Social jetlag negatively correlates with academic performance in undergraduates

Circadian disruptions and their role in the development of hypertension

Circadian fluctuations in physiological setpoints are determined by the suprachiasmatic nucleus (SCN) which exerts control over many target structures within and beyond the hypothalamus via projections. The SCN, or central pacemaker, orchestrates synchrony between the external environment and the internal circadian mechanism. The resulting cycles in hormone levels and autonomic nervous system (ANS) activity provide precise messages to specific organs, adjusting, for example, their sensitivity to approaching hormones or metabolites. The SCN responds to both photic (light) and non-photic input. Circadian patterns are found in both heart rate and blood pressure, which are linked to daily variations in activity and autonomic nervous system activity. Variations in blood pressure are of great interest as several cardiovascular diseases such as stroke, arrhythmias, and hypertension are linked to circadian rhythm dysregulation. The disruption of normal day-night cycles, such as in shift work, social jetlag, or eating outside of normal hours leads to desynchronization of the central and peripheral clocks. This desynchronization leads to disorganization of the cellular processes that are normally driven by the interactions of the SCN and photic input. Here, we review autonomic system function and dysfunction due to regulation and interaction between different cardiorespiratory brain centers and the SCN, as well as social, lifestyle, and external factors that may impact the circadian control of blood pressure.

Sex Differences in Temporal Sleep Patterns, Social Jetlag, and Attention in High School Adolescents

Insufficient sleep and irregular sleep hours are common in adolescents, who experience a delayed sleep phase due to biopsychosocial changes associated with puberty, resulting in later sleep times. However, early morning class hours shorten sleep duration on weekdays. This condition is harmful to cognitive performance, which may be accentuated in girls due to a greater sleep need and less resistance to sleep deprivation. In this study, we evaluated sex differences concerning temporal sleep patterns, social jetlag, and attention in high school adolescents attending morning classes. Students ( n  = 146 - F: 73-16.1 ± 0.8 years; M: 73-16.2 ± 0.9 years) completed a Health and Sleep questionnaire, kept a sleep diary for 10 days, which incorporated a Maldonado Sleepiness Scale, and performed a Continuous Performance Task. Girls went to bed earlier and woke up on weekends, and spent more time in bed at night and in 24 h on weekdays and weekends, while they also had a greater irregularity in wake-up times ( p  < 0.05). There were no differences between sexes in terms of social jetlag, sleep debt, and sleepiness upon awakening ( p  > 0.05). Regarding attention, the girls had a longer reaction time in phasic alertness ( p  < 0.01) and a tendency to have fewer errors in selective attention ( p  = 0.06). These results persisted when controlled for sleep parameters. Therefore, we suggest that girls have a greater sleep need and less resistance to sleep deprivation, while the differences in attention performance could be due to different strategies, the girls could be making a trade, increasing reaction time in favor of better accuracy, while the boys could be prioritizing a faster response time.

Greater social jetlag predicts poorer NIH Toolbox crystallized cognitive and academic performance in the Adolescent Brain Cognitive Development (ABCD) study

Academic performance plays a crucial role in long-term educational attainment and occupational function. Chronotype refers to an individual's daily tendencies for times for waking, activity, and sleep. Social jetlag reflects the mismatch between an individual's chronotype and their social schedule. Because school typically starts early in the morning, later chronotype is often associated with daytime sleepiness, insufficient sleep, and poor academic performance. However, the relationship between academic performance, chronotype, and social jetlag has not been extensively examined in large samples like the Adolescent Brain Cognitive Development (ABCD) study. We hypothesized that greater social jetlag would predict poorer cognitive and academic performance. Year 2 (ages 11-14) cross-sectional data from the ABCD cohort (n = 6,890 adolescents) were used to evaluate academic performance (i.e. self-reported past year grades), NIH Toolbox cognitive performance measures, chronotype, and social jetlag from the Munich Chronotype Questionnaire. We found that later chronotype and greater social jetlag predicted poorer cognitive and academic performance with small effect sizes. Our findings emphasize the importance of individual differences in chronotype and social jetlag when designing class schedules, as aligning school activities with student optimal sleep-wake times may contribute to improved academic performance.

Association between Social Jetlag and Objective Physical Activity among Female University Students of Japan: A Cross-Sectional Study

Objective  Discrepancies between sleep timing on work/school and free days, also known as social jetlag (SJL), can cause health problems. These issues occur most often in individuals from adolescence to the early 20s, which is equivalent to the age of university students. This study was designed to explore the recommended level of physical activity required to minimize SJL and to examine the relationship between SJL and objective physical activity among female university students. Methods  We assessed the SJL of 68 female students using the Japanese version of the Munich Chronotype Questionnaire. The objective physical activity and sleep variables of subjects were also evaluated at 3 to 4 weeks using a small triaxial accelerometer. Results  A significant negative correlation was found between SJL and physical activity on both free (r = - 0.435, p  < 0.001) and school days (r = - 0.341, p  < 0.01). According to the linear regression analysis, physical activity of 11,174 steps on school days and 10,713 steps on free days had the lowest SJL value. Total sleep time on free days had a significant positive correlation with SJL (r = 0.399, p  < 0.001) and a negative correlation with physical activity (r = - 0.520, p  < 0.001). Discussion  Our results suggest that substantial SJL may cause chronic fatigue and lead to a low level of physical activity in female university students. These results also imply that the recommended level of physical activity necessary to minimize SJL among these students is around 11,000 steps on both school and free days.

Effects of chronotype on sleep, mood and cardiovascular circadian rhythms in rotating night shift medical workers

PURPOSE

Whether chronotype affects the health outcomes of night shift work populations is unknown. This study aimed to assess the influence of different chronotypes in the rotating night shift population on sleep status, mood, blood pressure (BP), and heart rate variability (HRV), as well as the circadian rhythm of BP and HRV.

METHODS

A total of 208 rotating night shift workers were included. All participants completed structured questionnaires to assess chronotype, mood and sleep status. During their daily lives outside of the night shift, they underwent 24-hour Holter electrocardiogram monitoring and 24-hour ambulatory blood pressure monitoring. Day-time and night-time BP and BP dipping were obtained. Day-time and night-time HRV values (SDNN, RMSSD, LF, HF, LF nu, SD1, SD2 and SD2/SD1) were calculated and fitted to the cosine period curve. Three circandian parameters (mesor, amplitude and acrophase) were extracted to quantify the circadian rhythm of the HRV indices.

RESULTS

Among all three groups, E-type showed more fatigue and sleepiness. In addition, E-type showed blunted diastolic BP dipping. Notably, E-type showed association with higher RMSSD, LF, HF and SD1 in the night time, and higher mesors of RMSSD and LF and amplitude of SD2/SD1 in circadian analysis.

CONCLUSION

Chronotype is a factor affecting fatigue, sleepiness and cardiovascular circadian rhythms of rotating night shift workers. Chronotype should be taken into consideration for managing night-shift rotation to promote occupational health.

Association between social jetlag and self-rated health: Evidence from Korean representative working population

BACKGROUND

Social jetlag is a circadian misalignment that arises from a discrepancy between activity/sleep schedules on school/work days and free days. This study explored the correlation between social jetlag and self-rated health (SRH) in a representative sample of Korea.

METHODS

This study included 8259 working population in the Korea National Health and Nutrition Examination Survey, 2016-2018. Social jetlag was calculated as the difference between the midpoint of sleep time on work day and work-free day. Five-point Likert scale of SRH was used to assess subjective health perception on general health conditions. Multiple logistic regression analysis was performed to calculate the odds ratios (ORs) and 95 % confidence interval (CI) for poor SRH in the 1-2 h or longer than 2 h social jetlag groups compared to that in the reference group (less than 1 h), after adjusting for age, sex, marital status, occupation, household income, and weekly working hours.

