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21 pages, 1392 KiB

Open AccessArticle

The Impact of Sleep on Haematological Parameters in Firefighters

by Sara Alves, Francisca Silva, Filipa Esteves, Solange Costa, Klara Slezakova, Maria Alves, Maria Pereira, João Teixeira, Simone Morais, Adília Fernandes, Felisbina Queiroga and Josiana Vaz

Clocks & Sleep 2024, 6(3), 291-311; https://doi.org/10.3390/clockssleep6030021 - 26 Jun 2024

Viewed by 797

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 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)

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10 pages, 548 KiB

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

Viewed by 616

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 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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14 pages, 609 KiB

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

Viewed by 758

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 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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12 pages, 548 KiB

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

Viewed by 754

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 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. Full article

(This article belongs to the Section Impact of Light & other Zeitgebers)

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9 pages, 633 KiB

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

Viewed by 1115

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 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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12 pages, 233 KiB

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

Viewed by 1757

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 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)

23 pages, 2432 KiB

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

Viewed by 1492

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 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. Full article

(This article belongs to the Section Human Basic Research & Neuroimaging)

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n = 21) received a continuous stimulation, while the other group (n = 16) received a time-locked stimulation (0.5 s after each cue onset). In each cycle, we alternated TMR blocks coupled with stimulation with TMR blocks without stimulation until a maximum of 5 blocks or until REM sleep was noticed. In the morning, participants were tested on the German translation of the Dutch words using a cued recall procedure. (B) Difference between continuous and time-locked stimulation. The continuous stimulation was started at the beginning of the TMR blocks and lasted for its whole duration (9 min). The time-locked stimulation was a 2 s stimulation, applied 0.5 s after each TMR cue of the 9 min block. (C) Relative difference between pre- and post-sleep recall—with performance of the pre-sleep recall set to 100%—in the continuous and time-locked groups for TMR cues coupled with theta-tACS, TMR cues coupled with a control stimulation and unpresented words (uncued). Neither time-locked nor continuous stimulation with theta-tACS during the re-exposure of Dutch words increased memory performance tested after sleep. Thus, stimulation with theta-tACS either during or shortly after the TMR of Dutch words did not improve memory consolidation compared with a control stimulation and with unpresented words.

Full article ">p = 0.028), as illustrated with the black dashed box. (E) Comparison of the oscillatory power changes between Hits and Misses combined for all conditions and groups: no difference was found.

Full article ">p = 0.044). The dashed box indicates the time (550–800 ms)-frequency (5–5.5 Hz) area used to illustrate the topographical distribution shown in subfigure (B). Significant electrodes are represented in filled black dots. (C) This cluster was found neither in the control-tACS of the time-locked group nor in the continuous group in both (D) the theta-tACS condition and (E) the control condition. (E) Control-Hits vs. control-Misses in the continuous group: there was a statistical trend for a lower theta power for Hits, 1.92–2.26 s after cue onset in the control-tACS condition, in the frontal region (p = 0.079). (F) Theta-Hits vs. theta-Misses in the time-locked group, in the frontal right region: the cluster shown in (A) was observed specifically in the frontal right region (F4, F8, FC6; p = 0.012) of the theta-tACS condition in the time-locked group. (G) Mean theta power from the cluster shown in (F): exploratory t-tests on the extracted mean theta power in this time window in the right frontal region revealed that theta power was indeed higher for Hits compared to Misses in the theta-tACS condition of the time-locked group (t₁₄ = −2.71, p = 0.017, d = 0.70), but not in the continuous group, nor in the control-tACS condition (all p-value > 0.284). (H) Correlation between theta power difference between Hits and Misses in the frontal right region and memory performance, both groups and stimulation conditions together: no correlation was found. The shaded area represents 95% confidence interval. *: p < 0.05.

Full article ">p = 0.011; right: p = 0.001). Neither main effect of the stimulation condition nor interaction were observed. Comparison of the theta mean power in TMR-only vs. TMR + tACS blocks in the time-locked group: in the time-locked group only, an analysis was performed to compare the theta mean power in TMR blocks without stimulation (TMR-only) and TMR blocks coupled with stimulation (TMR + tACS), 3–5 s after cue onset. In the frontal left (C) and frontal right (D) regions, theta mean power in the time-locked group was higher in the blocks without stimulation compared to the blocks coupled with tACS (left: p = 0.057; right: p = 0.008). Neither main effect of the stimulation condition nor interaction were observed. +: p ≤ 0.06, *: p < 0.05, **: p ≤ 0.01, ***: p ≤ 0.001.

Full article ">

11 pages, 739 KiB

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

Viewed by 1491

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 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, CI_95% 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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17 pages, 2669 KiB

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

Viewed by 1644

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 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. Full article

(This article belongs to the Section Impact of Light & other Zeitgebers)

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13 pages, 2120 KiB

Open AccessArticle

Disruption of Circadian Sleep/Wake Rhythms in Infants May Herald Future Development of Autism Spectrum Disorder

by 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

Viewed by 1611

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 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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14 pages, 2298 KiB

Open AccessArticle

Association of Meal Timing with Sleep Quality and Anxiety According to Chronotype: A Study of University Students

by 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

Viewed by 2289

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 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. Full article

(This article belongs to the Section Society)

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27 pages, 4395 KiB

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 | Viewed by 1753

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. 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. Full article

(This article belongs to the Section Human Basic Research & Neuroimaging)

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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 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. Full article

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