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Background: Chronotype defines an organism's biological preference for timing of activity and sleep. Being a morning chronotype (i.e., tending to wake up early and go to bed earlier at night) is associated with protection against chronic musculoskeletal pain and headaches, but the relationship between chronotype and neuropathic pain sensitivity remains unclear., Objectives: The aim of this pilot study was to explore the relationship among chronotype, neuropathic pain sensitivity, and pain interference in patients with chronic neuropathic pain disorders., Study Design: This was a prospective, observational, single-center, cross-sectional study., Setting: Patients were recruited from pain management clinics., Methods: The Morningness-Eveningness Questionnaire (MEQ) was used to evaluate circadian typology. Linear mixed-effects models, principal component analysis, and principal component regression were used to determine the predictors of pain intensity and pain interference evaluated by the Numeric Rating Scale (NRS) and Patient-Reported Outcomes Measurement Information System Pain Interference (PROMIS-PI) scores, respectively., Results: We analyzed 38 adults who had at least one documented chronic neuropathic pain diagnosis. Morning-chronotype patients reported higher NRS scores over time and lower PROMIS-PI t-scores than did intermediate chronotypes. MEQ, depression, risk of sleep apnea, sleep quality, and body mass index (BMI) were all significant independent predictors of average NRS scores and PROMIS-PI t-scores., Limitations: The population was small and homogeneously white, with an average age of 57 years. However, this population was representative of our pain clinic., Conclusions: Morning chronotypes are more sensitive to chronic neuropathic pain, reporting higher pain scores than do intermediate chronotypes. However, in this study, morning chronotypes were more resistant to neuropathic pain interference, suggesting that they may experience less disturbance of their physical, mental, and social activities than intermediate chronotypes. Further, larger studies are needed.

Background: Evidence assessing the relationship between chronotype and disordered eating in adolescents is scarce. The current study tried to evaluate the association between chronotype and disordered eating in a sample of Spanish adolescents., Methods: This secondary cross-sectional study analyzed data from the Eating Healthy and Daily Life Activities (EHDLA) study. The sample consisted of 703 adolescents (56.3% girls) aged between 12 and 17 years from the Valle de Ricote (Region of Murcia, Spain). Chronotype was assessed using the Morningness/Eveningness Scale in Children (MESC). Disordered eating was evaluated by two psychologists using the Sick, Control, One, Fat, and Food (SCOFF) questionnaire., Results: Adolescents with an eveningness chronotype showed a higher SCOFF score (estimated marginal mean [ M ] = 1.1; 95% confidence interval [CI] 0.7 to 1.5) in comparison with adolescents with a morningness chronotype ( M = 0.7; 95% CI 0.5 to 0.8) ( p = 0.010), as well as with those with an intermediate chronotype ( M = 0.6; 95% CI 0.5 to 0.8) ( p = 0.032). A higher predictive probability of having disordered eating was identified in adolescents with an eveningness chronotype (39.5%; 95% CI 22.8% to 59.1%), compared to adolescents with an intermediate chronotype (14.9%; 95% CI 10.8% to 20.1%) ( p = 0.008) and with their counterparts with a morningness chronotype (16.9%; 95% CI 11.6% to 24.0%) ( p = 0.021)., Conclusions: This study reveals that adolescents with an eveningness chronotype are more likely to exhibit disordered eating behaviors compared to those with morningness or intermediate chronotypes. These findings highlight the importance of considering chronotype in adolescent health, particularly in developing targeted interventions to prevent eating disorders.

Chronotype is an established concept designed to capture the internal clock's phase in real-life conditions. It is vital in many aspects of daily life and can interfere considerably with numerous factors in a given population. Recognizing nonmodifiable and modifiable factors is crucial for identifying covariates of interest when studying the link between chronotype and health status. To date, chronotype and its related factors have not been extensively investigated. The present study aimed to explore the association of chronotypes with meal frequency, physical activity, and demographic factors among the Saudi population. This cross-sectional web-based questionnaire involved 1369 adults (aged 18 years and above) from the general public in Saudi Arabia and was conducted between March and May 2019. Chronotype was assessed using the reduced version of the original Horne and Ostberg morningness-eveningness questionnaire (MEQ). Meal frequencies and demographics data (age, gender, marital status, place of residence, educational level, employment status, income) were obtained. Physical activity level was also obtained using the international physical activity questionnaire. The MEQ scores group individuals into three categories: morning-type, neither-type, and evening-type. The neither-type individuals represented 41.6% (95% confidence interval [CI], 37.5% - 45.6%) of the study population, followed by the morning-type (34.1%; 95% [CI], 29.8% - 38.4%), then the evening-type (24.3%, 95% [CI], 19.6% - 28.9%). Chronotype was significantly associated with age, marital status, employment status and monthly income (All p  < 0.05). Significant associations between chronotype with meal frequencies (number of meals per day, breakfast frequency, lunch frequency, and dinner frequency) and physical activity were also observed (All p  < 0.05). This study highlights that meal frequencies and physical activity levels are associated with chronotype distribution. Furthermore, demographics, including age, marital status, employment status, and income, were associated with chronotype distribution.

Circadian typology, or "morningness" and "eveningness," is generally assessed using the Morningness-Eveningness Questionnaire (MEQ), a 19-item scale that could be burdensome in large-scale surveys. To overcome this, a 5-item version known as the reduced morningness-eveningness questionnaire (rMEQ), which is sensitive to the assessment of circadian typology, was developed; however, a validated Japanese version of the rMEQ is yet to be established. This study aimed to develop and validate the Japanese version of the rMEQ. Five essential items for the rMEQ were selected from existing Japanese MEQ data ( N  = 2,213), and the rMEQ was compiled. We conducted a confirmatory factor analysis for the psychometric properties of the rMEQ and confirmed its robust one-factor structure for evaluating morningness-eveningness (GFI = 0.984, AGFI = 0.951, CFI = 0.935, and RMSEA = 0.091). Reliability was evaluated via internal consistency of rMEQ items using Cronbach's α and McDonald's ω , and the values were 0.618 and 0.654, respectively. The rMEQ scores strongly correlated with MEQ ( ρ  = 0.883, p  < 0.001), and classification agreement (Morning, Neither, and Evening types) between rMEQ and MEQ was 77.6% (Cramer's V  = 0.643, Weighted Cohen's κ  = 0.72), confirming the validity. The Japanese rMEQ may be a valuable tool for the efficient assessment of circadian typologies.

Objectives: This study investigated (non)linear associations between different eveningness characteristics (bedtime, wake time, morning affect, and peak performance time) and insomnia symptoms (difficulties initiating sleep, difficulties maintaining sleep, and nonrestorative sleep) in a large general population sample., Methods: The data came from digital surveys about insomnia (Minimal Insomnia Scale) and circadian preferences (Children's Chronotype Questionnaire/Composite Scale of Morningness) completed by the Dutch general population (37,389 participants aged 4-91years, 42.4% men) in the Lifelines cohort substudy Comorbid Conditions of ADHD., Results: Using generalized additive modeling, we found that different characteristics of eveningness related to insomnia either exponentially (later wake time/peak performance time, worse morning affect) or quadratically (early and late bedtime/midpoint of sleep). While difficulties initiating sleep and nonrestorative sleep were strongly associated with all eveningness characteristics, difficulties maintaining sleep related only to earlier bedtimes. These relationships were similar for men and women but varied partly in shapes and strengths across the lifespan. Additional analyses showed that bedtime and wake time were associated with insomnia symptoms only when their combination would result in an unusually long or short preferred time in bed., Conclusion: The association between eveningness and insomnia symptoms highly depends on whether eveningness is reflected by daytime performance or sleep-wake time. The pattern and strength of these associations also vary depending on age and insomnia symptom, but less so on sex. Future sleep-related research and policies relying on circadian preferences should account for the nonlinearity, dimension/symptom-related specificity and age-related differences in the association between eveningness and insomnia symptoms., Competing Interests: Declaration of conflicts of interest None., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)

Circadian rhythms influence a preference for people's time of activity and sleep time during the day and the hours of best performance. The aim of the study was to assess the associations between chronotype, physical activity, and well-being in adults aged 20-50. The chronotype, physical activity and well-being scores were determined based on the Composite Scale of Morningness (CSM) questionnaire, the International Physical Activity Questionnaire (IPAQ) and the Well-Being Index (WHO-5) questionnaire, respectively. Study data consisted of the answers of 213 respondents (including 64 men) who took part in an online survey. The Spearman rank correlation coefficient and the matrix scatter plots were used to check the correlations between the CSM score and quality of life parameters' values. General linear models (GLMs) were performed to find differences in quality-of-life parameters between different combinations of sex and chronotype. Morning types showed the highest value of well-being score (mean = 13.48) while evening types the lowest one (mean = 8.35). Evening types spent the most time sitting compared to other chronotypes. Results of this study revealed the significant effect of chronotype on well-being and physical activity among adults. These findings suggest that chronotype is an important factor that psychologists and personal trainers should take into account.

