Journal Description
Clocks & Sleep
Clocks & Sleep
is a peer-reviewed, open access journal that investigates a wide range of sleep related topics and is published quarterly online by MDPI. The Australasian Chronobiology Society, Society for Light Treatment and Biological Rhythms, and Swiss Society of Sleep Research, Sleep Medicine and Chronobiology are affiliated with Clocks & Sleep and the society members receive a discount on the article processing charges.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High visibility: indexed within Scopus, ESCI (Web of Science), PubMed, PMC, FSTA, and other databases.
- Journal Rank: CiteScore - Q2 (Neuroscience (miscellaneous))
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 27.3 days after submission; acceptance to publication is undertaken in 4.6 days (median values for papers published in this journal in the first half of 2024).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
Impact Factor:
2.1 (2023);
5-Year Impact Factor:
2.4 (2023)
Latest Articles
The Impact of Sleep on Haematological Parameters in Firefighters
Clocks & Sleep 2024, 6(3), 291-311; https://doi.org/10.3390/clockssleep6030021 - 26 Jun 2024
Abstract
Sleep is a vital process that impacts biological functions such as cell renewal, bone regeneration, and immune system support. Disrupted sleep can interrupt erythropoiesis, leading to fewer red blood cells, reduced haemoglobin concentration, and decreased haematocrit levels, potentially contributing to haematological disorders. This
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Sleep is a vital process that impacts biological functions such as cell renewal, bone regeneration, and immune system support. Disrupted sleep can interrupt erythropoiesis, leading to fewer red blood cells, reduced haemoglobin concentration, and decreased haematocrit levels, potentially contributing to haematological disorders. This is particularly concerning for shift workers for example firefighters. While previous studies have explored sleep’s adverse effects on various professions, research specific to firefighters is limited. This study investigates the relationship between sleep quality and haematological parameters among firefighters in Northeast Portugal. From a sample of 201 firefighters, variations in red blood cells, haemoglobin, and haematocrit values were linked to sleep quality. The study utilised non-parametric tests (Wilcoxon-Mann-Whitney, Spearman’s correlation) to explore the connection between sleep quality and haematological profile. The impact of covariates on haematological parameters was assessed using non-parametric ANCOVA (Quade’s). A multiple regression analysis was employed to further understand how sleep quality and various confounding variables impact haematological levels. Findings suggest a negative link between sleep quality and haematological levels, meaning that as sleep quality deteriorates, there is a tendency for haematological levels to decrease, as indicated by Spearman’s correlation (rRBC = −0.157, pRBC = 0.026; rHb = −0.158, pHb = 0.025; rHCT = −0.175, pHCT = 0.013). As observed in scientific literature, the correlation found suggests a possible inhibition of erythropoiesis, the process responsible for red blood cell production. Despite firefighters presenting a haematological profile within the reference range (RBC: 5.1 × 106/mm3 (SD ± 0.4), Hb: 15.6 g/dL (SD ± 1.3), 47% (SD ± 1.0), there is already an observable trend towards lower levels. The analysis of co-variables did not reveal a significant impact of sleep quality on haematological levels. In conclusion, this study underscores the importance of sleep quality in determining haematological parameters among firefighters. Future research should investigate the underlying mechanisms and long-term implications of poor sleep quality on firefighter health. Exploring interventions to enhance sleep quality is vital for evidence-based strategies promoting firefighter well-being.
Full article
(This article belongs to the Special Issue Shift-Work and the Individual II)
Open AccessBrief Report
Time of Day and Sleep Deprivation Effects on Risky Decision Making
by
Noelia Ruiz-Herrera, Mia Friedman, Melissa A. St. Hilaire, Arturo Arrona-Palacios, Charles A. Czeisler and Jeanne F. Duffy
Clocks & Sleep 2024, 6(2), 281-290; https://doi.org/10.3390/clockssleep6020020 - 20 Jun 2024
Abstract
Previous research has revealed that daily variations in human neurobehavioral functions are driven in part by the endogenous circadian system. The objective of this study was to explore whether there exists a circadian influence on performance regarding a risky decision-making task and to
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Previous research has revealed that daily variations in human neurobehavioral functions are driven in part by the endogenous circadian system. The objective of this study was to explore whether there exists a circadian influence on performance regarding a risky decision-making task and to determine whether the performance changes with sleep deprivation (SD). Thirteen participants underwent a 39 h constant routine (CR) protocol, during which they remained awake in constant conditions and performed the BART (balloon analogue risk task) every two hours. The mean pumps (gains) (p < 0.001) and balloons popped (losses) (p = 0.003) exhibited variation during the CR. The reaction time (RT) also showed significant variation across the CR (p < 0.001), with slower mean RTs in the morning hours following SD. A greater risk propensity was observed around midday before SD and a lower risk propensity after 29.5 h of being awake. The sensitivity to punishment varied during the CR, but did not follow a predictable trend. Further research using real monetary incentives and neurophysiological measures is warranted to elucidate these findings.