RESULTS

The proportions of those with <1 h, 1-2 h, >2 h of social jetlag were 63.80 %, 25.67 %, and 10.53 %, respectively. The risk of poor SRH increased as social jetlag increased. Greater social jetlag was significantly associated with an increased likelihood of reporting poor SRH. The adjusted ORs for the groups with social jetlag between 1 and <2 h, and >2 h were 1.100 (95 % CI = 0.935-1.295), and 1.503 (95 % CI = 1.097-1.727), respectively. Moreover, the OR trend was statistically significant (p for trend = 0.008).

CONCLUSION

This study found that social jetlag and poor SRH were significantly related in the Korean working population.

Lifestyle factors, dietary patterns, and social determinants of social and eating jetlag: A cross-sectional survey

Social jetlag (SJL) and, more recently, eating jetlag have been linked with an increased risk of non-communicable diseases. Here we aim to investigate lifestyle factors (diet, eating behavior, smoking, perceived stress, time spent sedentary/day) and social determinants (education level, employment status, and place of residence) associated with SJL corrected for sleep duration (SJLsc) and eating jetlag. Self-declared data on age, gender, lifestyle, and eating behavior were collected online from March 2021 to February 2022 of 432 adults. Principal component analysis was used to extract three dietary patterns (Prudent, Western, and Risky). Prevalence of SJLsc was 35.2%, with no significant difference between men and women (p = 0.558). Adults with SJLsc had significantly larger eating jetlag (56.0 min vs 41.2 min, p = 0.001). Increasing SJLsc duration was associated with an increased adherence to a Risky dietary pattern (standardized β coefficient = .165, p = 0.012); increasing eating jetlag duration was associated with an increased adherence to a Western dietary pattern (standardized β coefficient = .127, p = 0.039) and a shorter sleep duration (standardized βcoefficient = -0.147, p = 0.011). Among social determinants analyzed, only being a student or employed was associated with eating jetlag (standardized β coefficient = 0.125, p = 0.044), while none displayed any relationship with SJLsc. Our survey provides evidence on a risky behavior among young persons with SJLsc and eating jetlag, characterized by a higher alcohol consumption, and a diet rich in processed meat and high-fat food, eating during nights, and shorter sleep duration with potential long-term negative health outcomes.

The motivation behind better sleep: self-determination as a framework for examining sleep outcomes in college students

OBJECTIVE

To examine sleep health within a self-determination framework across a diverse college sample.

PARTICIPANTS

A nonclinical sample of undergraduate students (n = 399) from a large, urban, public university in the Mid-Atlantic United States in Spring 2020.

METHODS

Participants were recruited via an online research participation portal and received extra credit for participation. All measures were administered via an online survey.

RESULTS

Basic psychological need satisfaction was associated with sleep health. This association was partially mediated by sleep hygiene but not by regulatory style. There were no racial/ethnic differences in sleep health, sleep hygiene, basic need satisfaction, or regulatory style. Men reported more maladaptive motivational styles for sleep health, and non-binary/transgender students reported worse sleep hygiene.

CONCLUSION

Basic psychological need satisfaction and sleep hygiene are critical targets for intervention across diverse college student populations. Motivation may be less critical for nonclinical interventions.

Association of Chrononutrition Indices with Anthropometric Parameters, Academic Performance, and Psychoemotional State of Adolescents: A Cross-Sectional Study

Adolescents are an at-risk group for circadian misalignment. The contribution of sleep-wake rhythm instability to the psychoemotional, cognitive, and weight disorders of adolescents has been studied in sufficient detail. At the same time, there is insufficient information about the association between chrononutrition indices and the well-being of adolescents. The aim of this study is to investigate the relationship between chrononutrition indices and academic achievement, psychoemotional state, and anthropometric indicators in adolescents. The study involved 12,759 students in grades 6-11 of secondary schools, aged 14.2 ± 1.7 years old; 57.2% of whom were girls. Participants provided personal data, frequency and time of meals during the day and at night, on weekdays and weekends, and completed the Zung Self-Rating Depression Scale and the Yale Food Addiction Scale. There is a U-shaped association between eating mid-phase (EPFc), eating jetlag (EJL), and eating window (EW) with GPA, ZSDSI, and FA. At the same time, the frequency of night eating (NE) is linearly associated with the studied parameters. NE is the strongest predictor of ZSDSI (β = 0.24), FA (β = 0.04), and GPA (β = -0.22). EPFc, EJL, and EW practically do not differ in the strength of their association with the studied indicators. ZSDSI is most closely associated with the chrononutrition indices. There is a weak negative association between BMI and EW (β = -0.03) and NE (β = -0.04). Thus, circadian eating disorders are more often observed in adolescents with poor academic performance, high levels of depression, and food addiction.

Protocol of the Budapest sleep, experiences, and traits study: An accessible resource for understanding associations between daily experiences, individual differences, and objectively measured sleep

Sleep is both a neurophysiological state and a biologically necessary behavior that performs a variety of indispensable roles for human health, development, and cognitive functioning. Despite this, comparatively little is known about the relationships between daily experiences and sleep features. Importantly, these relationships are bidirectional in nature, may be differently associated with subjectively and objectively assessed sleep, and may also be modulated by individual differences To address this challenge, we created the Budapest Sleep, Experiences, and Traits Study (BSETS), a multidisciplinary observational sleep study utilizing novel remote EEG devices. BSETS was designed to establish a dataset for future use in investigating the relationships between sleep features and daily experiences. In this paper we describe the protocol of the currently ongoing BSETS, which examines a community-dwelling sample of over 250 healthy participants who are studied in a naturalistic setting using a large questionnaire assessing psychological, demographic, and anthropometric information, as well as evening/morning diaries of sleep and daily experiences, and mobile EEG recordings over a period of 7 days. This dataset will become an accessible resource to the wider scientific community and can be utilized to investigate the complex multidirectional relationships between objectively and subjectively measured sleep, daily experiences, and individual differences, bestowing it with significant value for sleep researchers as well as practitioners working in clinical settings with patients suffering from disordered sleep.

The prevalence of temporomandibular disorder and temporomandibular morphology among diverse chronotype profiles

This study investigates the influence of chronotype on the prevalence of temporomandibular joint disorders (TMD) and the morphology of temporomandibular joint (TMJ). According to the Morningness-Eveningness Questionnaire-Self-Assessment, the participants were divided into morning group (n = 30), intermediate group (n = 83), and evening group (n = 30). Thirty participants were randomly selected from the intermediate group for subsequent examination and measurements. The morphology of TMJs was investigated using questionnaire and clinical examination form in Diagnostic Criteria for Temporomandibular Disorder. Meanwhile, the morphological results of TMJs were measured from cone-beam computed tomography images. The prevalence rate of TMD in the morning group (23%) was significantly lower than that in the intermediate group (56.7%), while there was no difference between the evening (53.4%) and intermediate groups. As to morphological measurements, there was no significant difference among three groups in mediolateral width of condylar process, anteroposterior width of condylar process, radius of condyle, medial joint space, lateral joint space, condylar stress angle, horizontal condylar inclination, width of glenoid fossa, depth of glenoid fossa, and posterior joint space, while there was a significant difference in horizontal condylar angle (p = 0.00490), articular eminence inclination (p < .0001), anterior joint space (p = 0.0163), and superior joint space (p = 0.0004). The morphology of TMJ in the morning group was better than that in the evening and intermediate groups. An association was found between TMD prevalence, temporomandibular morphology, and chronotype.

