Biological rhythms during residence in polar regions

Environmental, social, and behavioral challenges of the human circadian clock in real-life conditions

Urban environments, in which ambient light has become a less-reliable entrainer, are challenging for the biological clock to maintain performance. As a consequence, human circadian rhythms are less robust and more variable among individuals. Assessing the individual phase of entrainment, as well as its plastic shifts in response to disturbances of the physical and social environment, is a way to measure circadian disruption. However, this is still difficult to address in real-life scenarios in which several factors modulate the circadian phase not always in a concerted manner. In this perspective, we present the contribution of two real-life situations, in which the circadian system is challenged by important alterations in entraining signals: 1) a trip to the Antarctic summer (socio-environmental challenge), and 2) dancers trained in morning/night shifts (socio-behavioral challenge). Both natural chronobiological experiments are helpful in exploring the functioning and plasticity of the circadian clock and allow for considering individual characteristics and history.

The effects of ambient temperature and feeding regimens on cecum bacteria composition and circadian rhythm in growing rabbits

Seasonal environmental shifts and improper eating habits are the important causes of diarrhea in children and growing animals. Whether adjusting feeding time at varying temperatures can modify cecal bacterial structure and improve diarrhea remains unknown. Three batches growing rabbits with two groups per batch were raised under different feeding regimens (fed at daytime vs. nighttime) in spring, summer and winter separately, and contents were collected at six time points in 1 day and used 16S rRNA sequencing to investigate the effects of feeding regimens and season on the composition and circadian rhythms of cecum bacteria. Randomized forest regression screened 12 genera that were significantly associated with seasonal ambient temperature changes. Nighttime feeding reduced the abundance of the conditionally pathogenic bacteria Desulfovibrio and Alistipes in summer and Campylobacter in winter. And also increases the circadian rhythmic Amplicon Sequence Variants in the cecum, enhancing the rhythm of bacterial metabolic activity. This rhythmic metabolic profile of cecum bacteria may be conducive to the digestion and absorption of nutrients in the host cecum. In addition, this study has identified 9 genera that were affected by the combination of seasons and feeding time. In general, we found that seasons and feeding time and their combinations affect cecum composition and circadian rhythms, and that daytime feeding during summer and winter disrupts the balance of cecum bacteria of growing rabbits, which may adversely affect cecum health and induce diarrhea risk.

Effect of daily light exposure on sleep in polar regions: A meta-analysis

Although studies have shown that light affects sleep in polar populations, the sample size of most studies is small. This meta-analysis provides the first systematic review of the effects of summer glare, spring and fall moderate daylight, and artificial lighting on general sleep problems (sleep duration, efficiency, and delay). This analysis included 18 studies involving 986 participants. We calculated the random effect size via an evidence-based meta-analysis that analysed the effect of bright/auxiliary light on sleep and the effect of three different types of light on sleep compared with conventional light. There was no significant correlation between specific light types and sleep duration. Intense summer light has a negative effect on sleep time and efficiency. Moderate, natural light in spring and autumn effectively delayed sleep but could not improve sleep efficiency. For artificial fill light, neither blue light nor enhanced white light has been found to have a significant effect. In summary, summer light has a detrimental effect on sleep in polar populations, and moderate natural light may be superior to conventional light. However, specific strategies to improve sleep and artificial lighting in polar populations must be explored further.

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

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

Circannual seizure provocation as the day lengthens in the northern and southern hemispheres

Circannual status epilepticus (SE) patterns in communities near Earth's poles best test the hypothesis that SE susceptibility varies with light exposure because these communities are routinely subject to large changes in annual light exposure, which may result in changes to daily sleep time. We compared northern hemispheric circannual SE occurrence in Kivalliq, Canada (latitude-62.8° N) to southern hemispheric Auckland, New Zealand (latitude-36.9° S). Instead of peaking at a similar calendar time, SE peaked at a similar solar time during the increasing daylight phase after each region's respective winter solstice. This demonstrates that cumulative effects of increasing light exposure can mediate SE susceptibility.

Night work, season and alertness as occupational safety hazards in the Arctic: protocol for the Noralert observational crossover study among Norwegian process operators

INTRODUCTION

The objective of this study is to determine the effects of night work, Arctic seasonal factors and cold working environments on human functions relevant to safety. The study aims to quantify the contribution of (1) several consecutive night shifts, (2) seasonal variation on sleepiness, alertness and circadian rhythm and (3) whether a computational model of sleep, circadian rhythms and cognitive performance can accurately predict the observed sleepiness and alertness.

METHODS AND ANALYSIS

In an observational crossover study of outdoor and indoor workers (n=120) on a three-shift schedule from an industrial plant in Norway (70 °N), measurements will be conducted during the summer and winter. Sleep duration and quality will be measured daily by smartphone questionnaire, aided by actigraphy and heart rate measurements. Sleepiness and alertness will be assessed at regular intervals by the Karolinska Sleepiness Scale and the psychomotor vigilance test, respectively. Saliva samples will assess melatonin levels, and a blood sample will measure circadian time. Thermal exposures and responses will be measured by sensors and by thermography.

ETHICS AND DISSEMINATION

All participants will give written informed consent to participate in the study, which will be conducted in accordance with the Declaration of Helsinki. The Norwegian Regional Committee for Medical Research Ethics South-East D waivered the need for ethics approval (reference 495816). Dissemination plans include academic and lay publications, and partnerships with national and regional policymakers.

Chronotype and lipid metabolism in Arctic Sojourn Workers

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

Individual light history matters to deal with the Antarctic summer

The effect of light, main zeitgeber of the circadian system, depends on the time of day it is received. A brief trip to the Antarctic summer (ANT) allowed us to explore the impact of a sudden and synchronized increase in light exposure on activity-rest rhythms and sleep patterns of 11 Uruguayan university students, and to assess the significance of light history in determining individual circadian phase shift. Measurements collected in the peri-equinox in Montevideo, Uruguay (baseline situation, MVD) and in ANT, included sleep logs, actigraphy, and salivary melatonin to determine dim-light melatonin onset (DLMO), the most reliable marker of circadian phase. The increase in light exposure in ANT with respect to MVD (affecting both light-sensitive windows with opposite effects on the circadian phase) resulted in no net change in DLMO among participants as some participants advanced their DLMO and some others delayed it. The ultimate cause of each participant's distinctive circadian phase shift relied on the unique change in light exposure each individual was subjected to between their MVD and ANT. This study shows an association between the individual light history and the circadian phase shift.

The circadian clock and extracellular matrix homeostasis in aging and age-related diseases

The extracellular matrix (ECM) is the noncellular scaffolding component present within all tissues and organs. It provides crucial biochemical and biomechanical cues to instruct cellular behavior and has been shown to be under circadian clock regulation, a highly conserved cell-intrinsic timekeeping mechanism that has evolved with the 24-hour rhythmic environment. Aging is a major risk factor for many diseases, including cancer, fibrosis, and neurodegenerative disorders. Both aging and our modern 24/7 society disrupt circadian rhythms, which could contribute to altered ECM homeostasis. Understanding the daily dynamics of ECM and how this mechanism changes with age will have a profound impact on tissue health, disease prevention, and improving treatments. Maintaining rhythmic oscillations has been proposed as a hallmark of health. On the other hand, many hallmarks of aging turn out to be key regulators of circadian timekeeping mechanisms. In this review, we summarize new work linking the ECM with circadian clocks and tissue aging. We discuss how the changes in the biomechanical and biochemical properties of ECM during aging may contribute to circadian clock dysregulation. We also consider how the dampening of clocks with age could compromise the daily dynamic regulation of ECM homeostasis in matrix-rich tissues. This review aims to encourage new concepts and testable hypotheses about the two-way interactions between circadian clocks and ECM in the context of aging.

