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Clocks & Sleep, Volume 5, Issue 1 (March 2023) – 13 articles

Cover Story (view full-size image): Activity plays a very important role in keeping bodies strong and healthy, slowing senescence, and decreasing morbidity and mortality. Drosophila models of evolution under various selective pressures were used to examine whether changes in activity are required for the adaptation of this species to longer or harder lives. Descendants of wild flies were reared in a laboratory without and with selection pressure. Flies of the starch strain were reared on an adverse (starch-based) food substrate. The long-lived strain was maintained through artificial selection for late reproduction. The 24 h patterns of locomotor activity and sleep in flies were studied in constant darkness. Flies become more active and sleep less in response to these two different selection pressures. View this paper
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11 pages, 738 KiB  
Systematic Review
Determinants of Health Inequalities in Iran and Saudi Arabia: A Systematic Review of the Sleep Literature
by Comsar Ndiaye, Yosr Ayedi and Faustin Armel Etindele Sosso
Clocks & Sleep 2023, 5(1), 141-151; https://doi.org/10.3390/clockssleep5010013 - 22 Mar 2023
Cited by 2 | Viewed by 2368
Abstract
Sleep health inequalities represent an increasing public health concern. Among multiple determinants affecting sleep health, there is people’s socioeconomic status (SES), and no systematic review on the relationship between SES and sleep health has been previously conducted in Iran and Saudi Arabia. Following [...] Read more.
Sleep health inequalities represent an increasing public health concern. Among multiple determinants affecting sleep health, there is people’s socioeconomic status (SES), and no systematic review on the relationship between SES and sleep health has been previously conducted in Iran and Saudi Arabia. Following the Prisma protocol, ten articles were selected. Findings revealed that the combined number of participants was N = 37,455 participants, including 73.23% of children and adolescents (n = 27,670) and 26.77% of adults (n = 10,026). The smallest sample was N = 715 and the larger was N = 13,486. In all these studies, sleep variables were assessed using self-reported questionnaires. The studies conducted in Iran assessed the risk of obstructive sleep apnea (OSA), while those in Saudi Arabia were interested in sleep duration, nap time, bedtime, rise time and insomnia. The studies performed on adult populations in Iran and Saudi Arabia concluded that there is no significant association between SES determinants and sleep components in adult populations. One study in Iran found a significant association between parent’s low SES and children and adolescent insomnia; and one study in Saudi Arabia found a significant association between the father’s education and the longer sleep duration of their children. More longitudinal studies are necessary to establish a causal relationship between public health policies and sleep health inequalities. An extension of the investigation to more sleep disturbances is required to cover the entirety of sleep health inequalities in Iran and Saudi Arabia. Full article
(This article belongs to the Section Human Basic Research & Neuroimaging)
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25 pages, 2511 KiB  
Review
Light as a Modulator of Non-Image-Forming Brain Functions—Positive and Negative Impacts of Increasing Light Availability
by Islay Campbell, Roya Sharifpour and Gilles Vandewalle
Clocks & Sleep 2023, 5(1), 116-140; https://doi.org/10.3390/clockssleep5010012 - 17 Mar 2023
Cited by 5 | Viewed by 4099
Abstract
Light use is rising steeply, mainly because of the advent of light-emitting diode (LED) devices. LEDs are frequently blue-enriched light sources and may have different impacts on the non-image forming (NIF) system, which is maximally sensitive to blue-wavelength light. Most importantly, the timing [...] Read more.
Light use is rising steeply, mainly because of the advent of light-emitting diode (LED) devices. LEDs are frequently blue-enriched light sources and may have different impacts on the non-image forming (NIF) system, which is maximally sensitive to blue-wavelength light. Most importantly, the timing of LED device use is widespread, leading to novel light exposure patterns on the NIF system. The goal of this narrative review is to discuss the multiple aspects that we think should be accounted for when attempting to predict how this situation will affect the NIF impact of light on brain functions. We first cover both the image-forming and NIF pathways of the brain. We then detail our current understanding of the impact of light on human cognition, sleep, alertness, and mood. Finally, we discuss questions concerning the adoption of LED lighting and screens, which offer new opportunities to improve well-being, but also raise concerns about increasing light exposure, which may be detrimental to health, particularly in the evening. Full article
(This article belongs to the Section Impact of Light & other Zeitgebers)
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18 pages, 1039 KiB  
Article
Motus Vita Est: Fruit Flies Need to Be More Active and Sleep Less to Adapt to Either a Longer or Harder Life
by Lyudmila P. Zakharenko, Dmitrii V. Petrovskii, Margarita A. Bobrovskikh, Nataly E. Gruntenko, Ekaterina Y. Yakovleva, Alexander V. Markov and Arcady A. Putilov
Clocks & Sleep 2023, 5(1), 98-115; https://doi.org/10.3390/clockssleep5010011 - 03 Mar 2023
Viewed by 2270
Abstract
Background: Activity plays a very important role in keeping bodies strong and healthy, slowing senescence, and decreasing morbidity and mortality. Drosophila models of evolution under various selective pressures can be used to examine whether increased activity and decreased sleep duration are associated with [...] Read more.
