ABSTRACT The aim of this study was to detect whether the COVID-19 pandemic has caused changes in the sleep cycle (subjective sleep shifts) of high school students divided into a sample of young women – W (n = 1999, age = 17.65 ± 2.39 y) and young men – M (n = 1094, age = 17.49 ± 1.74 y) in Slovakia depending on circadian preference in comparison with the term before COVID-19. The present cross-sectional study employed a self-reported standardized questionnaire (Morningness-Eveningness Questionnaire) to study circadian preference, which was complemented by a question focused on subjective sleep shifts before and during the pandemic. The results revealed significant strong dependence between circadian preference and subjective sleep shift in both W (χ 2 (8) = 153.1, p < .01, Cramer’s V = .20, p < .01) and M (χ 2 (8) = 98.3, p < .01, Cramer’s V =.21, p < .01). The delay of the sleep cycle has mainly become apparent in the case of definite evening types (W: 75.7%; M: 71.8%) and moderate evening types (W: 83.1%; M: 70.3%). The delay also prevailed in the intermediate types (W: 61.9%; M: 53.8%). Subjective sleep shifts were not confirmed (W: 93.8%; M: 35.3%) in the definite morning type. The sleep cycle was changed to earlier hours of definite morning types (W: 6.3%; M: 52.9%). It is necessary to focus on definite and moderate evening types and regulate the unsuitable state to time shift of the sleep cycle.

ABSTRACT Modern society is structured around early routines which cause evening types to suffer from health and performance detriments associated with sleep times being misaligned with biological needs (circadian preference). Given that COVID-19 lockdowns were less constrained by social schedules, the current study explores whether temporal behaviours became better aligned with biological needs, and whether these changes benefited work engagement. 406 UK participants reported circadian preference and pre-lockdown and lockdown sleep times, work times, and work engagement. Results found that sleep health improved under lockdown measures in terms of increased sleep duration and reduced social jetlag, and sleep and work times became better aligned with circadian preferences. The most circadian-misaligned participants – students and young adults – exhibited the largest changes to sleep and work habits. However, work engagement decreased more in participants with improved social jetlag and delayed work habits, which is surprising given that these temporal changes reflect improved circadian alignment. We discuss potential moderators including poor sleep quality, non-engaging work-from-home environments, and mental health. These findings have implications for encouraging flexible educational and employment schedules post-COVID-19 to satisfy the common drive to improve circadian alignment, but future work must determine the moderating factors that impair work engagement during remote work.

ABSTRACT Sprint and jump performances represent performance-determining parameters in individual and team sports. Fluctuations in performance depending on the daytime raise the question of the best time to train and compete. Given the scarce research on females, this study aimed to analyze the influence of daytime on sprint and jump performances and to investigate whether the performance difference is related to the chronotype. Thus, 23 female sports students completed a questionnaire to assess their chronotype followed by performing two 30 m sprints, 5 Repeated Jump Tests (5RJT), and countermovement jumps (CMJ) in the morning (7:00–9:00 h) and evening (17:00–19:00 h). Time after 5 m, 10 m, and 30 m during the sprints, reactive strength index (RSI) during the 5RJTs, and jump height during the CMJs were examined. The performance during the 30 m sprint (t(22) = 5.28, p < 0.01 moderate effect size: 0.50) and the two jump tests (5RJT: t(22) = 8.27, p < 0.01 large effect size: 0.95; CMJ: t(22) = 5.46, p < 0.01 moderate effect size: 0.79) were significantly better in the evening than in the morning. There was no significant correlation between chronotype and the time-of-day effect. The results should be considered when planning training and competition.

ABSTRACT Biological changes contribute to preferences for later bed and wake times during adolescence, yet the social constraints of school start times necessitate early wake times. This often results in social jetlag (i.e. misalignment between preferred sleep timing on weekends and school days). We examined whether social jetlag predicts adolescent internalizing and externalizing behavior over time and/or whether associations differ based on sex. We used data from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development Study (n = 767) to test whether social jetlag at 6th grade (ages 12–13 years) predicted internalizing and externalizing behavior at age 15 years and whether child sex moderated associations. Controlling for internalizing and externalizing behavior at 6th grade (ages 12–13 years), results were that social jetlag at 6th grade (ages 12–13 years) predicted more internalizing and externalizing behaviors at age 15 for females, but not males. These findings show that social jetlag during early adolescence confers risk for internalizing and externalizing behavior in females at mid-adolescence. Greater attention should be placed on identifying and addressing social jetlag in adolescent females.

