Circadian typology: a comprehensive review

Enhanced fear acquisition in individuals with evening chronotype. A virtual reality fear conditioning/extinction study

Circadian rhythms have received increasing attention within the context of mental disorders. Evening chronotype has been associated with enhanced risk to develop anxiety and post-traumatic stress disorder (PTSD). The classical fear conditioning paradigm is a powerful tool to reveal key mechanisms of anxiety and PTSD. We used this paradigm to study the neurocognitive basis of the association between chronotype and fear responses in healthy humans. 20 participants with evening chronotype and 20 controls (i.e., intermediate chronotype) completed a 2-day Pavlovian fear learning and extinction virtual reality task. Participants received fear conditioning, and extinction learning on day 1. Extinction memory recall was tested on day 2. To address interactions between chronotype and time of day of the fear conditioning, and extinction performance, half of the participants were tested in the morning, and the other half in the evening. Skin conductance response (SCR) and subjective fear ratings were measured as primary outcomes. Chronotype was established via the morningness-eveningness questionnaire (MEQ). We found an overall higher SCR for fear acquisition in participants with the evening chronotype profile, compared to controls. Moreover, the higher the MEQ scores -indicative of less eveningness - the lower the SCR was. No effects of chronotype were found for extinction and extinction recall. The higher vulnerability of the evening chronotype for anxiety and related disorders may thus be explained by enhanced fear acquisition of this group.

Chronotype, circadian rhythm, and psychiatric disorders: Recent evidence and potential mechanisms

The circadian rhythm is crucial for physiological and behavioral functions. Chronotype, which represents individual preferences for activity and performance, is associated with human health issues, particularly psychiatric disorders. This narrative review, which focuses on the relationship between chronotype and mental disorders, provides an insight into the potential mechanism. Recent evidence indicates that (1) the evening chronotype is a risk factor for depressive disorders and substance use disorders, whereas the morning chronotype is a protective factor. (2) Evening chronotype individuals with bipolar disorder tend to have more severe symptoms and comorbidities. (3) The evening chronotype is only related to anxiety symptoms. (4) The relationship between chronotype and schizophrenia remains unclear, despite increasing evidence on their link. (5) The evening chronotype is significantly associated with eating disorders, with the majority of studies have focused on binge eating disorders. Furthermore, the underlying mechanisms or influence factors are described in detail, including clock genes, brain characteristics, neuroendocrinology, the light/dark cycle, social factors, psychological factors, and sleep disorders. These findings provide the latest evidence on chronotypes and psychiatric disorders and serve as a valuable reference for researchers.

The mediating roles of depression, anxiety, and psychological pain in the relationship between chronotype and suicide in patients with depressive disorder

The evening chronotype has been associated with depressive symptoms and suicidality; however, the underlying mechanisms are still under investigation. Research has shown that psychological pain, or feelings of suffering, is closely related to suicidality. Therefore, the aim of the study is to determine whether psychological pain, anxiety, and depressive symptoms mediate the association between chronotype and depressive symptoms in patients with depression and in healthy controls. A total of 118 patients with depressive disorder and 85 healthy controls completed the Morningness-Eveningness Questionnaire, the Hospital Anxiety and Depression Scale, the Suicide Probability Scale, and the Mee-Bunney Psychological Pain Assessment Scale. Mediation analysis revealed that the relationship between eveningness and suicidality was fully mediated by depression and psychological pain and not by anxiety. These findings highlight that psychological pain is an important psychological dimension in the relationship between eveningness and suicidality.

Diurnal variations of resting-state fMRI data: A graph-based analysis

Circadian rhythms (lasting approximately 24 h) control and entrain various physiological processes, ranging from neural activity and hormone secretion to sleep cycles and eating habits. Several studies have shown that time of day (TOD) is associated with human cognition and brain functions. In this study, utilizing a chronotype-based paradigm, we applied a graph theory approach on resting-state functional MRI (rs-fMRI) data to compare whole-brain functional network topology between morning and evening sessions and between morning-type (MT) and evening-type (ET) participants. Sixty-two individuals (31 MT and 31 ET) underwent two fMRI sessions, approximately 1 hour (morning) and 10 h (evening) after their wake-up time, according to their declared habitual sleep-wake pattern on a regular working day. In the global analysis, the findings revealed the effect of TOD on functional connectivity (FC) patterns, including increased small-worldness, assortativity, and synchronization across the day. However, we identified no significant differences based on chronotype categories. The study of the modular structure of the brain at mesoscale showed that functional networks tended to be more integrated with one another in the evening session than in the morning session. Local/regional changes were affected by both factors (i.e., TOD and chronotype), mostly in areas associated with somatomotor, attention, frontoparietal, and default networks. Furthermore, connectivity and hub analyses revealed that the somatomotor, ventral attention, and visual networks covered the most highly connected areas in the morning and evening sessions: the latter two were more active in the morning sessions, and the first was identified as being more active in the evening. Finally, we performed a correlation analysis to determine whether global and nodal measures were associated with subjective assessments across participants. Collectively, these findings contribute to an increased understanding of diurnal fluctuations in resting brain activity and highlight the role of TOD in future studies on brain function and the design of fMRI experiments.

Association between chronotype, sleep pattern, and eating behaviours in a group of Italian adults

A cross-sectional study was conducted to assess the possible relationship between chronotype, sleeping, and eating patterns in 74 Italian adults (71.6% women). Based on Morningness-Eveningness Questionnare (MEQ) score, participants were classified as morning (n = 24), intermediate (n = 25), and evening (n = 25) chronotypes. From analysis, no significant differences among chronotypes emerged for sleep habits. As to eating behaviours, the evening subjects showed a significant (p < 0.05) shift towards later hours of the day in the consumption of all meals, except dinner. In addition, the evening subjects had a later midpoint of energy intake (EI) of about 35 min and 1 h (p < 0.001), respectively, than the intermediate and morning subjects. Analysing the diet quality, morning subjects reported significantly (p = 0.030) lower consumption of sweets and sweeteners, and significantly (p = 0.035) lower intake of ultra-processed fats and seasonings. Evening subjects showed a significant delay in EI during the day, while morning subjects reported a better-quality diet.

The fall of vulnerability to sleep disturbances in evening chronotypes when working from home and its implications for depression

Eveningness is distinctively associated with sleep disturbances and depression symptoms due to the misalignment between biological and social clocks. The widespread imposition of remote working due to the COVID-19 pandemic allowed a more flexible sleep schedule. This scenario could promote sleep and mental health in evening-type subjects. We investigated the effect of working from home on sleep quality/quantity and insomnia symptoms within the morningness-eveningness continuum, and its indirect repercussions on depressive symptomatology. A total of 610 Italian office workers (mean age ± standard deviation, 35.47 ± 10.17 years) and 265 remote workers (40.31 ± 10.69 years) participated in a web-based survey during the second contagion wave of COVID-19 (28 November–11 December 2020). We evaluated chronotype, sleep quality/duration, insomnia, and depression symptoms through validated questionnaires. Three moderated mediation models were performed on cross-sectional data, testing the mediation effect of sleep variables on the association between morningness-eveningness continuum and depression symptoms, with working modality (office vs. remote working) as moderator of the relationship between chronotype and sleep variables. Remote working was associated with delayed bedtime and get-up time. Working modality moderated the chronotype effect on sleep variables, as eveningness was related to worse sleep disturbances and shorter sleep duration among the office workers only. Working modality also moderated the mediation of sleep variables between chronotype and depression. The above mediation vanished among remote workers. The present study suggests that evening-type people did not show their characteristic vulnerability to sleep problems when working from home. This result could imply a reduction of the proposed sleep-driven predisposition to depression of late chronotypes. A working environment complying with individual circadian preferences might ensure an adequate sleep quantity/quality for the evening-type population, promoting their mental health.