The emerging role of circadian rhythms in the development and function of thermogenic fat

Circadian rhythms regulate many biological processes in response to ambient influences. A disrupted circadian rhythm has been shown to be associated with obesity and obesity-related metabolic disorders. Thermogenic fat, including brown and beige fat, may play an important role in this process since it displays a high capacity to burn fat and release the stored energy as heat, contributing to the combat against obesity and its associated metabolic disorders. In this review, we summarize the relationship between the circadian clock and thermogenic fat and the prominent mechanisms which are involved in the regulation of the development and function of thermogenic fat by circadian rhythms, which may provide novel therapeutics for the prevention and treatment of metabolic diseases by targeting thermogenic fat in a circadian manner.

To what extent is circadian phase predictive of subjective jet lag in long-haul cabin crew pre- and post-trip?

Long-haul cabin crew regularly report misalignment between their circadian phase and the external world (i.e. jet lag). The extent to which changes in circadian phase relate to reported levels of jet lag remains unclear. The main aim of the present study was first to evaluate the relationship between objective (circadian phase) and subjective jet lag and second to explore the relative role of both subjective and objective psycho-behavioural factors in predicting the subjective experience of jet lag. Twenty-eight long-haul cabin crew completed questionnaires measuring diurnal preference, trip characteristics and subjective jet lag as a single and as a multidimensional measure. Sleep was monitored using actigraphy and urinary melatonin peak time was measured, at baseline (T1), e.g. before a long-haul trip and post-trip on the crew's first recovery day (T2). Subjective jet lag was also measured at both time points. At T1, later circadian phase related to increased unidimensional jet lag, however, a post-trip discrepancy was found between objective and subjective uni- and multidimensional jet lag measured at T2 and change from T1 to T2. After controlling for direction and size of circadian phase, increased uni- and multidimensional subjective jet lag was predicted by depressed mood states. The regression models including phase, diurnal preference, departure time on the outbound sector and arousal levels accounted for 28% of the variance in unidimensional jet lag and 53% of the variance in multidimensional jet lag. It was concluded that there is a discordance between objective and subjective jet lag post-trip. Further, subjective jet lag in long-haul cabin crew is better explained by mood impairment than circadian phase. The results are discussed with reference to the gap between subjective and objective jet lag and the role of psychology rather than just biology in the jet lag experience. The implications for improving health and safety in the workplace, through a better understanding of the role of human factors in the management of jet lag, are discussed.

The gut microbiota as a target to improve health conditions in a confined environment

Confined environments increase psychological stress and lead to health problems such as abnormal mood and rhythm disruption. However, the mechanism by which confined environments impact health has remained unclear. Significant correlations have been reported between psychological stress and changes in gut microbiota. Therefore, we investigated the effect of a confined environment on the composition of the gut microbiota by 16s rDNA high-throughput sequencing, and analyzed the correlation between gut microbiota and health indicators such as uric acid (UA), sleep, and mood. We found that the gut microbiota of the subjects clustered into two enterotypes (Bi and Bla), and that the groups differed significantly. There were notable differences in the abundances of genera such as Bifidobacterium, Dorea, Ruminococcus_torques_group, Ruminococcus_gnavus_group, Klebsiella, and UCG-002 (p < 0.05). A confined environment significantly impacted the subjects' health indicators. We also observed differences in how the subjects of the two enterotypes adapted to the confined environment. The Bi group showed no significant differences in health indicators before and after confinement; however, the Bla group experienced several health problems after confinement, such as increased UA, anxiety, and constipation, and lack of sleep. Redundancy analysis (RDA) showed that UA, RBC, mood, and other health problems were significantly correlated with the structure of the gut microbiota. We concluded that genera such as UCG-002, Ruminococcus, CAG352, and Ruminococcus_torques_group increased vulnerability to confined environments, resulting in abnormal health conditions. We found that the differences in the adaptability of individuals to confined environments were closely related to the composition of their gut microbiota.

Disruption of regulatory mechanisms as a stress factor for patients with metabolic syndrome

Introduction. Throughout history, humanity has lived and developed in accordance with its biological rhythms, which provided the adaptation of the body to the factors of external and internal environment, ensuring the normal synchronous functioning of all its components.

The purpose of this work was to study the stressful influence of circadian rhythms disturbance on patients with metabolic syndrome (MS) under conditions of dark deprivation.

Material and methods of investigation. We selected patients with MS and disturbed circadian rhythms – a total of 102 people (all men) from among those who constantly work at night, in whom a decrease in melatonin levels was recorded at the preliminary stage. According to the set objectives, 102 patients (young age according to WHO criteria) were divided into three groups of 33, 37 and 32 persons according to the criterion "duration of influence of dark deprivation and MS history duration": 0–5, 5–10 and over 10 years. In the first group the mean age was 30.1 ± 1.4 years, in the second group – 36.5 ± 1.5 years, in the third group the mean age did not exceed 40.3 ± 0.9 years. Melatonin levels (as confirmation of circadian rhythm disturbances) in blood serum were studied in all study participants using Melatonin ELISA immunoassay kit (IBL, Germany).

Results and discussion. Normally, when blood cortisol is measured before 10 a.m., its average value varies in a wide range from138 to 635 nmol/l. The increase up to 700 nmol/l is admitted, which is regarded as a negative influence of external factors during the examination. However, one should keep in mind that during evening measurements, cortisol levels in men may normally decrease to 80 nmol/l.

Conclusions. Thus, dark deprivation in patients with metabolic syndrome leads to the formation of a stress response. Maximum changes occur after 10 years of disturbance of regulatory mechanisms and lead to a pronounced imbalance between the sympathetic and parasympathetic nervous system, increased vascular tone and changes in the profile of blood pressure during the day towards the predominance of Non-dippers and Night-peers, which increases the risk of progression of metabolic syndrome symptoms.

Prevalence of depression and depressive symptoms at high altitudes: A systematic review and meta-analysis

BACKGROUND

The aim of the present study was to determine the prevalence of depression or depressive symptoms in people residing in high-altitude regions.

METHODS

Eleven databases were searched for studies on depression and depressive symptoms: PubMed, ISI Web of Science, CINAHL, Embase, Scopus, PsycINFO, Psychology and Behavioral Sciences Collection, Psychology Database, Academic Search Ultimate, SciELO and LILACS. Systematic review and meta-analysis were performed based on the inclusion of these articles measuring the prevalence of depressive symptoms in people living at high altitude (≥1500 m above sea level [masl]). The protocol was registered in PROSPERO (CRD42021271069).

RESULTS

Eight articles with >40,000 participants from 4 different countries were included. Among the samples treated, the combined prevalence of depressive symptoms was 17.9 % (I²: 99 %) and the only estimate by subpopulation at the country level was possible for China, with >36,000 participants, being 28.7 % (I²: 4 %).

LIMITATIONS

Considerable heterogeneity was reported in the estimation of overall prevalence due to the quality of the studies and the instruments used to screen for depressive symptoms.

CONCLUSION

Almost two out of every 10 people living at high-altitude regions suffer from depressive symptoms. Therefore, it is necessary to adapt interventions to this condition and further research in the field is required.

The prognostic implication of latitude in uveal melanoma: a nationwide observational cohort study of all patients born in Sweden between 1947 and 1989

BACKGROUND

The incidence of uveal melanoma increases with latitude. In this study, we examine the importance of latitude for uveal melanoma prognosis.

