Abstract: Individuals vary in how their circadian system synchronizes with the cyclic environment (zeitgeber). Assessing these differences in “phase of entrainment”—often referred to as chronotype—is an impo...

Abstract: Growing evidence shows a link between mood and chronotype. The majority of studies measure chronotype as a preference for morning/evening activities, rather than actual sleep behaviour (i.e. midsleep) or biological markers of sleep timing (e.g. dim light melatonin onset). Most studies show an association between chronotype and mood and identify eveningness as a potential risk for depression, but the directionality is unclear. Some evidence shows a stronger association between misalignment with the biological clock and depressive symptoms. This review provides a snapshot of recent research on chronotype and unipolar depression. We conclude that future studies should strive to integrate different measures of chronotype. This will give a clearer picture of the association between early/late chronotype and mood, which will in turn better inform clinical practice.

Abstract: Chronotype reflects time of day preferences for performing daily activities. Previous research within Asian and European cohorts indicates evening chronotype is associated with elevated cardiometab...

Abstract: This study aimed to investigate the relationship between chronotype preference/sleep problems and symptom severity of children with Autism spectrum disorder (ASD) during the confinement and social isolation of the COVID-19 outbreak. This study included 46 drug-naive children aged 4-17 y diagnosed with ASD. The Autism Behavior Checklist (AuBC), Children's Sleep Habits Questionnaire (CSHQ), and Children's chronotype questionnaire (CCQ) were filled out before and at the end of the COVID-19 mandated home confinement by the children's parents. Children with ASD during the home confinement reported higher chronotype scores, i.e., eveningness chronotype, sleep problems, and autism symptom scores compared to the normal non-hone confinement state. The chronotype score and sleep problems of children with ASD during the home confinement period varied according to the AuBC score. The sleep problems of the children with ASD during the home confinement period mediated the relationship between chronotype score and severity of autism symptoms. It is essential to validate the role of the mediator effect of sleep problems and chronotype in larger samples of children with ASD with restricted to home confinement during the pandemic period. If sleep problems can be controlled with parental education, pharmacotherapy, and psychotherapeutic interventions, the impact on children with ASD of home confinement can be reduced.

Abstract: Most adolescents exhibit very late chronotypes and attend school early in the morning, a misalignment that can affect their health and psychological well-being. Here we examine how the interaction between the chronotype and school timing of an individual influences academic performance, studying a unique sample of 753 Argentinian students who were randomly assigned to start school in the morning (07:45), afternoon (12:40) or evening (17:20). Although chronotypes tend to align partially with class time, this effect is insufficient to fully account for the differences with school start time. We show that (1) for morning-attending students, early chronotypes perform better than late chronotypes in all school subjects, an effect that is largest for maths; (2) this effect vanishes for students who attend school in the afternoon; and (3) late chronotypes benefit from evening classes. Together, these results demonstrate that academic performance is improved when school times are better aligned with the biological rhythms of adolescents.

Abstract: Study objectives Bedtime procrastination (BP) is defined as going to bed later than intended despite absence of external reasons. This study investigated sleep and psychological factors associated with BP in young adults, and further compared how high and low BP groups spend their time over 24 h and also 3 h prior to bedtime using time use surveys. Methods Young adults (N = 106) from the community were classified as either high (n = 54) or low (n = 52) BP group based on the Bedtime Procrastination Scale. All participants were asked to complete questionnaires on insomnia, depression, anxiety, stress, and chronotype, in addition to keeping a 7-day sleep diary and completing time use surveys over 48 h. Results Participants were 61.3% female, mean age 22.7 (±2.89) years old. Individuals in the high BP group reported significantly more depression, anxiety, and insomnia, went to bed later, woke up later, and had more eveningness tendencies compared to the low BP group. Results from the time use surveys revealed that the high BP group spent significantly more time engaging in leisure and social activity with the majority of time spent using media over 24 h compared to the low BP group. Finally, the high BP group spent on average approximately 451% (or 61 min) more time per day on their smartphone 3 h prior to bedtime compared to the low BP group. Conclusions Our results suggest that BP is negatively associated with sleep and mood, and should be considered a serious health-interfering behavior.

