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Clocks & Sleep, Volume 3, Issue 1 (March 2021) – 13 articles

Cover Story (view full-size image): External light cues strongly affect our “inner” clock. Growing evidence suggests that short-wavelength light emitted by smartphones has a negative impact on sleep, circadian rhythmicity, and alertness. This study aimed to assess whether blue light filters can prevent such undesired effects. Their preliminary results corroborate and extend previous findings by showing a negative impact of evening smartphone usage on sleep, circadian parameters as well as alertness, but blue light filters were able to attenuate these effects at least partially. View this paper.
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Review
Effects of Exercise in Patients with Obstructive Sleep Apnoea
Clocks & Sleep 2021, 3(1), 227-235; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010013 - 03 Mar 2021
Viewed by 1083
Abstract
Obstructive sleep apnoea (OSA) constitutes a public health problem, with various systemic consequences that can increase cardiovascular morbidity and mortality as well as increase healthcare expenditure. This review discusses the rationale and effects of using general physical exercise, oropharyngeal exercises, and respiratory muscle [...] Read more.
Obstructive sleep apnoea (OSA) constitutes a public health problem, with various systemic consequences that can increase cardiovascular morbidity and mortality as well as increase healthcare expenditure. This review discusses the rationale and effects of using general physical exercise, oropharyngeal exercises, and respiratory muscle training as an adjunctive treatment for patients with sleep apnoea. The recommended treatment for OSA is the use of continuous positive airway pressure, which is a therapy that prevents apnoea events by keeping the airways open. In the last decade, coadjuvant treatments that aim to support weight loss (including diet and physical exercise) and oropharyngeal exercises have been proposed to lower the apnoea/hypopnoea index among patients with OSA. Based on the available evidence, health professionals could decide to incorporate these therapeutic strategies to manage patients with sleep apnoea. Full article
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Review
Circadian Rhythms of the Hypothalamus: From Function to Physiology
Clocks & Sleep 2021, 3(1), 189-226; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010012 - 25 Feb 2021
Viewed by 1376
Abstract
The nearly ubiquitous expression of endogenous 24 h oscillations known as circadian rhythms regulate the timing of physiological functions in the body. These intrinsic rhythms are sensitive to external cues, known as zeitgebers, which entrain the internal biological processes to the daily [...] Read more.
The nearly ubiquitous expression of endogenous 24 h oscillations known as circadian rhythms regulate the timing of physiological functions in the body. These intrinsic rhythms are sensitive to external cues, known as zeitgebers, which entrain the internal biological processes to the daily environmental changes in light, temperature, and food availability. Light directly entrains the master clock, the suprachiasmatic nucleus (SCN) which lies in the hypothalamus of the brain and is responsible for synchronizing internal rhythms. However, recent evidence underscores the importance of other hypothalamic nuclei in regulating several essential rhythmic biological functions. These extra-SCN hypothalamic nuclei also express circadian rhythms, suggesting distinct regions that oscillate either semi-autonomously or independent of SCN innervation. Concurrently, the extra-SCN hypothalamic nuclei are also sensitized to fluctuations in nutrient and hormonal signals. Thus, food intake acts as another powerful entrainer for the hypothalamic oscillators’ mediation of energy homeostasis. Ablation studies and genetic mouse models with perturbed extra-SCN hypothalamic nuclei function reveal their critical downstream involvement in an array of functions including metabolism, thermogenesis, food consumption, thirst, mood and sleep. Large epidemiological studies of individuals whose internal circadian cycle is chronically disrupted reveal that disruption of our internal clock is associated with an increased risk of obesity and several neurological diseases and disorders. In this review, we discuss the profound role of the extra-SCN hypothalamic nuclei in rhythmically regulating and coordinating body wide functions. Full article
(This article belongs to the Special Issue Role of Sleep and Circadian Rhythms in Health)
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Comment
Comment Concerning the Effects of Light Intensity on Melatonin Suppression in the Review “Light Modulation of Human Clocks, Wake, and Sleep” by A. Prayag et al.