Background: Activity plays a very important role in keeping bodies strong and healthy, slowing senescence, and decreasing morbidity and mortality. Drosophila models of evolution under various selective pressures can be used to examine whether increased activity and decreased sleep duration are associated with the adaptation of this nonhuman species to longer or harder lives. Methods: For several years, descendants of wild flies were reared in a laboratory without and with selection pressure. To maintain the “salt” and “starch” strains, flies from the wild population (called “control”) were reared on two adverse food substrates. The “long-lived” strain was maintained through artificial selection for late reproduction. The 24 h patterns of locomotor activity and sleep in flies from the selected and unselected strains (902 flies in total) were studied in constant darkness for at least, 5 days. Results: Compared to the control flies, flies from the selected strains demonstrated enhanced locomotor activity and reduced sleep duration. The most profound increase in locomotor activity was observed in flies from the starch (short-lived) strain. Additionally, the selection changed the 24 h patterns of locomotor activity and sleep. For instance, the morning and evening peaks of locomotor activity were advanced and delayed, respectively, in flies from the long-lived strain. Conclusion: Flies become more active and sleep less in response to various selection pressures. These beneficial changes in trait values might be relevant to trade-offs among fitness-related traits, such as body weight, fecundity, and longevity. Full article
(This article belongs to the Section Animal Basic Research)
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4 pages, 457 KiB  
Obituary
Obituary for Dr. Konstantin Danilenko (19.03.1962–18.01.2023)
by Arcady A. Putilov
Clocks & Sleep 2023, 5(1), 94-97; https://doi.org/10.3390/clockssleep5010010 - 02 Mar 2023
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9 pages, 1379 KiB  
Article
Creating the Cave: Conducting Circadian Science in Early Childhood
by Lauren E. Hartstein, Sachi D. Wong, Leen Abbas, Sophia Choubai, Jonah N. Wilson, Trace Jablin and Monique K. LeBourgeois
Clocks & Sleep 2023, 5(1), 85-93; https://doi.org/10.3390/clockssleep5010009 - 20 Feb 2023
Cited by 1 | Viewed by 1874
Abstract
In humans, physiological outputs of the body’s internal clock (i.e., saliva, serum, and temperature) can be collected to quantify the timing of the circadian system. In-lab assessment of salivary melatonin in a dimly lit environment is a common approach for adolescents and adults; [...] Read more.
In humans, physiological outputs of the body’s internal clock (i.e., saliva, serum, and temperature) can be collected to quantify the timing of the circadian system. In-lab assessment of salivary melatonin in a dimly lit environment is a common approach for adolescents and adults; however, the reliable measurement of melatonin onset in toddlers and preschoolers requires a modification of laboratory methods. For > 15 years, we have successfully collected data from ~250 in-home dim light melatonin onset (DLMO) assessments of children aged 2–5 years. Although in-home studies of circadian physiology may introduce a host of challenges and may increase the risk of incomplete data (e.g., accidental light exposure), in-home studies afford more comfort (e.g., less arousal in children) and flexibility for families. Here, we provide effective tools and strategies to assess children’s DLMO, a reliable marker of circadian timing, through a rigorous in-home protocol. We first describe our basic approach, including the study protocol, collection of actigraphy data, and strategies for training child participants to complete procedures. Next, we detail how to convert the home into a “cave”, or dim-light environment, and present guidelines for timing the salivary data collection. Lastly, we provide helpful tips to increase participants’ compliance based upon behavioral and developmental science tenets. Full article
(This article belongs to the Section Human Basic Research & Neuroimaging)
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13 pages, 1757 KiB  
Article
Does Motor Memory Reactivation through Practice and Post-Learning Sleep Modulate Consolidation?
by Whitney Stee and Philippe Peigneux
Clocks & Sleep 2023, 5(1), 72-84; https://doi.org/10.3390/clockssleep5010008 - 17 Feb 2023
Cited by 2 | Viewed by 2139
Abstract
Retrieving previously stored information makes memory traces labile again and can trigger restabilization in a strengthened or weakened form depending on the reactivation condition. Available evidence for long-term performance changes upon reactivation of motor memories and the effect of post-learning sleep on their [...] Read more.