METHODS

All uveal melanoma patients born in Sweden between 1947 and 1990 were included (n = 745). The latitude of patients' birthplaces and home counties at the time of uveal melanoma diagnosis were collected. For all latitudes, data on sunlight and UV intensity parameters, temperature, daytime length variations, and socioeconomic factors were added. The prognostic implication of birthplace latitude and of moving > 1 degree of latitude was examined with multivariate Cox regressions and competing risk analyses.

FINDINGS

There were no significant differences in patient sex, age, tumor size, T-category, or BAP-1 immunoexpression between patients born in the south, central or northern regions of Sweden. Decreasing birthplace latitude was a predictor of uveal melanoma-related mortality in multivariate Cox regression. Patients that were born in southern regions or moved > 1 degree south between birth and diagnosis had higher incidence of uveal melanoma-related mortality in competing risk analysis. The sum of yearly sunshine hours, global sunlight radiation, average daily ultraviolet light intensity, average annual temperature, or net wealth were not predictors of uveal melanoma-related mortality.

INTERPRETATION

Latitude is a prognostic factor in uveal melanoma. This does not seem to be related to variations in patient or tumor characteristics at presentation, in management, in sunlight intensity, in ultraviolet light irradiance, in temperature, or in wealth. Future studies should examine if periodical changes in daylight hours or other factors could explain the prognostic implication.

The role of circadian phase in sleep and performance during Antarctic winter expeditions

The Antarctic environment presents an extreme variation in the natural light-dark cycle which can cause variability in the alignment of the circadian pacemaker with the timing of sleep, causing sleep disruption, and impaired mood and performance. This study assessed the incidence of circadian misalignment and the consequences for sleep, cognition, and psychological health in 51 over-wintering Antarctic expeditioners (45.6 ± 11.9 years) who completed daily sleep diaries, and monthly performance tests and psychological health questionnaires for 6 months. Circadian phase was assessed via monthly 48-h urine collections to assess the 6-sulphatoxymelatonin (aMT6s) rhythm. Although the average individual sleep duration was 7.2 ± 0.8 h, there was substantial sleep deficiency with 41.4% of sleep episodes <7 h and 19.1% <6 h. Circadian phase was highly variable and 34/50 expeditioners had sleep episodes that occurred at an abnormal circadian phase (acrophase outside of the sleep episode), accounting for 18.8% (295/1565) of sleep episodes. Expeditioners slept significantly less when misaligned (6.1 ± 1.3 h), compared with when aligned (7.3 ± 1.0 h; p < .0001). Performance and mood were worse when awake closer to the aMT6s peak and with increased time awake (all p < .0005). This research highlights the high incidence of circadian misalignment in Antarctic over-wintering expeditioners. Similar incidence has been observed in long-duration space flight, reinforcing the fidelity of Antarctica as a space analog. Circadian misalignment has considerable safety implications, and potentially longer term health risks for other circadian-controlled physiological systems. This increased risk highlights the need for preventative interventions, such as proactively planned lighting solutions, to ensure circadian alignment during long-duration Antarctic and space missions.

Sleep disturbances among women in a Subarctic region: a nationwide study

STUDY OBJECTIVES

To date, few studies have assessed sleep problems among women residing in Subarctic regions. Therefore, the aim of this large-scale population-based study was to assess the prevalence of severe sleep problems and associated factors among Icelandic women, living at 63-66°N.

METHODS

Participants were 29 681 women (18-69 years old) who took part in the Icelandic Stress-And-Gene-Analysis study in 2018-2019. Background information, health-related behavior, and mental health symptoms were assessed with an online questionnaire. The Pittsburgh Sleep Quality Index (PSQI) was used to assess severe sleep problems during the past month. Adjusting for age, marital status, number of children, education, personal income, work schedule, region, and response period, we used modified Poisson log-linear models to obtain prevalence ratios (PRs) with 95% confidence intervals (CIs).

RESULTS

Overall, 24.2% of women reported severe sleep problems (PSQI >10). Women responding in the winter presented with an overall higher prevalence of severe sleep problems, compared to those responding in the summer (PR 1.21; 95% CI, 1.15 to 1.28). Severe sleep problems were more prevalent among young and late-midlife women, those who were single, had children, socio-economic challenges, worked shifts, and flexible hours. Furthermore, obesity, suboptimal health behaviors, excessive screen time, and mental health problems were associated with severe sleep problems.

CONCLUSION

Severe sleep problems are more common among women in Subarctic regions than elsewhere, particularly during winter. These findings motivate the development of preventive strategies and interventions for women in the Subarctic who suffer from sleep problems.

Translational Approaches to Influence Sleep and Arousal

Sleep disorders are widespread in society and are prevalent in military personnel and in Veterans. Disturbances of sleep and arousal mechanisms are common in neuropsychiatric disorders such as schizophrenia, post-traumatic stress disorder, anxiety and affective disorders, traumatic brain injury, dementia, and substance use disorders. Sleep disturbances exacerbate suicidal ideation, a major concern for Veterans and in the general population. These disturbances impair quality of life, affect interpersonal relationships, reduce work productivity, exacerbate clinical features of other disorders, and impair recovery. Thus, approaches to improve sleep and modulate arousal are needed. Basic science research on the brain circuitry controlling sleep and arousal led to the recent approval of new drugs targeting the orexin/hypocretin and histamine systems, complementing existing drugs which affect GABA_A receptors and monoaminergic systems. Non-invasive brain stimulation techniques to modulate sleep and arousal are safe and show potential but require further development to be widely applicable. Invasive viral vector and deep brain stimulation approaches are also in their infancy but may be used to modulate sleep and arousal in severe neurological and psychiatric conditions. Behavioral, pharmacological, non-invasive brain stimulation and cell-specific invasive approaches covered here suggest the potential to selectively influence arousal, sleep initiation, sleep maintenance or sleep-stage specific phenomena such as sleep spindles or slow wave activity. These manipulations can positively impact the treatment of a wide range of neurological and psychiatric disorders by promoting the restorative effects of sleep on memory consolidation, clearance of toxic metabolites, metabolism, and immune function and by decreasing hyperarousal.

Human adaptative behavior to Antarctic conditions: A review of physiological aspects

The Antarctic environment induces adaptive metabolic and neuroendocrine changes associated with survival, as well as increased risks to physical and mental health. Circadian disruption has been observed in Antarctic expeditioners. The main consequences appear in quality of sleep, which can affect physical and cognitive performance. Physiological adaptation to cold is mediated by the norepinephrine and thyroid hormones (T₃ and 3,5-T₂ metabolite). The observed changes in the hypothalamic-pituitary-thyroid (HPT) axis of expeditioners varied according to temperature, photoperiod, time spent in the cold environment and stress level. The decrease in T₃ levels has frequently been associated with mood swings. Psychological and physical stressors cause disturbances in the hypothalamic-pituitary-adrenal (HPA) axis, with consequent maintenance of high cortisol levels, leading to memory impairment, immunosuppression, and cardiometabolic and reproductive disorders. Preventive measures, such as provision of adequate food, well-established eating times, physical activity and even the use of phototherapy, can all help maintain the circadian rhythm. In addition, the use of high-tech clothing and room temperature control in research stations provide greater protection against the effects of intense cold. However, psychological stress requires a more individualized approach based on the crew's sociocultural characteristics, but it can be mitigated by mental healthcare and training in coping strategies. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Cardiovascular Diseases > Environmental Factors Metabolic Diseases > Environmental Factors.

Circannual incidence of seizure evacuations from the Canadian Arctic

OBJECTIVES

Emerging evidence suggests that circadian rhythms affect seizure propensity in addition to, and possibly independent of, sleep-wake states. Subject to extreme seasonal changes in light and dark, the northerly Arctic can serve as a "natural experiment" to assess the real-life impact of environmental influences on seizure severity. Therefore, we evaluated the timing of seizure evacuations over 11.25 years in a well-defined region of the Canadian Arctic.