Abstract: OBJECTIVE Circulating vitamin D concentrations have been associated with the risk of type 2 diabetes (T2D), but the results are inconsistent. Emerging evidence suggests that vitamin D metabolism is linked to sleep behaviors. We investigated the prospective association between serum 25-hydroxyvitamin D (25OHD) and the risk of incident T2D and whether such association was modified by sleep behaviors. RESEARCH DESIGN AND METHODS The study included 350,211 individuals free of diabetes in the UK Biobank. Serum 25OHD (nmol/L) concentrations were measured. Five sleep behaviors including sleep duration, insomnia, snoring, chronotype, and daytime sleepiness were included to generate overall sleep patterns, defined by healthy sleep scores. We also calculated genetic risk scores of sleep patterns. RESULTS During a median follow-up of 8.1 years, we documented 6,940 case subjects with incident T2D. We found that serum 25OHD was significantly associated with a lower risk of incident T2D, and the multivariate adjusted hazard ratio (HR) (95% CI) per 10 nmol/L increase was 0.88 (0.87–0.90). We found a significant interaction between 25OHD and overall sleep patterns on the risk of incident T2D (P for interaction = 0.002). The inverse association between high 25OHD and T2D was more prominent among participants with healthier sleep patterns. Among the individual sleep behaviors, daytime sleepiness showed the strongest interaction with 25OHD (P for interaction = 0.0006). The reduced HR of T2D associated with high 25OHD appeared to be more evident among participants with no frequent daytime sleepiness compared with those with excessive daytime sleepiness. The genetic variations of the sleep patterns did not modify the relation between 25OHD and T2D. CONCLUSIONS Our study indicates that higher serum 25OHD concentrations are associated with a lower risk of incident T2D, and such relations are modified by overall sleep patterns, with daytime sleepiness being the major contributor.

Abstract: Chronotype is the attitude of a subject in determining individual circadian preference in behavioral and biological rhythm relative to the external light–dark cycle. Obesity and unhealthy eating habits have been associated with evening chronotype. The Mediterranean diet (MD) is a healthy nutritional pattern that has been reported to be associated with better health and quality of sleep. Thus, the aim of the study was to investigate the association of chronotype categories with adherence to the MD in a population of middle-aged Italian adults. This cross-sectional study included 172 middle-aged adults (71.5% females; 51.8 ± 15.7 years) that were consecutively enrolled in a campaign to prevent obesity called the OPERA (obesity, programs of nutrition, education, research and assessment of the best treatment) Prevention Project that was held in Naples on 11–13 October 2019. Anthropometric parameters, adherence to the MD and chronotype were studied. Chronotype was classified as morning in 58.1% of subjects, evening in 12.8% and intermediate in 28.1%. Our results demonstrated that individuals with evening chronotype, when compared to intermediate (p < 0.001) and morning chronotype (p < 0.001), were more prone to follow unhealthy lifestyle, performing less regular activity and being more frequently smokers. In addition, they showed the lowest adherence to the MD compared to morning (p < 0.001) and intermediate chronotypes (p < 0.001). The lower the chronotype score, the higher body mass index (BMI) values in the whole population (r = −0.158; p = 0.038), thus suggesting that evening chronotype was a common finding in subjects with obesity. In addition, positive correlations of chronotype score with age (r = 0.159; p = 0.037) and PREDIMED score (r = 0.656; p < 0.001) were found. The adherence to the MD, more than the intake of the single food items, was found to predict morning and evening chronotypes. In conclusion, evening chronotype was associated with unhealthy lifestyle and low adherence to the MD. Chronotype score was inversely associated to BMI and positively associated to age and adherence to the MD. Thus, the assessment of chronotype should be taken into account in the management of obesity and in the development of nutritional strategies.