Full article
(This article belongs to the Section Human Basic Research & Neuroimaging)
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Open AccessArticle
SleepSync: Early Testing of a Personalised Sleep–Wake Management Smartphone Application for Improving Sleep and Cognitive Fitness in Defence Shift Workers
by
Prerna Varma, Svetlana Postnova, Stuart Knock, Mark E. Howard, Eugene Aidman, Shantha W. M. Rajaratnam and Tracey L. Sletten
Clocks & Sleep 2024, 6(2), 267-280; https://doi.org/10.3390/clockssleep6020019 - 29 May 2024
Abstract
Shift work, long work hours, and operational tasks contribute to sleep and circadian disruption in defence personnel, with profound impacts on cognition. To address this, a digital technology, the SleepSync app, was designed for use in defence. A pre-post design study was undertaken
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Shift work, long work hours, and operational tasks contribute to sleep and circadian disruption in defence personnel, with profound impacts on cognition. To address this, a digital technology, the SleepSync app, was designed for use in defence. A pre-post design study was undertaken to examine whether four weeks app use improved sleep and cognitive fitness (high performance neurocognition) in a cohort of shift workers from the Royal Australian Air Force. In total, 13 of approximately 20 shift-working personnel from one base volunteered for the study. Sleep outcomes were assessed using the Insomnia Severity Index (ISI), the Patient-Reported Outcomes Measurement Information System (PROMIS), Sleep Disturbance and Sleep-Related Impairment Scales, the Glasgow Sleep Effort Scale, the Sleep Hygiene Index, and mental health was assessed using the Depression, Anxiety, and Stress Scale-21. Sustained attention was measured using the 3-min Psychomotor Vigilance Task (PVT) and controlled response using the NBack. Results showed significant improvements in insomnia (ISI scores 10.31 at baseline and 7.50 after app use), sleep-related impairments (SRI T-scores 53.03 at baseline to 46.75 post-app use), and healthy sleep practices (SHI scores 21.61 at baseline to 18.83 post-app use; all p < 0.001). Trends for improvement were recorded for depression. NBack incorrect responses reduced significantly (9.36 at baseline; reduced by −3.87 at last week of app use, p < 0.001), but no other objective measures improved. These findings suggest that SleepSync may improve sleep and positively enhance cognitive fitness but warrants further investigation in large samples. Randomised control trials with other cohorts of defence personnel are needed to confirm the utility of this intervention in defence settings.
Full article
(This article belongs to the Section Human Basic Research & Neuroimaging)
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Open AccessReview
Efficacy of Morning Shorter Wavelength Lighting in the Visible (Blue) Range and Broad-Spectrum or Blue-Enriched Bright White Light in Regulating Sleep, Mood, and Fatigue in Traumatic Brain Injury: A Systematic Review
by
Chin Moi Chow, Kanchana Ekanayake and Daniel Hackett
Clocks & Sleep 2024, 6(2), 255-266; https://doi.org/10.3390/clockssleep6020018 - 28 May 2024
Abstract
Traumatic brain injury (TBI) profoundly affects sleep, mood, and fatigue, impeding daily functioning and recovery. This systematic review evaluates the efficacy of morning shorter wavelength lighting in the visible (blue) range and broad-spectrum or blue-enriched bright white light exposure in mitigating these challenges
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Traumatic brain injury (TBI) profoundly affects sleep, mood, and fatigue, impeding daily functioning and recovery. This systematic review evaluates the efficacy of morning shorter wavelength lighting in the visible (blue) range and broad-spectrum or blue-enriched bright white light exposure in mitigating these challenges among TBI patients. Through electronic database searches up to May 2023, studies assessing sleep, circadian rhythm, sleepiness, mood, and fatigue outcomes in TBI patients exposed to morning shorter wavelength lighting in the visible (blue) range and broad-spectrum or blue-enriched bright white light were identified. Seven studies involving 309 participants met the inclusion criteria. Results indicated consistent advancement in sleep timing among individuals with mild TBI, alongside improvements in total sleep time, mood, and reduced sleepiness with both types of light exposure, particularly in mild TBI cases. Notably, two studies demonstrated alleviation of fatigue exclusively in severe TBI cases following light exposure. Despite promising findings, evidence remains limited, emphasizing the need for future research with standardized protocols to confirm the potential and optimize the benefits of light therapy for TBI recovery.
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(This article belongs to the Section Impact of Light & other Zeitgebers)
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Open AccessCommunication
Associations between Sleep Hygiene and Mental Complaints in a French Healthcare Worker Population during the COVID-19 Crisis: A Cross-Sectional Analysis to Personalize Sleep Health Interventions
by
Julien Coelho, Jean-Arthur Micoulaud-Franchi and Pierre Philip
Clocks & Sleep 2024, 6(2), 246-254; https://doi.org/10.3390/clockssleep6020017 - 22 Apr 2024
Abstract
Healthcare workers often have irregular work schedules and experience significant stress, which can lead to poor sleep quality and frequent mental health issues, especially in the context of the COVID-19 pandemic. In this cross-sectional study, we aimed to assess the prevalence of poor
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Healthcare workers often have irregular work schedules and experience significant stress, which can lead to poor sleep quality and frequent mental health issues, especially in the context of the COVID-19 pandemic. In this cross-sectional study, we aimed to assess the prevalence of poor sleep hygiene and mental health complaints among healthcare workers and examine their associations. We investigated participants’ typical sleep–wake patterns on workdays and free days as indicators of sleep hygiene. Sleep efficiency and social jetlag were calculated as the ratio of mean sleep duration to time spent in bed, while sleep rebound was defined as the difference in mean sleep duration between workdays and free days. Social jetlag was determined as the difference in mid-sleep timing between workdays and free days, with mid-sleep defined as the midpoint between bedtime and wake-up time. Insomnia severity was assessed using the Insomnia Severity Index (ISI), daytime sleepiness using the Epworth Sleepiness Scale (ESS), and symptoms of anxiety and depression using the Patient Health Questionnaire 4 (PHQ-4). Fatigue was measured using a single item inspired by the Maslach Burnout Inventory (MBI). A total of 1562 participants (80.5% women, mean age 40.0 years) were included in the study. The results revealed that 25.9% of participants slept less than 6 h, 24.3% had a sleep efficiency of less than 85%, 27.3% experienced a sleep rebound of more than 2 h, and 11.5% reported a social jetlag exceeding 2 h. Additionally, 33.9% of participants reported insomnia, 45.1% reported excessive daytime sleepiness, 13.1% reported fatigue, 16.5% reported symptoms of depression, and 35.7% reported symptoms of anxiety. After adjustment, mean sleep duration and sleep efficiency were associated with most mental health complaints. Sleep rebound and social jetlag were associated with significant insomnia but not with anxiety or depression symptoms. Our findings underscore the high prevalence of poor sleep hygiene and mental health complaints among healthcare workers, exacerbated by the COVID-19 crisis. We advocate for the promotion of sleep health through behavioral sleep strategies to safeguard the well-being of healthcare professionals.