METHODS

Retrospective review of EEG database and patient records at the single "bottleneck" hospital to which all patients from the Kivalliq Region in Nunavut, Canada are evacuated for seizure emergencies. We calculated the mean resultant length (MRL) of circular data for circannual analysis, and conducted Rayleigh's test to assess for a statistical departure from circular uniformity.

RESULTS

Screening 40,392 EEGs, we found 117 medical evacuations from 99 distinct individuals from September 2009 to November 2020. Most evacuations occurred month-wise in May (19%); week-wise within a 7-day period in February (5%), June (5%), or November (5%); and day-wise within a 24-hour period in June (3%) or November (3%). Maximal MRL clustering occurred in April no matter if analyzed by day (0.16333, p = 0.04), week (0.16296, p = 0.04), or month (0.1736, p = 0.03).

CONCLUSIONS

A relative circannual increase in seizure evacuations between the winter and summer solstices may be related to increasing sleep loss when day length grows. Fewer evacuations between the summer and winter solstices may be related to decreased daylight and "catching up" on sleep when night length grows. Additional factors likely also play a role in circannual variation of seizure evacuations in the Arctic, which warrants further research.

A Growing Link between Circadian Rhythms, Type 2 Diabetes Mellitus and Alzheimer's Disease

Type 2 diabetes mellitus (T2DM) patients are at a higher risk of developing Alzheimer’s disease (AD). Mounting evidence suggests the emerging important role of circadian rhythms in many diseases. Circadian rhythm disruption is considered to contribute to both T2DM and AD. Here, we review the relationship among circadian rhythm disruption, T2DM and AD, and suggest that the occurrence and progression of T2DM and AD may in part be associated with circadian disruption. Then, we summarize the promising therapeutic strategies targeting circadian dysfunction for T2DM and AD, including pharmacological treatment such as melatonin, orexin, and circadian molecules, as well as non-pharmacological treatments like light therapy, feeding behavior, and exercise.

Coping with Antarctic demands: Psychological implications of isolation and confinement

Working in extreme environments requires a wide range of cognitive, psychological and social competences. Antarctica represents one of the most challenging habitats to work in due to its aridity, extremely cold weather, and isolated conditions. This study aimed to assess mood variations and coping strategies, as well as their possible modulation by group dynamics in a crew at the Belgrano II Argentine Antarctic Station throughout 1 year of confinement. Thirteen members of the Argentine Army completed emotional, coping and social dynamics questionnaires bimonthly in March, May, July, September and November. Results showed a significant decline in social dynamics scales, evidenced by decreases in perceived peer and hierarchical support. Additionally, coping strategies displayed a drop in mature defence throughout the expedition. A positive correlation was found between social support and recovery from stress. Our results highlight the importance of interpersonal relationships in psychological adjustment to isolation and extreme environments.

Desynchronised times? Chronobiology, (bio)medicalisation and the rhythms of life itself

This paper takes a critical look at the role of chronobiology in society today, with particular reference to its entanglements with health and medicine and whether or not this amounts to the (bio)medicalisation of our bodily rhythms. What we have here, we show, is a complex unfolding storyline, within and beyond medicine. On the one hand, the promises and problems of these circadian, infradian and ultradian rhythms for our health and well-being are now increasingly emphasised. On the other hand, a variety of new rhythmic interventions and forms of governance are now emerging within and beyond medicine, from chronotherapies and chronopharmacology to biocompatible school and work schedules, and from chronodiets to the optimisation of all we do according to our 'chronotypes'. Conceptualising these developments, we suggest challenges us to think within and beyond medicalisation to wider processes of biomedicalisation and the biopolitics of our body clocks: a vital new strand of chronopolitics today indeed which implicates us all in sickness and in health as the very embodiment of these rhythms of life itself. The paper concludes with a call for further research on these complex unfolding relations between chronobiology, health and society in these desynchronised times of ours.

[Change of transcription level of photoreceptor-specific CRX gene in the peripheral blood of the participants of an arctic world oceanic international flight]

The CRX gene encoding the cone-rod homeobox protein is a specific photoreceptor transcription factor crucial for retinal function. Persons temporarily residing in the Arctic zone during the polar summer may suffer from disturbances associated with extremely high ambient illumination. These environmental changes are mediated by retinal photoreceptors; therefore, it is important to study the expression of retinal genes in order to assess individual capacities of sensory adaptation to polar day conditions.

PURPOSE

To reveal the dynamics of CRX expression level in humans after a prolonged temporary exposure to polar day conditions.

MATERIAL AND METHODS

The study included 6 pilots (males from 39 to 69 y.o.) who participated in the Arctic World Oceanic International Flight Sever Vash (West to East, from 62°N 74°E to 72°N 114°E). Samples of peripheral blood for RNA isolation were collected at the start and at the end of the flight. The level of mRNA in the samples was evaluated based on the data of quantitative real-time PCR of the CRX gene, as well as the b2M and TBP housekeeping genes (reference).

RESULTS

Expression of the CRX gene in the studied group (p<0.01) was revealed; the total average level of mRNA was about 3 times higher prior to, and approximately 7 times higher after normalization to the b2M gene. Five pilots had increased expression of the CRX gene within the range of -1.53 to -3.07 (Z-score of <0 before the flight and >0 after the flight). In one pilot, the level of CRX expression was higher at the start, but it reduced by the end of the circumnavigation flight.

CONCLUSIONS

The results confirm the hypothesis that the CRX gene is expressed after a prolonged temporary exposure to polar day conditions. It was also revealed that during rapid adaptation, equal changes in the illumination of retinal photoreceptors lead to different individual dynamics of CRX expression.

Psychosocial issues in isolated and confined extreme environments

PALINKAS, L.A., and P. SUEDFELD. Psychosocial Issues in Isolated and Confined Extreme Environments. NEUROSCI BIOBEHAV REV (1) XXX-XXX, 2020. Psychosocial elements of behavior and performance will significantly impact the outcomes of long duration missions in space, ranging from individual and team decrements to positive benefits associated with successful adaptation. This paper reviews our current understanding of the individual, interpersonal and organizational issues related to living and working in isolated and confined extreme (ICE) environments. Individual issues include changes in emotions and cognitive performance; seasonal syndromes linked to changes in the physical environment; and positive effects of adapting to ICE environments. Interpersonal issues include processes of crew cohesion, tension and conflict; interpersonal relations and social support; the impact of group diversity and leadership styles on small group dynamics; and crew-mission control interactions. Organizational issues include the influence of organizational culture and mission duration on individual and group performance, crew autonomy, and managerial requirements for long duration missions. Improved screening and selection, leadership, coping and interpersonal skills training, and organizational change are key elements to optimizing adjustment to the environment and preventing decrements during and after long duration missions.

The effect of age and chronotype on seasonality, sleep problems, and mood

Seasonal affective disorder has been associated with sleep problems, young age, and an evening chronotype. A chronotype refers to an individual's preference in the timing of their sleep-wake cycle, as well as the time during the sleep-wake cycle when a person is most alert and energetic. Seasonality refers to season-dependent fluctuations in sleep length, social activity, mood, weight, appetite, and energy level. Evening chronotype is more common in young adults and morning chronotype more common in the elderly. This study aimed to estimate the differential contribution of chronotype and age on seasonality. A sample of n=410 participants were included in the study. The age groups showed significantly different results according to sleep parameters, depression, anxiety, stress, seasonality, and chronotype. The oldest group (>59 years) showed the lowest scores on all of these scales. According to a path analysis, chronotype and age predict propensity for seasonality. However, sleep problems were linked to chronotype but not to age. Older adults seem to be more resistant to seasonal changes that are perceived as a problem than young and middle aged adults. Future studies would benefit from considering cultural aspects and examine seasonality, chronotype, depression, and insomnia in longitudinal designs.