The impact of COVID-19 on Italian adolescents' sleep and its association with psychological factors

Insomnia and circadian dysregulation during adolescence represent important risk factors for emotional and psychological problems. Recent studies have shown that the coronavirus disease 2019 (COVID‐19) pandemic has been linked to a high prevalence of behavioural sleep problems in the general population. This study aimed to provide two pictures of two different time points of the pandemic regarding the prevalence of sleep problems in adolescents and their association with psychological health variables. Two different independent large samples of Italian adolescents aged 13–17 years were recruited at two pandemic time points. A total of 1,146 adolescents at Time 1 (T1; April 2020) and 1,406 at Time 2 (T2; April 2021) took part in the study. Measures of insomnia symptoms, sleep hygiene, chronotype, psychological distress and emotion regulation were collected. Prevalence of insomnia was 12.13% at T1 and 23.19% at T2. Furthermore, high levels of poor sleep habits (late bedtime, poor sleep hygiene, use of electronic devices at bedtime) were also detected at both time points. Insomnia symptoms strongly correlated with poor sleep hygiene, higher psychological distress, and emotional suppression at both time points. Results highlighted an alarming picture for two large samples at two different time points of the pandemic that showed a potential negative impact of the COVID‐19 pandemic, in both the first outbreak and in the later phase of the pandemic, on sleep habits, psychological distress and insomnia symptoms in adolescents. This strongly suggests the need for monitoring these variables and their interaction in the post‐pandemic period and to develop and promote interventions for insomnia and circadian disturbances during adolescence.

Adaptive Individual Differences in Math Courses

A higher education that can be defined as sustainable ensures the acquisition of competencies that are necessary to address the current and future needs of the society in which it exists. Because math competencies are an essential component of college students’ academic and professional success, poor performance outcomes are particularly problematic in the context of an education that aims to be sustainable. This research sought to identify dispositions that are predictive of math performance in the post-pandemic world to develop an early detection system for at-risk students of an understudied population (college students of Middle Eastern descent from Saudi Arabia). It specifically targeted female and male students in STEM or non-STEM majors who were enrolled in a math course of the general education curriculum. During the second semester of a return to entirely face-to-face instruction, their self-efficacy, math learning anxiety, math evaluation anxiety, and preference for morning or evening study activities were surveyed. In the post-pandemic world of this understudied population, the math performance of STEM male and female students was hurt by concerns about learning math. The math performance of non-STEM male students benefited from self-efficacy, whereas that of non-STEM female students was unaffected by any of the dispositions surveyed in the present investigation. These findings suggest that individual difference measures can inform early interventions intended to address performance deficiencies in selected groups of students with the overreaching goal of ensuring a sustainable education for all.

Paradoxical association between chronotype and academic achievement: eveningness reduces academic achievement through sleep disturbance and daytime sleepiness

There are conflicting reports about the association between chronotype and academic achievement. Eveningness persons tend to have lower academic achievement, but have higher cognitive abilities. We hypothesized that sleep disturbance and daytime sleepiness, which are known to affect academic achievement, will interact with this association. To investigate the association, a sleep survey and covariance structure analysis was performed on high-school students. Among a total of 344 first-year high-school students, 294 students validly completed the questionnaire. The association between the recent change in their academic achievement, chronotype, daytime sleepiness, and sleep disturbance were analyzed. A simple comparison demonstrated that not chronotype but sleep disturbance and excessive daytime sleepiness were significant associated factors. Chronotype affects academic achievement through sleep disturbance and daytime sleepiness. Chronotype did not have a significant total effect on the reduction in academic achievement, whereas morningness had a significant direct effect and a significant indirect inverse effect through better sleep and less daytime sleepiness. This model accounted for 13.0% of the variance of the reduction in academic achievement. When discussing the association between chronotype and academic achievement, the effect of sleep disturbance and daytime sleepiness should be considered. Reducing sleep disturbance and daytime sleepiness with consideration to the chronotype of each person would be beneficial for the improvement of academic achievement.

Sleep well, mind wander less: A systematic review of the relationship between sleep outcomes and spontaneous cognition

Despite an upsurge of research on spontaneous cognition, little is known about its associations with sleep-related outcomes. This systematic review, following PRISMA guidelines, examined the relationship between sleep and spontaneous thoughts, across different definitions and measurements of sleep outcomes and spontaneous cognition, and a diversity of methodologies. Twenty-one articles with survey and/or experimental designs were identified. Self-reported disturbed sleep-comprising poor sleep quality, more insomnia symptoms, more daytime sleepiness and a tendency towards eveningness-and experimentally induced sleep deprivation were associated with a tendency to engage in disruptive mind wandering and daydreaming, but not positive-constructive daydreaming. Findings regarding circadian fluctuation in spontaneous thoughts were mixed and inconclusive. This systematic review bridges the gap between the sleep and spontaneous cognition research by contributing to the understanding of potential psychological and cognitive mechanisms of spontaneous cognition, as well as by elucidating the emotional and cognitive consequences of disturbed sleep.

The Effect of Personality on Chrononutrition during the COVID-19 Lockdown in Qatar

The COVID-19 lockdown has had a significant impact on people’s lives worldwide. This study aimed to investigate the effect of personality on chrononutrition during the COVID-19 lockdown. Using a cross-sectional design, a convenient sample of 543 adults in Qatar completed an online questionnaire using validated tools to assess personality and chrononutrition behaviors during the first COVID-19 lockdown. Participants scoring high in openness were more likely to eat at night (mean difference (MD) = 0.41, 95% confidence interval (CI): 0.10, 0.72) compared to those scoring high in agreeableness, while those scoring high in extraversion and openness had a shorter eating window (MD = −76.6, 95%CI: −146.3, −6.93 and MD = −29.8, 95%CI: −56.5, −3.01, respectively). Participants high in extraversion had longer evening latency (MD = 66.3, 95%CI: 25.4, 107.3) and evening eating (MD = −62.0, 95%CI: −114.0, −9.0) compared those high in agreeableness. Participants high in conscientiousness showed evidence of first eating event misalignment during the weekend (MD = 22.0, 95%CI: 0.15, 43.9) and last eating event misalignment during weekdays (MD = −27.8, 95%CI: −47.3, −8.41) compared to those high in agreeableness. Lastly, participants high in openness showed evidence of eating window misalignment during the weekend (MD = 30.6, 95%CI: 5.01, 56.2). This study suggests that personality traits can inform personalized nutritional approaches when aiming for healthy habits during unexpected periods, such as the COVID-19 pandemic.

Social support mediates the effect of morningness on changes in subjective well-being over 6 months

Studies show that morningness is positively associated with subjective well-being. Our previous research investigated factors that could underlie this relationship, finding that the association between morningness-eveningness and subjective well-being can be partially attributed to the higher levels of perceived social support received by morning-oriented individuals. In the present study, we examine the longitudinal effects of perceived social support in mediating the relationship between morningness-eveningness and subjective well-being. Our results show that this mediating effect remains significant with respect to changes in well-being over a 6-month period. It seems that the causal effect of morningness on well-being may be partially mediated by the causal effect of social support. The findings provide further support for the conclusion that perceived social support is an important contributing factor to the greater well-being reported by morning-oriented individuals. Additionally, our results provide seminal evidence for the causal effect of morningness on well-being.