Full article
(This article belongs to the Special Issue Role of Sleep and Circadian Rhythms in Health III)
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Open AccessArticle
Neighborhood Light at Night and Noise Levels, and Long-Term Sleep Trajectories in the Southern Community Cohort Study
by
Samuel H. Nyarko and Qian Xiao
Clocks & Sleep 2024, 6(2), 234-245; https://doi.org/10.3390/clockssleep6020016 - 5 Apr 2024
Abstract
While light at night (LAN) and noise levels have been linked to suboptimal sleep outcomes, little is known about the link between these factors and long-term suboptimal sleep trajectories. The current study examined the association of neighborhood LAN and nighttime noise with long-term
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While light at night (LAN) and noise levels have been linked to suboptimal sleep outcomes, little is known about the link between these factors and long-term suboptimal sleep trajectories. The current study examined the association of neighborhood LAN and nighttime noise with long-term sleep trajectories in a cohort of Black individuals and White individuals predominantly from low-income communities. We used data from the Southern Community Cohort Study (N = 28,759 Black individuals and 16,276 White individuals). Sleep duration was self-reported at baseline and after an average of five years of follow-up, based on which we constructed nine sleep trajectories: normal–normal (optimal, reference), short–short, long–long, short–long, long–short, normal–short, normal–long, short–normal, and long–normal. LAN and nighttime noise were derived from satellite imagery and model-based estimates, respectively. Multinomial logistic regression was used to determine the relationship between LAN and noise exposures and sleep trajectories. Higher exposures to LAN and nighttime noise were associated with multiple suboptimal long-term sleep trajectories. In the total sample, higher LAN was associated with higher odds of long–long (OR Q5 vs. Q1 = 1.23 (CI = 1.02, 1.48)) and long–short (OR = 1.35 (CI = 1.06, 1.72)) trajectories, while higher nighttime noise was associated with short–short (1.19 (1.07, 1.31)), long–short (1.31 (1.05, 1.64)), and normal–song (1.16 (1.01, 1.34)) trajectories. Black and White individual-specific results showed qualitatively similar patterns between Black individuals and White individuals, although we also observed suggestive evidence for Black–White individual differences. In conclusion, elevated LAN and nighttime noise levels were associated with various suboptimal long-term sleep trajectories. However, it is noteworthy that the light and noise measures in our study may not accurately reflect individual-level exposures, and residual confounding from other factors is a concern. Future studies should use more accurate exposure measurements, collect information on and control for a wider range of factors, and examine whether reductions in neighborhood light and noise levels may contribute to improved long-term sleep health.
Full article
(This article belongs to the Section Impact of Light & other Zeitgebers)
Open AccessArticle
No Benefit in Memory Performance after Nocturnal Memory Reactivation Coupled with Theta-tACS
by
Sandrine Baselgia, Florian H. Kasten, Christoph S. Herrmann, Björn Rasch and Sven Paβmann
Clocks & Sleep 2024, 6(2), 211-233; https://doi.org/10.3390/clockssleep6020015 - 25 Mar 2024
Abstract
Targeted memory reactivation (TMR) is an effective technique to enhance sleep-associated memory consolidation. The successful reactivation of memories by external reminder cues is typically accompanied by an event-related increase in theta oscillations, preceding better memory recall after sleep. However, it remains unclear whether
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Targeted memory reactivation (TMR) is an effective technique to enhance sleep-associated memory consolidation. The successful reactivation of memories by external reminder cues is typically accompanied by an event-related increase in theta oscillations, preceding better memory recall after sleep. However, it remains unclear whether the increase in theta oscillations is a causal factor or an epiphenomenon of successful TMR. Here, we used transcranial alternating current stimulation (tACS) to examine the causal role of theta oscillations for TMR during non-rapid eye movement (non-REM) sleep. Thirty-seven healthy participants learned Dutch–German word pairs before sleep. During non-REM sleep, we applied either theta-tACS or control-tACS (23 Hz) in blocks (9 min) in a randomised order, according to a within-subject design. One group of participants received tACS coupled with TMR time-locked two seconds after the reminder cue (time-locked group). Another group received tACS in a continuous manner while TMR cues were presented (continuous group). Contrary to our predictions, we observed no frequency-specific benefit of theta-tACS coupled with TMR during sleep on memory performance, neither for continuous nor time-locked stimulation. In fact, both stimulation protocols blocked the TMR-induced memory benefits during sleep, resulting in no memory enhancement by TMR in both the theta and control conditions. No frequency-specific effect was found on the power analyses of the electroencephalogram. We conclude that tACS might have an unspecific blocking effect on memory benefits typically observed after TMR during non-REM sleep.