Retrieving previously stored information makes memory traces labile again and can trigger restabilization in a strengthened or weakened form depending on the reactivation condition. Available evidence for long-term performance changes upon reactivation of motor memories and the effect of post-learning sleep on their consolidation remains scarce, and so does the data on the ways in which subsequent reactivation of motor memories interacts with sleep-related consolidation. Eighty young volunteers learned (Day 1) a 12-element Serial Reaction Time Task (SRTT) before a post-training Regular Sleep (RS) or Sleep Deprivation (SD) night, either followed (Day 2) by morning motor reactivation through a short SRTT testing or no motor activity. Consolidation was assessed after three recovery nights (Day 5). A 2 × 2 ANOVA carried on proportional offline gains did not evidence significant Reactivation (Morning Reactivation/No Morning Reactivation; p = 0.098), post-training Sleep (RS/SD; p = 0.301) or Sleep*Reactivation interaction (p = 0.257) effect. Our results are in line with prior studies suggesting a lack of supplementary performance gains upon reactivation, and other studies that failed to disclose post-learning sleep-related effects on performance improvement. However, lack of overt behavioural effects does not detract from the possibility of sleep- or reconsolidation-related covert neurophysiological changes underlying similar behavioural performance levels. Full article
(This article belongs to the Section Human Basic Research & Neuroimaging)
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10 pages, 923 KiB  
Review
Cavefishes in Chronobiological Research: A Narrative Review
by Vera V. Pavlova and Viacheslav V. Krylov
Clocks & Sleep 2023, 5(1), 62-71; https://doi.org/10.3390/clockssleep5010007 - 10 Feb 2023
Cited by 1 | Viewed by 2071
Abstract
Cavefish are vertebrates living in extreme subterranean environments with no light, temperature changes, and limited food. Circadian rhythms in these fish are suppressed in natural habitats. However, they can be found in artificial light–dark cycles and other zeitgebers. The molecular circadian clock has [...] Read more.
Cavefish are vertebrates living in extreme subterranean environments with no light, temperature changes, and limited food. Circadian rhythms in these fish are suppressed in natural habitats. However, they can be found in artificial light–dark cycles and other zeitgebers. The molecular circadian clock has its peculiarities in cavefish. In Astyanax mexicanus, the core clock mechanism is tonically repressed in the caves due to the overactivation of the light input pathway. A lack of functional light input pathway but rather the entrainment of circadian genes’ expression by scheduled feeding were revealed in more ancient Phreatichthys andruzzii. Different evolutionarily determined irregularities in the functioning of molecular circadian oscillators can be expected in other cavefish. The unique property of some species is the existence of surface and cave forms. Along with the ease of maintenance and breeding, it made cavefish a promising model for chronobiological studies. At the same time, a divergence of the circadian system between cavefish populations requires the strain of origin to be indicated in further research. Full article
(This article belongs to the Section Animal Basic Research)
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15 pages, 1478 KiB  
Article
The Influence of Light and Physical Activity on the Timing and Duration of Sleep: Insights from a Natural Model of Dance Training in Shifts
by Ignacio Estevan, Natalia Coirolo, Bettina Tassino and Ana Silva
Clocks & Sleep 2023, 5(1), 47-61; https://doi.org/10.3390/clockssleep5010006 - 31 Jan 2023
Cited by 3 | Viewed by 1965
Abstract
Environmental, social, and behavioral variables influence sleep timing and duration. Using wrist-worn accelerometers, we recorded 31 dancers (age = 22.6 ± 3.5) for 17 days and who trained either in the morning (n = 15) or in the late evening (n [...] Read more.