Mid-luteal phase progesterone effects on vigilance tasks are modulated by women's chronotype

BACKGROUND

In this study we assessed the effects of progesterone on vigilance tasks that require sustained attention. In contrast to previous research, we differentiated two components of vigilance: the exogenous component, involved in monotonous and tedious tasks such as the Psychomotor Vigilance Task (PVT); and the endogenous component, involved in tasks that require cognitive control such as the Sustained Attention to Response Task (SART).

METHODS

A sample of 32 female participants differing in extreme chronotypes were tested at their optimal and non-optimal time-of-day, as secretion of sex hormones follows biological rhythms. Ovulation tests that measure the presence of luteinizing hormone (LH) in urine were used to minimize methodological errors. Women of Morning-type or Evening-type chronotypes completed 4 experimental sessions of the two attentional tasks when they were in their follicular (low progesterone level) and mid-luteal (high progesterone level) phases, both in the morning (8:00 AM) and the evening (8:30 PM).

RESULTS

Compared with the follicular phase, performance in the mid-luteal phase improved in the Morning-type participants and worsened in the Evening-type participants. This pattern of results was observed only when testing occurred at the optimal time-of-day and with both the PVT and the SART tasks.

CONCLUSION

These results suggest that the simultaneous presence of both progesterone and cortisol at 8:00 AM may explain the benefit observed in Morning-type females. In contrast, the low concentration of cortisol along with the reduced benefit of mid-luteal phase progesterone in the evening may account for the worsening in performance observed in Evening-type females.

Evaluation of environmental, social, and behavioral modulations of the circadian phase of dancers trained in shifts

The interplay of environmental, social, and behavioral factors influencing human circadian phase in ecological conditions remains elusive. The Uruguayan national dance school END-SODRE operating in two shifts (morning: 8:30–12:30 and night: 20:00–24:00) allowed us to evaluate how social demands, chronotype, environmental light, physical activity, and sleep patterns affected individual circadian phase measured by the onset of the nocturnal increase of melatonin (DLMO) in a single study. The DLMO was 1.5 h earlier in morning-shift dancers (n = 7) compared to night-shift dancers (n = 11). Sleep time and chronotype (only in night-shift dancers) were associated with the circadian phase. In training days, during each participant’s phase-advance and phase-delay time windows, light exposure was similar between morning and night-shift dancers and did not correlate with DLMO. In contrast, the time spent in moderate-vigorous physical activity during each participant’s phase-lag time window was higher in night-shift dancers than in morning-shift dancers and positively correlated with DLMO.

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Circadian phase was earlier in morning than in night dancers in real-life conditions

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Sleep time (and night-shift chronotypes) correlated with the circadian phase

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In the phase-advance and phase-lag windows, light was not associated with DLMO

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In the phase-lag time window, the longer the intense exercise the later the phase

Adolescent circadian patterns link with psychiatric problems: A multimodal approach

Circadian rhythms orchestrate brain function and mental wellbeing. We compared circadian patterns derived from continuous measurements of body temperature, sleep actigraphy and self-reported circadian preference in relation to different psychiatric disorders. 342 adolescents (70% females) aged 17.4y underwent M.I.N.I. psychiatric interviews, wore Ibutton 1922L skin temperature loggers (n = 281; 3 days), completed one-week GeneActiv Original actigraphy measurements (n = 306) and responded to Morningness-Eveningness Questionnaire (MEQ; n = 330). We derived circadian period length and amplitude from the temperature loggers. Actigraphy measures included sleep duration, midpoint, efficiency, and irregularity as well as Delayed Sleep Phase (DSP) characteristics (bedtime after 1 a.m. 3 times/week). M.I.N.I. psychiatric interviews suggested that 36% of participants had one or more psychiatric problem, with 21% suffering from comorbidity. Severe depression was associated with longer circadian period (p = 0.002). Suicidality was associated with later midpoint (p = 0.007) and more irregular sleep (p = 0.007). Those with agoraphobia slept longer (p = 0.013). Manic episodes and psychotic disorders were associated with irregular sleep (p-values <0.02). DSP was related to suicidality (p = 0.026), panic disorder (p = 0.022), and greater comorbidity (p = 0.026). Preference for eveningness was similarly related to higher prevalence of Generalized Anxiety Disorder (p = 0.014), social anxiety (p = 0.03), agoraphobia (p = 0.026), panic disorder (p = 0.004), suicidality (p = 0.018), severe depression (p < 0.001), and comorbidity (p < 0.001). Deviations in circadian rhythms were widely associated with psychiatric problems, whereas sleep duration was not. Especially suicidality linked with several markers of circadian disruption: later sleep midpoint, irregular sleep, and DSP characteristics. Longer circadian period length was associated with severe depression.

The role of circadian typology in the relationship between perfectionism and workaholism

Workaholism is a work-related addiction, and the study of its antecedents has a strong individual and social impact. Several studies reported high trait perfectionism in individuals exhibiting workaholism. Although the relationship between perfectionism and workaholism is quite consistent in the literature, it is not yet clear which biological underlying mechanisms might explain this relationship. From a chronopsychological perspective, it has been widely demonstrated that evening-type individuals are more prone to develop addictive behaviour. In the present study, we investigated, for the first time, the role of circadian typology in the relationship between perfectionistic concerns and workaholism. A group of Italian workers (N = 369; 60.70% females; mean age of 38.60 years) took part in a survey. Participants filled in the Bergen Work Addiction Scale (for workaholism), the Morningness-Eveningness Questionnaire (for circadian typology), and the Short Almost-Perfect Scale (for perfectionism). In addition to age, we controlled for workload using the Job Content Questionnaire. Beyond the confirmation of the relationship between perfectionism and workaholism, we found that in high perfectionistic individuals, evening-types reported higher score in Bergen Work Addiction Scale. Based on these findings, limitations and suggestions for future research are discussed.

Chronotype at the beginning of secondary school and school timing are both associated with chronotype development during adolescence

The misalignment between late chronotypes and early school start times affect health, performance and psychological well-being of adolescents. Here we test whether, and how, the baseline chronotype (i.e. chronotype at the beginning of secondary school) and the school timing affect the magnitude and the direction of the developmental change in chronotype during adolescence. We evaluated a sample of Argentinian students (n = 259) who were randomly assigned to attend school in the morning (07:45 a.m.–12:05 p.m.), afternoon (12:40 p.m.–05:00 p.m.) or evening (05:20 p.m.–09:40 p.m.) school timings. Importantly, chronotype and sleep habits were assessed longitudinally in the same group of students along secondary school (at 13–14 y.o. and 17–18 y.o.). Our results show that: (1) although chronotypes partially align with class time, this effect is insufficient to fully account for the differences observed in sleep-related variables between school timings; (2) both school timing and baseline chronotype are independently associated with the direction and the magnitude of change in chronotype, with greater delays related to earlier baseline chronotypes and later school timings. The practical implications of these results are challenging and should be considered in the design of future educational timing policies to improve adolescents’ well-being.