Background: Morningness-Eveningness Questionnaire (MEQ) has been used to assess working efficiency of an individual. The self-reporting MEQ is available in English language, and its applicability to Indian scenario is limited to educated/ English proficient individuals only. Since, majority in India still depend on the regional languages for communication, it is difficult to make live translation of the questionnaire while administration and results may also vary due to tester's language proficiency. The present study focused on adapting MEQ in Bengali language., Method: The English version of Morningness-Eveningness Questionnaire (MEQ) was a self-assessment questionnaire consisting of 19 questions to measure whether a person's peak alertness was in the morning, evening or in between. The translation of the questionnaire was done using forward-backward-translation method by six experts in Bengali language, and was content validated by thirty native Bengali speakers. The speakers were asked to rate the questions on a 5-point rating scale with 1 being very familiar and 5 being not at all familiar. All the questions rated as 1 or 2 were considered for the Bengali version of MEQ, while those rated as 3 or above were reframed and revalidated., Result: The Bengali version of the MEQ has good reliability (Cronbach's alpha 0.74). Item analysis revealed it as a good consistent scale for estimating the circadian type of the participants. Participants were classified into 5 Circadian types based on the cut-off scores. Majority of participants are intermediate type, followed by Morningness., Conclusion: The application of MEQ will help in management of tinnitus.

Objective: The aim of this study was to investigate proper sleep hours to reduce the risk of cognitive decrease considering morningness-eveningness type., Methods: The Korean Community Health Survey was used, which includes adults aged over 19 years old. These data were obtained from a cross-sectional study and assessed sleep hours using questionnaire of Pittsburgh Sleep Quality Index. Based on the wake-up time of each participant, they were classified into the morningness, intermediate, eveningness, and none groups. The change in cognitive function was determined by a single question about memory loss experience., Results: A total of 224,714 participants were included in the analysis. Of the participants, 55.6 % and 5.0 % of whom had morningness and eveningness, respectively. The risk of cognitive decline was significantly different by sleep hours and morningness-eveningness type. Without considering sleep quality, the intermediate and eveningness groups showed a higher risk of cognitive decline than the morningness group, and the risk was lowest in those with 7-9 sleep hours. However, when sleep quality showing significant effect was included in the analysis, sleep hours showing the lowest risk were different among morningness, intermediate, eveningness groups, and it was the shortest in the morningness type at 5-6 h and the longest in the eveningness type at 7-8 h., Conclusion: Proper sleep hours to decrease the risk of cognitive decline may be different by morningness-eveningness types. However, when considering sleep quality, sleep duration had little influence on cognitive decline. Future studies investigating healthy sleep hours need to consider sleep quality as well as the habitual sleep schedules., Limitations: The morningness-eveningness types were classified based on wake-up time not morningness-eveningness types. The morningness-eveningness types in this study would be interpreted as habitual sleep schedule rather than chronotype., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest regarding the publication of this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Morningness-eveningness preference, also known as chronotype, is the tendency for a person to sleep during certain hours of the day and is broadly categorised into morning and evening types. In-laboratory polysomnography (iPSG) is the gold-standard to assess sleep, however, an individual's chronotype is not accounted for in current protocols, which may confound collected sleep data. The objective of our study was to assess if chronotype had an association with sleep physiology. Patients who completed the diagnostic iPSG and the Morningness-Eveningness Questionnaire (MEQ), which categorises patients into morning type, neither or evening type, were assessed. Multivariable linear regression models were used to assess if chronotype was associated with sleep quality, duration, and physiology during iPSG. The study sample included 2612 patients (mean age of 53.6 years, 48% male) recruited during 2010-2015. Morning type, compared with neither type, was significantly associated with an increase in total sleep time and rapid eye movement (REM) sleep, and a decrease in sleep onset latency and the arousal index. Evening type, compared with neither type, was significantly associated with a decrease in total sleep time, sleep efficiency, and REM sleep, and an increase in sleep onset latency and wake after sleep onset. Additionally, iPSG lights out time was significantly different between the different chronotypes. Overall, a morningness chronotype was associated with favourable sleep quality and duration while an eveningness chronotype was associated with reduced sleep quality. Our study quantifies the association of chronotype with iPSG metrics and suggests that laboratory protocols should consider chronotype in their evaluations., (© 2023 The Authors. Journal of Sleep Research published by John Wiley & Sons Ltd on behalf of European Sleep Research Society.)

Background: The aim of this systematic review is to compile and assess the scientific evidence about the relationship between chronotypes and physical activity (PA) . Methods: A systematic review was executed using a structured electronic search in PubMED, Cochrane Library, PsycInfo and Trip Database. The searches employed keywords such as chronotype, sleep, acrophase, chronotype preference, morningness, physical activity and sedentary, using MeSH terms. JBI critical tools were used to appraise methodological aspects., Results: This systematic review includes 23 studies and a total of 505,375 participants. The results show that evening chronotypes are associated with less PA and more time in sedentary activities. It occurs independently of the instruments used to collect information about chronotype and PA. Nevertheless, this association could be mitigated in young populations and university stages., Conclusions: The chronotypes are clearly associated with the PA level and the sedentary behaviour, especially in the population over their mid-twenties. Evening chronotypes are associated with less PA and more time in sedentary activities compared to morning chronotypes.

The aim of the present study was to develop a Polygenic Score-based model for molecular chronotype assessment. Questionnaire-based phenotypical chronotype assessment was used as a reference. In total, 54 extremely morning/morning (MM/M; 35 females, 39.7 ± 3.8 years) and 44 extremely evening/evening (EE/E; 20 females, 27.3 ± 7.7 years) individuals donated a buccal DNA sample for genotyping by sequencing of the entire genetic variability of 19 target genes known to be involved in circadian rhythmicity and/or sleep duration. Targeted genotyping was performed using the single primer enrichment technology and a specifically designed panel of 5526 primers. Among 2868 high-quality polymorphisms, a cross-validation approach lead to the identification of 83 chronotype predictive variants, including previously known and also novel chronotype-associated polymorphisms. A large (35 single-nucleotide polymorphisms [SNPs]) and also a small (13 SNPs) panel were obtained, both with an estimated predictive validity of approximately 80%. Potential mechanistic hypotheses for the role of some of the newly identified variants in modulating chronotype are formulated. Once validated in independent populations encompassing the whole range of chronotypes, the identified panels might become useful within the setting of both circadian public health initiatives and precision medicine.

There is a scarcity of evidence on the association between heart rate variability (HRV) and chronotype, i.e., morningness and eveningness. The aim of this systematic review was to examine the association between chronotype, HRV, mood and stress response. We searched PubMed, Web of Science, Scopus, Cinahl, PsycINFO and Google Scholar for peer-reviewed articles published in English between January 2000 and June 2020. A total of 11 articles met the inclusion criteria and were on study population, assessment of HRV and chronotype, main results and study limitations. Seven of the included studies were experimental and four were crossovers. The sample size varied from 9 to 221 participants, and both females and males were included. HRV was assessed using mostly time-domain and frequency-domain parameters; nonlinear parameters were used in only one study. The most used assessments for measuring chronotype were the Horne-Östberg Morningness-Eveningness Questionnaire (MEQ) and the Munich Chronotype Questionnaire (MCTQ). The results showed that chronotype was associated with HRV, but the study designs were situation-specific, focusing, for example, on the effects of shiftwork, stressful situations, exercise, or sleep deprivation on HRV. In addition, some studies showed that evening types (E-type) performed better during evening or nighttime tasks, whereas morning types (M-type) performed better during morning activities. Specifically, E-types showed decreased HRV and HRV recovery in relation to tasks performed during morning or daytime when compared to M-types. As the findings are somewhat contradictory and include some methodological limitations (e.g., small sample sizes, age groups), it is important for future studies to evaluate the association between chronotype and HRV in a longitudinal setting. In addition, further research is needed to determine how chronotype can be optimally and individually utilized to increase the health and well-being of M-type and E-type individuals.