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(This article belongs to the Section Human Basic Research & Neuroimaging)
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Open AccessArticle
Temporal Considerations in Brain Metastases Radiation Therapy: The Intersection of Chronobiology and Patient Profiles
by
Nicolas G. Nelson, Sara E. Burke, Louis Cappelli, Lauren E. Matlack, Alexandria P. Smith, Noelle Francois, Joseph F. Lombardo, Yash B. Shah, Kuang-Yi Wen, Ayesha A. Shafi and Nicole L. Simone
Clocks & Sleep 2024, 6(1), 200-210; https://doi.org/10.3390/clockssleep6010014 - 21 Mar 2024
Abstract
The circadian system, a vital temporal regulator influencing physiological processes, has implications for cancer development and treatment response. Our study assessed circadian timing’s impact on whole-brain radiotherapy outcomes in brain metastases for personalized cancer therapy insights. The aim of the study was to
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The circadian system, a vital temporal regulator influencing physiological processes, has implications for cancer development and treatment response. Our study assessed circadian timing’s impact on whole-brain radiotherapy outcomes in brain metastases for personalized cancer therapy insights. The aim of the study was to evaluate circadian influence on radiation treatment timing and its correlation with clinical outcomes and to identify patient populations benefiting from interventions synchronizing circadian rhythms, considering subgroup differences and potential disparities. An IRB-approved retrospective analysis of 237 patients undergoing whole-brain radiotherapy for brain metastases (2017–2021), receiving over 80% of treatments in the morning or afternoon, was performed. Survival analyses utilized Kaplan–Meier curves. This was a single-institution study involving patients receiving whole-brain radiotherapy. Demographic, disease, and socioeconomic parameters from electronic medical records were collected. Morning treatment (n = 158) showed a trend toward improved overall survival vs. afternoon (n = 79); the median survival was 158 vs. 79 days (p = 0.20, HR = 0.84, CI95% 0.84–0.91). Subgroup benefits for morning treatment in females (p = 0.04) and trends in controlled primary disease (p = 0.11) and breast cancer metastases (p = 0.08) were observed. Black patients exhibited diminished circadian influence. The present study emphasized chronobiological factors’ relevance in brain metastases radiation therapy. Morning treatment correlated with improved survival, particularly in specific subgroups. Potential circadian influence disparities were identified, laying a foundation for personalized cancer therapy and interventions synchronizing circadian rhythms for enhanced treatment efficacy.
Full article
(This article belongs to the Special Issue Sleeping for Health: Mechanistic Insights)
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Open AccessArticle
The Efficacy of a Multimodal Bedroom-Based ‘Smart’ Alarm System on Mitigating the Effects of Sleep Inertia
by
Carolina Campanella, Kunjoon Byun, Araliya Senerat, Linhao Li, Rongpeng Zhang, Sara Aristizabal, Paige Porter and Brent Bauer
Clocks & Sleep 2024, 6(1), 183-199; https://doi.org/10.3390/clockssleep6010013 - 18 Mar 2024
Abstract
Previous work has demonstrated the modest impact of environmental interventions that manipulate lighting, sound, or temperature on sleep inertia symptoms. The current study sought to expand on previous work and measure the impact of a multimodal intervention that collectively manipulated light, sound, and
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Previous work has demonstrated the modest impact of environmental interventions that manipulate lighting, sound, or temperature on sleep inertia symptoms. The current study sought to expand on previous work and measure the impact of a multimodal intervention that collectively manipulated light, sound, and ambient temperature on sleep inertia. Participants slept in the lab for four nights and were awoken each morning by either a traditional alarm clock or the multimodal intervention. Feelings of sleep inertia were measured each morning through Psychomotor Vigilance Test (PVT) assessments and ratings of sleepiness and mood at five time-points. While there was little overall impact of the intervention, the participant’s chronotype and the length of the lighting exposure on intervention mornings both influenced sleep inertia symptoms. Moderate evening types who received a shorter lighting exposure (≤15 min) demonstrated more lapses relative to the control condition, whereas intermediate types exhibited a better response speed and fewer lapses. Conversely, moderate evening types who experienced a longer light exposure (>15 min) during the intervention exhibited fewer false alarms over time. The results suggest that the length of the environmental intervention may play a role in mitigating feelings of sleep inertia, particularly for groups who might exhibit stronger feelings of sleep inertia, including evening types.