It's About Time: The Circadian Network as Time-Keeper for Cognitive Functioning, Locomotor Activity and Mental Health

A variety of organisms including mammals have evolved a 24h, self-sustained timekeeping machinery known as the circadian clock (biological clock), which enables to anticipate, respond, and adapt to environmental influences such as the daily light and dark cycles. Proper functioning of the clock plays a pivotal role in the temporal regulation of a wide range of cellular, physiological, and behavioural processes. The disruption of circadian rhythms was found to be associated with the onset and progression of several pathologies including sleep and mental disorders, cancer, and neurodegeneration. Thus, the role of the circadian clock in health and disease, and its clinical applications, have gained increasing attention, but the exact mechanisms underlying temporal regulation require further work and the integration of evidence from different research fields. In this review, we address the current knowledge regarding the functioning of molecular circuits as generators of circadian rhythms and the essential role of circadian synchrony in a healthy organism. In particular, we discuss the role of circadian regulation in the context of behaviour and cognitive functioning, delineating how the loss of this tight interplay is linked to pathological development with a focus on mental disorders and neurodegeneration. We further describe emerging new aspects on the link between the circadian clock and physical exercise-induced cognitive functioning, and its current usage as circadian activator with a positive impact in delaying the progression of certain pathologies including neurodegeneration and brain-related disorders. Finally, we discuss recent epidemiological evidence pointing to an important role of the circadian clock in mental health.

Association of accelerometry-derived social jetlag and sleep with temperament in children less than 6 years of age

STUDY OBJECTIVES

Social jetlag (SJL) measures the discrepancy between circadian and social clocks. Using accelerometry-derived data, our objective was to assess the prevalence of SJL in young healthy children and determine the association of SJL and sleep with temperament.

METHODS

Of 117 children participating in TARGet Kids!, a Canadian cohort of healthy preschool-aged children, 78 children (39 girls (50%)); mean age [SD]: 35.1[20.5] months) were included. Sleep was measured objectively using accelerometry. Temperament dimensions (surgency, negative affectivity, and effortful control) were assessed with the very short forms of Rothbart's child and infant behavior questionnaires. We examined associations of SJL and sleep with temperament using multivariable linear regression models adjusted for sex, age, ethnicity, and preschool/daycare attendance.

RESULTS

20 out of 78 (25.6%) experienced SJL of greater than 30 minutes. SJL was greater in children who attended preschool/daycare compared with children who did not (26.3[18.8]min vs. 17.6[14.8]min; p<0.05). There was no evidence of an association between SJL and any temperament dimension. We found evidence of an association between increased sleep duration and increased negative affectivity scores (longer 24h sleep (ß:0.347, 95% CI:0.182,0.512, p<0.0001); longer nighttime sleep duration (ß:0.413, 95% CI:0.163,0.663, p=0.002)).

CONCLUSIONS

In our cohort, 1 in 4 preschool-aged children experienced SJL. Increased sleep duration was associated with increased negative affect, which could have implications for children developing internalizing behavior such as depression or low-self-esteem. We found that sleep duration, but not SJL, was associated with temperament and may impact daytime behavior of young children.

The role of REV-ERB in NASH

REV-ERBs are atypical nuclear receptors as they function as ligand-regulated transcriptional repressors. The natural ligand for the REV-ERBs (REV-ERBα and REV-ERBβ) is heme, and heme-binding results in recruitment of transcriptional corepressor proteins such as N-CoR that mediates repression of REV-ERB target genes. These two receptors regulate a large range of physiological processes including several important in the pathophysiology of non-alcoholic steatohepatitis (NASH). These include carbohydrate and lipid metabolism as well as inflammatory pathways. A number of synthetic REV-ERB agonists have been developed as chemical tools and they show efficacy in animal models of NASH. Here, we will review the functions of REV-ERB with regard to their relevance to NASH as well as the potential to target REV-ERB for treatment of this disease.

Predicting Math Performance of Middle Eastern Students: The Role of Dispositions

The present research examines the contribution of individual differences in chronotype and self-efficacy to the math performance of male and female students in STEM and no-STEM majors. Questionnaires assessing the selected individual differences were distributed to students of Middle Eastern descent enrolled in math courses of the general education curriculum. Summative assessment indices were used to measure performance comprehensively across the entire semester (course grades) and as a one-time occurrence (final test grades). The contribution of morningness and self-efficacy to both course and test performance of STEM students was sensitive to the interaction of gender and major. Instead, neither factor contributed to no-STEM students’ course and test performance. These findings were used to plan improvements in the instruction and advising of students in STEM majors, thereby complying with a key tenet of action research.

High School Students' Social Jetlag, Lifelong Competency, and Academic Stress During the COVID-19 Pandemic: A Cross-Sectional Study

With the prolongation of non-ordinary situations such as school closures due to the coronavirus disease 2019 (COVID-19) pandemic, high school students have experienced irregular sleep-wake cycles and elevated academic stress resulting from reduced academic achievement and widened gaps in academic performance. This cross-sectional study aimed to investigate the associations among chronotype, social jetlag, lifelong learning competency, and academic stress in high school students during the COVID-19 pandemic. Data were collected through an online survey from May-June 2021. The mean social jetlag was found to be 2 h and 9 min, and multiple regression analysis revealed that social jetlag and lifelong competency affected academic stress. Thus, measures to minimize social jetlag and improve lifelong learning competencies should be implemented to reduce academic stress among high school students. School nurses should identify students with severe social jetlag and provide guidance and interventions to promote sleep hygiene and regular lifestyles.

The moderating role of personality traits in the associations between seasonal fluctuations in chronotype and depressive symptoms

Recent research provided evidence that the well-established association between morningness-eveningness and depressive symptoms may be moderated by personality features - conscientiousness and neuroticism. In the present study, we attempted to broaden these findings using a longitudinal design. We hypothesized that these personality traits may influence the degree to which morningness-eveningness and depressiveness covary in time. Participants (n = 380) filled measures of morningness-eveningness, the Big Five personality, and depressive symptoms twice, in December and in June. Consistent with previous results, we observed a significant seasonal shift towards morningness and lower depressive symptoms from December to June. Seasonal shifts in chronotype and depressive symptoms were interrelated: a seasonal shift towards morningness was associated with a decrease in depressive symptoms. The strength of this association was exaggerated by neuroticism but attenuated by conscientiousness, suggesting that among neurotic individuals seasonal changes in depressive symptomatology are more dependent on seasonal shifts in morningness-eveningness but less dependent among conscientious ones. This result suggests that conscientiousness and emotional stability play a protective role against maladaptive consequences of eveningness.

Health-promoting work schedules: protocol for a large-scale cluster randomised controlled trial on the effects of a work schedule without quick returns on sickness absence among healthcare workers

INTRODUCTION

In shift work, quick returns refer to transitions between two shifts with less than 11 hours available rest time. Twenty-three per cent of employees in European countries reported having quick returns. Quick returns are related to short sleep duration, fatigue, sleepiness, work-related accidents and sickness absence. The present study is the first randomised controlled trial (RCT) to investigate the effect of a work schedule without quick returns for 6 months, compared with a work schedule that maintains quick returns during the same time frame.

METHODS AND ANALYSIS

A parallel-group cluster RCT in a target sample of more than 4000 healthcare workers at Haukeland University Hospital in Norway will be conducted. More than 70 hospital units will be assessed for eligibility and randomised to a work schedule without quick returns for 6 months or continue with a schedule that maintains quick returns. The primary outcome is objective records of sickness absence; secondary outcomes are questionnaire data (n≈4000 invited) on sleep and functioning, physical and psychological health, work-related accidents and turnover intention. For a subsample, sleep diaries and objective sleep registrations with radar technology (n≈ 50) will be collected.