Morningness-Eveningness Stability Scale improved (MESSi) is an assessment tool that evaluates distinctness of daily changes as well as the person's propensity for morningness and eveningness. The aim of this study is to evaluate psychometric properties of the Turkish version of MESSi and associations of chronotypes and diurnal variations with personality, affect, sleep quality as well as validity of the scale in Turkish adolescents. The sample of this study consisted of 445 students between ages of 10-19. Participants filled in MESSi, Morningness/Eveningness Scale for Children, Composite Scale of Morningness, Personality Traits Scale (BIG-5), Positive and Negative Affect Scale (PANAS), Pittsburgh Sleep Quality Index (PSQI). Reliability analysis of the scale showed quite reliable internal consistency values. Confirmatory factor analysis (CFA) was used to test construct validity of three-factor model of MESSi. An acceptable model fit was demonstrated in CFA. There was a moderate and significant relationship between MA and DI subscale scores of MESSi. A moderate but negative correlation was found between MA and EV subscale scores of MESSi. MA and DI subscale scores of MESSi were found to be weakly correlated with conscientiousness, emotional stability, openness to experience and subscale scores of BIG-5, respectively. There was a positive correlation of positive affect subscale scores of PANAS with MA and DI subscale scores of MESSi. MA subscale scores of MESSi were found to be negatively correlated with scores of subjective sleep quality, latency, duration, disturbances, habitual sleep efficiency, daytime dysfunction, and global scores of PSQI. This study shows that Turkish version of MESSi is valid and reliable for use in adolescents. Three-factor MESSi provides an advantage over other chronotype scales in adolescence since it includes DI subscale as well as MA and EV subscales. Psychometric results were supported by other chronotype scales and clinical features such as sleep, affect, and personality.

When adducing temporal relationship, we can either adopt the perspective of conceiving ourselves as moving toward the future (called Moving Ego perspective), or we can adopt the perspective of the future time coming toward us (called Moving Time perspective). Previous research has shown that the adoption of these two types of temporal perspectives is highly flexible, influenced by a complex of factors. However, it remains largely unknown whether chronotype, characterized by one's tendency to conduct activities and sleep at a particular time during the day-night cycle, is correlated to metaphorical perspectives of time. Some evidence suggests a possible link between procrastination and the Moving Ego perspective. An additional line of research has shown that the evening chronotype is significantly associated with procrastination. Integrating these various lines of research led us to hypothesize that having a preference for eveningness may predispose a person toward adopting the ego-moving perspective. We tested this hypothesis and found robust support for this association in an online sample of Chinese speakers ( N = 284). We found that participants who favor the ego-moving representation exhibited a high level of eveningness. This work suggests that individual differences in circadian preference play a unique role in the resolution of temporal ambiguity.

Objectives: A lack of "morningness" predicts greater depression symptom severity over time, including in a vulnerable group of older adults: family dementia caregivers (dCGs). Evidence regarding the neurobiological basis of these correlations is needed to guide future research towards biomarker-informed detection and prevention approaches. We therefore primarily aimed to identify simple resting-state biomarkers that correlated with a lack of "morningness" in dCGs., Method: We examined 54 dCGs (mean age = 70, range: 61-84; 70% female) of whom 40% were definite "morning types" according to Composite Scale of Morningness (CSM). Using a 7 Tesla resting-state sequence, we compared the functional connectivity of nodes in networks previously implicated in depression (fronto-parietal, default mode, limbic, and salience) between caregivers who were and were not "morning types.", Results: Correcting for voxel-wise comparisons, "morning-type" dCGs had less amygdala-posterior cingulate connectivity (Cohen's d = -1.3), which statistically mediated ~32% of the association between the degree of "morningness" and lower depression severity. Post hoc analyses of CSM items found significant correlations, with both amygdala-posterior cingulate FC and depression severity, for 4/6 items pertaining to difficulty, 2/5 items pertaining to preference, and 0/2 items pertaining to typical patterns., Discussion: Prior research shows that amygdala-posterior cingulate connectivity increases when allocating attention to peripheral aspects of negative emotional stimuli. As such, difficulty with morning activation may relate to the ongoing direction of focus around distressing content; in contrast, morning activity participation may serve to limit focus on distress. Replication and experimental studies are required to confirm these associations and their modifiability., (© The Author(s) 2020. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

There is growing interest in personality profiles associated with morningness-eveningness to foster an understanding of the behaviors and mental states of chronotypes. This study aimed to analyze the domains of emotionality, activity and sociability (EAS) temperament in relation to morningness-eveningness in adolescents. A sample of 539 school pupils aged 13-19 years completed the EAS Temperament Survey, the Composite Scale of Morningness and the Munich Chronotype Questionnaire. Amongst the five EAS domains (emotionality-distress, emotionality-fearfulness, emotionality-anger, activity and sociability), greater emotionality-anger was related to eveningness, while greater emotionality-distress was related to lower social jet lag. The results suggest that evening chronotypes can be temperamentally inclined to anger. The possible mechanisms of this association are discussed.

Later chronotypes have been found to be associated with unhealthy diets in adolescents and adults, but no study has been conducted in children. The aim of this study was to investigate the associations between the chronotypes and dietary patterns of school-aged children. Children aged 7-11 and their parents were recruited from five mainstream schools in Hong Kong. The parents were told to complete questionnaires on the children's circadian preferences, food frequency, and dietary behaviors. All of the questionnaires were distributed and collected by schoolteachers. No gender differences in chronotype were observed (all p > 0.05). The evening-type was associated with significantly greater odds of viewing television (TV) during meals (adjusted odds ratios (OR) = 5.62 in boys and 5.39 in girls). Evening-oriented boys were prone to skipping breakfast (adjusted OR = 14.78), whereas evening-oriented girls were at risk of consuming fast food (adjusted OR = 7.74). There are indications of some gender differences in chronotype-related eating patterns. Sleep duration and screen time significantly mediated the associations between later chronotypes and unhealthy eating habits. Individualized dietary recommendations in accordance with circadian preferences may be effective at promoting healthy and nutritious diets for school-aged children.

Since emotions and regulatory control are relevant for decision-making, their circadian fluctuation should influence the outcome of such decisions, but this question has been rarely addressed. A review of the literature suggests that the evidence regarding circadian synchrony effects (better performance at optimal vs. non-optimal times of day according to chronotype) on decision-making is mixed, likely due to the use of different approaches to estimate chronotype. The current experiment studied economic decision-making as a function of both chronotype and the time of day when decisions are made. The influence of chronotype (Morning-type: N = 28 vs. Evening-type: N = 30) and time of day (8 am vs. 10 pm) on decision-making was measured by the acceptance rate of unfair and fair offers in the Ultimatum Game, and the event-related potentials time-locked to such offers. Subjective affect (PANAS), and appraisal of emotional images (IAPS) were also measured. Chronotype was estimated through questionnaires (MEQ, rMEQ, MCTQ) and the circadian rhythm of wrist temperature. Synchrony effects were found for both wrist temperature and subjective affect, but not for behavioral performance. Morning-types showed earlier phases of circadian rhythms in temperature, reported better sleep quality, more positive affective balance, accepted more unfair offers, and their frontal P200 potential was attenuated as compared to Evening-types in the Ultimatum Game. Acceptance rate of unfair offers correlated with the chronotype measured by questionnaires (positive correlation with rMEQ and MEQ scores, and negative correlation with Midsleep time in workdays -MSWsc from MCTQ) but not with midsleep time estimated through wrist temperature. Finally, participants who accepted more unfair offers later judged positive IAPS stimuli as more pleasant. We did not observe a synchrony effect in the Ultimatum Game, but morningness was related to rational decision-making as indexed by increased acceptance of unfair offers. Since morning-types show higher emotional regulation and positive mood than evening-types, it is possible that unfair offers did not elicit negative emotions as intense in morning-types as in evening-types, making it easier for them to accept. Abbreviations: ACC: anterior cingulate cortex; ANOVA: analysis of variance; BART: Balloon Analogue Risk Task; DLPFC: dorsolateral prefrontal cortex; EEG: electroencephalography; IAPS: International Affective Picture System; ICA: Independent component analysis; KSS: Karolinska Sleepiness Scale; LPP: Late Positive Potential; M: mean; MCTQ: Munich Chronotype Questionnaire; MEQ: Morningness Eveningness Questionnaire; MFN: Medial Frontal Negativity; MSWsc: midsleep time for working days corrected for sleep debt; MSFsc: midsleep time for free days corrected for sleep debt; N: number of participants; PANAS: Positive and Negative Affect Schedule; PSQI: Pittsburgh Sleep Quality Index; PVT: Psychomotor Vigilance Task; rMEQ: reduced Morningness Eveningness Questionnaire; RNA: Ribonucleic acid; RT: reaction time; SAM: Self-Assessment Manikin; SD: standard deviation; UG: Ultimatum Game.