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(This article belongs to the Section Impact of Light & other Zeitgebers)
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Open AccessArticle
Disruption of Circadian Sleep/Wake Rhythms in Infants May Herald Future Development of Autism Spectrum Disorder
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Teruhisa Miike, Kentaro Oniki, Makiko Toyoura, Shiro Tonooka, Seiki Tajima, Jun Kinoshita, Junji Saruwatari and Yukuo Konishi
Clocks & Sleep 2024, 6(1), 170-182; https://doi.org/10.3390/clockssleep6010012 - 15 Mar 2024
Abstract
We investigated whether the abnormal rhythms in infants are related to the future development of autism spectrum disorder (ASD), using a questionnaire from September to October 2016. The parents of 160 children with ASD (male, n = 123; female, n = 37) were
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We investigated whether the abnormal rhythms in infants are related to the future development of autism spectrum disorder (ASD), using a questionnaire from September to October 2016. The parents of 160 children with ASD (male, n = 123; female, n = 37) were recruited from two hospitals in K and H cities, and as a control group, 145 children (male, n = 75; female, n = 70) were recruited from four nursery schools in T city. The associations between ASD and bedtime and waking time on weekdays and weekends in infancy (<1 years of age), at 1–3 years, and at 3–5 years of ages were studied using a multivariable logistic regression analysis. In particular, at <3 years of age, the following factors were associated with an increased prevalence of ASD in the future: (1) short sleep periods (<8 h); (2) taking a long time to fall asleep (>60 min); (3) sleep beginning after 22:00; (4) a wake-up time after 08:00; and (5) frequent (>3 times) and long-term awakening periods (>60 min). The misalignment and/or shift of the circadian rhythm in infants may be one of the precursors and/or risk factors for the future development of ASD.
Full article
(This article belongs to the Special Issue Role of Sleep and Circadian Rhythms in Health III)
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Open AccessArticle
Association of Meal Timing with Sleep Quality and Anxiety According to Chronotype: A Study of University Students
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Cristina Souza da Silva Luz, Ana Elizabeth Teixeira Pimentel da Fonseca, Jefferson Souza Santos, John Fontenele Araujo, Leandro Lourenção Duarte and Claudia Roberta de Castro Moreno
Clocks & Sleep 2024, 6(1), 156-169; https://doi.org/10.3390/clockssleep6010011 - 11 Mar 2024
Abstract
There are several determinants of mental health symptoms, ranging from individual characteristics to social factors. Consistent with patterns in the general population, students with evening characteristics tend to exhibit more anxiety symptoms and poorer sleep quality compared to morning students. Meal timing also
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There are several determinants of mental health symptoms, ranging from individual characteristics to social factors. Consistent with patterns in the general population, students with evening characteristics tend to exhibit more anxiety symptoms and poorer sleep quality compared to morning students. Meal timing also appears to affect sleep and may be associated with mental health symptoms. In this context, the aim of the present study was to investigate the association of the timing of the main and last meals of the day with sleep quality and anxiety levels, according to the chronotype of university students. This study was conducted in colleges in São Paulo, Brazil, and involved application of a questionnaire to 162 university students. The questionnaire collected sociodemographic information meal and study times, and included scales assessing eveningness and morningness, sleep quality, and anxiety. Students demonstrating a phase delay in both chronotype and dinner timing exhibited higher levels of anxiety compared to morning-type students. Although no associations were observed between meal timing and sleep quality, sleeping later was associated with poorer sleep quality. The study suggests that evening students and those who eat late at night are more prone to presenting mental health symptoms. More studies are needed to further investigate this association.
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(This article belongs to the Section Society)
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Open AccessArticle
A Protocol for Evaluating Digital Technology for Monitoring Sleep and Circadian Rhythms in Older People and People Living with Dementia in the Community
by
Ciro della Monica, Kiran K. G. Ravindran, Giuseppe Atzori, Damion J. Lambert, Thalia Rodriguez, Sara Mahvash-Mohammadi, Ullrich Bartsch, Anne C. Skeldon, Kevin Wells, Adam Hampshire, Ramin Nilforooshan, Hana Hassanin, The UK Dementia Research Institute Care Research & Technology Research Group, Victoria L. Revell and Derk-Jan Dijk
Clocks & Sleep 2024, 6(1), 129-155; https://doi.org/10.3390/clockssleep6010010 - 29 Feb 2024
Cited by 1
Abstract
Sleep and circadian rhythm disturbance are predictors of poor physical and mental health, including dementia. Long-term digital technology-enabled monitoring of sleep and circadian rhythms in the community has great potential for early diagnosis, monitoring of disease progression, and assessing the effectiveness of interventions.
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Sleep and circadian rhythm disturbance are predictors of poor physical and mental health, including dementia. Long-term digital technology-enabled monitoring of sleep and circadian rhythms in the community has great potential for early diagnosis, monitoring of disease progression, and assessing the effectiveness of interventions. Before novel digital technology-based monitoring can be implemented at scale, its performance and acceptability need to be evaluated and compared to gold-standard methodology in relevant populations. Here, we describe our protocol for the evaluation of novel sleep and circadian technology which we have applied in cognitively intact older adults and are currently using in people living with dementia (PLWD). In this protocol, we test a range of technologies simultaneously at home (7–14 days) and subsequently in a clinical research facility in which gold standard methodology for assessing sleep and circadian physiology is implemented. We emphasize the importance of assessing both nocturnal and diurnal sleep (naps), valid markers of circadian physiology, and that evaluation of technology is best achieved in protocols in which sleep is mildly disturbed and in populations that are relevant to the intended use-case. We provide details on the design, implementation, challenges, and advantages of this protocol, along with examples of datasets.
