are prominent changes in motor activity. Here, we quantified the magnitudes of electromyographic activity (EMG) measured separately during different sleep-wake states across the rest-activity cycle, thereby separating amplitude measurements from the known dependance of the timing of wake and sleep on the phase of circadian rest-activity cycle. In seven rats chronically instrumented for electroencephalogram and EMG monitoring, nuchal and lingual muscle EMGs were measured as a commonly used postural output in behavioral sleep studies and as a cranial motor output with potential clinical relevance in obstructive sleep apnea (OSA) syndrome, respectively. We found that, for both motor outputs, EMG measured during wake episodes was significantly higher during the active phase, than during the rest phase, of circadian cycle. The corresponding patterns observed during slow-wave sleep (SWS) and rapid eye movement sleep (REMS) were different. During SWS, lingual EMG was very low and did not differ between the rest and active phase, whereas nuchal EMG had pattern similar to that during wakefulness. During REMS, lingual EMG was, paradoxically, higher during the rest phase due to increased twitching activity, whereas nuchal EMG was very low throughout the rest and active periods (postural atonia). In the follow-up comparison of differences in transcript levels in tissue samples obtained from the medullary hypoglossal motor nucleus and inferior olive (IO) at rest onset and active period onset conducted using microarrays, we identified significant differences for multiple transcripts representing the core members of the molecular circadian clock and other genes important for the regulation of cell metabolism and activity (up to n = 130 at p < 0.001). Collectively, our data indicate that activity of motoneurons is regulated to optimally align it with the rest-activity cycle, with the process possibly involving transcriptional mechanisms at the motoneuronal level. Our data also suggest that OSA patients may be relatively better protected against sleep-related upper airway obstructions during REMS episodes generated during the rest phase, than during active phase, of the circadian cycle.

Sleep disorders in the elderly: Diagnosis and management

Compared with younger people, elderly people show age‐related sleep changes, including an advanced sleep phase and decreased slow‐wave sleep, which result in fragmented sleep and early awakening. Multiple etiologies contribute to insomnia in the elderly, consistent with the observation that elderly people are likely to have comorbid conditions and medications. When elderly individuals complain of insomnia, it is important to assess treatable medical conditions and medication use that may be responsible for the insomnia before the use of hypnotics is initiated. Also, screening for primary sleep disorders, such as sleep apnea syndrome, restless legs syndrome and rapid eye movement sleep behavior disorder, is essential. We review sleep disorders commonly observed in the elderly and describe their diagnosis and management.

Occupational Health and Sleep Issues in Underserved Populations

Sleep disorders and occupational hazards, injuries, and illnesses impact an individual's overall health. In the United States, substantial racial, ethnic, and socioeconomic disparities exist in sleep and occupational health. Primary care physicians working in underserved communities should be aware of this disparity and target these higher-risk populations for focused evaluation and intervention.

Timing and quality of sleep in a rural Brazilian family-based cohort, the Baependi Heart Study

Sleep is modulated by several factors, including sex, age, and chronotype. It has been hypothesised that contemporary urban populations are under pressure towards shorter sleep duration and poorer sleep quality. Baependi is a small town in Brazil that provides a window of opportunity to study the influence of sleep patterns in a highly admixed rural population with a conservative lifestyle. We evaluated sleep characteristics, excessive daytime sleepiness, and chronotype using the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale and Morningness-Eveningness Questionnaire questionnaires, respectively. The sample consisted of 1,334 subjects from the Baependi Heart study (41.5% male; age: 46.5 ± 16.2 y, range: 18-89 years). Average self-reported sleep duration was 07:07 ± 01:31 (bedtime 22:32 ± 01:27, wake up time: 06:17 ± 01:25 hh:min), sleep quality score was 4.9 + 3.2, chronotype was 63.6 ± 10.8 and daytime sleepiness was 7.4 ± 4.8. Despite a shift towards morningness in the population, chronotype remained associated with reported actual sleep timing. Age and sex modulated the ontogeny of sleep and chronotype, increasing age was associated with earlier sleep time and shorter sleep duration. Women slept longer and later, and reported poorer sleep quality than men (p < 0.0001). This study provides indirect evidence in support of the hypothesis that sleep timing was earlier prior to full urbanisation.