Daily associations between sleep and pain in patients with chronic musculoskeletal pain

Patients with chronic pain commonly report sleep problems, and the evidence for a relationship between sleep disturbance and pain seems robust. The day-to-day associations between these constructs are less well studied, particularly with objective sleep measures such as actigraphy. Moreover, the concurrent presence of negative affective symptoms, as well as seasonality effects at extreme latitudes may complicate it further. Here, we studied 56 patients with chronic primary musculoskeletal pain conditions, contributing data in two separate 7-day data-collection periods during the summer and winter, respectively. The effect of self-reported sleep quality, and actigraphy measured sleep duration, efficiency and timing on next-day pain, as well as the effect of pain on the same sleep indices were estimated by generalised linear mixed regression models. The models were additionally adjusted for age, sex, education, data collection period, weekend, season and mental distress, with the latter two also specified as moderators. We observed a significant effect of pain as a predictor of next-night sleep quality (p = .003) and marginally of next-night sleep duration (p = .079). Conversely, sleep quality tentatively predicted next-day pain (p = .063). No other day-to-day associations were present. Mental distress was the strongest predictor of pain, but it did not modify the sleep-pain associations, nor did season. In conclusion pain, sleep quality and mental distress are closely related, underscoring the importance of encompassing this complexity in assessment and treatment of patients with chronic pain.

Seasonal variations in serum levels of vitamin D and other biochemical markers among KSA patients prior to thyroid surgery

Objectives

Serum levels of vitamin D can vary between seasons, which may affect serum calcium levels in post-thyroidectomy patients. This study aimed to determine seasonal variations in serum levels of vitamin D and other biochemical markers in patients prior to thyroid surgery in a KSA hospital.

Methods

In this study, we analysed the data of 685 post-thyroidectomy patients. The preoperative laboratory values of all patients were collected, and the patients were categorized into groups based on the month when the surgical procedure was performed as follows: cold (November–February) and warm/hot groups (March–October).

Results

Serum vitamin D levels were deficient in 70% of the patients, insufficient in 18%, and optimal in 12%. The mean age of patients in the deficient group was significantly lower than that in the optimal group. There were significantly more patients who had vitamin D deficiency during the cold season than during the warm/hot season (p = 0.024). Serum vitamin D levels did not vary between seasons (p = 0.836); however, the preoperative magnesium and thyroid stimulating hormone (TSH) levels were significantly higher during the warm/hot season than during the cold season (p = 0.039 and p < 0.001, respectively). Preoperative calcium level was not significantly different between the cold and warm/hot months (p = 0.282).

Conclusion

This study suggests a non-significant seasonal fluctuation in serum levels of vitamin D with insignificant variation in serum calcium levels during cold and warm/hot seasons. The findings necessitate a careful review of the patients’ biochemical status prior to surgery. Future prospective longitudinal studies are needed to confirm this variability.

Jet Lag Recovery and Memory Functions Are Correlated with Direct Light Effects on Locomotion

Jet lag is a circadian disruption that affects millions of people, resulting, among other things, in extreme sleepiness and memory loss. The hazardous implications of such effects are evident in situations in which focus and attention are required. Remarkably, there is a limited understanding of how jet lag recovery and associated memory loss vary year round under different photoperiods. Here we show, using different cycles representing winter, summer, and equinox in male mice, that jet lag recovery and memory vary significantly with photoperiod changes. We uncover a positive correlation of acute light effects on circadian-driven locomotion (known as negative masking) with photoentrainment speed and memory enhancement during jet lag. Specifically, we show that enhancing or reducing negative masking is correlated with better or worse memory performance, respectively. This study indicates that in addition to timed-light exposure for phase shifting, the negative masking response could also be biologically relevant when designing effective treatments of jet lag.

Sleep in Isolated, Confined, and Extreme (ICE): A Review on the Different Factors Affecting Human Sleep in ICE

The recently renewed focus on the human exploration of outer space has boosted the interest toward a variety of questions regarding health of astronauts and cosmonauts. Among the others, sleep has traditionally been considered a central issue. To extend the research chances, human sleep alterations have been investigated in several analog environments, called ICEs (Isolated, Confined, and Extreme). ICEs share different features with the spaceflight itself and have been implemented in natural facilities and artificial simulations. The current paper presents a systematic review of research findings on sleep disturbances in ICEs. We looked for evidence from studies run in polar settings (mostly Antarctica) during space missions, Head-Down Bed-Rest protocols, simulations, and in a few ICE-resembling settings such as caves and submarines. Even though research has shown that sleep can be widely affected in ICEs, mostly evidencing general and non-specific changes in REM and SWS sleep, results show a very blurred picture, often with contradictory findings. The variable coexistence of the many factors characterizing the ICE environments (such as isolation and confinement, microgravity, circadian disentrainment, hypoxia, noise levels, and radiations) does not provide a clear indication of what role is played by each factor per se or in association one with each other in determining the pattern observed, and how. Most importantly, a number of methodological limitations contribute immensely to the unclear pattern of results reported in the literature. Among them, small sample sizes, small effect sizes, and large variability among experimental conditions, protocols, and measurements make it difficult to draw hints about whether sleep alterations in ICEs do exist due to the specific environmental characteristics, and which of them plays a major role. More systematic and cross-settings research is needed to address the mechanisms underlying the sleep alterations in ICE environments and possibly develop appropriate countermeasures to be used during long-term space missions.

Altitude and latitude variations in trait-impulsivity, depression, anxiety, suicidal risk, and negative alcohol-related consequences in Argentinean adolescents

The aims of this research were threefold: 1) to analyze mental health state both general (GMHS, i.e., self-perceived health and psychological distress) and specific (SMHS; i.e., depression, trait-anxiety, negative alcohol-related consequences, and suicidal risk), and impulsivity-related traits (i.e., negative urgency, positive urgency, [lack of] perseverance, [lack of] premeditation, and sensation seeking) in a sample of Argentinean adolescent college students, in function of sex (women, men) and three different altitude-latitude regions (high-north, middle-center, low-south), for identifying common and specific features; 2) to analyze relationships between impulsivity-related traits and indicators of GMHS and SMHS, in the entire sample and in each altitude-latitude region, for understanding the importance of impulsivity-related traits in these forms of mental disorders; and 3) to analyze bivariate relationships between depression, trait-anxiety, negative alcohol-related consequences, and suicidal risk, in the entire sample and considering the three altitude-latitude regions, for testing two-disorder comorbidities. Scores on impulsivity-related traits differed by sex and by altitude-latitude region. GMHS and SMHS differed by sex but not by altitude-latitude region. Several relationships were found between impulsivity-related traits, GMHS, and SMHS as well as between indicators of SMHS. Some of these relationships were dependent on altitude-latitude regions, and implications of these findings were discussed.