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(This article belongs to the Section Human Basic Research & Neuroimaging)
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Open AccessArticle
Power Analysis for Human Melatonin Suppression Experiments
by
Manuel Spitschan, Parisa Vidafar, Sean W. Cain, Andrew J. K. Phillips and Ben C. Lambert
Clocks & Sleep 2024, 6(1), 114-128; https://doi.org/10.3390/clockssleep6010009 - 26 Feb 2024
Abstract
In humans, the nocturnal secretion of melatonin by the pineal gland is suppressed by ocular exposure to light. In the laboratory, melatonin suppression is a biomarker for this neuroendocrine pathway. Recent work has found that individuals differ substantially in their melatonin-suppressive response to
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In humans, the nocturnal secretion of melatonin by the pineal gland is suppressed by ocular exposure to light. In the laboratory, melatonin suppression is a biomarker for this neuroendocrine pathway. Recent work has found that individuals differ substantially in their melatonin-suppressive response to light, with the most sensitive individuals being up to 60 times more sensitive than the least sensitive individuals. Planning experiments with melatonin suppression as an outcome needs to incorporate these individual differences, particularly in common resource-limited scenarios where running within-subjects studies at multiple light levels is costly and resource-intensive and may not be feasible with respect to participant compliance. Here, we present a novel framework for virtual laboratory melatonin suppression experiments, incorporating a Bayesian statistical model. We provide a Shiny web app for power analyses that allows users to modify various experimental parameters (sample size, individual-level heterogeneity, statistical significance threshold, light levels), and simulate a systematic shift in sensitivity (e.g., due to a pharmacological or other intervention). Our framework helps experimenters to design compelling and robust studies, offering novel insights into the underlying biological variability in melatonin suppression relevant for practical applications.
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(This article belongs to the Special Issue Reproducibility in Sleep and Circadian Science)
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Open AccessArticle
Can the Brain’s Thermostatic Mechanism Generate Sleep-Wake and NREM-REM Sleep Cycles? A Nested Doll Model of Sleep-Regulating Processes
by
Arcady A. Putilov
Clocks & Sleep 2024, 6(1), 97-113; https://doi.org/10.3390/clockssleep6010008 - 19 Feb 2024
Abstract
Evidence is gradually accumulating in support of the hypothesis that a process of thermostatic brain cooling and warming underlies sleep cycles, i.e., the alternations between non-rapid-eye-movement and rapid-eye-movement sleep throughout the sleep phase of the sleep-wake cycle. A mathematical thermostat model predicts an
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Evidence is gradually accumulating in support of the hypothesis that a process of thermostatic brain cooling and warming underlies sleep cycles, i.e., the alternations between non-rapid-eye-movement and rapid-eye-movement sleep throughout the sleep phase of the sleep-wake cycle. A mathematical thermostat model predicts an exponential shape of fluctuations in temperature above and below the desired temperature setpoint. If the thermostatic process underlies sleep cycles, can this model explain the mechanisms governing the sleep cyclicities in humans? The proposed nested doll model incorporates Process s generating sleep cycles into Process S generating sleep-wake cycles of the two-process model of sleep-wake regulation. Process s produces ultradian fluctuations around the setpoint, while Process S turns this setpoint up and down in accord with the durations of the preceding wake phase and the following sleep phase of the sleep-wake cycle, respectively. Predictions of the model were obtained in an in silico study and confirmed by simulations of oscillations of spectral electroencephalographic indexes of sleep regulation obtained from night sleep and multiple napping attempts. Only simple—inverse exponential and exponential—functions from the thermostatic model were used for predictions and simulations of rather complex and varying shapes of sleep cycles during an all-night sleep episode. To further test the proposed model, experiments on mammal species with monophasic sleep are required. If supported, this model can provide a valuable framework for understanding the involvement of sleep-wake regulatory processes in the mechanism of thermostatic brain cooling/warming.
Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Sleep and Circadian Rhythms Models)
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Open AccessArticle
The Impact of Education Level on Individual Lifestyle Behaviors among Dietetics Students and Professionals
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Joanna Popiolek-Kalisz, Cansu Cakici, Karolina Szczygiel and Agata Przytula
Clocks & Sleep 2024, 6(1), 85-96; https://doi.org/10.3390/clockssleep6010007 - 10 Feb 2024
Abstract
Lifestyle and habits are acquired in the family environment and then shaped by the potential influence of the environment and received education. In recent years, there has been growing interest in understanding the relationship between sleep and dietary behaviors in various health professionals,
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Lifestyle and habits are acquired in the family environment and then shaped by the potential influence of the environment and received education. In recent years, there has been growing interest in understanding the relationship between sleep and dietary behaviors in various health professionals, including medical and dietetics professionals and students, as well as their self-perceived knowledge and attitudes. Despite the importance of this topic, there is a lack of research on the assessment of individual behaviors in dietetics students and professionals. The aim of this study was to assess the impact of education level on individual behaviors regarding nutrition, sleep, and physical activity in dietetics students and professionals. 71 dietetics students and professionals were enrolled in this study. Their overall knowledge, sleep, and nutritional behavior were assessed with a validated Questionnaire of Eating Behaviors at the beginning of their dietetics university education and then prospectively after a year. It was also compared to dieticians who already graduated. The analysis showed that the educational level did not correlate with sleep length or the physical activity level. However, the educational level was correlated with dietary knowledge and properly self-assessed by the participants. Significant differences were observed in both the prospective and comparative analyses. The educational level and knowledge were not correlated with eating behaviors. The self-assessment of nutritional behaviors also did not correlate with the objective assessment. Sleep length did not correlate with BMI, but it was inversely correlated with overall and healthy diet scores and knowledge levels. On the other hand, physical activity levels were positively correlated with healthy diet scores. Dietary education results in better nutritional knowledge; however, it does not significantly impact individual nutritional behaviors among dietetics students and professionals. Moreover, the inverse relationship between sleep length and nutritional knowledge and behaviors, as well as the positive relationship between physical activity level and dietary behaviors, shows that nutritional aspects of lifestyle are probably prioritized among dietetic students and professionals, with an acknowledgment of the role of physical activity and a neglect of sleep hygiene importance. Dietetics students should be advised to use their theoretical knowledge not only to guide their patients but also to implement it in their own lives.