Social jetlag and dietary intake: A systematic review

The objective of the current systematic review was to critically review the available evidence regarding the link between social jetlag and diet among the general population using observational studies. Electronic databases, including PubMed, Scopus, and ISI Web of Sciences were searched systematically. We reviewed 348 references, of which 17 studies met inclusion criteria with a total sample size of 28,905. Qualitative analysis indicated a negative association between social jetlag and adherence to healthy eating habits, including a negative association with empirically-derived healthy dietary patterns, Japanese dietary patterns, Baltic Sea dietary patterns, and the Mediterranean diet, as well as a positive association with Meat and Starchy dietary pattern. On the other hand, the findings on the link of social jetlag with food groups and nutrients were mixed and controversial, except for a more consistent increase in sugar-sweetened beverages, total fat, and saturated fat intake. Our results indicate a possible link between social jetlag and dietary intake. Research suggests that individuals experiencing greater social jetlag exhibit reduced adherence to a healthy eating pattern. However, it is important to note that the reported association lacks consensus, emphasizing the need for additional longitudinal studies to gain further insights into this matter."

Measuring light regularity: sleep regularity is associated with regularity of light exposure in adolescents

STUDY OBJECTIVES

Light is the main time cue for the human circadian system. Sleep and light are intrinsically linked; light exposure patterns can influence sleep patterns and sleep can influence light exposure patterns. However, metrics for quantifying light regularity are lacking, and the relationship between sleep and light regularity is underexplored. We developed new metrics for light regularity and demonstrated their utility in adolescents, across school term and vacation.

METHODS

Daily sleep/wake and light patterns were measured using wrist actigraphy in 75 adolescents (54% male, 17.17 ± 0.83 years) over 2 weeks of school term and a subsequent 2-week vacation. The Sleep Regularity Index (SRI) and social jetlag were computed for each 2-week block. Light regularity was assessed using (1) variation in mean daily light timing (MLiT); (2) variation in daily photoperiod; and (3) the Light Regularity Index (LRI). Associations between SRI and each light regularity metric were examined, and within-individual changes in metrics were examined between school and vacation.

RESULTS

Higher SRI was significantly associated with more regular LRI scores during both school and vacation. There were no significant associations of SRI with variation in MLiT or daily photoperiod. Compared to school term, all three light regularity metrics were less variable during the vacation.

CONCLUSIONS

Light regularity is a multidimensional construct, which until now has not been formally defined. Irregular sleep patterns are associated with lower LRI, indicating that irregular sleepers also have irregular light inputs to the circadian system, which likely contributes to circadian disruption.

Afternoon school shift is associated with increased risk of overweight/obesity in 11-14-year-old females with early and intermediate chronotype

OBJECTIVE

The purpose of this study was to compare the anthropometric and sleep-wake rhythm characteristics of schoolchildren that attend school in morning and afternoon school shifts.

METHODS

We recruited 18 481 individuals (females: 56.4%) aged 11 to 18 years old with an average age of 14.4 ± 1.7 years old. In total, 812 (4.2%) questionnaires were incomplete. The self-reported height and weight were used to assess the sex- and age-corrected body mass index of the participants. The Munich ChronoType Questionnaire was used to assess the chronotype, social jetlag, and sleep duration of the participants.

RESULTS

In total, 12.6% of the participants were affected by overweight or obesity. The overweight and obesity incidence rate was higher among the students studying in the afternoon (odd ratio [95%CI]: 1.33 [1.16-1.52]). The afternoon school shift had a negative impact on the anthropometric indicators only in the 11-14-year-olds (1.29 [1.11-1.50]) and girls (1.26 [1.04-1.54]) with an early (1.27 [1.03-1.56]) and intermediate (1.30 [1.07-1.58]) chronotype.

CONCLUSION

The data obtained indicated that the afternoon school shift is not ideal, especially for female children and adolescents under 15 years old with an early and intermediate chronotype.

Daily rhythms, light exposure and social jetlag correlate with demographic characteristics and health in a nationally representative survey

The timing of daily activity in humans have been associated with various demographic and health-related factors, but the possibly complex patterns of confounding and interaction between these has not been systematically explored. We use data from Hungarostudy 2021, a nationally representative survey of 7000 Hungarian adults to assess the relationship between self-reported chronotype, social jetlag (using the Munich Chronotype Questionnaire), demographic variables and self-reported health and demographic variables, including ethnic minority membership. Supporting the validity of self-reports, participants with later chronotypes reported the lowest daytime sleepiness at a later clock time. We found that older age, female sex, a more eastward and southward geographical position, residence in a smaller settlement, less education and income, religiousness and cohabiting with small children were associated with an earlier chronotype. Younger age, higher education and income, and cohabiting with small children were associated with increased social jetlag. Of the 48 health-related variables surveyed, the relationship with both chronotype and social jetlag were mostly accounted for by age, sex, and socioeconomic effects, but we identified alcohol consumption, smoking, and physical activity as predictors of both social jetlag and chronotype, while a number of disorders were either positively or negatively associated with chronotype and social jetlag. Our findings from a large, nationally representative sample indicate that both biological and social factors influence chronotype and identified both demographic and health-related variables as risk factors for social jetlag. Our results, however, do not support a causal relationship between light exposure and mental health.

The Association between Melatonin-Containing Foods Consumption and Students' Sleep-Wake Rhythm, Psychoemotional, and Anthropometric Characteristics: A Semi-Quantitative Analysis and Hypothetical Application

Food is an important source of melatonin (MT), which belongs to a group known as chronobiotics, a class of substances that affect the circadian system. Currently, no studies have been conducted on how the consumption of foods containing MT (FMT) is associated with indicators characterizing the human circadian system. In this study, we tested the hypothesis that FMT consumption is associated with chronotype and social jetlag. A total of 1277 schoolchildren and university students aged M (SD) 19.9 (4.1) years (range: 16-25 years; girls: 72.8%) participated in a cross-sectional study. Each participant completed an online questionnaire with their personal data (sex, age, height, weight, waist circumference, and academic performance) and a sequence of tests to assess their sleep-wake rhythm (the Munich Chronotype Questionnaire), sleep quality (the Pittsburgh Sleep Quality Index), and depression level (the Zung Self-Rating Depression Scale). Study participants also completed a modified food frequency questionnaire that only included foods containing MT (FMT). They were asked how many foods containing MT (FMT) they had eaten for dinner, constituting their daily serving, in the past month. The consumption of foods containing MT (FMT) during the day (FMTday) and at dinner (FMTdinner) was assessed using this test. Multiple regression analyses were performed to assess the association between the studied indicators. We found that higher FMTday values were associated with early chronotype (β = -0.09) and less social jetlag (β = -0.07), better sleep quality (β = -0.06) and lower levels of depression (β = -0.11), as well as central adiposity (β = -0.08). Higher FMTdinner values were associated with a lower risk of central adiposity (β = -0.08). In conclusion, the data obtained confirm the hypothesis that the consumption of foods containing MT (FMT) is associated with chronotype and social jetlag in adolescents and young adults.

Efficacy of sleep extension therapy using a remote support system in university students with increased social jetlag: a parallel, single-blind, randomized controlled trial

Purpose

The efficacy of sleep extension therapy using a remote support system (SET-R) was investigated in university students with increased social jetlag (SJL).