Environmental, social, and behavioral variables influence sleep timing and duration. Using wrist-worn accelerometers, we recorded 31 dancers (age = 22.6 ± 3.5) for 17 days and who trained either in the morning (n = 15) or in the late evening (n = 16). We estimated the dancers’ daily sleep pattern: onset, end, and duration. In addition, their minutes of moderate-to-vigorous physical activity (MVPA) and mean light illuminance were also calculated daily and for the morning-shift and late-evening-shift time windows. On training days, the shifts involved differences in sleep timing, alarm-driven waking frequency, and the pattern of light exposure and MVPA duration. Sleep was strongly advanced when dancers trained in the morning and when alarms were used, while morning light had a low influence. Sleep was delayed when dancers were more exposed to light and displayed longer MVPA during the late evening. Sleep duration was strongly reduced on weekends and when alarms were used. A small reduction in sleep duration was also observed when morning illuminance was lower or when late evening MVPA was longer. Training in shifts influenced the timing of environmental and behavioral factors, which added up to shape dancers’ sleep timing and duration. Full article
(This article belongs to the Section Impact of Light & other Zeitgebers)
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2 pages, 179 KiB  
Editorial
Acknowledgment to the Reviewers of Clocks & Sleep in 2022
by Clocks & Sleep Editorial Office
Clocks & Sleep 2023, 5(1), 45-46; https://doi.org/10.3390/clockssleep5010005 - 28 Jan 2023
Viewed by 1199
Abstract
High-quality academic publishing is built on rigorous peer review [...] Full article
11 pages, 490 KiB  
Article
Pregnant Women’s Attitudes and Beliefs towards Sleep and Exercise: A Cross-Sectional Survey
by Summer Cannon, Melanie Hayman and Michele Lastella
Clocks & Sleep 2023, 5(1), 34-44; https://doi.org/10.3390/clockssleep5010004 - 17 Jan 2023
Cited by 2 | Viewed by 2360
Abstract
As many as 80% of women report experiencing poor sleep throughout pregnancy. Exercise is associated with many health benefits during pregnancy and is established as a non-pharmacological method to improve sleep in both pregnant and non-pregnant populations. Given the importance of sleep and [...] Read more.
As many as 80% of women report experiencing poor sleep throughout pregnancy. Exercise is associated with many health benefits during pregnancy and is established as a non-pharmacological method to improve sleep in both pregnant and non-pregnant populations. Given the importance of sleep and exercise during pregnancy, the aim of this cross-sectional study was to (1) examine pregnant women’s attitudes and beliefs towards sleep and exercise during pregnancy, and (2) investigate the barriers women face to achieving good sleep and engaging in healthy levels of exercise. Participants were comprised of 258 pregnant Australian women (31.3 ± 5.1 years) who completed a 51-question online survey. Almost all (98%) participants believed exercise during pregnancy to be safe, whilst over half (67%) believed participating in more exercise will improve their sleep. Over 70% of participants reported experiencing barriers such as physical symptoms related to pregnancy that negatively impacted their ability to exercise. Almost all (95%) participants reported experiencing barriers to sleep in their current pregnancy. Present findings suggest that overcoming intrapersonal barriers should be a priority for any intervention aiming to improve sleep or increase exercise levels in pregnant populations. Findings from the present study highlight the need for a better understanding of women’s sleep experiences during pregnancy, and demonstrate how exercise may improve sleep and health outcomes. Full article
(This article belongs to the Special Issue Role of Sleep and Circadian Rhythms in Health II)
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13 pages, 279 KiB  
Article
Habitual Sleep Patterns and Chronic Sleep Problems in Relation to Sex, Age, and Circadian Preference in a Population-Based Sample of Norwegian Adults
by Ingvild West Saxvig, Bjørn Bjorvatn and Siri Waage
Clocks & Sleep 2023, 5(1), 21-33; https://doi.org/10.3390/clockssleep5010003 - 06 Jan 2023
Cited by 3 | Viewed by 2014
Abstract
Sleep patterns and problems vary in relation to internal (e.g., sex, age, circadian preference) and external (e.g., social structures) factors. The main aim of the present study was to describe habitual sleep patterns and chronic sleep problems in a population-based sample of Norwegian [...] Read more.