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(This article belongs to the Special Issue Sleeping for Health: Mechanistic Insights)
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Insomnia and Migraine: A Missed Call?
by
Angelo Torrente, Lavinia Vassallo, Paolo Alonge, Laura Pilati, Andrea Gagliardo, Davide Ventimiglia, Antonino Lupica, Vincenzo Di Stefano, Cecilia Camarda and Filippo Brighina
Clocks & Sleep 2024, 6(1), 72-84; https://doi.org/10.3390/clockssleep6010006 - 5 Feb 2024
Abstract
Migraine is one of the most prevalent and disabling neurological conditions, presenting episodes of throbbing headache that limit activities of daily living. Several factors may influence migraine frequency, such as lifestyle or alcohol consumption. Among the most recognised ones, sleep plays a biunivocal
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Migraine is one of the most prevalent and disabling neurological conditions, presenting episodes of throbbing headache that limit activities of daily living. Several factors may influence migraine frequency, such as lifestyle or alcohol consumption. Among the most recognised ones, sleep plays a biunivocal role, since poor sleep quality may worsen migraine frequency, and a high migraine frequency may affect sleep quality. In this paper, the authors evaluate the relationship between migraine and insomnia by exploring a cohort of patients affected by episodic or chronic migraine. To do so, a phone interview was performed, asking patients about their migraine frequency and mean pain intensity, in addition to the questions of the Insomnia Severity Index. The last one explores several symptoms impairing sleep that focus on insomnia. Patients complaining of insomnia showed an increased migraine frequency, and a weak but significant correlation was found between headache days per month and insomnia scores. Such results were particularly evident in patients affected by chronic migraine. Such results suggest how insomnia, in the presented data, seems to be associated with migraine frequency but not with pain intensity.
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(This article belongs to the Special Issue Sleeping for Health: Mechanistic Insights)
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Bright Light Therapy for Major Depressive Disorder in Adolescent Outpatients: A Preliminary Study
by
Rachel Ballard, John T. Parkhurst, Lisa K. Gadek, Kelsey M. Julian, Amy Yang, Lauren N. Pasetes, Namni Goel and Dorothy K. Sit
Clocks & Sleep 2024, 6(1), 56-71; https://doi.org/10.3390/clockssleep6010005 - 30 Jan 2024
Abstract
Background: Bright light therapy (BLT) has not been well-studied in adolescents with major depressive disorder, particularly in outpatient settings. Methods: We conducted an 8-week clinical trial of BLT in adolescents recruited from a primary care practice with moderate to severe major depression. Acceptability
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Background: Bright light therapy (BLT) has not been well-studied in adolescents with major depressive disorder, particularly in outpatient settings. Methods: We conducted an 8-week clinical trial of BLT in adolescents recruited from a primary care practice with moderate to severe major depression. Acceptability and feasibility were defined by daily use of the light box and integration into daily routines. To assess treatment effects, we utilized the Short Mood and Feelings Questionnaire (SMFQ) and actigraphic sleep variables. Results: Of the nine enrolled adolescents, the rate of daily use of the light therapy box was 100% at week 2, 78% at week 4 (n = 7), and 67% at weeks 6 and 8 (n = 6). Participants were better able to integrate midday BLT compared to morning BLT into their day-to-day routines. Mean depression scores improved during the 2-week placebo lead-in (dim red light—DRL) and continued to show significant improvement through 6 weeks of BLT. Sleep efficiency increased significantly (p = 0.046), and sleep onset latency showed a trend toward a significant decrease (p = 0.075) in the BLT phase compared to the DRL phase. Conclusion: Bright light treatment that was self-administered at home was feasible, acceptable, and effective for adolescent outpatients with depression. Findings support the development of larger, well-powered, controlled clinical trials of BLT in coordination with primary care.