Methods

For this two-arm parallel randomized controlled trial, we recruited Japanese university students with SJL ≥ 60 min. The SET-R provided an individualized sleep schedule for gradual sleep extension using email and sleep hygiene education, stimulus control therapy, and progressive muscle relaxation as web content. The control group was sent an email that encouraged them to record their sleep. The duration of the intervention program was two weeks. The primary outcome was the mean change in SJL two weeks later, assessed using the Munich ChronoType Questionnaire (MCTQ). The other outcomes included Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale (ESS), Insomnia Severity Index, Patient Health Questionnaire-9 (PHQ-9), and sleep quiz. A follow-up survey was conducted 6 months after the intervention.

Results

Of 54 students, 26 were assigned to an intervention group and 28 to a control group. The difference in the mean change in SJL between the two groups (n = 26, n = 27) at two weeks was statistically significant (27.7 min, P = 0.048). The scores for the ESS, PHQ-9, and sleep quiz were improved in the intervention group relative to the control group. At the 6-month follow-up point, the difference in the mean change in SJL between the two groups (n = 22, n = 27) was not statistically significant, but scores for the PHQ-9, and sleep quiz remained significant.

Conclusions

This study demonstrated the efficacy of the SET-R among university students with increased SJL.

Trial Registration

The study was registered with the UMIN Clinical Trials Registry (UMIN000042634, 2021/02/01).

Sleep quality and sleep deprivation: relationship with academic performance in university students during examination period

The beginning of the university brings together maturational, psychosocial and academic changes that make university students more prone to suffer from insufficient or poor quality sleep, which can negatively influence their academic performance. The period of taking exams is a key part of the academic year. However, there are few studies that analyze sleep during this period of time. Our aim is to study the association of sleep quality and sleep deprivation with academic performance during the examination period. A descriptive, cross-sectional and correlational study was carried out with the participation of 640 subjects in the first three years of five faculties belonging to the Universidad Autónoma de Madrid. The instrument used consisted of a questionnaire that included sociodemographic and academic data, Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale and information about the academic performance. During the examination period, a positive association was found between sleep quality and academic performance. University students slept less than desired, both on weekdays and weekends, and the sleep debt during the week was associated with a worse students' perception of their academic performance. In total, 61.3% of the students believed that their performance would improve by getting more sleep. In addition, low drowsiness and napping were also found. In conclusion, during periods of greater academic demand, an insufficient sleep and poor quality is commonly observed, affecting negatively to their academic performance. Actually, about 2/3 of our subjects believed that their performance would improve by getting more sleep.

Sleep Quality and Social Jetlag in Young Adults During the Social Distancing Caused by COVID-19

Introduction:  This study aimed to evaluate the sleep quality and the Social Jetlag frequency in young adults during social distancing because of COVID-19. Methods:  This is a cross-sectional study with 308 students aged ≥18 years and with Internet access. Questionnaires used: Pittsburgh Sleep Quality Index - Brazil (PSQI-BR), Epworth Sleepiness Scale, and Munich Chronotype Questionnaire. Results:  The mean age of the students was 21 ± 3 years (17 - 42y), with no statistically significant difference between genders. The PSQI-BR indicated that 257 (83.4%) had poor sleep quality. The mean of Social Jetlag for young adults was 02:00 ± 01:49h, and we observed that 16.6% (n = 51) had Social Jetlag. Compared to men in the good sleep quality group, women had higher means for sleep duration on study days and free days, mid-point of sleep on study days and free days and corrected mid-point of sleep on free days. However, when compared to men in the group of poor sleep quality, we observed higher means for women regarding sleep duration on study days, the mid-point of sleep on study days, and the corrected mid-point of sleep on free days. Conclusions:  Thus, the high frequency of young adult students who had poor sleep quality associated with Social Jetlag (2 hours) in the present study may reflect a pattern of sleep irregularity, which may be associated with impairment of environmental synchronizers and stimulation of social synchronizers during the lockdown resulting from the COVID-19 pandemic.

Effects of Additional Granola in Children's Breakfast on Nutritional Balance, Sleep and Defecation: An Open-Label Randomized Cross-Over Trial

The contribution of breakfast to daily nutrient intake is low, particularly among children, at only about 20%, and it is difficult to determine whether children are receiving adequate nutrients at breakfast. Although alterations in breakfast content are considered to affect lifestyle habits such as sleep and defecation, there have been few intervention studies in children. The relationship between nutritional balance, dietary intake, and lifestyle habits in children remains unclear. We conducted an intervention study on elementary school children's breakfasts and observed the effects of improving the nutritional balance of breakfast on sleep parameters and defecation status. An intervention study was conducted with 26 elementary school students in Tokyo. The study design was an open-label randomized cross-over trial. Subjects consumed their usual breakfast during the control period and a granola snack containing soy protein in addition to their usual breakfast during the intervention period. Questionnaires regarding breakfast, sleep, and bowel movements were administered during each period. Based on the answers to these questionnaires, we compared the nutritional sufficiency of macronutrients, vitamins, and minerals (29 in total), as well as changes in sleep parameters and defecation status. The additional consumption of granola snacks increased the breakfast intake of 15 nutrients. The changes were particularly significant for iron, vitamin B1, vitamin D, and dietary fiber. During the intervention, sleep duration was decreased and wake-up time became earlier. In terms of defecation, the intervention did not change stool characteristics, but the frequency of defecations per week increased on average by 1.2 per week. These results suggest that the nutritional balance and the amount of breakfast are linked to sleep and defecation and that improving breakfast content can lead to lifestyle improvements in children.

School Attendance, Chronotype, and Day-of-the-Week Effect in Adolescent Male Basketball Players

Adolescents' conflict between circadian rhythm and early school start time is more pronounced in evening chronotypes, who tend to reduce sleep duration during school days compensating during the free days by oversleeping (i.e., social jetlag). Cumulative weekly sleep debt may impair sport performance, which relies on physical and cognitive skills modulated by sleep. We hypothesized that chronotype predicts sport performance, and that it may interact with the day of the week. Moreover, given the role sleep plays in motor memory consolidation, we tested the hypothesis that school attendance, and the related chronic sleep deprivation, might be detrimental for participants in a training phase. Ninety-three adolescent male basketball players performed multiple free throw sessions (n = 7880) during both the school and holiday periods. Chronotype and its interaction with the day of the week significantly predicted shooting accuracy when attending school, but not on holidays. Evening types' performance gradually decreased from Monday to Friday. Participants with a more unstable performance (i.e., who did not complete the acquisition of the free throw motor scheme) worsened their accuracy when attending school. Our results suggest that the impact of chronotype and day of the week on sport performance is related to the presence of an externally imposed sleep/wake schedule and is consistent with evening types' increased likelihood of experiencing social jetlag. Possibly due to early school start time, attending school worsened the performance of participants in a training phase. Further investigations are required to assess whether reducing the mismatch between biological and social clocks might improve sport performance, along with other aspects of adolescents' life.

Beyond sleep: A multidimensional model of chronotype

Chronotype can be defined as an expression or proxy for circadian rhythms of varied mechanisms, for example in body temperature, cortisol secretion, cognitive functions, eating and sleeping patterns. It is influenced by a range of internal (e.g., genetics) and external factors (e.g., light exposure), and has implications for health and well-being. Here, we present a critical review and synthesis of existing models of chronotype. Our observations reveal that most existing models and, as a consequence, associated measures of chronotype have focused solely or primarily on the sleep dimension, and typically have not incorporated social and environmental influences on chronotype. We propose a multidimensional model of chronotype, integrating individual (biological and psychological), environmental and social factors that appear to interact to determine an individual's true chronotype with potential feedback loops between these factors. This model could be beneficial not only from a basic science perspective but also in the context of understanding health and clinical implications of certain chronotypes as well as designing preventive and therapeutic approaches for related illnesses.