Clocks & Sleep 2021, 3(1), 181-188; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010011 - 10 Feb 2021
Cited by 2 | Viewed by 933
Abstract
Dose-response curves for circadian phase shift and melatonin suppression in relation to white or monochromatic nighttime illumination can be scaled to melanopic weighed illumination for normally constricted pupils, which makes them easier to interpret and compare. This is helpful for a practical applications. [...] Read more.
Dose-response curves for circadian phase shift and melatonin suppression in relation to white or monochromatic nighttime illumination can be scaled to melanopic weighed illumination for normally constricted pupils, which makes them easier to interpret and compare. This is helpful for a practical applications. Full article
(This article belongs to the Section Clocks & Sleep and Zeitgebers (Light))
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Editorial
Acknowledgment to Reviewers of Clocks & Sleep in 2020
Clocks & Sleep 2021, 3(1), 179-180; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010010 - 01 Feb 2021
Viewed by 750
Abstract
The peer review process represents the driving force of journal development, with reviewers acting as the gatekeepers who ensure that Clocks & Sleep maintains its high-quality standard of published papers [...] Full article
Review
Non-Pharmacological Interventions to Improve Chronic Disease Risk Factors and Sleep in Shift Workers: A Systematic Review and Meta-Analysis
Clocks & Sleep 2021, 3(1), 132-178; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010009 - 28 Jan 2021
Cited by 2 | Viewed by 1495
Abstract
Shift work is associated with adverse chronic health outcomes. Addressing chronic disease risk factors including biomedical risk factors, behavioural risk factors, as well as sleep and perceived health status, affords an opportunity to improve health outcomes in shift workers. The present study aimed [...] Read more.
Shift work is associated with adverse chronic health outcomes. Addressing chronic disease risk factors including biomedical risk factors, behavioural risk factors, as well as sleep and perceived health status, affords an opportunity to improve health outcomes in shift workers. The present study aimed to conduct a systematic review, qualitative synthesis, and meta-analysis of non-pharmacological interventions targeting chronic disease risk factors, including sleep, in shift workers. A total of 8465 records were retrieved; 65 publications were eligible for inclusion in qualitative analysis. Random-effects meta-analysis were conducted for eight eligible health outcomes, including a total of thirty-nine studies. Interventions resulted in increased objective sleep duration (Hedges’ g = 0.73; CI: 0.36, 1.10, k = 16), improved objective sleep efficiency (Hedges’ g = 0.48; CI: 0.20, 0.76, k = 10) and a small increase in both subjective sleep duration (Hedges’ g = 0.11; CI: −0.04, 0.27, k = 19) and sleep quality (Hedges’ g = 0.11; CI: −0.11, 0.33, k = 21). Interventions also improved perceived health status (Hedges’ g = 0.20; CI: −0.05, 0.46, k = 8), decreased systolic (Hedges’ g = 0.26; CI: −0.54, 0.02, k = 7) and diastolic (Hedges’ g = 0.06; CI: −0.23, 0.36, k = 7) blood pressure, and reduced body mass index (Hedges’ g = −0.04; CI: −0.37, 0.29, k = 9). The current study suggests interventions may improve chronic disease risk factors and sleep in shift workers; however, this could only be objectively assessed for a limited number of risk factor endpoints. Future interventions could explore the impact of non-pharmacological interventions on a broader range of chronic disease risk factors to better characterise targets for improved health outcomes in shift workers. Full article
(This article belongs to the Special Issue Effects of Pre-Sleep Artificial Light on Cognition and Sleep)
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Review
Light, Sleep and Performance in Diurnal Birds
Clocks & Sleep 2021, 3(1), 115-131; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010008 - 28 Jan 2021
Cited by 1 | Viewed by 1446
Abstract
Sleep has a multitude of benefits and is generally considered necessary for optimal performance. Disruption of sleep by extended photoperiods, moonlight and artificial light could therefore impair performance in humans and non-human animals alike. Here, we review the evidence for effects of light [...] Read more.