ETHICS AND DISSEMINATION

The study protocol was approved by the Regional Committee for Medical and Health Research Ethics in Western Norway (2020/200386). Findings from the trial will be disseminated in peer-reviewed journals and presented at national and international conferences. Exploratory analyses of potential mediators and moderators will be reported. User-friendly outputs will be disseminated to relevant stakeholders, unions and other relevant societal groups.

TRIAL REGISTRATION NUMBER

NCT04693182.

Chronotype and trait self-control as unique predictors of sleep quality in Chinese adults: The mediating effects of sleep hygiene habits and bedtime media use

This study examined the distinctive roles of chronotype and trait self-control in predicting sleep quality and the mediation of sleep hygiene habits and bedtime media use of the relations between chronotype, trait self-control and sleep quality. Self-report questionnaire measuring chronotype, trait self-control, sleep hygiene behaviors, bedtime media use and sleep quality was administered to 224 Chinese adult participants (83.5% female). A multiple mediation model was estimated with sleep hygiene habits and bedtime media use as parallel mediators of the relations between chronotype, trait self-control, and sleep quality. Chronotype and trait self-control positively predicted sleep quality. Results of mediation analyses indicated that trait self-control predicted sleep quality both directly and indirectly through pre-sleep stress management and keeping a restful sleep environment, whereas chronotype predicted sleep quality indirectly through pre-sleep stress management and bedtime media use. This study provides evidence for the possible mechanism through which eveningness and low trait self-control undermine sleep quality: Whereas bedtime media use and sleep timing irregularity are linked to poor sleep quality in evening types, environmental interference (e.g., noise or disorganization) appears to be more relevant to poor sleep quality in individuals low in self-control. These findings can inform the design of personalized sleep hygiene recommendations appropriate for the target population. Practical implications regarding sleep hygiene education and interventions are discussed.

Detailed Analysis of Zebrafish Larval Behaviour in the Light Dark Challenge Assay Shows That Diel Hatching Time Determines Individual Variation

Research on stress coping style, i.e., the response of an organism to adverse conditions, which is constant over time and context, gained momentum in recent years, to better understand behavioural patterns in animal welfare. However, knowledge about the ontogeny of stress coping style is still limited. Here, we performed a detailed analysis of the light dark challenge behavioural assay in zebrafish larvae, where after acclimation in ambient light sudden alternating dark and light phases elicit an anxiety-like response. A principal component analysis on parameters related to locomotion (distance moved, swimming velocity, acceleration, mobility) and directionality (angular velocity, meandering of swimming path) revealed independence between the parameters determined in the light and the dark phases of the assay, indicating unrelated generalised behaviours per phase. However, high collinearity was observed between behavioural parameters within the same phase, indicating a robust response to the stimulus within behavioural phenotypes. Subsequently, this assay was used to determine the correlation between individual hatching time and the behavioural phenotype. The results show that fish that had hatched during daytime have a stronger behavioural response to the dark phase at 5 days post-fertilisation in locomotion related parameters and a weaker response in directionality related parameters, than fish that had hatched during nighttime. These results show that behavioural responses to the light dark challenge assay are robust and can be generalised for the light and the dark phase, and that diel hatching time may determine the behavioural phenotype of an individual.

Circadian motor activity of non-dominant hand reaches acrophase later than dominant hand

Motor activity during the first half of nocturnal sleep is lateralized to the non-dominant hand. What remains is to determine which account could explain this phenomenon: the more pronounced homeostatic deactivation of the dominant hemisphere or the circadian asymmetry in the hemispheric activation. To better understand the nature of these motor asymmetries, we performed an ecological study assessing the circadian motor activity in 34 evening, 52 intermediate, and 27 morning types. We observed a significant circadian phase delay of the 24-h motor activity pattern of the left hand in comparison to the right hand, regardless of chronotype. Moreover, we replicated higher motor activity in the left hand in comparison to the right hand in late evening that reached statistical significance only in evening and intermediate types. Analysing motor activity around bedtime and wake-up time, we observed a reverse pattern between circadian typologies: evening types showed higher activity in the left hand in comparison to the right hand before bedtime, while morning types showed significantly higher motor activity in the right hand in comparison to the left after wake-up time. Results support the hypothesis of a different circadian phase relationship between the two hemispheres.

Quantifying daily rhythms with non-negative matrix factorization applied to mobile phone data

Human activities follow daily, weekly, and seasonal rhythms. The emergence of these rhythms is related to physiology and natural cycles as well as social constructs. The human body and its biological functions undergo near 24-h rhythms (circadian rhythms). While their frequencies are similar across people, their phases differ. In the chronobiology literature, people are categorized into morning-type, evening-type, and intermediate-type groups called chronotypes based on their tendency to sleep at different times of day. Typically, this typology builds on carefully designed questionnaires or manually crafted features of time series data on people’s activity. Here, we introduce a method where time-stamped data from smartphones are decomposed into components using non-negative matrix factorization. The method does not require any predetermined assumptions about the typical times of sleep or activity: the results are fully context-dependent and determined by the most prominent features of the activity data. We demonstrate our method by applying it to a dataset of mobile phone screen usage logs of 400 university students, collected over a year. We find four emergent temporal components: morning activity, night activity, evening activity and activity at noon. Individual behavior can be reduced to weights on these four components. We do not observe any clear categories of people based on the weights, but individuals are rather placed on a continuous spectrum according to the timings of their phone activities. High weights for the morning and night components strongly correlate with sleep and wake-up times. Our work points towards a data-driven way of characterizing people based on their full daily and weekly rhythms of activity and behavior, instead of only focusing on the timing of their sleeping periods.

Protocol for Characterization of Addiction and Dual Disorders: Effectiveness of Coadjuvant Chronotherapy in Patients with Partial Response

This protocol aims to characterize patients with dual disorders (DD; comorbid major depression and schizophrenia) compared with patients with only a diagnosis of substance use disorder (SUD) and those with only a diagnosis of severe mental illness (SMI; major depression and schizophrenia), evaluating clinical and personality characteristics, circadian rhythmic functioning, genetic polymorphism and neuropsychological performance in order to obtain a clinical endophenotype of differential vulnerability for these diagnostic entities. Patients will be divided into three groups: DD (45 men with comorbid schizophrenia, 45 men and 30 women with major depression), SUD (n = 90, with a minimum of 30 women) and SMI males (45 with schizophrenia, 45 with major depression). All patients will be under treatment, with at least three months of SUD abstinence and/or with SMI in remission or with stabilized symptoms. Outpatients of both sexes with insufficient restoration of circadian rhythmicity with SUD (n = 30) and dual depression (n = 30) will be asked to participate in a second two-month study, being alternately assigned to the condition of the chronobiological adjuvant approach to the treatment of regular hour habits and exposure to light or to the usual treatment (control). The effect of the intervention and patient compliance will be monitored with a Kronowise KW6^® ambulatory device during the first two weeks of treatment and again at weeks 4 and 8 weeks. After completing the evaluation, follow-up of the clinical evolution will be carried out at 3, 6 and 12 months. This project will allow us to analyze the functional impact of DD comorbidity and to develop the first study of chronobiological therapy in the treatment of SUD and dual depression, with results transferable to the clinical setting with cost-effective recommendations for a personalized approach.