The Association between Sleep Patterns, Educational Identity, and School Performance in Adolescents

Adolescents' school experience can be developmentally related to adolescents' sleep. This study aimed to understand how sleep patterns (i.e., sleep duration and sleep-schedule) and weekend sleep-recovery strategies (i.e., social jetlag and weekend catch-up sleep) are associated with adolescents' school experience (i.e., educational identity and school performance). Moreover, the differences in the school experiences between adolescents with different numbers of weekend-sleep-recovery strategies were assessed. For this purpose, 542 Italian adolescents (55.2% females, mean age 15.6 years) wore an actigraph for one week. After the actigraphic assessment, questionnaires on educational identity and school performance were administered. Results showed that short sleep-duration, later bedtime during weekdays and weekends, and a higher amount of social jetlag were negatively associated with school performance. Furthermore, adolescents who did not use any sleep-recovery strategy during the weekend presented lower levels of educational in-depth exploration compared to adolescents with higher levels of catch-up sleep but not social jetlag. These data pointed out a potentially detrimental role of social jetlag on school performance and differences in identity processes between adolescents who used and those who did not use sleep-recovery strategies, which could affect adolescents' psychosocial adjustment.

Food addiction and emotional eating are associated with intradaily rest-activity rhythm variability

PURPOSE

The aim of the present investigation was to study the associations among parameters characterizing eating behavior and actimetry-derived indices of circadian rhythm of motor activity.

METHODS

The study involved 81 healthy participants (average age: 21.5 ± 9.6 y, women: 77.8%). Each study participant provided personal data, filled out the Yale Food Addiction Scale and the Dutch Eating Behavior Questionnaire, and wore a wrist actimeter for 7 consecutive days to record motor activity. Using time series treatments, we obtained: (a) three cosinor-derived parametric indices [Medline Estimating Statistics of Rhythm (MESOR), amplitude, and acrophase], and (b) four non-parametric indices [interdaily stability, intradaily variability (I.V.), most active 10-h period (M10), and least active 5-h period] characterizing the 24-h rhythm of motor activity. A multiple regression analysis adjusted for age, sex, and BMI was performed to assess the associations among the studied indicators.

RESULTS

It was shown that I.V. is a predictor of symptoms of food addiction (β = 0.242, P = 0.037) and emotional eating (β = 0.390, P = 0.004), MESOR is a predictor of symptoms of food addiction (β = 0.342, P = 0.003), and M10 predicts restraint (β = 0.257, P = 0.015) and emotional eating (β = 0.464, P = 0.001).

CONCLUSION

It was shown for the first time that an increase in symptom counts of food addiction is associated with an increase in the average level and fragmentation of 24-h rhythm of motor activity.

LEVEL OF EVIDENCE

Level V, cross-sectional descriptive study.

Different levels of circadian (de)synchrony -- where does it hurt?

A network of cellular timers ensures the maintenance of homeostasis by temporal modulation of physiological processes across the day. These so-called circadian clocks are synchronized to geophysical time by external time cues (or zeitgebers). In modern societies, natural environmental cycles are disrupted by artificial lighting, around-the-clock availability of food or shift work. Such contradictory zeitgeber input promotes chronodisruption, i.e., the perturbation of internal circadian rhythms, resulting in adverse health outcomes. While this phenomenon is well described, it is still poorly understood at which level of organization perturbed rhythms impact on health and wellbeing. In this review, we discuss different levels of chronodisruption and what is known about their health effects. We summarize the results of disrupted phase coherence between external and internal time vs. misalignment of tissue clocks amongst each other, i.e., internal desynchrony. Last, phase incoherence can also occur at the tissue level itself. Here, alterations in phase coordination can emerge between cellular clocks of the same tissue or between different clock genes within the single cell. A better understanding of the mechanisms of circadian misalignment and its effects on physiology will help to find effective tools to prevent or treat disorders arising from modern-day chronodisruptive environments.

Later school start time is associated with better academic performance, sleep-wake rhythm characteristics, and eating behavior

There are numerous studies which show that an early school start time has a negative impact on the sleep, well-being, and academic performance of students. There is not enough information on the association between school start time and eating disorders, however: the disruption of the circadian rhythm is known to be a risk factor for eating disorders. The aim of this study is to analyze the relationship between school start time (SST) and the sleep, well-being, academic performance, and eating behavior of children and adolescents. The study was conducted in April and May 2021 in two regions of Russia: the Komi Republic and Yekaterinburg. The online study involved the anonymous and voluntary participation of 6571 students in grades 6-11 (mean age: 14.5 ± 1.6 years, 60.1% female), who have morning classes. All participants were divided into three groups according to SST: 08:00 (n = 3661), 08:30 (n = 2020), and 09:00 (n = 890). Each participant of the study indicated their place of residence, SST, age, sex, height, weight, academic performance, and filled out the Munich Chronotype Questionnaire, the Zung Self-Rating Depression Scale, and the Yale Food Addiction Scale for Children. As a result of multiple regression analysis, it was shown that schoolchildren with SST of 09:00 wake up at a later time on school days (B = 0.432; ΔR² = 0.039), sleep more (B = 0.293; ΔR² = 0.004), have less pronounced social jetlag (B = -0.223; ΔR² = 0.005) and sleep loss (B = -0.292; ΔR² = 0.005), and higher academic performance (B = 0.113; ΔR² = 0.003) than schoolchildren with SST of 08:00. As a result of logistic regression analysis, it was found that the frequency of the detection of food addiction is ~30% lower in schoolchildren with SST of 09:00 (OR = 0.690; 95% CI = 0.485-0.981) than in their peers with SST of 08:00. Thus, an overly early SST in Russia has a negative impact on the sleep function, academic performance, and eating behavior of children and adolescents.

Living at the Wrong Time: Effects of Unmatching Official Time in Portugal and Western Spain

Human circadian rhythmicity is subjected to the internal circadian clock, the sun and social clocks (official time, social/work schedules). The discrepancy among these clocks, as occurs when official time does not match its geographical time zone, may produce circadian disruption. Western Spain (GMT+1/+2) and Portugal (GMT0/+1) share similar longitudes (sun time) but have different official times. This provides a unique opportunity to evaluate the effects of official time on circadian rhythmicity and sleep in elderly and retired populations (with no remunerated duties presumed, although other social commitments may be present) at both locations. Although both populations slept enough for their age (7-8 h), circadian robustness (e.g., interdaily stability, relative amplitude) was greater in Portugal, especially during weekdays, while greater desynchronization (both body temperature vs. motor activity and body temperature vs. light exposure) tended to occur in the Spaniards. Once corrected by GMT0, meals took place later in Spain than in Portugal, especially as the day progresses, and a possible interplay between bed/meal timings and internal desynchronization was found. Our results point to the possible deleterious effect on circadian system robustness when official time is misaligned with its geographical time zone.