Sleep has a multitude of benefits and is generally considered necessary for optimal performance. Disruption of sleep by extended photoperiods, moonlight and artificial light could therefore impair performance in humans and non-human animals alike. Here, we review the evidence for effects of light on sleep and subsequent performance in birds. There is accumulating evidence that exposure to natural and artificial sources of light regulates and suppresses sleep in diurnal birds. Sleep also benefits avian cognitive performance, including during early development. Nevertheless, multiple studies suggest that light can prolong wakefulness in birds without impairing performance. Although there is still limited research on this topic, these results raise intriguing questions about the adaptive value of sleep. Further research into the links between light, sleep and performance, including the underlying mechanisms and consequences for fitness, could shed new light on sleep evolution and urban ecology. Full article
(This article belongs to the Special Issue Effects of Pre-Sleep Artificial Light on Cognition and Sleep)
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Article
Prevalence of Insomnia in Two Saskatchewan First Nation Communities
Clocks & Sleep 2021, 3(1), 98-114; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010007 - 28 Jan 2021
Viewed by 866
Abstract
Insomnia is a common problem in Canada and has been associated with increased use of health care services and economic burden. This paper examines the prevalence and risk factors for insomnia in two Cree First Nation communities in Saskatchewan, Canada. Five hundred and [...] Read more.
Insomnia is a common problem in Canada and has been associated with increased use of health care services and economic burden. This paper examines the prevalence and risk factors for insomnia in two Cree First Nation communities in Saskatchewan, Canada. Five hundred and eighty-eight adults participated in a baseline survey conducted as part of the First Nations Sleep Health Collaborative Project. The prevalence of insomnia was 19.2% among participants with an Insomnia Severity Index score of ≥15. Following the definition of nighttime insomnia symptoms, however, the prevalence of insomnia was much higher, at 32.6%. Multivariate logistic regression modeling revealed that age, physical health, depression diagnosis, chronic pain, prescription medication use for any health condition, and waking up during the night due to terrifying dreams, nightmares, or flashbacks related to traumatic events were risk factors for insomnia among participants from two Saskatchewan Cree First Nation communities. Full article
(This article belongs to the Section Clocks & Sleep and Society)
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Article
General Anaesthesia Shifts the Murine Circadian Clock in a Time-Dependant Fashion
Clocks & Sleep 2021, 3(1), 87-97; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010006 - 26 Jan 2021
Viewed by 1147
Abstract
Following general anaesthesia (GA), patients frequently experience sleep disruption and fatigue, which has been hypothesized to result at least in part by GA affecting the circadian clock. Here, we provide the first comprehensive time-dependent analysis of the effects of the commonly administered inhalational [...] Read more.
Following general anaesthesia (GA), patients frequently experience sleep disruption and fatigue, which has been hypothesized to result at least in part by GA affecting the circadian clock. Here, we provide the first comprehensive time-dependent analysis of the effects of the commonly administered inhalational anaesthetic, isoflurane, on the murine circadian clock, by analysing its effects on (a) behavioural locomotor rhythms and (b) PER2::LUC expression in the suprachiasmatic nuclei (SCN) of the mouse brain. Behavioural phase shifts elicited by exposure of mice (n = 80) to six hours of GA (2% isoflurane) were determined by recording wheel-running rhythms in constant conditions (DD). Phase shifts in PER2::LUC expression were determined by recording bioluminescence in organotypic SCN slices (n = 38) prior to and following GA exposure (2% isoflurane). Full phase response curves for the effects of GA on behaviour and PER2::LUC rhythms were constructed, which show that the effects of GA are highly time-dependent. Shifts in SCN PER2 expression were much larger than those of behaviour (c. 0.7 h behaviour vs. 7.5 h PER2::LUC). We discuss the implications of this work for understanding how GA affects the clock, and how it may inform the development of chronotherapeutic strategies to reduce GA-induced phase-shifting in patients. Full article
(This article belongs to the Section Clocks & Sleep in Animal Basic Research)
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Article
Preliminary Results: The Impact of Smartphone Use and Short-Wavelength Light during the Evening on Circadian Rhythm, Sleep and Alertness
Clocks & Sleep 2021, 3(1), 66-86; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010005 - 22 Jan 2021
Viewed by 2034
Abstract
Smartphone usage strongly increased in the last decade, especially before bedtime. There is growing evidence that short-wavelength light affects hormonal secretion, thermoregulation, sleep and alertness. Whether blue light filters can attenuate these negative effects is still not clear. Therefore, here, we present preliminary [...] Read more.