Exponential state transition dynamics in the rest-activity architecture of patients with bipolar disorder

OBJECTIVE

Our goal was to model the temporal dynamics of sleep-wake transitions, represented by transitions between rest and activity obtained from actigraphic data, in patients with bipolar disorder using a probabilistic state transition approach.

METHODS

We collected actigraphic data for 14 days from 20 euthymic patients with bipolar disorder, who had been characterized clinically, demographically, and with respect to their circadian preferences (chronotype). We processed each activity record to generate a series of transitions in both directions between the states of rest (R) and activity (A) and plotted the estimated transition probabilities (pRA and pAR). Each 24-hour period was also divided into a rest phase consisting of the eight consecutive least active hours in each day and an active phase consisting of the 16 consecutive most active hours in each day. We then calculated separate transition probabilities for each of these phases for each participant. We subsequently modeled the rest phase data to find the best fit for rest-activity transitions using maximum likelihood estimation. We also examined the association of transition probabilities with clinical and demographic variables.

RESULTS

The best-fit model for rest-activity transitions during the rest phase was a mixture (bimodal) of exponential functions. Of those patients with rapid cycling, 75% had an evening-type chronotype. Patients with bipolar II disorder taking antidepressants had a lower probability of transitioning back to rest than those not on antidepressants [mean ± SD = 0.050 ± 0.006 versus 0.141 ± 0.058, F(1,15) = 3.40, p < 0.05].

CONCLUSIONS

The dynamics of transitions between rest and activity in bipolar disorder can be accounted for by a mixture (bimodal) of exponential functions. Patients taking antidepressants had a reduced probability of sustaining and returning to sleep.

Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise

Although its true function remains unclear, sleep is considered critical to human physiological and cognitive function. Equally, since sleep loss is a common occurrence prior to competition in athletes, this could significantly impact upon their athletic performance. Much of the previous research has reported that exercise performance is negatively affected following sleep loss; however, conflicting findings mean that the extent, influence, and mechanisms of sleep loss affecting exercise performance remain uncertain. For instance, research indicates some maximal physical efforts and gross motor performances can be maintained. In comparison, the few published studies investigating the effect of sleep loss on performance in athletes report a reduction in sport-specific performance. The effects of sleep loss on physiological responses to exercise also remain equivocal; however, it appears a reduction in sleep quality and quantity could result in an autonomic nervous system imbalance, simulating symptoms of the overtraining syndrome. Additionally, increases in pro-inflammatory cytokines following sleep loss could promote immune system dysfunction. Of further concern, numerous studies investigating the effects of sleep loss on cognitive function report slower and less accurate cognitive performance. Based on this context, this review aims to evaluate the importance and prevalence of sleep in athletes and summarises the effects of sleep loss (restriction and deprivation) on exercise performance, and physiological and cognitive responses to exercise. Given the equivocal understanding of sleep and athletic performance outcomes, further research and consideration is required to obtain a greater knowledge of the interaction between sleep and performance.

How is the inner circadian clock controlled by interactive clock proteins?: Structural analysis of clock proteins elucidates their physiological role

Most internationally travelled researchers will have encountered jetlag. If not, working odd hours makes most of us feel somehow dysfunctional. How can all this be linked to circadian rhythms and circadian clocks? In this review, we define circadian clocks, their composition and underlying molecular mechanisms. We describe and discuss recent crystal structures of Drosophila and mammalian core clock components and the enormous impact they had on the understanding of circadian clock mechanisms. Finally, we highlight the importance of circadian clocks for the daily regulation of human/mammalian physiology and show connections to overall fitness, health and disease.