Background: Earlier evidence indicated an association between chronotype and the cortisol awakening response (CAR). However, these earlier data were collected without objective control for participant compliance being available, which, following recent guidelines, is considered critical for ensuring data validity. Here, we are seeking to replicate these earlier findings within a well-controlled sleep laboratory set up., Methods: The sample consisted of 103 young males, including 12 participants defined as 'evening' (MEQ < 41) and 20 participants defined as 'morning type' (MEQ > 59) types. All participants slept for one night in a sleep laboratory and were wakened at 6:30 AM the next morning. Saliva samples for the assessment of the CAR were collected under strict supervision at 0, 15, and 30 min post-awakening., Results: Significant effects of chronotype emerged consistently from both dimensional analyses across the entire sample and from comparisons between morning vs. evening type. Overall, greater morningness was associated with an increased cortisol level upon awakening (S1) as well as with a greater overall cortisol output (AUC G ), however, it was not associated with the CAR (AUC I )., Discussion: Our data corroborate earlier evidence by showing that, under well-controlled sleep-laboratory conditions, chronotype is related to an altered cortisol secretion over the post-awakening period with no association with the CAR. However, the results have to be replicated since it is only a single day study design., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

It is still not clear how chronotype influences caffeine consumption (CC) and caffeine use disorder (CUD). The aim of the study was to investigate the relationship between chronotype, CC, CUD, and wellbeing. Participants of an online survey in Hungary (N = 2259) answered the CUD Questionnaire, Morningness-Eveningness Questionnaire and the WHO-5 Well-Being Index. Morningness positively associated with tea consumption, and negatively with cola and energy drink consumption. Severe CUD was more common among evening-type participants. Two significant mediations were found in the path model: Morningness→Tea consumption→Wellbeing and Eveningness→Energy drink consumption→CUD. It is concluded that CUD like other substance use disorders is associated with eveningness. The results indicate that the carrier beverages of the chemical compound of caffeine should be examined separately. Energy drink use can be accompanied by more unfavorable consequences, especially for evening-types, while tea consumption, which was associated with morningness, had more favorable consequences, like higher wellbeing.

Chronotype is an individual difference trait that is closely linked to biological variables. Usually, men and women differ in their chronotype with men being more evening oriented than women. The aim of the study was to assess gender differences in chronotype based on a systematic review and meta-analysis. In addition, many recent studies do not report gender differences any more although researchers collected data on men and women. This motivated us to contact many researchers directly to obtain and use these additional data. We included 164 studies giving 201 effect size measures in a data set, which only included the most commonly used questionnaires (MEQ, rMEQ and CSM) totaling 186,289 participants in total, of which 75,622 were men and 110,667 were women. We calculated an effect size of the standardized mean difference of -0.072 (95% CI from -0.062 to -0.082) in the fixed effects and of -0.066 (95% CI from -0.043 to- 0.089) in the random effects model. Men were on average more evening oriented than women. Type of questionnaire did not influence the standardized mean difference in chronotype between genders. Mean age, standard deviation of age and publication year (p ≤ 0.05) were found to have significant effects on the standardized mean difference in chronotype between genders. The standardized mean difference in chronotype between genders is predicted to change from negative to positive with increasing mean age (young women were more morning orientated than young men, but older women were less morning orientated than older men). This suggests that the differences between men and women diminish with time. The standardized mean difference in chronotype between genders is decreasing with increasing publication year, as well as with high variation in age of the samples. Abbreviations: CSM: Composite Scale of Morningness (Smith et al. 1989); MEQ: Morningness-Eveningness Questionnaire (Horne and Ostberg, 1976); rMEQ: reduced Morningness-Eveningness Questionnaire (Adan & Almiral, 1991); SMD: standardized mean difference (measure of effect size).

Case studies have a long tradition in biomedical research. Here, I will analyze an important person from a chronobiological aspect, Santa Claus. Although it might be dangerous for researchers to publish analyses about Santa Claus, because, given the possibility that he may be unsatisfied with my analysis, this could lead to an embargo of parcels for my whole family. Nevertheless, some intrepid researches already diagnosed Santa Claus, ending up in some important research results. A search in Web of Science revealed only N = 224 publications about Santa Claus, which is really low. The question, I am addressing here is, whether Santa Claus is an "evening owl" or a night chronotype. In this report, I summarize the facts known about Santa Claus on the one side and about evening chronotypes on the other and sum up these results in a "vote counting" manner as pros and cons. The results are summarized in Table 1. In total, there is 12 times support for the hypothesis, 2 times against and 1 equivocal (Table 1). This result is significant (binomial test, p = 0.013). Therefore, the conclusion is "Santa Claus is an evening type".

The medical career is considered highly stressful, especially during internships when academic and clinical demands, combined with changes in sleep patterns, increase students' likelihood to develop depression. Resilience, which is considered as opposite vulnerability to stress and, along with another protective factor, namely morningness, may cause a student to be less reactive to stimuli and, therefore, less prone to depression. The objective of this study was to evaluate the role of resilience and morningness facing to sleep quality and main risk factors, on the development of depression symptoms in a group of students with sleep pattern alterations. To this end, an observational and longitudinal study was performed with 30 undergraduate interns, with an average age of 22.63 years (SE ± 0.13), 33% men and 67% women. A survey was conducted in three different times during the year of internship: at the beginning (T 1 ), in the middle (T 2 ) and the end (T 3 ). The instruments were the Brief Resilience Scale, Composite Scale of Morningness, Pittsburgh Sleep Quality Index and Patient Health Questionnaire. The path analysis examined the roles of morningness, sleep quality and resilience as potential mediators between family history of depression and depression symptoms at different times. The results showed that resilience had a protective effect on depression symptoms at T 2 (β = -0.18, p < 0.05) and with greater power at T 3 (β = -0.41, p < 0.05), as did morningness, although less strongly, on the symptoms at T 3 (β = -0.13, p < 0.05). A relationship between these two mediating variables was also observed (β = 0.30, p < 0.05). The initial sleep quality had an effect on the increase of depression symptoms at T 1 (β = 0.61, p < 0.05) and T 3 (β = 0.21, p < 0.05), while family history of depression had a direct effect on the measures of depression at T 2 (β = 0.49, p < 0.05) and T 3 (β = 0.19, p < 0.05). Aside from personal risk factors, it is possible to conclude that the levels of resilience, morningness and sleep quality manifested by students at the beginning of their internship may explain the decrease in depression symptoms at the end of the course.

The Morningness-Eveningness Questionnaire (MEQ) is among the most commonly used scales to measure chronotype. We aimed to evaluate psychometric properties and clinical correlates of MEQ in bipolar disorder. Patients with a clinical diagnosis of bipolar disorder (n = 53) answered questionnaires for chronotype (MEQ), mood (Quick Inventory of Depressive Symptoms-16, Altman Self-Rating Mania Scale), insomnia (Athens Insomnia Scale, AIS), and sleepiness (Epworth Sleepiness Scale). Mood was evaluated using Montgomery-Åsberg Depression Rating Scale and Young Mania Rating Scale. The MEQ showed high internal consistency with Cronbach's alpha of .85. Lower MEQ scores (eveningness) correlated with insomnia (AIS) (r = -.34, p = .013). The estimate for eveningness (13/53, 24.5%) in our study was higher than in comparable studies in the general population. Patients on lithium exhibited a higher mean MEQ score (56.0 on lithium vs 46.9 with no lithium, p = .007), whereas this score was lower for patients on an antidepressant (46.0 on antidepressants vs 52.6 with no antidepressants, p = .023). We conclude that the MEQ score is psychometrically reliable. However, future studies should further evaluate the association of medication with chronotype. Validation of categorical cut-offs for MEQ in a larger sample of bipolar patients is needed to increase clinical utility., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Objectives: To assess differences relating to circadian preference in objectively measured sleep patterns from childhood to adolescence over a 9-year period. We hypothesized there is developmental continuity in sleep timing and duration according to circadian preference., Study Design: Young participants (N = 111, 65% girls) from a community-based birth cohort underwent sleep actigraphy at mean ages 8.1 (SD = 0.3), 12.3 (SD = 0.5), and 16.9 (SD = 0.1) years. A short version of Morningness-Eveningness Questionnaire was administered in late adolescence. At each follow-up, sleep midpoint, duration, wake after sleep onset, sleep efficiency, and weekend catch-up sleep were compared between those reporting morning, intermediate, and evening preferences in late adolescence., Results: Mixed model analyses indicated that sleep timing was significantly earlier among morning types compared with evening types at all ages (P values < .04). The mean differences in sleep midpoint between morning and evening types increased from a mean of 19 minutes (age 8), 36 minutes (age 12), to 89 minutes (age 17). The largest change occurred from age 12 to 17 years. Sleep duration, wake after sleep onset, sleep efficiency, and catch-up sleep did not differ according to circadian preference., Conclusions: This study found significant continuity in sleep timing from childhood to adolescence over 9 years, indicating that late circadian preference reported in late adolescence begins to manifest in middle childhood. Further studies are needed to establish whether sleep timing has its origins at an even earlier age., (Crown Copyright © 2017. Published by Elsevier Inc. All rights reserved.)