Abstract: Obesity is associated with increased general mortality and comorbidities, it is multifactorial and some evidence has shown that sleep duration and shift work may be implicated in its pathogenesis. The aim of this study was to evaluate the association between shift work, quality of life and obesity among healthcare workers of a Brazilian University Hospital. A cross-sectional study was performed from April 2013 to December 2014 with 200 workers of a University Hospital. Sociodemographic data were evaluated and BREF WHOQOL was used for quality of life. The physical activity was evaluated using the International Physical Activity Questionnaire (IPAQ), Chronotypes and daily sleep preference were investigated using Munich Chronotype Questionnaire (MCTQ). Venous blood was collected after 12-h of fasting for laboratory tests. In this sample, the night shift workers had higher income and were older compared to day shift workers. Night shift workers sleep less hours, had higher weight, body mass index and abdominal circumference when compared to the day shift workers. Night shift workers had almost 3 times higher association with abdominal obesity independent of age and gender, than day shift workers. MCTQ parameters showed that night shift workers had lower sleep duration during working days and also during free days, associated with a higher level of social jetlag. Social jetlag had an association with obesity. We found no difference for quality of life between shifts. Night work was a risk factor for abdominal obesity, social jetlag was higher in night shift workers and it was associated with presence of obesity.

Abstract: The timing of sleep is under the control of the circadian clock, which uses light to entrain to the external light-dark cycle. A combination of genetic, physiological and environmental factors produces individual differences in chronotype (entrained phase as manifest in sleep timing). A mismatch between circadian and societal (e.g., work) clocks leads to a condition called social jetlag, which is characterized by changing sleep times over work and free days and accumulation of sleep debt. Social jetlag, which is prevalent in late chronotypes, has been related to several health issues. One way to reduce social jetlag would be to advance the circadian clock via modifications of the light environment. We thus performed two intervention field studies to describe methods for decreasing social jetlag. One study decreased evening light exposure (via blue-light-blocking glasses) and the other used increased morning light (via the use of curtains). We measured behaviour as well as melatonin; the latter in order to validate that behaviour was consistent with this neuroendocrinological phase marker of the circadian clock. We found that a decrease in evening blue light exposure led to an advance in melatonin and sleep onset on workdays. Increased morning light exposure advanced neither melatonin secretion nor sleep timing. Neither protocol led to a significant change in social jetlag. Despite this, our findings show that controlling light exposure at home can be effective in advancing melatonin secretion and sleep, thereby helping late chronotypes to better cope with early social schedules.

Abstract: Sleep impacts academic performance. Past studies focused on the negative influence of shorter sleep duration and poor sleep quality on GPA. New novel sleep measures have emerged. Sleep consistency measures how likely a student is to be awake or asleep at the same time each day. Students with greater sleep consistency have better academic performance. A morning circadian preference and earlier classes are associated with higher grades. Later high school start times may increase sleep duration, but do not consistently increase GPA, but improve mood and well-being. If a student is struggling academically, screening for a sleep disorder is vital. Devices are under development which may allow students to better monitor their sleep habits, sleep consistency, chronotype and sleep behaviors. For the proactive student, these devices may enhance sleep behaviors and academic performance. Schools need to develop sleep friendly policies and interventions to promote healthy sleep for their students.

Abstract: Background: Chronotype is an individual's preferred timing of sleep and activity, and is often referred to as a later chronotype (or evening-type) or an earlier chronotype (or morning-type). Having an evening chronotype is associated with more severe depressive and anxiety symptoms. Based on these findings it is has been suggested that chronotype is a stable construct associated with vulnerability to develop depressive or anxiety disorders. To examine this, we test the stability of chronotype over 7 years, and its longitudinal association with the change in severity of depressive and anxiety symptoms. Methods: Data of 1,417 participants with a depressive and/or anxiety disorder diagnosis and healthy controls assessed at the 2 and 9-year follow-up waves of the Netherlands Study of depression and anxiety were used. Chronotype was assessed with the Munich chronotype questionnaire. Severity of depressive and anxiety symptoms were assessed with the inventory of depressive symptomatology and Beck anxiety inventory. Results: Chronotype was found to be moderately stable (r = 0.53) and on average advanced (i.e., became earlier) with 10.8 min over 7 years (p <.001). Controlling for possible confounders, a decrease in severity of depressive symptoms was associated with an advance in chronotype (B = 0.008, p =.003). A change in severity of anxiety symptoms was not associated with a change in chronotype. Conclusion: Chronotype was found to be a stable, trait-like construct with only a minor level advance over a period of 7 years. The change in chronotype was associated with a change in severity of depressive, but not anxiety, symptoms.