ABSTRACT This study aimed to investigate the relationships between chronotype and addiction-like eating behavior, mindful eating and ultra-processed food consumption among undergraduate students. Specific and validated scales were used in order to evaluate chronotype, addiction-like eating behavior and mindful eating (N = 605). Dietary intake was determined by food frequency questionnaire and percentage energy from ultra-processed food was calculated. Self-reported weights and heights were obtained from the participants. Mean scores of scales, social jetlag, energy intake, ultra-processed food intake and BMI were compared by chronotypes. Associations between chronotype, addiction-like eating behavior, mindful eating, ultra-processed food consumption and BMI were determined by Pearson’s test. The relationships between chronotype and addiction-like eating behavior, mindful eating and ultra-processed food intake were assessed by linear regression models and adjusted for sex, BMI, energy intake, season, smoking and alcohol consumption. Evening-type participants had higher scores of social jetlag (2.01 ± 0.09), appetitive drive (26.02 ± 0.63), low dietary control (20.50 ± 0.41), addiction-like eating behavior (46.52 ± 0.85), lower scores of recognition (21.91 ± 0.43) and higher percentage energy from ultra-processed food (32.24 ± 1.26%). Chronotype score showed negative associations with addiction like eating behavior (β=-0.247, p < 0.001) and ultra-processed food consumption (β=-0.247, p < 0.001), and a positive association with recognition (β = 0.124, p < 0.001). Results suggest that chronotype is inversely associated with addiction-like eating behavior and ultra-processed food consumption, and positively associated with mindful eating among undergraduate students.

ABSTRACT Artificial light at night (ALAN) is related to various diseases, such as cancer, obesity, and coronary heart disease. However, its impact on blood pressure in adolescents is not well understood. To investigate this, we conducted a cross-sectional study with a nationwide sample of college students in China, who were freshmen from four disperse universities during Sep. and Oct. 2018. Mean levels of ALAN at participants’ residential addresses during 2013–2018 were estimated using time-varying satellite data. The association of the 6-y average of ALAN with blood pressure was estimated by using generalized linear mixed models. A total of 17 046 participants (18.2 ± 0.7 y of age, 46.79% female) from 2,412 counties and cities were included in the final analysis. After a full adjustment for potential confounders, ALAN was positively associated with systolic blood pressure (β = 0.20, p = 0.032) and pulse pressure (β = 0.28, p  = 0.001), but there was no association between ALAN and diastolic blood pressure (β = -0.08, p = 0.213). In the sensitivity analysis, the results consistent with the main analysis were observed. The blood pressure of males and those with a BMI ≤24 kg/m2 were more susceptible to ALAN exposure. Our findings highlight the importance of ALAN management for blood pressure control, particularly among male and normal-weight individuals.

ABSTRACT For a long time, cyclical changes in the body were assumed to be caused by the cyclicity of the environment (day-night, seasons). The concept of daily and seasonal changes was first documented in the 18th century by astronomer D’Ortous de Mairan, who demonstrated that plant leaf motions varied depending on the time of day, and by Linné’s description of his floral clock in 1751. In 1832, De Candolle was the first to experimentally establish the endogeneity of rhythms in plants, underlining the notion of what we now term free-running rhythms. Julien-Joseph Virey made his own contribution in his thesis, published in 1814, against this backdrop, in which he examined the knowledge of his day on the daily and seasonal biological fluctuations of living matters. He emphasized the relevance of the environment’s day-night cycle on plant life and created a list of plants based on their diurnality or nocturnality. He expanded on the issue of rhythmic changes in human health and sickness and provided his own data on the daily fluctuations in patient mortality he discovered at the Val-de-Grâce military hospital where he was chief pharmacist. What is crucial is his use of terms such as “living clock,” “entrainment,” and “innate rhythm” and the applicability of the advanced concepts Because Virey introduced the notion of temporal variations and the impact of the alternation of day and night on these variations, this thesis is a historic testimonial to understanding of biological rhythms in the first half of the 19th century. We may assume from his writings on rhythmic fluctuations that he offered the theory, followed by an experiment, however primitive, from which he drew conclusions and postulated a mechanism (the living clock) that would later prove accurate. All of these aspects indicate that this study represents an early exploration of the notion of temporal variations in humans.