Background/objective: During adolescence, chronotype shifts toward "eveningness." "Eveningness" is related to negative physical and mental health outcomes. Little is known about what influences the shift in chronotype beyond pubertal status. The current study examined the influence of earlier depression predicting later individual differences in adolescent chronotype, accounting for pubertal status, and the prospective prediction of later increases in depression from earlier chronotype., Methods: Youth (age M = 12.06, SD = 2.35; 56.5% girls) from the community completed repeated assessments of depression, including both self-reports (14 assessments) and diagnostic interviews (eight assessments), over a 48-month period. At the 36-month timepoint, participants completed chronotype and pubertal development measures. Regression and ANOVA analyses examined: (1) the influence of earlier depression levels (baseline to 36 months) upon chronotype, and (2) chronotype (at 36 months) upon later depression (48 months)., Results: Youth with higher earlier depression symptoms (β = -0.347, P < .001) and history of depression diagnosis (β = -0.13, P = .045) showed a greater eveningness preference controlling for pubertal status, age, and gender. Further, depression diagnosis history interacted with pubertal status to predict chronotype: (F(1,243) = 4.171, P = .045) such that the influence of depression on chronotype was greatest among postpubertal youth (t = 3.271, P = .002). Chronotype (greater eveningness preference) predicted prospective increases in depression symptoms (β = -0.16, P = .03) and onset of depressive episode (b = -0.085, OR = 0.92, P = .03) 1 year later., Conclusion: Depression, experienced earlier in life, predicts greater preference for eveningness, especially among postpubertal youth. In turn, later depression is predicted by evening preference. These findings suggest the reciprocal interplay between mood and biological rhythms, especially depression and chronotype, during adolescence., (© 2017 Wiley Periodicals, Inc.)

Objective: Circadian preference refers to the tendency of individuals to be more alert and effective in the morning (larks) or the evening (owls). Given the rigors of medical residency training and perceived lifestyle differences among specialties, circadian preference may play a role in choice of medical specialty and subsequent job satisfaction during training. This study aimed to determine the circadian preferences of residents across specialties and correlations with specialty choice and job satisfaction., Study Design: Single-institution, cross-sectional survey., Methods: The Horne-Ostberg Morningness-Eveningness questionnaire, the standard to identify circadian preference, was modified to include demographic and job satisfaction variables and administered to residents at our tertiary care hospital in 2014. Independent t tests were used to correlate circadian preference and specialty choice, and Spearman's correlations were used to correlate circadian preference and job satisfaction., Results: A total of 160 residents from postgraduate years 1 through 7 and 10 specialties responded. The mean chronotype scores from all specialties met the category of "neither" morning nor evening type. A significant difference occurred between emergency medicine residents and residents from anesthesiology (P = 0.0007), surgery (P < 0.0001), and medicine (P = 0.0005). Residents in the surgical specialties trended toward the morning chronotype, whereas emergency medicine trended toward evening chronotype. There was no significant correlation between chronotype and job satisfaction., Conclusion: Although preliminary because of the low response rate, this study points to the potential of considering circadian preference in choice of specialty training and for designing resident on-call schedules., Level of Evidence: NA. Laryngoscope, 127:2236-2238, 2017., (© 2017 The American Laryngological, Rhinological and Otological Society, Inc.)

Background: Diurnal preference (and chronotype more generally) has been implicated in exercise behavior, but this relation has not been examined using objective exercise measurements nor have potential psychosocial mediators been examined. Furthermore, time-of-day often moderates diurnal preference's influence on outcomes, and it is unknown whether time-of-exercise may influence the relation between chronotype and exercise frequency., Purpose: The current study examined whether individual differences in diurnal preference ("morningness-eveningness") predict unique variance in exercise frequency and if commonly studied psychosocial variables mediate this relation (i.e., behavioral intentions, internal exercise control, external exercise control, and conscientiousness). Moreover, the study sought to test whether individuals' typical time-of-exercise moderated the impact of diurnal preference on exercise frequency., Methods: One hundred twelve healthy adults (mean age = 25.4; SD = 11.6 years) completed baseline demographics and then wore Fitbit Zips® for 4 weeks to objectively measure exercise frequency and typical time-of-exercise. At the end of the study, participants also self-reported recent exercise., Results: Diurnal preference predicted both self-reported exercise and Fitbit-recorded exercise frequency. When evaluating mediators, only conscientiousness emerged as a partial mediator of the relation between diurnal preference and self-reported exercise. In addition, time-of-exercise moderated diurnal preference's relation to both self-reported exercise and Fitbit-recorded exercise frequency such that diurnal preference predicted higher exercise frequency when exercise occurred at a time that was congruent with one's diurnal preference., Conclusion: Based on these findings, diurnal preference is valuable, above and beyond other psychological constructs, in predicting exercise frequency and represents an important variable to incorporate into interventions seeking to increase exercise.

There is evidence that a decrease in alertness is associated with a rightward shift of attention. Alertness fluctuates throughout the day and peak times differ between individuals. Some individuals feel most alert in the morning; others in the evening. Our aim was to investigate the influence of morningness/eveningness and time of testing on spatial attention. It was predicted that attention would shift rightwards when individuals were tested at their non-optimal time as compared to tests at peak times. A crowdsourcing internet marketplace, Amazon Mechanical Turk (AMT) was used to collect data. Given questions surrounding the quality of data drawn from such virtual environments, this study also investigated the sensitivity of data to demonstrate known effects from the literature. Five-hundred and thirty right-handed participants took part between 6 am and 11 pm. Participants answered demographic questions, completed a question from the Horne and Östberg Morningness/Eveningness Scale, and performed a spatial attentional task (landmark task). For the landmark task, participants indicated whether the left or right segment of each of 72 pre-bisected lines was longer (longer side counterbalanced). Response bias was calculated by subtracting the 'number of left responses' from the 'number of right responses', and dividing by the number of trials. Negative values indicate a leftward attentional bias, and positive values a rightward bias. Well-supported relationships between variables were reflected in the dataset. Controlling for age, there was a significant interaction between morningness/eveningness and time of testing (morning=6 am-2.30 pm, evening=2.30 pm-11 pm) (p<0.05) such that there was a relative rightward shift of attention from peak to off-peak times of testing for those identifying as morning types, but not evening types. Findings support the utility of crowdsourcing internet marketplaces as data collection vehicles for research. Results also suggest that the deployment of spatial attention is modulated by an individual's peak time (morningness/eveningness) and time of testing., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Morningness is a trait-like variable which has been extensively studied within chronobiology. Despite the number of existing measures to assess morningness, there is a need for brief instruments that are psychometrically sound to be used in applied settings. Accordingly, the modified version of the Preferences Scale (PS-6) comprises six items and was reported to have adequate reliability and satisfactory validity indicators. In this article, the psychometric properties of the Portuguese version of the PS-6 are reported. A total of 700 students attending medical school were recruited, and this sample was randomly divided into two groups. In the first group (n = 352), we assessed the internal consistency calculations and conducted a principal component analysis of the posited structure. In the second group (n = 348), we conducted a confirmatory factor analysis (CFA) using structural equation modeling. Overall, the results indicated that the PS-6 has adequate reliability (α = .75) and is constituted by two components: (I) preferred cognitive activities timings and (II) preferred sleeping-eating timings, respectively. In conclusion, the Portuguese version of the PS seems suitable for use in research and applied settings such as shift work schedules management. However, the applicability of the PS-6 in other samples and further validity indicators should be both investigated. The use of actigraphy and biological measures should also be collected to enhance the robustness of the PS-6.

Decision-making is affected by psychological factors like emotional state or cognitive control, which may also vary with circadian rhythmicity. Here, we tested the influence of chronotype (32 morning-type versus 32 evening-type) and time of day (9 a.m. versus 5 p.m.) on interpersonal decision-making as measured by the Ultimatum Game. Participants had to accept or reject different economic offers proposed by a virtual participant. Acceptance involved distribution of gains as proposed, whereas rejection resulted in no gain for either player. The results of the game showed a deviation from rational performance, as participants usually rejected the unfair offers. This behaviour was similar for both chronotype groups, and in both times of day. This result may reflect the robustness of decision-making strategies across standard circadian phases under ecological conditions. Furthermore, morning-types invested more time than evening-types to respond to high-uncertainty offers. This more cautious decision-making style of morning-types fits with our finding of higher proactive control as compared to evening-types when performing the AX-Continuous Performance Task. In line with the literature on personality traits, our results suggest that morning-types behave with more conscientiousness and less risk-taking than evening-type individuals.