The mediating effect of attachment insecurity on circadian consequences of childhood trauma

Circadian preferences have been associated with mental health as well as social and physical health in recent years. However, factors associated with circadian preferences have not been fully elucidated. The main aim of this study is to investigate the associations of childhood trauma and attachment styles with circadian preferences. A total of 673 participants were evaluated using the Morningness-Eveningness Questionnaire (MEQ), the Childhood Trauma Questionnaire 28 (CTQ-28), and the Experiences in Close Relationships-Revised (ECR-R) questionnaire. The results indicated that 14.9% (n = 100) of the participants were morning type, 20.6% (n = 139) were evening type, and 64.5% (n = 434) were intermediate type. Both childhood trauma and attachment-related anxiety/avoidance scores were associated with being evening type (p < .01). Moreover, attachment-related anxiety and avoidance fully mediated the association between childhood trauma and circadian preferences. The present study showed that attachment styles might be associated with circadian preferences. Further studies are needed to replicate these results and to infer explanatory mechanisms for these cross-sectional associations.

Time-of-day effects on eyewitness reports in morning and evening types

Our performance varies throughout the day as a function of alignment with our circadian rhythms. The current experiment tested whether similar performance patterns can be observed in eyewitness memory performance. One-hundred-and-three morning-type and evening-type participants watched a stimulus event, provided a free report and answered cued questions in the morning and the evening hours, respectively. We expected eyewitness reports to be more detailed and more accurate at participants' circadian peaks than at circadian troughs. Contrary to our predictions, time of testing did not significantly affect quantity and accuracy of eyewitness statements. Future studies might investigate whether matching chronotype with time of day would be beneficial when encoding or retrieval conditions are suboptimal or when eyewitnesses are vulnerable.

The Relationship between Acceptance and Sleep–Wake Quality before, during, and after the First Italian COVID-19 Lockdown

Several studies have reported that the COVID-19 pandemic has had deleterious effects on sleep quality and mood, but the mechanisms underlying these effects are not clearly understood. Recently, it has been shown that the acceptance component of mindfulness reduces anxiety, and, in turn, lower anxiety improves sleep quality. The purpose of this cross-sectional study was to assess changes in mindfulness traits, sleep–wake quality, and general distress, before, during, and after the first COVID-19 wave, testing the model in which acceptance influences sleep through anxiety in each period. A total of 250 participants were recruited before (Pre-Lockdown group: 69 participants, 29 females, 33.04 ± 12.94 years), during (Lockdown group: 78 participants, 59 females, 29.174 ± 8.50 years), and after (After-Lockdown group: 103 participants, 86 females, 30.29 ± 9.46 years) the first Italian lockdown. In each group, self-report questionnaires, assessing mindfulness facets, distress, and sleep–wake quality, were administered and assessed. The Lockdown group reported lower acceptance and higher depression, while the After-Lockdown group reported lower sleep–wake quality and higher anxiety. The results of the path analysis confirmed that higher acceptance reduced anxiety and higher anxiety decreased sleep–wake quality in all groups. Our results confirm that acceptance influences sleep through the mediating role of anxiety.

Validity of chronotype questionnaires in adolescents: Correlations with actigraphy

There are only a few validated chronotype and morningness-eveningness questionnaires for adolescents. We evaluated three such questionnaires, namely Morningness-Eveningness Stability Scale improved; reduced Morningness-Eveningness Questionnaire for Children and Adolescents; and Composite Scale of Morningness in adolescents against actigraphy. Fifty-five healthy 13- to 16-year-old adolescents completed the Morningness-Eveningness Stability Scale improved, reduced Morningness-Eveningness Questionnaire for Children and Adolescents, Composite Scale of Morningness, and Pediatric Daytime Sleepiness Scale, and provided a 7-day actigraphy and sleep diary recording about their sleep-wake patterns. We examined the correlations between sleep-wake and activity parameters, and the questionnaires. The influence of age and sex on chronotype classification was studied using uni- and multivariate analyses. All three chronotype questionnaires showed good internal consistency and convergent validity. Spearman correlations reflected less daytime sleepiness, earlier sleep times, midpoints of sleep, and acrophase in morning-oriented participants. Evening-oriented participants had more sleepiness and later respective sleep-wake times. Chronotype classification differed significantly between questionnaires. The Composite Scale of Morningness classified more participants as morning types when compared with the reduced Morningness-Eveningness Questionnaire for Children and Adolescents (12 versus 7, respectively), and fewer adolescents as evening types (5 versus 9, respectively). Age and sex had no significant influence on questionnaire scores. The Morningness-Eveningness Stability Scale improved, reduced Morningness-Eveningness Questionnaire for Children and Adolescents, and Composite Scale of Morningness are valid instruments to determine circadian preference in adolescents; however, chronotype classification from the Composite Scale of Morningness and reduced Morningness-Eveningness Questionnaire for Children and Adolescents cannot be used interchangeably.

Chronotype and well-being in adults with established type 2 diabetes: A cross-sectional study

AIMS

'Chronotype' describes an individual's sleep-wake schedule, and can be classified into morning, intermediate or evening types. Evening chronotype has been widely associated with increased cardiometabolic risk and mortality in people with type 2 diabetes. We explored associations between chronotype and markers of well-being in people with type 2 diabetes.

METHODS

Participants of the 'Chronotype of Patients with Type 2 Diabetes and Effect on Glycaemic Control' (CODEC) observational study completed questionnaires to determine chronotype (Morningness-Eveningness Questionnaire, MEQ) and concurrent measures of well-being (Diabetes-related Distress scale, Patient Health Questionnaire-9 to measure depression, and Self-Compassion Scale), as a secondary endpoint of the study. Adjusted generalised linear models were used to compare well-being between chronotype subgroups in this cohort.

RESULTS

Of the 808 individuals included in the CODEC study, from convenience sampling, 476 individuals completed the psychosocial questionnaire substudy. Of these, 67% (n = 321) were male, and 86% (n = 408) were white European. From the MEQ, 24% (n = 114) were morning chronotype, 24% (n = 113) were evening and 52% (n = 249) were intermediate chronotype. Diabetes-related distress was significantly higher in evening chronotypes (exponentiated adjusted coefficient = 1.18 (CI: 1.05-1.32)), compared to morning (p_adjusted  = 0.005) and intermediate chronotypes (p_adjusted  = 0.039). Similarly, depression was significantly higher in evening chronotypes (exponentiated adjusted coefficient = 1.84 (CI: 1.28-2.65)) compared to morning (p_adjusted  = 0.001) and intermediate chronotypes (p_adjusted  = 0.016).

DISCUSSION

Evening chronotype in people with type 2 diabetes may be associated with higher levels of diabetes-related distress and depression. These findings warrant further investigation to establish causality and evidence-based interventions that negate the effects of evening chronotype in people with type 2 diabetes.

The effect of ultraviolet radiation on the incidence and severity of major mental illness using birth month, birth year, and sunspot data

Background and objectives

The evaluation of the severity of patients afflicted with major mental illness (MMI) has been problematic because of confounding variables and genetic variability. There have been multiple studies that suggest several human diseases, especially schizophrenia, are predisposed to be born in certain months or seasons. This observation implied an epigenetic effect of sunlight, likely ultraviolet radiation (UVR), which is damaging to DNA, especially in an embryo. This paper outlines a method to evaluate the severity of schizophrenia (SZ), bipolar disorder (BPD), and schizoaffective disorder (SZ-AFF) using the month/year of birth of those affected compared to the month/year of birth of the general population (GP).