Sleep patterns and problems vary in relation to internal (e.g., sex, age, circadian preference) and external (e.g., social structures) factors. The main aim of the present study was to describe habitual sleep patterns and chronic sleep problems in a population-based sample of Norwegian adults. During spring 2022, a sample of 1028 adults completed an online survey on sleep habits and problems. Response rate was 33.5%. The survey included the Munich ChronoType Questionnaire and items on circadian preference and chronic sleep problems. Mean workday sleep duration was 7:19 h (±199 min), and shorter in males (p = 0.035) and evening persons (p = 0.003). Short workday sleep duration (<6 h) was reported by 3.1% and was associated with evening preference (p = 0.001). Mean social jetlag was 0:51 h (±75 min), and longer in males (p = 0.036), younger adults (p < 0.001) and evening persons (p < 0.001). Long social jetlag (≥2 h) was reported by 11.2% and associated with younger age (p < 0.001) and evening preference (p < 0.001). Chronic sleep problems (≥3 months) were reported by 44.1%, and associated with female sex (p < 0.001) and evening preference (p = 0.002). Results underscore the importance of considering evening circadian preference as a risk factor for short workday sleep duration, long social jetlag and self-reported chronic sleep problems. Full article
(This article belongs to the Section Society)
11 pages, 1083 KiB  
Article
Portability of Polygenic Risk Scores for Sleep Duration, Insomnia and Chronotype in 33,493 Individuals
by Anna Perkiö, Ilona Merikanto, Katri Kantojärvi, Tiina Paunio, Nasa Sinnott-Armstrong, Samuel E. Jones and Hanna M. Ollila
Clocks & Sleep 2023, 5(1), 10-20; https://doi.org/10.3390/clockssleep5010002 - 30 Dec 2022
Cited by 2 | Viewed by 2387
Abstract
Polygenic risk scores (PRSs) estimate genetic liability for diseases and traits. However, the portability of PRSs in sleep traits has remained elusive. We generated PRSs for self-reported insomnia, chronotype and sleep duration using summary data from genome-wide association studies (GWASs) performed in 350,000 [...] Read more.
Polygenic risk scores (PRSs) estimate genetic liability for diseases and traits. However, the portability of PRSs in sleep traits has remained elusive. We generated PRSs for self-reported insomnia, chronotype and sleep duration using summary data from genome-wide association studies (GWASs) performed in 350,000 to 697,000 European-ancestry individuals. We then projected the scores in two independent Finnish population cohorts (N = 33,493) and tested whether the PRSs were associated with their respective sleep traits. We observed that all the generated PRSs were associated with their corresponding traits (p < 0.05 in all cases). Furthermore, we found that there was a 22.2 min difference in reported sleep between the 5% tails of the PRS for sleep duration (p < 0.001). Our findings indicate that sleep-related PRSs show portability across cohorts. The findings also demonstrate that sleep measures using PRSs for sleep behaviors may provide useful instruments for testing disease and trait associations in cohorts where direct sleep parameters have not yet been measured. Full article
(This article belongs to the Special Issue Genetic Markers in Sleep Disorders)
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9 pages, 1723 KiB  
Article
Changes in Sleep Regularity and Perceived Life Stress across the COVID-19 Pandemic: A Longitudinal Analysis of a Predominately Female United States Convenience Sample
by Ryan Bottary, Eric C. Fields, Loren Ugheoke, Dan Denis, Janet M. Mullington and Tony J. Cunningham
Clocks & Sleep 2023, 5(1), 1-9; https://doi.org/10.3390/clockssleep5010001 - 26 Dec 2022
Cited by 2 | Viewed by 2089
Abstract
The Coronavirus Disease 2019 (COVID-19) pandemic had a profound impact on sleep and psychological well-being for individuals worldwide. This pre-registered investigation extends our prior study by tracking self-reported social jetlag (SJL), social sleep restriction (SSR), and perceived life stress from May 2020 through [...] Read more.
The Coronavirus Disease 2019 (COVID-19) pandemic had a profound impact on sleep and psychological well-being for individuals worldwide. This pre-registered investigation extends our prior study by tracking self-reported social jetlag (SJL), social sleep restriction (SSR), and perceived life stress from May 2020 through October 2021. Using web-based surveys, we collected self-reported sleep information with the Ultrashort Munich Chronotype Questionnaire at three additional timepoints (September 2020, February 2021 and October 2021). Further, we measured perceived life stress with the Perceived Stress Scale at two additional timepoints (February 2021 and October 2021). In a subsample of 181, predominantly female (87%), United States adults aged 19–89 years, we expanded our prior findings by showing that the precipitous drop in SJL during the pandemic first wave (May 2020), compared to pre-pandemic (February, 2020), rapidly rose with loosening social restrictions (September 2020), though never returned to pre-pandemic levels. This effect was greatest in young adults, but not associated with self-reported chronotype. Further, perceived life stress decreased across the pandemic, but was unrelated to SJL or SSR. These findings suggest that sleep schedules were sensitive to pandemic-related changes in social restrictions, especially in younger participants. We posit several possible mechanisms supporting these findings. Full article
(This article belongs to the Special Issue Role of Sleep and Circadian Rhythms in Health II)
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