The pineal gland, as part of the human epithalamus, is the main production site of peripheral melatonin, which promotes the modulation of sleep patterns, circadian rhythms and circadian preferences (morningness vs. eveningness). The present study analyses the pineal gland volume (PGV) and its association with circadian preferences and symptom severity in adult ADHD patients compared to healthy controls. PGV was determined manually using high-resolution 3T MRI (T1-magnetization prepared rapid gradient echo) in medication free adult ADHD patients (N=74) compared to healthy controls (N=86). Moreover, the Morningness-Eveningness Questionnaire (MEQ), the ADHD Diagnostic Checklist and the Wender-Utah Rating Scale were conducted. PGV differed between both groups (patients: 59.9±33.8mm(3); healthy controls: 71.4±27.2mm(3), P=0.04). In ADHD patients, more eveningness types were revealed (patients: 29%; healthy controls: 17%; P=0.05) and sum scores of the MEQ were lower (patients: 45.8±11.5; healthy controls 67.2±10.1; P<0.001). Multiple regression analyses indicated a positive correlation of PGV and MEQ scores in ADHD (β=0.856, P=0.003) but not in healthy controls (β=0.054, P=0.688). Patients' MEQ scores (β=-0.473, P=0.003) were negatively correlated to ADHD symptoms. The present results suggest a linkage between the PGV and circadian preference in adults with ADHD and an association of the circadian preference to symptom severity. This may facilitate the development of new chronobiological treatment approaches for the add-on treatment in ADHD., (Copyright © 2016 Elsevier B.V. and ECNP. All rights reserved.)

Meta-analyses suggest that morning-oriented students obtain better school grades than evening-oriented students. This finding has generally been found for students in high school using self-report data for the assessment of circadian preference. Two studies (N = 2718/192) investigated whether these findings generalize across samples (i.e. elementary school-aged students) and methods (i.e. parent reports). These studies also explored whether the relation between circadian preference and school achievement could be explained within an expectancy-value framework. To this end, the Lark-Owl Chronotype Indicator (LOCI) was modified to obtain parents' evaluations of their children's circadian preference, while students completed a battery of assessments designed to explore the test-criterion evidence. Structural equation modeling and correlational analyses revealed: (1) morning and evening orientation were two separable factors of children's circadian preference; (2) correlations with behavioral (e.g. sleep and eating times) and psychological (e.g. cognitive ability) data supported the test-criterion validity of both factors; (3) morning orientation was positively related to school achievement and (4) consistent with an expectancy-value framework this relation was mediated by children's academic self-concept (ASC). These findings have important research and policy implications for considering circadian preference in the schooling of elementary students.

Our current 24-h society and the weekday-weekend switch of our social clocks may affect young children's sleep and circadian rhythms. However, such evidence is scarce. We conducted a nationwide epidemiological study of sleep and health in preschool children aged 3-5 years attending kindergarten or childcare centers in Japan, using stratified one-stage cluster sampling. The target population was 2 969 627 individuals (as of 1 April 2013). The Children's ChronoType Questionnaire was used to measure chronotypes (morning (M)-type, neither (N)-type and evening (E)-type), and weekday and weekend sleep-wake parameters. Randomly sampled population estimates were obtained via respondents with a person-level weight, which accounted for survey responses and poststratification. Standard errors and 95% confidence intervals were adjusted for the complex survey design using jackknife estimation. A linear regression model of the correlation between chronotype and sleep-wake parameters and a multivariate logistic regression model for the links between chronotype and putative associated factors were used for statistical analyses. The estimated prevalence of M-, N- and E-types were 31.6%, 55.9% and 10.0%, respectively. The corresponding numbers of children were 937 910, 1 659 574 and 296 083. The remaining 2.5% was not specified. The proportions of children who woke up by themselves during the weekdays were 55.1%, 43.0% and 1.9% for M-, N- and E-types, respectively. Overall, bedtime, sleep onset time, wake-up time and get-up time during the weekdays were 21:04, 21:26, 6:55 and 6:59, respectively. Nocturnal sleep period, time in bed (TIB) and 24 h TIB (TIB and nap) during the weekdays were 9.49, 9.93 and 10.55 h, respectively. Sleep-wake timings were significantly and linearly delayed from M-, N-, to E-types (p < 0.001). The weekday 24 h TIB (10.47-10.66 h) and weekend nocturnal sleep period (9.58-9.76 h) did not differ significantly among chronotypes. For E-types, socially advanced weekdays rising times (approximately 1 h) caused nocturnal sleep deficit (0.57 h). Children's socially scheduled times (e.g. start and finish times, mealtimes and daytime nap) and their parents' diurnal preferences had significant adjusted odds ratios among E-types, while the significant unadjusted odds ratios for morning sunlight and multimedia exposure disappeared. These results suggest the importance of chronobiologically planned sleep discipline at home as well as assessment of socially scheduled times in children.

Background: Preference to time the daily activities towards the evening hours has been associated with a greater likelihood for depression in earlier studies consisting of relatively small samples., Methods: In the current study, we analyzed the relationship between chronotype and depression using a combined population-based sample of 10,503 Finnish adults aged 25 to 74 years from the two national FINRISK 2007 and 2012 health examination studies., Results: Our results confirmed that eveningness was significantly associated with the increased odds for a diagnosed depressive disorder, antidepressant medication, and depressive symptoms (p<0.0001 for each), after controlling for a range of depression-attributed and potential confounding factors. Regardless of depressive symptoms, Evening-types had lower systolic and diastolic blood pressures, a smaller waist circumference, and a lower body weight than other chronotypes., Limitations: A limitation to our study is that the assessment of chronotype and information about depression was based on the self-report information only. However, the big population-based sample, which is derived from a national health examination survey, is a major strength of our study., Conclusions: In conclusion, our study is in line the results from the previous, smaller sample size studies confirming that Evening-types have higher risk for depression than other chronotypes. This risk is elevated even among those Evening-types with sufficient amount of sleep., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Sleep deprivation and time of day are both known to influence performance. A growing body of research has focused on how sleep and circadian rhythms impact athletic performance. This review provides a systematic overview of this research. We searched three different databases for articles on these issues and inspected relevant reference lists. In all, 113 articles met our inclusion criteria. The most robust result is that athletic performance seems to be best in the evening around the time when the core body temperature typically is at its peak. Sleep deprivation was negatively associated with performance whereas sleep extension seems to improve performance. The effects of desynchronization of circadian rhythms depend on the local time at which performance occurs. The review includes a discussion of differences regarding types of skills involved as well as methodological issues., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Objectives: To develop Arabic versions of English language questionnaires to estimate morningness/eveningness and sleep variables., Methods: We translated the Composite scale of morningness (CSM) and the sleep timing questionnaire (STQ) [with added siesta questions] into Arabic; the Arabic versions were then back translated. The revised Arabic and the original English versions were next administered to bi-lingual Egyptians using a crossover design (n=25). The Arabic versions of both scales were subsequently administered to an independent Egyptian sample (n=79) and the siesta variables examined in relation to the CSM., Results: Satisfactory correlations were present between the English and Arabic versions for total CSM scores (Spearman's ρ=0.90, p<0.001). All but one of the STQ variables were significantly correlated (Spearman's ρ=0.45-0.88, p≤0.05). In the Arabic version, the frequency of siesta naps per week was significantly correlated with the total CSM score, with evening types taking more naps (Spearman's ρ=-0.23, p≤0.05)., Conclusions: Arabic versions of the STQ and CSM have been developed in Egypt, and are freely available. They can be used for behavioral research related to sleep and circadian function and can be adapted for use in other Arab speaking populations., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The timing, duration, and intensity of sleep are determined by the interaction between a sleep-wake-dependent homeostatic process and a sleep-wake-independent, intrinsic, clock-like circadian process. Chronotype represents individual differences in diurnal preferences, which are not only genetically determined but also influenced by social and environmental factors. Thus, the discrepancy between biological and social clocks, so-called "social jetlag", occurs. Chronotype, social jetlag, and the links between chronotype and behavioral problems are well documented in adults and adolescents. However, such studies on young children are limited. We conducted a survey of sleep and health for preschool children attending kindergarten or childcare centers in Wako, Okayama and Kurashiki cities, Japan, between May and July 2012. A total of 654 children aged 4-6 years (342 boys and 312 girls, with an average age of 4.7 years) were assessed using the Children's ChronoType Questionnaire and the Strength and Difficulties Questionnaire. Morning (M)-type, neither (N)-type and evening (E)-type accounted for 36.2%, 54.0% and 9.8% of the participants, respectively. The weekday-to-weekend differences in midsleep time--originally proposed as the concept of social jetlag--were 11, 25 and 35 min for M-, N- and E-types, respectively. There was a negative correlation between chronotype and sleep period during weekdays (p < 0.001) and a positive correlation on weekends (p < 0.001). The weekday-to-weekend difference in sleep period was 0.5 h for E-types, whereas there was no difference for M-types. Binomial logistic regression analyses were used to examine the links between chronotype and behavioral problems, adjusted for participants' sex, age, childcare programs and locations. Chronotype was significantly associated with hyperactivity/inattention: N-type (adjusted OR = 1.74, 95% CI = 1.03-2.95, p < 0.05) and E-type (adjusted OR = 2.47, 95% CI = 1.18-5.20, p < 0.05). E-type was significantly associated with conduct problems (adjusted OR = 2.11, 95% CI = 1.03-4.31, p < 0.05) and peer problems (adjusted OR = 2.75, 95% CI = 1.18-6.44, p < 0.05). The results suggest that E-type children are vulnerable to higher social jetlag and more behavioral problems. The immature adjustment function of their endogenous circadian pacemakers may not be able to correct a small but significant social jetlag to synchronize with their social clocks. Furthermore, guidance based on chronobiological evidence is required for parents, teachers and health professionals to help children achieve optimal sleep and reduce behavioral problems.