Relevance

Our previous research found that more intense UVR (equal to or greater than 90 sunspot number (SSN)) had a negative effect on the average human lifespan. Also, human birth rates vary in frequency by month of birth reflecting variables like availability of food, sunlight, and other unknown epigenetic factors. We wanted to see if the patient month of birth varied from the average birth months of the general population and if UVR has an epigenetic effect promoting these diseases.

Methods

We obtained the month and year of birth of 1,233 patients admitted over a 15-year period to Maine's largest state psychiatric hospital and counted the months of birth for each diagnosis of SZ, BPD, and SZ-AFF, and compared these results to the general population's birth months of 4,265,555 persons from U. S. Census Year 2006. The number of patients in each month was normalized to August and compared with the normalized birth months of the general population (GP). Plots of the normalized months were considered rates of change (e.g., derivatives) and their respective integrals gave domains of each mental illness relative to the GP. Normalizing the GP to unity was then related to the factor 1.28, e.g., 28% more entropy, deduced from the Sun's fractal dimension imprinted on biological organisms.

Results

The percent of patients meeting our criterion for severity: SZ = 27%; BPD = 26%; SZ-AFF = 100%.

Conclusions

High UVR intensity or a rapid increase in UVR in early gestation are likely epigenetic triggers of major mental illness. BPD is more epigenetically affected than SZ or SZ-AFF disorders. We found that 52% of 1,233 patients comprised the core function of a tertiary-care psychiatric hospital. Also, mental illness exacerbated when the median SSN doubled. This work also validates the Kraeplinian dichotomy.

What is new in this research

This paper offers a new paradigm for evaluating the severity of MMI and supports significant epigenetic effects from UVR.

Match or mismatch between chronotype and sleep-wake cycle and their association with lean body mass gain among male high-school baseball players

For athletes, it is important to acquire lean body mass (LBM) involving the skeletal muscle mass during their growth periods; however, the influence of chronotype on LBM gain remains unclear. We therefore aimed to investigate whether chronotype, sleep-wake cycle on weekdays (SWC-W), and their interaction contribute to LBM gain among adolescent male athletes in a 4-month intervention study. The participants were 45 male high-school baseball players. The intervention, including exercise menu (running and muscle strength training) and nutritional education, was conducted during a 4-month period of season-off training. The chronotype, body composition, lifestyle, and dietary intake were investigated before intervention (baseline) and after 4 months. Among the participants [Morningness (n = 14), Eveningness (n = 15), Intermediate (n = 16); ME score based on the Morningness/Eveningness Scale for Children (MES-C)], the midpoint of sleep on weekdays (MSW) was calculated in the "Morningness" and "Eveningness" participants, respectively. They were divided into 4 groups based on a match/mismatch with the chronotype: Type M-match (n = 8), Type M-mismatch (n = 6), Type E-match (n = 7), and Type E-mismatch (n = 8) groups. The data were compared among the 4 groups. Moreover, multiple regression analysis was conducted using an increase (kg) LBM gain as a response variable. When comparing the data between the "Morningness" and "Eveningness" participants, there were no differences in nutrient intake, the duration of training, or each parameter of body composition (per body weight) at baseline or after 4 months. There were also no differences in the rates of change in the body weight or each parameter of body composition. In groups in which the chronotype was consistent with the SWC-W (the Type M-match and Type E-match groups), the LBM gain were slightly greater than in the Type M-mismatch and Type E-mismatch groups (Type M-match: 3.5 ± 2.0 kg, Type M-mismatch: 1.6 ± 1.7 kg, Type E-match: 3.4 ± 2.2 kg, and Type E-mismatch: 1.2 ± 1.8 kg, p = .057). Multiple regression analysis revealed that an extent of the LBM gain was associated with a match between the chronotype and SWC-W (ß = 0.37, p = .030), independent of a long duration of training (ß = 0.52, p = .004). The results suggested that training-related LBM gain is associated with interactions between the chronotype and SWC-W in adolescent male athletes.Abbreviations: LBM: Lean body mass; SWC-W: Sleep-wake cycle on weekdays; ME score: Morningness-eveningness score; MES-C: Morningness/Eveningness Scale for Children; MSW: Midpoint of sleep on weekdays; MSF: Midpoint of sleep on free days; MSFsc: Midpoint of sleep on free days corrected for sleep debt accumulated through weekdays.

Investigation of the relationship between chronotype, learning style and academic achievement of university students during distance education in the pandemic period

The purpose of this study was to investigate the relationship between chronotype, learning style, and academic achievement. The study sample consisted of 1884 volunteer undergraduate students from 58 different universities across Turkey. The data were collected online during distance education because of the Covid-19 pandemic. Turkish version of Morningness-Eveningness Questionnaire (MEQ) and Big16 Learning Modality Inventory were used for data collection. The correlation between chronotype and cumulative grade point average (CGPA) scores was analyzed using Spearman's rho, and differences among the chronotypes were analyzed with Kruskal-Wallis test. Chi-square tests with pairwise z-test were used to analyze the relationships between the participants' learning style preferences and chronotypes. Also, ANCOVA analyses were performed to evaluate the interactions of gender × chronotype and gender × learning style on CGPA scores. The results revealed that participants' preference for visual and auditory styles differed by chronotype. Visual learning style was more dominant among morning (M) types, while auditory style was more dominant among evening (E) types. However, the most preferred learning style was visual, followed by auditory and kinesthetic styles for all chronotypes. No relationship was found between chronotype and academic achievement. The CGPA scores of the participants with kinesthetic learning style were lower than the participants with auditory and visual learning styles. The female participants had higher CGPA score than males. However, the CGPA scores did not differ for both male and female participants with different chronotype and learning style preferences. From the results, we suggest that academic achievement can be enhanced by consideration of students' learning style preferences for all chronotypes.

Evening chronotype as a bipolar feature among patients with major depressive disorder: the results of a pilot factor analysis

Objectives:

The bipolar spectrum concept has resulted in a paradigm shift that has affected both the diagnosis and therapy of mood disorders, with bipolarity becoming an indicator of treatment resistance in depression. Evening circadian preference has also been linked to affective disorders. The aim of our study was to confirm the relationship between the severity of depressive symptoms, bipolar features, chronotype, and sleep quality among patients with major depressive disorder.

Methods:

A group of 55 individuals who were recruited from a mental health outpatient clinic completed the following psychometric tools: a Chronotype Questionnaire comprising morningness-eveningness (ME) and subjective amplitude of the rhythm (AM) scales, the Hypomania Checklist 32 (HCL-32), the Beck Depression Inventory (BDI) and the Pittsburgh Sleep Quality Index (PSQI).

Results:

Factor analysis identified two latent components, accounting cumulatively for 58% of variables: depressive symptoms (BDI and PSQI) and bipolarity (ME, AM, and HCL-32). After rotation, ME loading in the first factor increased the result to a significant level. The correlation between the two components was very low.

Conclusions:

Evening chronotype appears to be a bipolarity-related marker, with this relationship being independent of its link to depressive symptoms and sleep quality. Eveningness and high circadian rhythm amplitude may offer promise as diagnostic, prognostic, and therapeutic predictors.