Effect of sleep loss on executive function and plasma corticosterone levels in an arctic-breeding songbird, the Lapland longspur (Calcarius lapponicus)

Sleep is a fundamental component of vertebrate life, although its exact functions remain unclear. Animals deprived of sleep typically show reduced neurobiological performance, health, and in some cases, survival. However, a number of vertebrate taxa exhibit adaptations that permit normal activities even when sleep is reduced. Lapland longspurs (Calcarius lapponicus), arctic-breeding passerine birds, exhibit around-the-clock activity during their short breeding season, with an inactive period of ca. 4 h/day. Whether behavioral or physiological costs occur from sleep loss (SL) in this species is unknown. To assess the effects of SL, wild-caught male longspurs were placed in captivity (12L:12D) and trained for one month to successfully learn color association and spatial memory tasks. Birds were then placed in automated sleep fragmentation cages that utilize a moving wire to force movement every 1 min (60 arousals/h) during 12D (inactive period) or control conditions (during 12L; active period). After SL (or control) treatment, birds were presented with color association and spatial memory tasks a final time to assess executive function. Baseline plasma corticosterone concentration, body mass, and satiety were also measured. SL significantly elevated corticosterone levels and increased accuracy during color association recall but did not affect the overall time required to complete the task. SL had no effect upon spatial memory, body mass, or satiety. Taken together, these results suggest that Lapland longspurs exhibit a degree of behavioral, but not physiological, insensitivity to acute SL. Whether elevated plasma concentrations of corticosterone play a direct role in ameliorating cognitive deficits from SL require additional study.

Seasonality in pain, sleep and mental distress in patients with chronic musculoskeletal pain at latitude 69° N

Seasonality is evident in several aspects of human health and behavior, whereas seasonality in chronic pain is less well studied. We examined seasonal variation in pain severity and pain dissemination, as well as in pain-associated conditions, such as sleep impairment, sleep timing, mental distress, fatigue and physical activity. We also examined if any of these associated conditions moderated the seasonality in pain. This prospective study was conducted in the subarctic municipality of Tromsø, Norway (69º North), on a sample of patients with chronic musculoskeletal pain (N = 56). Data were collected with self-report questionnaires and objective actigraphy measures (7 days) twice: winter and summer. Mixed linear regression models were fitted. A modest seasonality effect was observed in pain severity (highest in summer), but not in pain dissemination. Seasonality with increased physical activity and delayed sleep timing in the summer was also present. The remaining pain-associated self-report or objective measures indicated no seasonality. The season-pain association was not significantly moderated by any of the pain-associated conditions. Previous studies on healthy individuals residing in polar areas have suggested an opposite seasonal effect with delay of the sleep-wake rhythm in winter. Our results based on a clinical sample thus represent a novel finding that needs to be examined further with regard to seasonal circadian entrainment and alignment in pain populations. These results may have clinical value for the treatment of patients with musculoskeletal pain as seasonality may require seasonal adjustments of pain treatment strategies.

Investigation on the influence of isolated environment on human psychological and physiological health

Crewmembers are working and living in isolated environment lacking natural light and perception. Although their health problems have been documented, the mechanism has not been thoroughly investigated. The aim of the present study is to investigate the psychological and physiological influences of isolated environment on crewmember's health. On account of complexity of the isolated environment, it is necessary to have a manually controllable system to simulate research platform-Bioregenerative Life Support System (BLSS). Symptom checklist 90 (SCL-90) was used to complete emotional status test. Urine samples were collected for metabonomics and hormone secretion analysis. Fecal samples were collected for intestinal microorganisms analysis. Crewmembers (n = 4) followed strict daily schedule during the experimental period. Five emotional factors were significantly (P < 0.05) increased, differential metabolites were enriched in tryptophan metabolism pathway, the relative abundance of Prevotella decreased significantly (P < 0.0001) when crewmembers in isolated environment without natural light. Hormone (melatonin, cortisol) secretion rhythm also changed. Significant positive correlation (r = 0.805, P < 0.05) between cortisol secretion and anxiety was observed. In conclusion, natural light simulation in an isolated environment may have a positive effect on the physiological and psychological health of the crewmember.

Is there a seasonal variation of survival after systemic chemotherapy for metastatic castration-resistant prostate cancer in a rural part of North Norway?

The winter darkness or polar night induces endocrine and metabolic mechanisms, which might reduce the efficacy of cancer treatment and thus contribute to shorter survival. Moreover, season-and weather-related treatment delays and irregularities might also cause reduced efficacy of anti-cancer drugs. Therefore, this study evaluated the prognostic impact of timing of chemotherapy (start during winter darkness or outside of this season), in terms of overall survival, in patients with metastatic castration-resistant prostate cancer (MCRPC) who received oncology care at the Nordland hospital Bodø. The study included 111 patients treated with first-line docetaxel chemotherapy for MCRPC. Twenty patients (18%) started their treatment during winter darkness (arbitrarily defined as ±4 weeks around 21 December). In unadjusted univariate analysis, survival was shorter in this group (median 10.2 vs. 18.9 months, p = 0.055). However, not all baseline parameters were equally distributed between the two groups. In multivariable-adjusted Cox regression analysis accounting for several confounding variables, only one factor was statistically significant: pre-chemotherapy serum lactate dehydrogenase level (a surrogate marker of disease burden). Thus, the present results suggest that seasonal variation is not a major contributor to the diverging survival outcomes observed after docetaxel chemotherapy.

Subjective time estimation in Antarctica: The impact of extreme environments and isolation on a time production task

Interval timing measures time estimation in the seconds-to-minutes range. Antarctica provides a real-world context to study the effect of extreme photoperiods and isolation on time perception. The aim of this study was to explore interval timing as a cognitive measure in the crew of Belgrano II Argentine Antarctic Station. A total of 13 subjects were assessed for interval timing in short (3 s), intermediate (6 s) and long (12 s) duration stimuli. Measures were taken during the morning and evening, five times along the year. Significant variations were found for 3 s and 6 s during the morning and 6 s during the evening. Results suggest an impact of isolation on morning performances and an effect of the polar night on evening measures. These findings shed some light on the use of interval timing as a cognitive test to assess performance in extreme environments.

An exploratory study examining the associations between sunlight exposure, sleep behaviours and sleep outcomes during an Arctic summer

Few evidence-based recommendations exist for maintaining healthy sleep during Arctic summers. Our study aimed to examine associations between sleep hygiene, sunlight exposure and sleep outcomes in workers living in and/or near the Arctic Circle during a 24-h light period. A survey was administered July 2017 to 19 workers at 3 Arctic base camps in Northeastern Alaska. Participants with poorer sleep hygiene reported increased sleepiness (r=.62, p=0.01); this correlation remained moderately strong, albeit not statistically significant (NS), after controlling for shift work (r=.46, p=0.06). No other statistically significant correlations between sleep hygiene and sleep outcomes were found. Weekly daytime (<8pm) and evening (>8pm) sunlight exposures, estimated from daily self-reported sunlight exposures for a typical workday and day off, were dichotomised, based on means, into: longer (>45 h/week) versus shorter (<45 h/week) daytime exposures, and longer (>16 h/week) versus shorter (<16 h/week) evening exposures. Participants reporting longer, versus shorter, weekly daytime sunlight exposure had statistically significantly (Mann-Whitney U=18.00, Z=-1.98, p≤0.05) decreased median sleep duration (6 h, 18 min versus 8 h, respectively) during the past month. Correlations of r≥.3 for longer, vis-à-vis shorter, daylight sunlight exposure suggest it could be related to poorer sleep outcomes, such as insufficient sleep and sleep quality, yet, as these correlations were NS, future work is needed to determine this. Weak or no correlations (and NS differences) were found for longer, versus shorter, weekly evening sunlight exposure and sleep outcomes. Findings support previous research suggesting self-regulation behaviours alone are not protective against poor sleep in Arctic environments. Sleep outcomes did not differ statistically significantly by evening sunlight exposure length. Longer weekly daytime sunlight exposure, versus shorter, was significantly associated with decreased sleep duration. Results from this exploratory study should be confirmed in studies using larger sample sizes.