Buying time: a rationale for examining the use of circadian rhythm and sleep interventions to delay progression of mild cognitive impairment to Alzheimer's disease

As of 2010, the worldwide economic impact of dementia was estimated at $604 billion USD; and without discovery of a cure or effective interventions to delay disease progression, dementia's annual global economic impact is expected to surpass $1 trillion USD as early as 2030. Alzheimer's disease (AD) is the leading cause of dementia accounting for over 75% of all cases. Toxic accumulation of amyloid beta (Aβ), either by overproduction or some clearance failure, is thought to be an underlying mechanism of the neuronal cell death characteristic of AD-though this amyloid hypothesis has been increasingly challenged in recent years. A compelling alternative hypothesis points to chronic neuroinflammation as a common root in late-life degenerative diseases including AD. Apolipoprotein-E (APOE) genotype is the strongest genetic risk factor for AD: APOE-ε4 is proinflammatory and individuals with this genotype accumulate more Aβ, are at high risk of developing AD, and almost half of all AD patients have at least one ε4 allele. Recent studies suggest a bidirectional relationship exists between sleep and AD pathology. Sleep may play an important role in Aβ clearance, and getting good quality sleep vs. poor quality sleep might reduce the AD risk associated with neuroinflammation and the ε4 allele. Taken together, these findings are particularly important given the sleep disruptions commonly associated with AD and the increased burden disrupted sleep poses for AD caregivers. The current review aims to: (1) identify individuals at high risk for dementia who may benefit most from sleep interventions; (2) explore the role poor sleep quality plays in exacerbating AD type dementia; (3) examine the science of sleep interventions to date; and (4) provide a road map in pursuit of comprehensive sleep interventions, specifically targeted to promote cognitive function and delay progression of dementia.

Morning/Evening differences in somatosensory inputs for postural control

The underlying processes responsible for the differences between morning and afternoon measurements of postural control have not yet been clearly identified. This study was conducted to specify the role played by vestibular, visual, and somatosensory inputs in postural balance and their link with the diurnal fluctuations of body temperature and vigilance level. Nineteen healthy male subjects (mean age: 20.5 ± 1.3 years) participated in test sessions at 6:00 a.m. and 6:00 p.m. after a normal night's sleep. Temperature was measured before the subjects completed a sign cancellation test and a postural control evaluation with eyes both open and closed. Our results confirmed that postural control improved throughout the day according to the circadian rhythm of body temperature and sleepiness/vigilance. The path length as a function of surface ratio increased between 6:00 a.m. and 6:00 p.m. This is due to a decrease in the centre-of-pressure surface area, which is associated with an increase in path length. Romberg's index did not change throughout the day; however, the spectral analysis (fast Fourier transform) of the centre-of-pressure excursions (in anteroposterior and mediolateral directions) indicated that diurnal fluctuations in postural control may occur via changes in the different processes responsible for readjustment via muscle contractions.

The periodicity of sleep duration - an infradian rhythm in spontaneous living

The sleep-wake cycle is a process not only dictated by homeostatic and circadian factors but also by social and environmental influences. Thus, the total sleep time partly reflects sleep need, which is integral to the dynamics of sleep loss recovery. This study explored the nature of the observed oscillations in total sleep time in healthy adults under spontaneous living conditions. Actigraph-measured sleep data for 13 healthy young male adults were collected over 14 consecutive days and analyzed for habitual sleep duration. The total sleep time periodicity was modeled using the cosinor method for each individual across the 14 days. The findings confirm the existence of periodicity in habitual sleep duration as there were clear periodic patterns in the majority of the participants. Although exclusive to each individual, the observed oscillations may be a resultant response of homeostatic sleep need, circadian timing, and/or social and environmental influences. These findings instigate further indepth studies into the periodicity of sleep duration in healthy individuals to provide a better understanding of sleep need in short versus long sleepers, in predicting work performance, and reducing sleepiness-related accidents following shift work, and how this periodicity may impact sleep treatment outcome in clinical populations.

Sleep disturbance in mental health problems and neurodegenerative disease

Sleep has been described as being of the brain, by the brain, and for the brain. This fundamental neurobiological behavior is controlled by homeostatic and circadian (24-hour) processes and is vital for normal brain function. This review will outline the normal sleep-wake cycle, the changes that occur during aging, and the specific patterns of sleep disturbance that occur in association with both mental health disorders and neurodegenerative disorders. The role of primary sleep disorders such as insomnia, obstructive sleep apnea, and REM sleep behavior disorder as potential causes or risk factors for particular mental health or neurodegenerative problems will also be discussed.