Abstract: The study explored the relationship between a specific type of procrastination – bedtime procrastination, and the amount (hours) of sleep and indicators of sleep deprivation in a sample of 175 Polish adolescents. It also examined the relationship between bedtime procrastination, morningness–eveningness and autonomous vs. controlled motivational regulations for sleep related behavior. Bedtime procrastination – or going to bed later than intended without any specific external reason – was prevalent in the adolescent sample and was negatively associated with the amount of sleep and positively related to signs of sleep deprivation. Evening-type adolescents showed a greater tendency to put off bedtime. The relationship between eveningness and bedtime procrastination was mediated by non-autonomous regulation of sleep related behavior. The results suggest some practical implications for improving the ability to self-regulate sleep related behavior.

Abstract: Question: Does genetic liability to insomnia, hypersomnia, and chronotype differentiate subtypes of bipolar disorder? Findings: In this case-control study of 4672 participants with bipolar disorder and 5714 control participants, individuals with bipolar disorder I had significantly greater genetic liability to longer sleep duration, whereas individuals with bipolar disorder II had significantly greater genetic liability to insomnia; these findings were replicated in an independent sample. Individuals with bipolar subtypes did not differ in genetic liability to morning or evening chronotype. Meaning: Associations between polygenic liability to insomnia and hypersomnia and clinical strata within bipolar disorder are shown in this study for the first time, to our knowledge.

Abstract: Chronotype has been mostly assessed with subjective scales. Objective assessment has been undertaken with actigraphy, although problems may occur in classifying chronotype. The aims of the study were to assess chronotype in school-age children using a novel integrative measurement (TAP) derived from non-invasive assessments of wrist temperature (T) physical activity (A) and body position (P) and to explore associations between chronotype, sleep disturbances, and metabolic components. Four-hundred-thirty-two children of 8-12 years were recruited from a Mediterranean area of Spain. Measurements were: (a) Chronotype objectively (7-day-rhythms of TAP) and subjectively measured (Munich-chronotype-self-reported questionnaire); (b) sleep rhythms and light exposition; (c) 7-day-diaries of food intake; (d) anthropometry and metabolic parameters; (e) academic scores. TAP acrophase was able to assess eveningness. As compared to more morning-types, more evening-types displayed lower amplitude in temperature rhythms, increased physical activity in the evening, delayed sleep and midpoint of intake and had more frequent social jet lag (P < 0.05). More evening-types had higher light intensity at 2 h before sleep and lower melatonin values (01:00 h). Eveningness associated with higher BMI and metabolic risk (higher values of insulin, glucose, triglycerides and cholesterol). Evening-types presented better grades in art. In conclusion, more evening-types, as objectively assessed, presented sleep alterations, social jet lag, obesity and higher metabolic risk.

Abstract: For decades, day–night patterns in behaviour have been investigated by asking people about their sleep–wake timing, their diurnal activity patterns, and their sleep duration. We demonstrate that th...

Abstract: Research indicates that sleep duration and quality are inter-related factors that contribute to obesity, but few studies have focused on sleep chronotype, representing an individual’s circadian pro...

Abstract: Both abdominal obesity and its visceral component are independently associated with cardiometabolic diseases. Among the non-modifiable and modifiable determinants, lifestyle plays a central role, while chronotype is an emerging factor. Evening type (E-Type), more active and efficient in the last part of the day, has been associated with a health-impairing style, resulting in a higher risk of obesity and cardiometabolic diseases than morning type (M-Type). However, no study has examined the contribution of chronotype to abdominal fat distribution, even considering adherence to the Mediterranean diet (MD). We conducted a cross-sectional study on 416 adults (69.5% females, 50 ± 13 years). Waist circumference (WC), visceral fat (VAT) using ultrasonography, chronotype through the reduced Morningness-Eveningness Questionnaire (rMEQ), and adherence to MD were studied. Our results showed no differences in WC and VAT between chronotypes. However, adherence to MD resulted significantly lower in the E-Types compared to M-Types. WC decreased with increasing Mediterranean score and rMEQ score, and VAT decreased with increasing rMEQ score, indicating that E-Types have +2 cm of WC and +0.5 cm of VAT compared to M-Types. In conclusion, these results showed that chronotype is independently associated with abdominal obesity and visceral fat, underlining the potential implications of the individual circadian typology on abdominal obesity.