Effects of timing of food intake on eating patterns, diet quality and weight gain during pregnancy

Studies have suggested that meal timing plays a role in nutritional health, but this subject has not been sufficiently studied in pregnant women. We analysed the effect that timing of food intake has on eating patterns, diet quality and weight gain in a prospective cohort study with 100 pregnant women. Data were collected once per trimester: 4th-12th, 20th-26th and 30th-37th weeks. Food intake was evaluated using three 24-h dietary recalls, which were used to assess eating patterns and diet quality. Distribution of energy and macronutrient intake throughout the day was considered eating patterns. Diet quality was assessed using the Brazilian Healthy Eating Index-Revised. Weight gain was evaluated during each trimester. Women were classified as early or late timing of the first and last eating episodes if these values were below or above the median of the population, respectively (first eating episode = 08.38 hours; last eating episode = 20.20 hours). Generalised estimating equation models adjusted for confounders were used to determine the effects of timing of the first and last eating episodes (groups) and gestational trimesters (time) (independent variable) on eating patterns, diet quality and weight gain (dependent variables). Early eaters of the first eating episode have a higher percentage of energy and carbohydrate intake in morning and a lower at evening meals. They also have a better diet quality for fruit components when compared with late eaters of the first eating episode. Our results emphasise the importance of considering meal timing in the nutritional antenatal guidelines to promote maternal-fetal health.

Preparing for Mars: human sleep and performance during a 13 month stay in Antarctica

Study Objectives

Manned spaceflights from Earth to Mars will likely become reality within the next decades. Humans will be exposed to prolonged isolation, confinement, and altered photoperiods under artificial atmospheric conditions, with potential adverse effects on sleep and performance. On Earth, polar environments serve as space analogs to study human adaptation; yet, few studies include polysomnography due to operational constraints.

Methods

Polysomnography, self-reported sleepiness and fatigue, and psychomotor performance were measured every 6 weeks in 13 males ("Hivernauts") during a 13 month winter-over campaign at Concordia (Antarctica). Stability and robustness of interindividual differences were examined by means of intraclass correlations.

Results

Hivernauts present with high-altitude periodic breathing, increased sleep onset latencies, and reduced psychomotor speed. Except for obstructive apneas, all sleep, sleepiness, and psychomotor performance variables remain stable over time. Individual differences in respiratory variables show the highest degree of stability and robustness, followed by fatigue and situational sleepiness, sleep fragmentation, and psychomotor speed, suggesting moderate to substantial trait-like characteristics for these variables. Phase delays are suspected in Hivernauts, both in individuals with imposed and self-selected bedtimes. A significant decline in psychomotor speed over time is observed in the latter group.

Conclusions

Space analog conditions such as isolated confinement, extreme photoperiods, and altered atmospheric conditions affect human sleep and performance. However, individual responses to these extreme environmental challenges show large differences and remain relatively stable under prolonged exposure. Ad hoc polysomnographic, including respiratory function monitoring is therefore recommended for selecting eligible candidates for extraterrestrial sojourns.

Metatranscriptomic and metabolite profiling reveals vertical heterogeneity within a Zygnema green algal mat from Svalbard (High Arctic)

Within streptophyte green algae Zygnematophyceae are the sister group to the land plants that inherited several traits conferring stress protection. Zygnema sp., a mat-forming alga thriving in extreme habitats, was collected from a field site in Svalbard, where the bottom layers are protected by the top layers. The two layers were investigated by a metatranscriptomic approach and GC-MS-based metabolite profiling. In the top layer, 6569 genes were significantly upregulated and 149 were downregulated. Upregulated genes coded for components of the photosynthetic apparatus, chlorophyll synthesis, early light-inducible proteins, cell wall and carbohydrate metabolism, including starch-degrading enzymes. An increase in maltose in the top layer and degraded starch grains at the ultrastructural levels corroborated these findings. Genes involved in amino acid, redox metabolism and DNA repair were upregulated. A total of 29 differentially accumulated metabolites (out of 173 identified ones) confirmed higher metabolic turnover in the top layer. For several of these metabolites, differential accumulation matched the transcriptional changes of enzymes involved in associated pathways. In summary, the findings support the hypothesis that in a Zygnema mat the top layer shields the bottom layers from abiotic stress factors such as excessive irradiation.

Chronotype-Dependent Changes in Sleep Habits Associated with Dim Light Melatonin Onset in the Antarctic Summer

Dim light melatonin onset (DLMO) is the most reliable measure of human central circadian timing. Its modulation by light exposure and chronotype has been scarcely approached. We evaluated the impact of light changes on the interaction between melatonin, sleep, and chronotype in university students (n = 12) between the Antarctic summer (10 days) and the autumn equinox in Montevideo, Uruguay (10 days). Circadian preferences were tested by validated questionnaires. A Morningness–Eveningness Questionnaire average value (47 ± 8.01) was used to separate late and early participants. Daylight exposure (measured by actimetry) was significantly higher in Antarctica versus Montevideo in both sensitive time windows (the morning phase-advancing and the evening phase-delaying). Melatonin was measured in hourly saliva samples (18–24 h) collected in dim light conditions (<30 lx) during the last night of each study period. Early and late participants were exposed to similar amounts of light in both sites and time windows, but only early participants were significantly more exposed during the late evening in Antarctica. Late participants advanced their DLMO with no changes in sleep onset time in Antarctica, while early participants delayed their DLMO and sleep onset time. This different susceptibility to respond to light may be explained by a subtle difference in evening light exposure between chronotypes.

Sleep, napping and alertness during an overwintering mission at Belgrano II Argentine Antarctic station

During Antarctic isolation personnel are exposed to extreme photoperiods. A frequent observation is a sleep onset phase delay during winter. It is not known if, as a result, daytime sleeping in the form of naps increases. We sought to assess sleep patterns - with focus on daytime sleeping - and alertness in a Latin American crew overwintering in Argentine Antarctic station Belgrano II. Measurements were collected in 13 males during March, May, July, September and November, and included actigraphy and psychomotor vigilance tasks. Sleep duration significantly decreased during winter. A total of eight participants took at least one weekly nap across all measurement points. During winter, the nap onset was delayed, its duration increased and its efficiency improved. We observed a significant effect of seasonality in the association of evening alertness with sleep onset. Our results replicate previous findings regarding sleep during overwintering in Antarctica, adding the description of the role of napping and the report of a possible modulatory effect of seasonality in the relation between sleep and alertness. Napping should be considered as an important factor in the scheduling of activities of multicultural crews that participate in Antarctica.

Human Physiology During Exposure to the Cave Environment: A Systematic Review With Implications for Aerospace Medicine

Background: Successful long-duration missions outside low-Earth orbit will depend on technical and physiological challenges under abnormal environmental conditions. Caves, characterized by absence of light, confinement, three-dimensional human movement and long-duration isolation, are identifiably one of the earliest examples of scientific enquiry into space analogs. However, little is known about the holistic human physiological response during cave exploration or prolonged habitation.

Objectives: The aim of our review was to conduct a systematic bibliographic research review of the effects of short and prolonged exposure to a cave environment on human physiology, with a view to extend the results to implications for human planetary exploration missions.

Methods: A systematic search was conducted following the structured PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for electronic databases.

Results: The search retrieved 1,519 studies. There were 50 articles selected for further consideration, of which 31 met our inclusion criteria. Short-term cave exposure studies have investigated visual dysfunction, cardiovascular, endocrine-metabolic, immunologic-hematological and muscular responses in humans. Augmentations of heart rate, muscular damage, initial anticipatory stress reaction and inflammatory responses were reported during caving activity. Prolonged exposure studies mainly investigated whether biological rhythms persist or desist in the absence of standard environmental conditions. Changes were evident in estimated vs. actual rest-activity cycle periods and external desynchronization, body temperature, performance reaction time and heart rate cycles. All studies have shown a marked methodological heterogeneity and lack reproduction under controlled conditions.