Smartphone usage strongly increased in the last decade, especially before bedtime. There is growing evidence that short-wavelength light affects hormonal secretion, thermoregulation, sleep and alertness. Whether blue light filters can attenuate these negative effects is still not clear. Therefore, here, we present preliminary data of 14 male participants (21.93 ± 2.17 years), who spent three nights in the sleep laboratory, reading 90 min either on a smartphone (1) with or (2) without a blue light filter, or (3) on printed material before bedtime. Subjective sleepiness was decreased during reading on a smartphone, but no effects were present on evening objective alertness in a GO/NOGO task. Cortisol was elevated in the morning after reading on the smartphone without a filter, which resulted in a reduced cortisol awakening response. Evening melatonin and nightly vasodilation (i.e., distal-proximal skin temperature gradient) were increased after reading on printed material. Early slow wave sleep/activity and objective alertness in the morning were only reduced after reading without a filter. These results indicate that short-wavelength light affects not only circadian rhythm and evening sleepiness but causes further effects on sleep physiology and alertness in the morning. Using a blue light filter in the evening partially reduces these negative effects. Full article
(This article belongs to the Special Issue Effects of Pre-Sleep Artificial Light on Cognition and Sleep)
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Review
Disorders of Arousal: A Chronobiological Perspective
Clocks & Sleep 2021, 3(1), 53-65; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010004 - 21 Jan 2021
Viewed by 990
Abstract
Non-rapid eye movement (NREM) sleep parasomnias are characterized by motor and emotional behaviors emerging from incomplete arousals from NREM sleep and they are currently referred to as disorders of arousal (DoA). Three main clinical entities are recognized, namely confusional arousal, sleep terror and [...] Read more.
Non-rapid eye movement (NREM) sleep parasomnias are characterized by motor and emotional behaviors emerging from incomplete arousals from NREM sleep and they are currently referred to as disorders of arousal (DoA). Three main clinical entities are recognized, namely confusional arousal, sleep terror and sleepwalking. DoA are largely present in pediatric populations, an age in which they are considered as transitory, unhabitual physiological events. The literature background in the last twenty years has extensively shown that DoA can persist in adulthood in predisposed individuals or even appear de novo in some cases. Even though some episodes may arise from stage 2 of sleep, most DoA occur during slow wave sleep (SWS), and particularly during the first two sleep cycles. The reasons for this timing are linked to the intrinsic structure of SWS and with the possible influence on this sleep phase of predisposing, priming and precipitating factors for DoA episodes. The objective of this paper is to review the intrinsic sleep-related features and chronobiological aspects affecting SWS, responsible for the occurrence of the majority of DoA episodes during the first part of the night. Full article
(This article belongs to the Special Issue Role of Sleep and Circadian Rhythms in Health)
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Article
Risk-Based Decision Making: A Systematic Scoping Review of Animal Models and a Pilot Study on the Effects of Sleep Deprivation in Rats
Clocks & Sleep 2021, 3(1), 31-52; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010003 - 20 Jan 2021
Viewed by 872
Abstract
Animals, including humans, frequently make decisions involving risk or uncertainty. Different strategies in these decisions can be advantageous depending the circumstances. Short sleep duration seems to be associated with more risky decisions in humans. Animal models for risk-based decision making can increase mechanistic [...] Read more.