Abstract: Objectives: To evaluate possible associations between chronotype, weight, sleep problems, anxiety, and depression among children from 6 to 12 years of age. Method: One-hundred children aged between 6 and 12 years were randomly recruited in five pediatrician clinics in the capital city of Beirut, Lebanon. The protocol was approved by the ethics committee of Saint-Joseph University and Hotel-Dieu Hospital and an informed written formal consent was obtained from one of the parents. The Sleep Disturbance Scale for Children (CCTQ), the Revised Child Anxiety and Depression Scale (RCADS)-Parent version, and the Children's Chronotype Questionnaire (CCTQ) were used. Results: The majority of the sample (47%) presented an intermediate chronotype. There was a shift toward evening chronotype with increased age and a significant association between electronic devices use and an evening chronotype. Higher sleep disturbances were also observed among children with an evening chronotype. In particular, disorders of initiating and maintaining sleep, non-restorative sleep, excessive somnolence, and total SDSC were significantly higher among evening type children in our study. Finally, major depression domain scores were significantly higher among children with an evening chronotype. Conclusions: Several findings of this study are important and explain factors associated to chronotype in children. Two important future perspectives can be highlighted: limiting electronic devices use among children in an effort to reduce circadian rhythm disturbances and identifying and treating sleep problems associated with eveningness, taking into account the possible presence of major depression among this population.

Abstract: Sleep problems in university students are important and have implications for health, quality of life, and academic performance. Using an ex post facto design, a total sample of 855 students (55.7% women) participated in the study. Sleep assessment was conducted using the Pittsburgh Sleep Quality Index, the Nightmare Frequency Scale, the Nightmare Proneness Scale, and the Composite Morningness Scale. Women show a higher risk [OR = 2.61] of presenting poor sleep quality (> 5 points on the PSQI) compared with men (p < 0.001). Similarly, women reported a greater frequency of nightmares (p < 0.001, d = 0.60), greater propensity for nightmares (p < 0.001, d = 0.70) and a higher score on Item-5h of the PSQI regarding nightmares (p < 0.001, d = 0.59). Women, compared with men, show higher risk [OR = 2.84] for a sleep disorder related to nightmares (p = 0.012). Women need more time to reach a state of alertness after getting up (p = 0.022), and there was an interaction between sex and the alertness factor when evaluating the subjective quality of sleep (p = 0.030). Women show worse sleep quality and a higher frequency and propensity for suffering nightmares. When considering the relationship between sleep quality and academic performance, it is observed that students with poor sleep quality obtain lower academic scores (M = 7.21, SD = 0.805) than those with good sleep quality (M = 7.32, SD = 0.685), an effect that reaches significance (t = 2.116, p = 0.035). Regarding the relationship between the categorized chronotype and academic performance, students with a morning chronotype achieve better academic results (M = 7.41, SD = 0.89) than their evening counterparts (M = 7.15, SD = 0.76), although these differences have a small effect size (d = 0.31).

Abstract: This study aimed to investigate the relationship between chronotype preference/sleep problems and symptom severity of children with Attention Deficit Hyperactivity Disorder (ADHD) during the COVID-19 outbreak and to assess the chronotype preference/sleep problems that may play a mediating role in the relationship between the reactions to trauma and severity of ADHD symptoms. The sample of this single-center cross-sectional study consisted of 76 children with ADHD and their parents. Trauma symptoms were evaluated with the Children's Impact of Event Scale (CRIES-8); sleep habits were assessed using the Children's Sleep Habits Questionnaire (CSHQ); and chronotype was assessed using the Children's Chronotype Questionnaire (CCQ). There were significant differences in CRIES-8 and CSHQ scores between the eveningness type group and the non-eveningness type group. The CRIES-8 scores of children with ADHD were related to the CCQ and CSHQ scores and severity of ADHD symptoms. In mediation analyses, sleep problems were found to be the full mediating factor in the relationship between CRIES-8 scores and severity of ADHD symptoms and the relationship between CCQ scores and the severity of ADHD symptoms. Our findings indicate that chronotype plays an important role on the negative effects of home confinement of ADHD children during the COVID-19 outbreak. The role of the full mediator of sleep problems in the path from cognition to the behavior of young ADHD and non-ADHD children confined to the home environment during the pandemic period requires further assessment.