ABSTRACT Chronobiology, which studies biological rhythms and their impacts on health, presents a potential avenue for treating amyotrophic lateral sclerosis. Clock gene-related therapies, focusing on genes responsible for regulating biological rhythms, may hold promise in the treatment. Among these clock genes, nuclear receptor subfamily 1 Group D member 1 (NR1D1) plays a vital role in neurodegenerative diseases. In this particular study, it was aimed to investigate the potential of FDA-approved drugs commonly used in amyotrophic lateral sclerosis treatment and melatonin, a hormone known for its role in regulating sleep-wake cycles, as ligands for clock gene-related therapy. The ligands were subjected to molecular docking and molecular dynamics simulation methods against the NR1D1 clock gene. These results suggested that combining melatonin with FDA-approved medications commonly used in the treatment might yield positive outcomes. This study provides preliminary data and lays the groundwork for future investigations involving in vitro (laboratory-based) and in vivo (animal or human-based) research on chronotherapy. In summary, this research highlights the potential of clock gene-related therapy utilizing melatonin in conjunction with FDA-approved drugs for amyotrophic lateral sclerosis treatment, offering insights into novel treatment strategies. The findings underscore the need for further studies to explore the effectiveness of this hypothetical approach in experimental and clinical settings.

ABSTRACT Circadian rhythm disruption is a core symptom of bipolar disorder (BD), also reflected in altered patterns of melatonin release. Reductions of grey matter (GM) volumes are well documented in BD. We hypothesized that levels and timing of melatonin secretion in bipolar depression could be associated with depressive psychopathology and brain GM integrity. The onset of melatonin secretion under dim light conditions (DLMO) and the amount of time between DLMO and midsleep (i.e. phase angle difference; PAD) were used as circadian rhythm markers. To study the time course of melatonin secretion, an exponential curve fitting the melatonin values was calculated, and the slope coefficients (SLP) were obtained for each participant. Significant differences were found between HC and BD in PAD measures and melatonin profiles. Correlations between PAD and depressive psychopathology were identified. Melatonin secretion patterns were found to be associated with GM volumes in the Striatum and Supramarginal Gyrus in BD. Our findings emphasized the role of melatonin secretion role as a biological marker of circadian synchronization in bipolar depression and provided a novel insight for a link between melatonin release and brain structure.

ABSTRACT Circadian rhythm and sleep disruption have been associated with depressive symptoms in children. This study was conducted to determine sleep disturbances and circadian preferences and their possible associations with depression in healthy children 6 to 12 years of age. A total of 111 healthy children (mean age 7.5 years; 62.2% male) were included. Sleep disturbances and depression were determined by the Sleep Disturbance Scale for Children (SDSC) and the Children’s Depression Inventory (CDI), respectively. Circadian preference was evaluated by the Morningness – Eveningness Stability Scale improved (MESSi). SDSC was correlated with CDI (r = 0.396, p < 0.001). Morning affect was inversely correlated with CDI (r = −0.405, p < 0.001), SDSC (r = −0.348, p < 0.001), and three subdimensions of SDSC, i.e. disorders of initiating and maintaining sleep (DIMS, r = −0.317, p = 0.001), disorders of arousal (DA, r = −0.375, p < 0.001) and disorders of excessive somnolence (DOES, r = −0.303, p = 0.001). Distinctness was inversely correlated with CDI (r = −0.402, p < 0.001) and SDSC (r = −0.274, p < 0.001). Increased use of electronic devices was associated with higher CDI (p = 0.003), while decreased duration of physical activity with higher SDSC (p = 0.017). Our findings support the recommendations addressing sleep and circadian preferences as lifestyle modifications in reducing depression in children.