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

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

Le sommeil des étudiants français en période de COVID-19 : influence des deux premiers confinements sur la quantité et la qualité de sommeil

La pandémie de la COVID-19 a entraîné deux périodes de confinement pendant l’année 2020 qui ont amené à des modifications des habitudes de vie. L’objectif de notre étude est d’évaluer l’impact des confinements sur la quantité (i.e., horaires et temps passé au lit) et la qualité (i.e., difficultés et parasomnies) du sommeil chez des étudiants français. Au cours du premier et du second confinement, les étudiants ont été invités à répondre à un questionnaire en ligne composé de 23 questions. Ce questionnaire s’intéressait aux horaires réels et idéaux de lever et de coucher, au temps passé au lit, ainsi qu’aux parasomnies et difficultés liées au sommeil. Les résultats obtenus ont montré que les étudiants dormaient plus tardivement et passaient plus de temps au lit le week-end qu’en semaine, ces effets étant plus marqués pendant le premier confinement que pendant le second. La majorité des étudiants a rapporté avoir un sommeil de mauvaise qualité, des difficultés d’endormissement, des réveils précoces, ainsi qu’une sensation de manque de sommeil. Les parasomnies les plus fréquentes se sont caractérisées par des épisodes de cauchemars et de somniloquie. Les difficultés liées au sommeil et les parasomnies rapportées étaient plus importantes pendant le second confinement qu’au cours du premier. La dette de sommeil était toujours présente au cours des confinements. Les difficultés de sommeil et les parasomnies rapportées ont témoigné d’un sommeil de mauvaise qualité chez les étudiants durant ces périodes. Des hypothèses explicatives ainsi que des perspectives de prévention quant à l’hygiène du sommeil sont discutées.

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

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

Chronotype Profile, Stress, Depression Level, and Temporomandibular Symptoms in Students with Type D Personality

Background: Despite a growing interest in the types of human circadian activity, different chronotypes and personality-related issues have been rarely studied. It has already been emphasized that ‘stress personality’ is considered a risk factor for certain psychosomatic diseases and may be a temporomandibular disorders (TMDs) predictor. Therefore, an attempt has been made to analyze the chronotypes, stress levels, stress factors, and the occurrence of depression and TMDs in students with type D personalities. People with this personality trait tend to experience negative emotions more—depression, anxiety, anger, or hostility—yet may have a negative image of themselves and report somatic complaints. Aim: The aim of this study was to analyze the importance of the chronotype profile for the level of stress perceived, as well as for the occurrence of depression and TMDs in people with type D personalities. Material and Methods: The study has been conducted on a group of 220 physical therapy students. The study group G1 consisted of 110 participants with type D personalities, the control group G2 consisted of the same number of participants without the stress personality. All participants have been analyzed for the chronotype (MEQ), stress perception (PSS10), the occurrence of depression (Beck scale-BDI), the occurrence of TMDs symptoms and have completed the stress factor assessment questionnaire during the study, followed by DS14 questionnaire—a tool for assessing the prevalence of type D personality. Results: In students with type D personalities (G1), the definitely evening and evening chronotypes have been significantly more predominant than in the control group (G2). A significantly higher number of stressors and TMDs symptoms have been observed in the respondents from the G1 group than in the control group (<0.001). Univariate logistic regression analysis showed that type D personality was strongly associated with a more frequent occurrence of all TMD symptoms. Additionally, a significant influence of the evening chronotype on the occurrence of type D personality was observed. Among the potential confounding variables, female gender and a mild and moderate degree of depression have an impact on the occurrence of type D personality (p < 0.05). In the multivariate model, adjusted with the above-mentioned factors, an increased risk of the type D personality trait was found. Conclusion: The evening chronotype and type D personality may imply greater feelings of stress, greater depression, and more frequent symptoms of TMDs in young adults.

Nighttime Sleep Awakening Frequency and Its Consistency Predict Future Academic Performance in College Students

Although the relationship between sleep and academic performance has been extensively examined, how sleep predicts future academic performance (e.g., 2-3 years) remains to be further investigated. Using wearable smartwatches and a self-report questionnaire, we tracked sleep activities of 45 college students over a period of approximately half a month to see whether their sleep activities predicted their academic performance, which was estimated by grade point average (GPA). Results showed that both nighttime sleep awakening frequency and its consistency in the tracking period were not significantly correlated with the GPA for the courses taken in the sleep tracking semester (current GPA). However, both nighttime sleep awakening frequency and its consistency inversely predicted the GPA for the rest of the courses taken after that semester (future GPA). Moreover, students with more difficulty staying awake throughout the day obtained lower current and future GPAs, and students with higher inconsistency of sleep quality obtained lower future GPA. Together, these findings highlight the importance of nighttime sleep awakening frequency and consistency in predicting future academic performance, and emphasize the necessity of assessing the consistency of sleep measures in future studies.

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

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

Interactions between nocturnal melatonin secretion, metabolism, and sleeping behavior in adolescents with obesity

Background/objectives

Sleeping behavior and individual prospensity in sleep timing during a 24 h period, known as chronotypes, are underestimated factors, which may favor the development of obesity and metabolic diseases. Furthermore, melatonin is known to play an important role in circadian rhythm, but was also suggested to directly influence metabolism and bodyweight regulation. Since disturbed and shifted sleep rhythms have been observed in adolescents with obesity, this study aimed to investigate potential interactions between melatonin secretion, chronobiology, and metabolism. In addition, the influence of artificial light especially emitted by electronic devices on these parameters was of further interest.

Subjects/methods

We performed a cross-sectional study including 149 adolescents (mean age 14.7 ± 2.1 years) with obesity. Metabolic blood parameters (e.g., cholesterol, triglycerides, uric acid, and insulin) were obtained from patients and correlated with nocturnal melatonin secretion. Melatonin secretion was determined by measuring 6-sulfatoxymelatonin (MT6s), the major metabolite of melatonin in the first-morning urine, and normalized to urinary creatinine levels to account for the urinary concentration. Chronobiologic parameters were further assessed using the Munich ChronoType Questionnaire.

Results

Subjects with insulin resistance (n = 101) showed significantly lower nocturnal melatonin levels compared to those with unimpaired insulin secretion (p = 0.006). Furthermore, triglyceride (p = 0.012) and elevated uric acid levels (p = 0.029) showed significant associations with melatonin secretion. Patients with late chronotype showed a higher incidence of insulin resistance (p = 0.018). Moreover, late chronotype and social jetlag were associated with the time and duration of media consumption.

Conclusion

We identified an association of impaired energy metabolism and lower nocturnal melatonin secretion in addition to late chronotype and increased social jetlag (misalignment of biological and social clocks) in adolescents with obesity. This might point towards a crucial role of chronotype and melatonin secretion as risk factors for the development of pediatric and adolescent obesity.

Social Jetlag and Related Risks for Human Health: A Timely Review

The term social jetlag is used to describe the discrepancy between biological time, determined by our internal body clock, and social times, mainly dictated by social obligations such as school or work. In industrialized countries, two-thirds of the studying/working population experiences social jetlag, often for several years. Described for the first time in 2006, a considerable effort has been put into understanding the effects of social jetlag on human physiopathology, yet our understanding of this phenomenon is still very limited. Due to its high prevalence, social jetlag is becoming a primary concern for public health. This review summarizes current knowledge regarding social jetlag, social jetlag associated behavior (e.g., unhealthy eating patterns) and related risks for human health.

Internet use and its impact on internalizing disorder symptoms and sleep in adolescents with an evening circadian preference

STUDY OBJECTIVES

This study sought to examine the relationship between internet use, sleep, and internalizing disorder symptoms in adolescents with an evening circadian preference.

METHODS

One hundred seventy-two adolescents aged 10-18 years with an evening circadian preference completed a week of sleep diaries and questionnaires about internet use and internalizing disorder symptoms.