Impact of Long-Haul Travel to International Competition on Sleep and Recovery in Elite Male and Female Soccer Athletes

PURPOSE

To investigate the impact of eastward travel across 7 time zones on sleep, jet lag, and recovery in elite soccer athletes.

METHODS

Twenty-one male and 20 female athletes (21.5 [1.7] y) traveled from Ireland to Taiwan to represent their national team at the World University Games 2017. Daily monitoring via actigraphy and subjective sleep and well-being measures were obtained for 1 week in Ireland (baseline), and for the duration of an international soccer tournament (days 1-5 [precompetition] and days 6-18 [competition]).

RESULTS

Sleep duration (P = .028) and time in bed (P = .006) were significantly lower at precompetition compared with baseline. Sleep quality (P < .001) was significantly decreased in precompetition compared with baseline and competition. Subjective jet lag symptoms continued for up to 13 days posttravel. Athletes reported significantly greater fatigue during precompetition compared with competition (P = .005); however, there were no significant differences for recovery (P = .35) and readiness to train (P = .35). Sleep hygiene changed significantly during precompetition and competition compared with baseline in relation to reduced electronic device use (P = .005) and reduced caffeine intake (P < .001). Females reported significantly greater presleep tension-anxiety compared with males at all timepoints (P = .02).

CONCLUSION

Long-haul eastward travel across 7 time zones has a significant impact on sleep duration and quality, likely related to changes in sleep patterns and jet lag. Athletes report changes in sleep hygiene posttravel; however, sleep remained negatively impacted for up to 5 days. Despite significant sleep disturbance and jet lag symptoms, young healthy athletes appear to recover well from long-haul travel; however, it is unknown if this interferes with training and competition performance.

Morningness-Eveningness Preference, Time Perspective, and Passage of Time Judgments

Recent studies have shown that making accurate passage of time judgments (POTJs) for long-time intervals is an important cognitive ability. Different temporal domains, such as circadian typology (biological time) and time perspective (psychological time), could have an effect on subjective POTJs, but few studies have investigated the reciprocal influences among these temporal domains. The present study is the first systematic attempt to fill this gap. A sample of 222 participants (53.20% females; 19-60 years) filled in the Zimbardo Time Perspective Inventory for the measurement of time perspective, the reduced version of the Morningness-Eveningness Questionnaire (rMEQ) for chronotypes, and an ad-hoc questionnaire assessing sleep habits during weekdays and the weekend (for social jetlag). The POTJ was measured using a modified version of a pictorial timeline presented at five different moments. Also, participants judged how different temporal expressions were related to the past, present, and future along a 7-point Likert scale. After confirming the association between eveningness and present-hedonism orientation and morningness and future-orientation, we found that evening-types produced higher scores for future expressions. The subjective POTJ expressed in minutes was predicted by Deviation from Balanced Time (DBTP), present-fatalism orientation, and social jetlag. Finally, the rMEQ score, past-positive orientation, and DBTP predicted the difference between subjective and objective POT. The results are discussed offering an explanation in terms of the interconnections between circadian typology, individual time perspective, and the sense of the POT, suggesting the multicomponent nature of the concept of time.

Sex differences in the relationship between morningness-eveningness components, mood and well-being among Bangladeshi university students

On the Morningness/Eveningness (M/E) continuum, eveningness has been related to mood disorder and poor well-being. M/E differs between men and women throughout their lifespan. However, there is a lack of information on sex differences in the relationship between M/E, mood, and well-being. This study aimed to test sex differences in the M/E, mood, and well-being relationship with consideration of two components of M/E, morning affect, and morning preference. A sample of 981 Bangladeshi university students (607 men) aged 18 to 27 (M = 21.95) completed Bangla versions of the Composite Scale of Morningness (CSM), BRUnel Mood Scale (BRUMS), and Positive Mental Health scale (PMH-scale) through an online survey. Multiple regression analyses were used to test the relationship of M/E components with mood and well-being. The results showed that the relationship between M/E, mood, and well-being was greater in women than in men. A lower score on both M/E components was related to higher negative moods (anger, confusion, depression, fatigue, and tension) and poor well-being. In regression analysis, only morning affect was found to be significant, which means that morning affect mainly contributes to the relation between M/E, mood, and well-being. Finally, sex by morning affect interaction indicated that the relation was higher for women. Therefore, higher eveningness could be more hazardous for women than men. Greater insight into the independent contribution of morning affect may facilitate understanding of the chronotype effects on psychological outcomes in men and women.

Integrative Identification of Genetic Loci Jointly Influencing Diabetes-Related Traits and Sleep Traits of Insomnia, Sleep Duration, and Chronotypes

Accumulating evidence suggests a relationship between type 2 diabetes mellitus and sleep problems. A comprehensive study is needed to decipher whether shared polygenic risk variants exist between diabetic traits and sleep traits. Methods: We integrated summary statistics from different genome-wide association studies and investigated overlap in single-nucleotide polymorphisms (SNPs) associated with diabetes-related traits (type 2 diabetes, fasting glucose, fasting insulin, and glycated hemoglobin) and sleep traits (insomnia symptoms, sleep duration, and chronotype) using a conditional/conjunctional false discovery rate approach. Pleiotropic genes were further evaluated for differential expression analysis, and we assessed their expression pattern effects on type 2 diabetes by Mendelian randomization (MR) analysis. Results: We observed extensive polygenic pleiotropy between diabetic traits and sleep traits. Fifty-eight independent genetic loci jointly influenced the risk of type 2 diabetes and the sleep traits of insomnia, sleep duration, and chronotype. The strongest shared locus between type 2 diabetes and sleep straits was FTO (lead SNP rs8047587). Type 2 diabetes (z score, 16.19; P = 6.29 × 10⁻⁵⁹) and two sleep traits, sleep duration (z score, −6.66; P = 2.66 × 10⁻¹¹) and chronotype (z score, 7.42; P = 1.19 × 10⁻¹³), were shared. Two of the pleiotropic genes, ENSA and PMPCA, were validated to be differentially expressed in type 2 diabetes, and PMPCA showed a slight protective effect on type 2 diabetes in MR analysis. Conclusions: Our study provided evidence for the polygenic overlap between diabetic traits and sleep traits, of which the expression of PMPCA may play a crucial role and provide support of the hazardous effect of being an “evening” person on diabetes risk.

Morningness-eveningness preference and shift in chronotype during COVID-19 as predictors of mood and well-being in university students

It is suggested that social obligations, such as early work/school starts, have a disadvantageous impact on sleep behavior that can further transfer to mental health problems. Lockdown as a result of the COVID-19 pandemic created a unique opportunity to research human sleep-wake behavior in naturalistic conditions of decreased social obligations. This study aimed to test whether a change in habitual sleep-wake timing (shift in chronotype) during the COVID-19 lockdown impacted mood and well-being, and whether the impact differs according to morningness-eveningness preference. University students (N = 1011; Mean_age = 21.95 ± 1.95 years) filled out self-report questionnaires containing measures of chronotype (midpoint of sleep) before and during the COVID-19 lockdown, morningness-eveningness preference, mood, and well-being. The impact of morningness-eveningness preference and shift in chronotype was tested via multiple regression analyses. Results showed that participants shifted their chronotype in line with their morningness-eveningness preference, and that shift toward earlier sleep-wake timing was related to better moods and well-being. Moreover, higher levels of positive mood (vigor) and well-being were found in individuals who shifted their sleep-wake timing earlier and were higher on morningness.