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(This article belongs to the Section Impact of Light & other Zeitgebers)
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Sleep Efficiency and Sleep Onset Latency in One Saskatchewan First Nation
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Chandima P. Karunanayake, Punam Pahwa, Shelley Kirychuk, Mark Fenton, Vivian R. Ramsden, Jeremy Seeseequasis, Warren Seesequasis, Robert Skomro, Donna C. Rennie, Kathleen McMullin, Brooke P. Russell, Niels Koehncke, Sylvia Abonyi, Malcolm King and James A. Dosman
Clocks & Sleep 2024, 6(1), 40-55; https://doi.org/10.3390/clockssleep6010004 - 10 Jan 2024
Abstract
Background: Sleep efficiency and sleep onset latency are two measures that can be used to assess sleep quality. Factors that are related to sleep quality include age, sex, sociodemographic factors, and physical and mental health status. This study examines factors related to sleep
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Background: Sleep efficiency and sleep onset latency are two measures that can be used to assess sleep quality. Factors that are related to sleep quality include age, sex, sociodemographic factors, and physical and mental health status. This study examines factors related to sleep efficiency and sleep onset latency in one First Nation in Saskatchewan, Canada. Methods: A baseline survey of the First Nations Sleep Health project was completed between 2018 and 2019 in collaboration with two Cree First Nations. One-night actigraphy evaluations were completed within one of the two First Nations. Objective actigraphy evaluations included sleep efficiency and sleep onset latency. A total of 167 individuals participated, and of these, 156 observations were available for analysis. Statistical analysis was conducted using logistic and linear regression models. Results: More females (61%) than males participated in the actigraphy study, with the mean age being higher for females (39.6 years) than males (35.0 years). The mean sleep efficiency was 83.38%, and the mean sleep onset latency was 20.74 (SD = 27.25) minutes. Age, chronic pain, ever having high blood pressure, and smoking inside the house were associated with an increased risk of poor sleep efficiency in the multiple logistic regression model. Age, chronic pain, ever having anxiety, heart-related illness, and smoking inside the house were associated with longer sleep onset latency in the multiple linear regression model. Conclusions: Sleep efficiency and sleep onset latency were associated with physical and environmental factors in this First Nation.
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(This article belongs to the Section Human Basic Research & Neuroimaging)
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Match and Mismatch between Lived Experiences of Daytime Sleepiness and Diagnostic Instruments: A Qualitative Study amongst Patients with Sleep Disorders
by
Vaida T. R. Verhoef, Karin C. H. J. Smolders, Lysanne Remmelswaal, Geert Peeters, Sebastiaan Overeem and Yvonne A. W. de Kort
Clocks & Sleep 2024, 6(1), 24-39; https://doi.org/10.3390/clockssleep6010003 - 5 Jan 2024
Abstract
Excessive daytime sleepiness is a common symptom of sleep disorders. Despite its prevalence, it remains difficult to define, detect, and address. The difficulties surrounding sleepiness have been linked to an ambiguous conceptualization, a large variety of scales and measures, and the overlap with
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Excessive daytime sleepiness is a common symptom of sleep disorders. Despite its prevalence, it remains difficult to define, detect, and address. The difficulties surrounding sleepiness have been linked to an ambiguous conceptualization, a large variety of scales and measures, and the overlap with other constructs, such as fatigue. The present study aims to investigate patients’ descriptions of sleepiness-related daytime complaints and their phenomenology. We performed semi-directed interviews with patients diagnosed with obstructive sleep apnea (N = 15) or narcolepsy (N = 5). The interviewers took care of utilizing the participants’ terminology when describing daytime complaints related to their sleep disorder. Various aspects of the daytime complaints were investigated, such as their description and temporality. The transcribed content was thematically analyzed using an eclectic coding system, yielding five themes. The participants used different interchangeable descriptors (tired, sleepy, fatigued, exhausted) to express their daytime complaints. They enriched their description with indexes of magnitude (ranging from ‘not especially’ to ‘most gigantic, extreme’), oppositions to other states (using antipodes like energy, alertness, wakefulness, or rest), and indications of fluctuations over the day. Interestingly, the participants often used metaphors to express their experiences and their struggles. The lived experiences of the patients were found to not always align with common self-reported monitoring tools of sleepiness and to relate only in part with current conceptions. In practice, it is important to probe daytime complaints, such as daytime sleepiness, with a broader consideration, for example, by exploring antipodes, consequences, and time-of-day fluctuations.
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(This article belongs to the Section Disorders)
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Thematic Daily Sleep Routine Analysis of Adults Not in Employment Living with Type 2 Diabetes Mellitus
by
Rachael M. Kelly, John H. McDermott and Andrew N. Coogan
Clocks & Sleep 2024, 6(1), 11-23; https://doi.org/10.3390/clockssleep6010002 - 29 Dec 2023
Abstract
Background: Day-to-day variations in sleep timing have been associated with poorer glycemic control in type 2 diabetes mellitus, although the factors that influence this sleep timing variability are poorly understood. Methods: Daily routines of sleep in a sample of seventeen adults with type
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Background: Day-to-day variations in sleep timing have been associated with poorer glycemic control in type 2 diabetes mellitus, although the factors that influence this sleep timing variability are poorly understood. Methods: Daily routines of sleep in a sample of seventeen adults with type 2 diabetes mellitus who were either retired or not currently working were examined qualitatively through the application of semi-structured interviews and a thematic analysis of the resulting transcripts. Results: Four themes were identified: “Consistent Sleeping Patterns”, “Fluctuating Sleep Timing”, “Night-Time Disruptions” and “Lasting Effort Needed with Type Two Diabetes Mellitus”. The subthemes reflected that many participants had consistent sleep schedules across the seven-day week, but that a desire to maintain a sense of normality, household routines, television schedules and socializing were associated with different sleep timing on weekends. Active disease monitoring and timed medication taking were not identified as important factors in shaping sleep timing. Nocturia, stress and rumination were identified as important factors linked to disrupted sleep. Sleep was not reported as an issue discussed during routine clinical care. Conclusion: Sleep timing in participants appears to be driven by interacting psychosocial and physiological factors, although active disease management does not emerge as a major influence on sleep schedules.
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(This article belongs to the Section Society)
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