RESULTS

Adolescents reported internet use for 3.81 hours on weekdays and 5.44 hours on weekends, with > 90% having access to both a computer with internet and a personal cell phone. A majority of adolescents used the internet from 4-8 pm (71%) and from 9-11 pm (62%). Common online activities included listening to music (77%), watching videos (64%), communicating with others (64%), and doing homework (58%). Late-night internet use (9-11 pm) was associated with more internalizing disorder symptoms. Middle-of-the-night internet use (midnight-5 am) was associated with a later bedtime, shorter total sleep time, and more internalizing disorder symptoms. Adolescents used the internet to fulfill social needs, to avoid or combat boredom, or for maladaptive activities. Using the internet for social interaction or avoidance/boredom was associated with higher internalizing disorder symptoms. Using the internet for maladaptive reasons was associated with more late-night and middle-of-the-night use.

CONCLUSIONS

Adolescent internet use late at night and in the middle of the night is common. Internet use may be motivated by desires for social connection, by boredom/avoidance, or for maladaptive behaviors. Because middle-of-the-night internet use was associated with higher internalizing disorder symptoms and worse sleep, it presents as a potential target for intervention.

CITATION

Asarnow LD, Gasperetti CE, Gumport NB, Harvey AG. Internet use and its impact on internalizing disorder symptoms and sleep in adolescents with an evening circadian preference. J Clin Sleep Med. 2021;17(10):2019-2027.

Daylight Saving Time: Pros and Cons

The original rationale for the adoption of daylight saving time (DST) was to conserve energy; however, the effects of DST on energy consumption are questionable or negligible. Conversely, there is substantial evidence that DST transitions have the cumulative effect on sleep deprivation with its adverse health effects. In light of current evidence, the European Commission in 2018 decided that biannual clock change in Europe would be abolished. Current indirect evidence supports the adoption of perennial standard time, which aligns best with the human circadian system and has the potential to produce benefits for public health and safety.

Sleep timing and consistency are associated with the standardised test performance of Icelandic adolescents

Sleep has been shown to affect cognitive function in laboratory studies; however, its association to the academic performance of adolescents has largely been demonstrated using self-reported measures. Studies with objective measures of both sleep and academic performance are limited. The aim of the present study was to determine whether the free-living sleep quantity, quality, and timing of 15-year-old adolescents measured with wrist actiography are associated with their scores on national standardised examinations as an objective measure of academic achievement. We measured sleep with wrist actiography for 1 week in 253 (150 girls) Icelandic adolescents with a mean (SD) age of 15.9 (0.3) years. Multiple linear regression was used to assess associations between sleep parameters and combined standardised examination scores in mathematics, English, and Icelandic obtained from the Icelandic Directorate of Education. We found that students went to bed at 00:49 hours (± 51.8 min) and slept for a mean (SD) of 6.6 (0.7) hr/night, with a median (interquartile range) night-to-night variation in sleep duration of 1.2 (0.7) hr and an efficiency of 88.1 (5.3)%. Combined analyses adjusted for sex, demonstrated that both bedtime and night-to-night variability in total sleep time were negatively associated with the average score across all topics. Sex-specific associations did not indicate clear differences between boys and girls. These findings suggest that, in addition to appropriate sleep duration, public health guidance should also highlight the importance of early and consistent sleep schedules to academic achievement for both boys and girls.

Insomnia symptoms mediate the association between eveningness and suicidal ideation, defeat, entrapment, and psychological distress in students

Chronotype describes a person's general preference for mornings, evenings, or neither. It is typically conceptualized as a continuous unidimensional spectrum from morningness to eveningness. Eveningness is associated with poorer outcomes across a myriad of physical and mental health outcomes. This preference for later sleep and wake times is associated with increased risk of depression, anxiety, and suicidal ideation in both clinical and community samples. However, the mechanisms underlying the negative consequences of this preference for evenings are not fully understood. Previous research has found that sleep disturbances may act as a mediator of this relationship. The present study aimed to explore the associations between chronotype and affective outcomes in a sample of students. Additionally, it aimed to investigate the potential role of insomnia as a mediator within these relationships. Participants (n = 190) completed an anonymous self-report survey of validated measures online which assessed chronotype, insomnia symptoms, and a range of affective outcomes (defeat, entrapment, suicide risk, stress, and depressive and anxious symptomology). Eveningness was associated with more severe or frequent experiences of these outcomes, with participants that demonstrated a preference for eveningness more likely to report poorer affective functioning and increased psychological distress. Mediation analysis found the relationship between chronotype and these outcome measures was completely or partially mediated by insomnia symptom severity measured by the validated Sleep Condition Indicator insomnia scale. Taken together, these findings add further evidence for the negative consequences of increased eveningness. Additionally, our results show that chronotype and sleep disturbances should be considered when assessing mental well-being. Implementing appropriate sleep-related behavior change or schedule alterations can offer a tool for mitigation or prevention of psychological distress in students that report a preference for later sleep and wake times.

Is the use of high correlated color temperature light at night related to delay of sleep timing in university students? A cross-country study in Japan and China

Background

Blue-enriched white light at night has the potential to delay the circadian rhythm in daily life. This study was conducted to determine whether the use of high correlated color temperature (CCT) light at home at night is associated with delay of sleep timing in university students.

Methods

The survey was conducted in 2014–2015 in 447 university students in Japan and 327 students in China. Habitual sleep timing and type of CCT light at home were investigated by using a self-administered questionnaire. The Japanese students were significantly later than the Chinese students in bedtime, wake time, and midpoint of sleep. They were asked whether the lighting in the room where they spend most of their time at night was closer to warm color (low CCT) or daylight color (high CCT). The amount of light exposure level during daily life was measured for at least 1 week by the use of a light sensor in 60 students in each country.

Results

The percentages of participants who used high CCT lighting at night were 61.6% for Japanese students and 80.8% for Chinese students. Bedtime and sleep onset time on school days and free days were significantly later in the high CCT group than in the low CCT group in Japan. The midpoint of sleep in the high CCT group was significantly later than that in the low CCT group on free days but not on school days. On the other hand, none of the sleep measurements on school days and free days were significantly different between the high CCT and low CCT groups in China. Illuminance level of light exposure during the night was significantly higher in Japanese than in Chinese, but that in the morning was significantly higher in China than in Japan.

Conclusions

The use of high CCT light at night is associated with delay of sleep timing in Japanese university students but not in Chinese university students. The effects of light at night on sleep timing and circadian rhythm may be complicated by other lifestyle factors depending on the country.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40101-021-00257-x.

[Association between social jetlag and presenteeism in Japanese industry: A cross-sectional study]

OBJECTIVES

Research suggests that misalignment of the biological clock and social time, referred to as social jetlag (SJL),can induce physical and mental disorders. SJL may also be associated with presenteeism (i.e., a state in which workers are unable to perform sufficiently due to mental and physical health problems, even though they are going to work). However, the association between SJL and presenteeism among workers in Japan remains unclear. This study aimed to verify the following hypotheses in a sample of workers in an industrial setting in Japan: "Workers exhibiting SJL have a high degree of work functioning impairment due to presenteeism" and "An association between SJL and presenteeism exists, even when taking work style and sleep-related factor into consideration."

METHODS

A self-administered questionnaire survey was conducted with 1,573 workers in the manufacturing industry. Of these, 1,501 participants responded (response rate: 95.4%). Individuals who provided invalid answers or used alarm clocks to wake on work-free days were excluded, according to the Munich Chronotype Questionnaire (MCTQ) guidelines. The final sample comprised 980 participants (80.7% male; average age: 44.4 [SD 11.3] years). SJL was assessed using the MCTQ. Presenteeism was measured using the work functioning impairment scale. Using presenteeism as the dependent variable, we conducted hierarchical multiple regression analyses to compare the explanatory power of the different models. Independent variables were SJL, daily rest period between workdays, weekday sleep duration, and subjective insomnia. Models 2 and 3 were adjusted for age, sex, employment position, occupation, employment status, and working regulations.