Conclusions: This review facilitates a further comparison of the proposed physiological impact of a subterranean space analog environment, with existing knowledge in related disciplines pertaining to human operative preparation under challenging environmental conditions. This comprehensive overview should stimulate more reproducible research on this topic and offer the opportunity to advance study design and focus future human research in the cave environment on noteworthy, reproducible projects.

Sex differences in stress and immune responses during confinement in Antarctica

Background

Antarctica challenges human explorers by its extreme environment. The effects of these unique conditions on the human physiology need to be understood to best mitigate health problems in Antarctic expedition crews. Moreover, Antarctica is an adequate Earth-bound analogue for long-term space missions. To date, its effects on human physiology have been studied mainly in male cohorts though more female expeditioners and applicants in astronaut training programs are selected. Therefore, the identification of sex differences in stress and immune reactions are becoming an even more essential aim to provide a more individualized risk management.

Methods

Ten female and 16 male subjects participated in three 1-year expeditions to the German Antarctic Research Station Neumayer III. Blood, saliva, and urine samples were taken 1–2 months prior to departure, subsequently every month during their expedition, and 3–4 months after return from Antarctica. Analyses included cortisol, catecholamine and endocannabinoid measurements; psychological evaluation; differential blood count; and recall antigen- and mitogen-stimulated cytokine profiles.

Results

Cortisol showed significantly higher concentrations in females than males during winter whereas no enhanced psychological stress was detected in both sexes. Catecholamine excretion was higher in males than females but never showed significant increases compared to baseline. Endocannabinoids and N-acylethanolamides increased significantly in both sexes and stayed consistently elevated during the confinement. Cytokine profiles after in vitro stimulation revealed no sex differences but resulted in significant time-dependent changes. Hemoglobin and hematocrit were significantly higher in males than females, and hemoglobin increased significantly in both sexes compared to baseline. Platelet counts were significantly higher in females than males. Leukocytes and granulocyte concentrations increased during confinement with a dip for both sexes in winter whereas lymphocytes were significantly elevated in both sexes during the confinement.

Conclusions

The extreme environment of Antarctica seems to trigger some distinct stress and immune responses but—with the exception of cortisol and blood cell counts—without any major relevant sex-specific differences. Stated sex differences were shown to be independent of enhanced psychological stress and seem to be related to the environmental conditions. However, sources and consequences of these sex differences have to be further elucidated.

Melatonin: Countering Chaotic Time Cues

Last year melatonin was 60 years old, or at least its discovery was 60 years ago. The molecule itself may well be almost as old as life itself. So it is time to take yet another perspective on our understanding of its functions, effects and clinical uses. This is not a formal review-there is already a multitude of systematic reviews, narrative reviews, meta-analyses and even reviews of reviews. In view of the extraordinary variety of effects attributed to melatonin in the last 25 years, it is more of an attempt to sort out some areas where a consensus opinion exists, and where placebo controlled, randomized, clinical trials have confirmed early observations on therapeutic uses. The current upsurge of concern about the multiple health problems associated with disturbed circadian rhythms has generated interest in related therapeutic interventions, of which melatonin is one. The present text will consider the physiological role of endogenous melatonin, and the mostly pharmacological effects of exogenous treatment, on the assumption that normal circulating concentrations represent endogenous pineal production. It will concentrate mainly on the most researched, and accepted area of therapeutic use and potential use of melatonin-its undoubted ability to realign circadian rhythms and sleep-since this is the author's bias. It will touch briefly upon some other systems with prominent rhythmic attributes including certain cancers, the cardiovascular system, the entero-insular axis and metabolism together with the use of melatonin to assess circadian status. Many of the ills of the developed world relate to deranged rhythms-and everything is rhythmic unless proved otherwise.

Delayed Sleep in Winter Related to Natural Daylight Exposure among Arctic Day Workers

Natural daylight exposures in arctic regions vary substantially across seasons. Negative consequences have been observed in self-reports of sleep and daytime functions during the winter but have rarely been studied in detail. The focus of the present study set out to investigate sleep seasonality among indoor workers using objective and subjective measures. Sleep seasonality among daytime office workers (n = 32) in Kiruna (Sweden, 67.86° N, 20.23° E) was studied by comparing the same group of workers in a winter and summer week, including work and days off at the weekend, using actigraphs (motion loggers) and subjective ratings of alertness and mood. Actigraph analyses showed delayed sleep onset of 39 min in winter compared to the corresponding summer week (p < 0.0001) and shorter weekly sleep duration by 12 min (p = 0.0154). A delay of mid-sleep was present in winter at workdays (25 min, p < 0.0001) and more strongly delayed during days off (46 min, p < 0.0001). Sleepiness levels were higher in winter compared to summer (p < 0.05). Increased morning light exposure was associated with earlier mid-sleep (p < 0.001), while increased evening light exposure was associated with delay (p < 0.01). This study confirms earlier work that suggests that lack of natural daylight delays the sleep/wake cycle in a group of indoor workers, despite having access to electric lighting. Photic stimuli resulted in a general advanced sleep/wake rhythm during summer and increased alertness levels.

Psychological Hibernation in Antarctica

Human activity in Antarctica has increased sharply in recent years. In particular during the winter months, people are exposed to long periods of isolation and confinement and an extreme physical environment that poses risks to health, well-being and performance. The present study aimed to gain a better understanding of processes contributing to psychological resilience in this context. Specifically, the study examined how the use of coping strategies changed over time, and the extent to which changes coincided with alterations in mood and sleep. Two crews (N = 27) spending approximately 10 months at the Concordia station completed the Utrecht Coping List, the Positive and Negative Affect Schedule (PANAS), and a structured sleep diary at regular intervals (x 9). The results showed that several variables reached a minimum value during the midwinter period, which corresponded to the third quarter of the expedition. The effect was particularly noticeable for coping strategies (i.e., active problem solving, palliative reactions, avoidance, and comforting cognitions). The pattern of results could indicate that participants during Antarctic over-wintering enter a state of psychological hibernation as a stress coping mechanism.

Body composition and metabolic changes during a 520-day mission simulation to Mars

PURPOSE

The "Mars-500 project" allowed to evaluate the changes in psychological/physiological adaptation over a prolonged confinement, in order to gather information for future missions. Here, we evaluated the impact of confinement and isolation on body composition, glucose metabolism/insulin resistance and adipokine levels.

METHODS

The "Mars-500 project" consisted of 520 consecutive days of confinement from June 3, 2010 to Nov 4, 2011. The crew was composed of six male subjects (three Russians, two Europeans, and one Chinese) with a median age of 31 years (range 27-38 years).

RESULTS

During the 520-day confinement, total body mass and BMI progressively decreased, reaching a significant difference at the end (417 days) of the observation period (- 9.2 and - 5.5%, respectively). Fat mass remained unchanged. A progressive and significant increase of fasting plasma glucose was observed between 249 and 417 days (+ 10/+ 17% vs baseline), with a further increase at the end of confinement (up to + 30%). Median plasma insulin showed a non-significant early increment (60 days; + 86%). Total adiponectin halved (- 47%) 60 days after hatch closure, remaining at this nadir (- 51%) level for a further 60 days. High molecular weight adiponectin remained significantly lower from 60 to 168 days.

CONCLUSIONS

Based on these data, countermeasures may be envisioned to balance the potentially harmful effects of prolonged confinement, including a better exercise program, with accurate monitoring of (1) the individual activity and (2) the relationship between body composition and metabolic derangement.