Effects of solar radiation on the skin

No one would underestimate the importance of sunlight to the evolution of life on the earth and its role in human development. However, all humans - especially individuals who are lightly pigmented or whose occupation or lifestyle exposes them to excessive amounts of sunlight - are potentially susceptible to its deleterious effects. These effects can range from acute biological responses, such as sunburn and skin tanning, to conditions resulting from chronic exposure such as photoaged skin and potentially life-threatening conditions such as skin cancer. The objective of this review is to present a concise and up-to-date perspective on the effects of UVB, UVA, visible, and infrared radiation on cutaneous biochemistry and physiology.

Daily rhythms of the sleep-wake cycle

The amount and timing of sleep and sleep architecture (sleep stages) are determined by several factors, important among which are the environment, circadian rhythms and time awake. Separating the roles played by these factors requires specific protocols, including the constant routine and altered sleep-wake schedules. Results from such protocols have led to the discovery of the factors that determine the amounts and distribution of slow wave and rapid eye movement sleep as well as to the development of models to determine the amount and timing of sleep. One successful model postulates two processes. The first is process S, which is due to sleep pressure (and increases with time awake) and is attributed to a 'sleep homeostat'. Process S reverses during slow wave sleep (when it is called process S'). The second is process C, which shows a daily rhythm that is parallel to the rhythm of core temperature. Processes S and C combine approximately additively to determine the times of sleep onset and waking. The model has proved useful in describing normal sleep in adults. Current work aims to identify the detailed nature of processes S and C. The model can also be applied to circumstances when the sleep-wake cycle is different from the norm in some way. These circumstances include: those who are poor sleepers or short sleepers; the role an individual's chronotype (a measure of how the timing of the individual's preferred sleep-wake cycle compares with the average for a population); and changes in the sleep-wake cycle with age, particularly in adolescence and aging, since individuals tend to prefer to go to sleep later during adolescence and earlier in old age. In all circumstances, the evidence that sleep times and architecture are altered and the possible causes of these changes (including altered S, S' and C processes) are examined.

Adrenal glucocorticoids as a target for jet lag therapies

When traveling across time zones, our physiological functions lose synchrony relative to the external day. The endogenous circadian clocks that usually prepare our body for times of eating, sleeping and other rhythmic behavioral and physiological processes become temporally disrupted. Owing to the fact that these clocks cannot immediately realign, we experience jet lag, which is characterized by multiple physiological and psychological symptoms. Despite recent advances in understanding circadian clock function and the mechanisms of jet lag, limited therapy is available at present for the treatment of disorders associated with long-distance travel. Recent studies demonstrate that adrenal glucocorticoids are central mediators of circadian clock re-entrainment and are themselves under circadian regulation. It is therefore attractive to consider glucocorticoid signaling as a promising target for therapeutic intervention in the treatment of jet lag.

Correlation of shift work and waist circumference, body mass index, chronotype and depressive symptoms

OBJECTIVE

Correlate shift work with body mass index (BMI), waist circumference, chronotype and depressive symptoms.

SUBJECTS AND METHODS

This study comprising 14 shift workers and 13 day workers. Subjects were workers from the health area aged 25 to 60 years. Minor psychiatric disorders were accessed by Self Report Questionnaire (SRQ-20) and depressive symptoms by Beck Depression Inventory (BDI). Chronotype was accessed using Morningness-Eveningness Questionnaire (MEQ). Anthropometric measures were taken.

RESULTS

Shift workers presented higher BMI (P = 0.03) and waist circumference (P = 0.004) than day workers. Years on shift work were significantly correlated to waist circumference (r = 0.43; P = 0.03) and age (r = 0.47; P = 0.02). Shift work was not correlated with depressive symptoms and chronotype.

CONCLUSION

These results may suggest a role played by shift work on the development and/or the early clinic manifestations of metabolic disturbances, becoming a risk factor to metabolic syndrome.