Animals, including humans, frequently make decisions involving risk or uncertainty. Different strategies in these decisions can be advantageous depending the circumstances. Short sleep duration seems to be associated with more risky decisions in humans. Animal models for risk-based decision making can increase mechanistic understanding, but very little data is available concerning the effects of sleep. We combined primary- and meta-research to explore the relationship between sleep and risk-based decision making in animals. Our first objective was to create an overview of the available animal models for risky decision making. We performed a systematic scoping review. Our searches in Pubmed and Psychinfo retrieved 712 references, of which 235 were included. Animal models for risk-based decision making have been described for rodents, non-human primates, birds, pigs and honey-bees. We discuss task designs and model validity. Our second objective was to apply this knowledge and perform a pilot study on the effect of sleep deprivation. We trained and tested male Wistar rats on a probability discounting task; a “safe” lever always resulted in 1 reward, a “risky” lever resulted in 4 or no rewards. Rats adapted their preferences to variations in reward probabilities (p < 0.001), but 12 h of sleep deprivation during the light phase did not clearly alter risk preference (p = 0.21). Full article
(This article belongs to the Section Clocks & Sleep in Animal Basic Research)
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Article
Health Behaviors of Higher Education Students from 7 Countries: Poorer Sleep Quality during the COVID-19 Pandemic Predicts Higher Dietary Risk
Clocks & Sleep 2021, 3(1), 12-30; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010002 - 15 Jan 2021
Cited by 4 | Viewed by 2802
Abstract
Health behaviors of higher education students can be negatively influenced by stressful events. The global COVID-19 pandemic presents a unique opportunity to characterize and compare health behaviors across multiple countries and to examine how these behaviors are shaped by the pandemic experience. Undergraduate [...] Read more.
Health behaviors of higher education students can be negatively influenced by stressful events. The global COVID-19 pandemic presents a unique opportunity to characterize and compare health behaviors across multiple countries and to examine how these behaviors are shaped by the pandemic experience. Undergraduate and graduate students enrolled in universities in China, Ireland, Malaysia, South Korea, Taiwan, the Netherlands and the United States (USA) were recruited into this cross-sectional study. Eligible students filled out an online survey comprised of validated tools for assessing sleep quality and duration, dietary risk, alcohol misuse and physical activity between late April and the end of May 2020. Health behaviors were fairly consistent across countries, and all countries reported poor sleep quality. However, during the survey period, the COVID-19 pandemic influenced the health behaviors of students in European countries and the USA more negatively than Asian countries, which could be attributed to the differences in pandemic time course and caseloads. Students who experienced a decline in sleep quality during the COVID-19 pandemic had higher dietary risk scores than students who did not experience a change in sleep quality (p = 0.001). Improved sleep quality was associated with less sitting time (p = 0.010). Addressing sleep issues among higher education students is a pressing concern, especially during stressful events. These results support the importance of making education and behavior-based sleep programming available for higher education students in order to benefit students’ overall health. Full article
(This article belongs to the Special Issue Role of Sleep and Circadian Rhythms in Health)
Article
Co-Sleeping between Adolescents and Their Pets May Not Impact Sleep Quality
Clocks & Sleep 2021, 3(1), 1-11; https://0-doi-org.brum.beds.ac.uk/10.3390/clockssleep3010001 - 04 Jan 2021
Viewed by 1105
Abstract
Pet–owner co-sleeping is increasingly common in some parts of the world. Adult owners often subjectively report benefits of co-sleeping with pets, although objective actigraphy reports conversely indicate sleep disruptions due to the pet. Because limited research is available regarding pet–owner co-sleeping in non-adult [...] Read more.
Pet–owner co-sleeping is increasingly common in some parts of the world. Adult owners often subjectively report benefits of co-sleeping with pets, although objective actigraphy reports conversely indicate sleep disruptions due to the pet. Because limited research is available regarding pet–owner co-sleeping in non-adult samples, the aim of this two-part study was to explore whether co-sleeping improves sleep quality in adolescents, an age group in which poor sleep patterns are well documented. In Study One, an online survey with 265 pet-owning 13-to-17-year-old participants found that over 78% co-slept with their pet. Average sleep quality scores for co-sleepers and non-co-sleepers indicated generally poor sleep, with no differences in sleep quality depending on age, gender, or co-sleeping status. Study Two consisted of two preliminary case studies, using actigraphy on dog–adolescent co-sleepers. In both cases, high sleep concordance was observed, but owners again experienced generally poor sleep quality. Future actigraphy research is needed, including larger sample sizes and a control group of non-co-sleepers, to validate the preliminary findings from this study, but our limited evidence suggests that co-sleeping with a pet may not impact sleep quality in adolescents. Full article
(This article belongs to the Section Clocks & Sleep in Human Basic Research)
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