The association between circadian preference and academic achievement has been assessed through a systematic review and meta-analysis. The literature searches retrieved 1647 studies; 31 studies, with a total sample size of 27 309 participants, fulfilled the inclusion criteria and were included in the meta-analysis. With reference to all these 31 studies, before running the meta-analysis, the sign of the correlation between the investigated variables was set in a way that a positive correlation showed that eveningness was related to worse academic performance. The meta-analysis yielded a small overall effect size of 0.143 (CI [0,129; 0,156]) under a fixed effects model (Z = 20.584, p < 0.001, I(2)( )= 72.656; Q = 109.715) and of 0.145 (CI [0.117; 0.172]) under a random effects model (Z = 10.077, p < 0.001). A random effects model with a grouping variable (participants) revealed 15 studies based on school pupils and 16 on university students. The random model showed a higher effect size in school pupils (0.166, CI from 0.127 to 0.206) compared to university students (0.121, CI from 0.080 to 0.163). Self-report measures of grades revealed a stronger effect size (0.171; CI: 0.137 to 0.206; N = 20) compared to objective measures (0.093; CI: 0.047 to 0.140; N = 19). Overall, the present results suggest that evening orientation is associated with a worse academic performance, both in school pupils and university students; for the first time, it has been shown that such relationship changes over time, being weaker in university students.

The study aimed at testing chronotype and gender differences in the time of day when humans feel the greatest need for sex and the time of day they actually undertake sexual activity. A Polish sample of 565 participants aged between 18 and 57 was tested. In females, regardless of chronotype, the greatest need for sex occurred between 18:00 and 24:00, but a secondary peak appeared only in morning types at 6:00-9:00. In males, the greatest need for sex occurred either in the morning or evening hours: in evening types at 9:00-12:00 and 18:00-3:00; in neither types at 6:00-9:00 and 18:00-24:00; in morning types at 6:00-12:00 and 18:00-24:00. Considering time of day when subjects were undertaking sexual activity most frequently, this appeared between 18:00 and 24:00 for all the participants, and prolonged until 3:00 at night in evening type males. Morningness preference was more strongly related to the timing of need for sex than to the timing of actual sexual activity (r = -0.275 vs. r = -0.174), while the timing of desire and the timing of sexual activity were positively, but moderately related (r = 0.320).

Sleep and health are closely interrelated and sleep quality is a well-known contributor to perceived health. However, effects of sleep-timing preference i.e. morningness-eveningness on health has yet to be revealed. In this study, we explored the relationship between morningness-eveningness and perceived health in a sample of female working professionals (N = 202). Sleep-timing preference was measured using the Composite Scale of Morningness. Perceived health was characterized by Center for Epidemiologic Studies Depression Scale, WHO Well-Being Scale-5 and Patient Health Questionnaire-15 scores. We also investigated possible mechanisms, including stress and health-impairing behaviours. In accordance with previous data, we found more depressive mood, lower well-being and poorer perceived health among evening types. To assess health-impairing behaviours we collected data on smoking habits, alcohol consumption, physical activity and diet. Among the possible mechanism variables, greater stress, less frequent physical activity and less healthy diet were associated with eveningness. Furthermore, stress diminished the strength of the association between morningness-eveningness and depressed mood. Physical activity attenuated the strength of the association between morningness-eveningness and well-being. No effects of alcohol consumption could be identified. Our data show that evening preference behaves as a health risk in terms of associating with poor perceived health. Our findings also suggest that this effect might be mediated by health behaviours and stress.

Many older adults (seniors) experience problems with getting enough sleep. Because of the link between sleep and circadian rhythms, changes in bedtime lead to changes in the amount of sleep obtained. Although primarily determined genetically, chronotype changes with advancing age towards a more morning-type (M-type) orientation. In a 2006 study, we have found a linear relationship, by which the earlier a senior's bedtime, the more sleep she/he will obtain. The aim of this study was to see whether this relationship differs for M-type seniors, as compared to seniors outside the M-type category. Retired seniors (n = 954, 535 M, 410F, 65 years+, mean age 74.4 years) taking part in a telephone interview were divided into M-types and Other types (O-types) using the Composite Scale of Morningness (CSM). The relationship between bedtime and Total Sleep Time (TST), and between rise-time and TST, was tested using linear regression separately for M-types and O-types. For each participant, habitual bedtime, rise-time and total Sleep Time (TST) [after removing time spent in unwanted wakefulness] were obtained using a telephone version of the Sleep Timing Questionnaire (STQ). Both chronotype groups showed a significant linear relationship between bedtime and TST (p < 0.001); with earlier bedtimes leading to more TST (M-type 5.6 min; O-type 4.4 min per 10 min change [slope difference p = 0.05]); and an opposite relationship between rise-time and TST with earlier rise-times leading to less TST (M-type 6.7 min; O-type 4.2 min per 10 min change [slope difference p = 0.001]). M-types retired to bed 56 min earlier (p < 0.001), awoke 93 min earlier (p < 0.001) and obtained 23 min less TST (p < 0.001) than O-types. In conclusion, both chronotypes showed TST to be related in a linear way to bedtime and rise-time; the overall shorter TST in M-types was due to them rising 93 min earlier, but only retiring to bed 56 min earlier than O-types; as well as having a steeper rise-time versus TST relationship.

The current study tested for the first time the effect of individual differences in circadian rhythmicity (chronotype) on both driving performance and its evolution along time on task. Morning-type and evening-type female participants were tested in morning (8 am) and evening (8 pm) sessions, in which we controlled for prior sleep duration and prior wake. Measures of body temperature, subjective activation and affect, reaction times (RT) in the Psychomotor Vigilance Task (PVT), behavioral performance (error position) and EEG alpha power during simulated driving were collected. The main result showed strong linear increments of mean and standard deviation of error position along time on task (vigilance decrement) when evening-type participants drove at their non-optimal time of day, that is, during the morning session. In contrast, driving performance in the morning-type group remained stable over time on task and was not affected by time of day. This finding can be due to differences in personality traits (e.g., conscientiousness, sensation seeking) and task appraisal associated to extreme chronotypes. The consideration of chronotype in vigilance and driving tasks can enhance safety and human performance by promoting work schedules and countermeasures to prevent failures in the accomplishment of tasks under non-optimal circadian conditions., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Study Objectives: Using telephone interview data from retired seniors to explore how inter-individual differences in circadian type (morningness) and bed-timing regularity might be related to subjective sleep quality and quantity., Design: MANCOVA with binary measures of morningness, stability of bedtimes, and stability of rise-times as independent variables; sleep measures as dependent variables; age, former shift work, and gender as covariates., Setting: Telephone interviews using a pseudo-random age-targeted sampling process., Participants: 654 retired seniors (65 y+, 363M, 291F)., Intervention: none., Independent Variables: (1) circadian type (from Composite Scale of Morningness [CSM]), and stability of (2) bedtime and (3) rise-time from the Sleep Timing Questionnaire (STQ)., Dependent Variables: Pittsburgh Sleep Quality Index (PSQI) score, time in bed, time spent asleep, and sleep efficiency, from Sleep Timing Questionnaire (STQ). Morning-type orientation, stability in bedtimes, and stability in rise-times were all associated with better sleep quality (P < 0.001, for all; effect sizes: 0.43, 0.33, and 0.27). Morningness was associated with shorter time in bed (P < 0.0001, effect size 0.45) and time spent asleep (P < 0.005, effect size 0.26). For bedtime and rise-time stability the direction of effect was similar but mostly weaker., Conclusions: In retired seniors, a morning-type orientation and regularity in bedtimes and rise-times appear to be correlated with improved subjective sleep quality and with less time spent in bed.

This systematic review investigates the bidirectional relationship between alcohol consumption and disrupted circadian rhythms. The goal of this study was to identify (i) the types of circadian rhythm disruptors (i.e. social jet lag, extreme chronotypes, and night shift work) associated with altered alcohol use and (ii) whether sex differences in the consequences of circadian disruption exist. We conducted a search of PubMed, Embase, and PsycINFO exclusively on human research. We identified 177 articles that met the inclusion criteria. Our analyses revealed that social jet lag and the extreme chronotype referred to as eveningness were consistently associated with increased alcohol consumption. Relationships between night shift work and alcohol consumption were variable; half of articles reported no effect of night shift work on alcohol consumption. Both sexes were included as participants in the majority of the chronotype and social jet lag papers, with no sex difference apparent in alcohol consumption. The night shift research, however, contained fewer studies that included both sexes. Not all forms of circadian disruption are associated with comparable patterns of alcohol use. The most at-risk individuals for increased alcohol consumption are those with social jet lag or those of an eveningness chronotype. Direct testing of the associations in this review should be conducted to evaluate the relationships among circadian disruption, alcohol intake, and sex differences to provide insight into temporal risk factors associated with development of alcohol use disorder. [ABSTRACT FROM AUTHOR]

Introduction: Numerous studies have suggested a connection between circadian rhythm and neurological disorders with cognitive and consciousness impairments in humans, yet little evidence stands for a causal relationship between circadian rhythm and the brain cortex. Methods: The top 10,000 morningness-related single-nucleotide polymorphisms of the Genome-wide association study (GWAS) summary statistics were used to filter the instrumental variables. GWAS summary statistics from the ENIGMA Consortium were used to assess the causal relationship between morningness and variates like cortical thickness (TH) or surficial area (SA) on the brain cortex. The inverse-variance weighted (IVW) and weighted median (WM) were used as the major estimates whereas MR-Egger, MR Pleiotropy RESidual Sum and Outlier, leave-one-out analysis, and funnel-plot were used for heterogeneity and pleiotropy detecting. Results: Regionally, morningness decreased SA of the rostral middle frontal gyrus with genomic control (IVW: ß = -24.916 mm, 95% CI: -47.342 mm to -2.490 mm, p = 0.029. WM: ß = -33.208 mm, 95% CI: -61.933 mm to -4.483 mm, p = 0.023. MR Egger: ß < 0) and without genomic control (IVW: ß = -24.581 mm, 95% CI: -47.552 mm to -1.609 mm, p = 0.036. WM: ß = -32.310 mm, 95% CI: -60.717 mm to -3.902 mm, p = 0.026. MR Egger: ß < 0) on a nominal significance, with no heterogeneity or no outliers. Conclusions and implications: Circadian rhythm causally affects the rostral middle frontal gyrus; this sheds new light on the potential use of MRI in disease diagnosis, revealing the significance of circadian rhythm on the progression of disease, and might also suggest a fresh therapeutic approach for disorders related to the rostral middle frontal gyrus-related. [ABSTRACT FROM AUTHOR]

Individuals can be classified into different chronotypes concerning their circadian rhythm features. Morningness-Eveningness (MEQ) can be defined as individual differences in sleep-wake patterns and people's time-of-day feel and perform the best. Various self-report instruments that measure the Morningness-Eveningness have been developed. The Morningness–Eveningness Questionnaire (MEQ), developed by Horne and Östberg, was the first and most used questionnaire for determining the chronotypes of an individual. The main aim of the current study was to translate and validate the Morningness-Eveningness Questionnaire (MEQ) to the Nepali language. The English version of the MEQ was translated to the Nepali language using the translation-back-translation method. Further, it was given to 10 native Nepali speakers for content validation. The final MEQ-Nepali version was then administered to 116 native Nepali speakers. Mean, standard deviation, variance, and reliability statistics such as Cronbach's alpha score, intraclass correlation coefficient, and item-total correlation were obtained for the data. Results showed that the MEQ-Nepali version has a Cronbach's alpha score and an inter-class correlation coefficient of 0.73, which is considered good reliability. The MEQ Nepali version developed in this study is found to be valid and reliable. Hence, it can be used to categorize Nepali-speaking populations into various circadian types. [ABSTRACT FROM AUTHOR]

Sport-specific skills display diurnal variation across various team sports such as badminton and tennis serving accuracy and soccer dribbling, volleying, and chipping execution. However, the effects of athlete chronotype on in-game sport-specific skill performance according to time of day across team sports is not well understood. Therefore, the aim of this study was to identify the effect of player chronotype on in-game basketball performance during evening games. Professional male basketball players (n = 11) completed a morningness–eveningness questionnaire and were categorized according to chronotype (morning-type: n = 4; neither-type: n = 6; evening-type: n = 1). Box score data from the 2019/20 season were utilized to determine individual in-game performance during evening games played after 18:00 h. Composite metrics (i.e., effective field goal percentage, offensive rating, defensive rating, and player efficiency) were used as indicators of player performance. Non-significant (p ≥ 0.21) differences were evident between M-types and N-types for most performance measures. Small to very large effects were observed in the number of rebounds favoring M-types, and three-point shots attempted and made, assists, and steals favored N-types. In-game performance appeared to not be affected by chronotype (i.e., M-type vs. N-type) in evening games among professional male basketball players. The lack of observed effect between chronotype and in-game performance suggest coaching staff may not need to consider player chronotype when developing a match strategy or assigning player roles if largely dealing with M-types and N-types. However, to ensure the greatest specificity, coaching staff may endeavor to schedule habitual training times in line with that of competition in an effort to align player circadian rhythms to games.

Sport-specific skills display diurnal variation across various team sports such as badminton and tennis serving accuracy and soccer dribbling, volleying, and chipping execution. However, the effects of athlete chronotype on in-game sport-specific skill performance according to time of day across team sports is not well understood. Therefore, the aim of this study was to identify the effect of player chronotype on in-game basketball performance during evening games. Professional male basketball players (n = 11) completed a morningness-eveningness questionnaire and were categorized according to chronotype (morning-type: n = 4; neither-type: n = 6; evening-type: n = 1). Box score data from the 2019/20 season were utilized to determine individual in-game performance during evening games played after 18:00 h. Composite metrics (i.e., effective field goal percentage, offensive rating, defensive rating, and player efficiency) were used as indicators of player performance. Nonsignificant (p >0.21) differences were evident between M-types and N-types for most performance measures. Small to very large effects were observed in the number of rebounds favoring M-types, and three-point shots attempted and made, assists, and steals favored N-types. In-game performance appeared to not be affected by chronotype (i.e., M-type vs. N-type) in evening games among professional male basketball players. The lack of observed effect between chronotype and in-game performance suggest coaching staff may not need to consider player chronotype when developing a match strategy or assigning player roles if largely dealing with M-types and N-types. However, to ensure the greatest specificity, coaching staff may endeavor to schedule habitual training times in line with that of competition in an effort to align player circadian rhythms to games. [ABSTRACT FROM AUTHOR]

Background and Objective: Previous studies had examined the effect of learning in young adults with generally worse results in cases with the delayed sleep-wake phase disorder. In this study, the relationship between circadian rhythm preferences and objective structured clinical examination (OSCE) results was examined in medical students. Materials and Methods: This study was conducted during the OSCE for clinical license in medical students who were graduation candidates. The reduced form of the Horne and Ostberg Morningness-Eveningness Questionnaire was used to estimate their circadian chronotype. The OSCE consisted of 12 stations, which evaluated different clinical skills, as well as participant’s medical knowledge. The effect of morningness-eveningness preference of each participant on score was evaluated within each station of OSCE. Results: In total, 78 students participated out of a total of 114 clinically competent candidates (aged 25-34 years) were evaluated. In terms of sex, 56% of the students were girl, who obtained significantly higher grades in three stations (P < 0.05). The grades of students with delayed sleep-wake chronotypes were higher in most of the stations; however, the difference was statistically significant in only one station (P = 0.045), which was the most difficult station of the exam. Nevertheless, the delayed sleep-wake chronotype was associated with excessive daytime sleepiness (P = 0.002). Conclusion: Contrary to other similar studies in medical students, normal circadian chronotype was associated with poorer outcome in the OSCE; which may be explained by unusual student training hours during shifts, and the resultant available time for undisturbed study .