RESULTS

Multiple regression analyses indicated that SJL was significantly and individually associated with presenteeism (β = .066, p = .038). After adjusting for work- and sleep-related variables (Models 2 and 3), SJL no longer contributed significantly to presenteeism. In the final model, daily rest periods (β = .076, p = .017) and subjective insomnia (β = .470, p < .001) remained significantly associated with presenteeism (adjusted R² = .239).

CONCLUSIONS

The hypothesis "Workers experiencing SJL have a high degree of work functioning impairment due to presenteeism" was supported in our univariate analysis. However, after considering the influence of subjective insomnia and daily rest periods, the association disappeared. Therefore, a direct relationship between SJL and presenteeism is not supported. Thus, the risk of presenteeism should be considered in two stages, first confirming the perception of insomnia among workers who experience SJL, and then considering the possibility of presenteeism occurring.

Biological Rhythm and Chronotype: New Perspectives in Health

The circadian rhythm plays a fundamental role in regulating biological functions, including sleep–wake preference, body temperature, hormonal secretion, food intake, and cognitive and physical performance. Alterations in circadian rhythm can lead to chronic disease and impaired sleep. The circadian rhythmicity in human beings is represented by a complex phenotype. Indeed, over a 24-h period, a person’s preferred time to be more active or to sleep can be expressed in the concept of morningness–eveningness. Three chronotypes are distinguished: Morning, Neither, and Evening-types. Interindividual differences in chronotypes need to be considered to reduce the negative effects of circadian disruptions on health. In the present review, we examine the bi-directional influences of the rest–activity circadian rhythm and sleep–wake cycle in chronic pathologies and disorders. We analyze the concept and the main characteristics of the three chronotypes.

Behavioural biometrics: Using smartphone keyboard activity as a proxy for rest-activity patterns

Rest–activity patterns are important aspects of healthy sleep and may be disturbed in conditions like circadian rhythm disorders, insomnia, insufficient sleep syndrome, and neurological disorders. Long‐term monitoring of rest–activity patterns is typically performed with diaries or actigraphy. Here, we propose an unobtrusive method to obtain rest–activity patterns using smartphone keyboard activity. The present study investigated whether this proposed method reliably estimates rest and activity timing compared to daily self‐reports within healthy participants. First‐year students (n = 51) used a custom smartphone keyboard to passively and objectively measure smartphone use behaviours and completed the Consensus Sleep Diary for 1 week. The time of the last keyboard activity before a nightly absence of keystrokes, and the time of the first keyboard activity following this period were used as markers. Results revealed high correlations between these markers and user‐reported onset and offset of resting period (r ranged from 0.74 to 0.80). Linear mixed models could estimate onset and offset of resting periods with reasonable accuracy (R² ranged from 0.60 to 0.66). This indicates that smartphone keyboard activity can be used to estimate rest–activity patterns. In addition, effects of chronotype and type of day were investigated. Implementing this method in longitudinal studies would allow for long‐term monitoring of (disturbances to) rest–activity patterns, without user burden or additional costly devices. It could be particularly interesting to replicate these findings in studies amongst clinical populations with sleep‐related problems, or in populations for whom disturbances in rest–activity patterns are secondary complaints, such as neurological disorders.

Effects of sleep disturbance on functional and physiological outcomes in collegiate athletes: A scoping review

OBJECTIVE

To investigate sleep disturbances and circadian timing changes on functional and physiological correlates specifically in collegiate athletes.

DESIGN

Scoping Review.

DATA SOURCES

PubMed MEDLINE, SPORT-Discus, CINAHL, ERIC ProQuest, Web of Science.

ELIGIBILITY CRITERIA

Articles in English, studying college athletes 18-24 years old, employing a sleep measurement, and a comparison measure of cognitive, academic performance, athletic performance, injury rate, biomarkers and physiological measures, or imaging.

RESULTS

Thirty articles met inclusion criteria. There was wide range of study design, sport studied, modality used to measure sleep, frequency of sleep measurements, and functional and physiological outcomes across studies. Sleep measurements varied greatly in frequency of data collection and type of measurement tool, with the majority using a sleep questionnaire. While all variables of interest were represented within the review, most had a focus on cognitive performance, athletic performance, or injury rate as a function of sleep. Studies using biomarkers and physiological measures or imaging were largely underrepresented. Few studies used biomarkers and physiological measures, and one study used imaging measures. Most studies in this review reported negative cognitive and academic outcomes with worse sleep quality and quantity.

CONCLUSIONS

Sleep is critical to maintaining optimal health and collegiate athletes represent a unique population given their unique time constraints, stresses, and sleep behaviors. Findings on athletic performance and injury rate as a function of sleep were mixed. Employing standardized objective methodologies in future work will allow for better understanding of the influence of sleep on the overall well-being and performance of college athletes.

The Effects of Sleep Quality and Resilience on Perceived Stress, Dietary Behaviors, and Alcohol Misuse: A Mediation-Moderation Analysis of Higher Education Students from Asia, Europe, and North America during the COVID-19 Pandemic

BACKGROUND

The coronavirus disease 2019 (COVID-19) pandemic has increased the already high levels of stress that higher education students experience. Stress influences health behaviors, including those related to dietary behaviors, alcohol, and sleep; yet the effects of stress can be mitigated by resilience. To date, past research studying the connections between dietary behaviors, alcohol misuse, sleep, and resilience commonly investigated singular relationships between two of the constructs. The aim of the current study was to explore the relationships between these constructs in a more holistic manner using mediation and moderation analyses.

METHODS

Higher education students from China, Ireland, Malaysia, South Korea, Taiwan, the Netherlands, and the United States were enrolled in a cross-sectional study from April to May 2020, which was during the beginning of the COVID-19 pandemic for most participants. An online survey, using validated tools, was distributed to assess perceived stress, dietary behaviors, alcohol misuse, sleep quality and duration, and resilience.

RESULTS

2254 students completed the study. Results indicated that sleep quality mediated the relationship between perceived stress and dietary behaviors as well as the relationship between perceived stress and alcohol misuse. Further, increased resilience reduced the strength of the relationship between perceived stress and dietary behaviors but not alcohol misuse.

CONCLUSION

Based on these results, higher education students are likely to benefit from sleep education and resilience training, especially during stressful events.

The mediating effect of conscientiousness on the academic consequences of social jetlag

Social jetlag (SJL) causes impairment of academic achievement; on the other hand, the personality factor of conscientiousness is related to better grades. We evaluated the impact of conscientiousness on the academic consequences of social jetlag. Undergraduate students (n = 556) were evaluated throughout their first 3 years of university education. Conscientiousness, as a mediating factor in the structural equation modeling, explained 20% of the effect of SJL on academic achievement. This is the first cohort study to evaluate the mediating effect of personality on the consequences of SJL.

Comparative analysis of sleep patterns and attention components in high school and college adolescents

Adolescence is a phase with physiological and behavioral changes. One of them occurs in the sleep-wake cycle pattern, manifested by a phase delay. However, morning school start time can decrease sleep duration during weekdays, impairing adolescent cognitive performance and well-being. Adolescents of different ages and educational level might suffer the impact of academic demand on sleep-wake cycle and cognition differently. Thus, the aim of this study is to compare the sleep habits and quality, sleepiness upon awakening and attention components among adolescents in the first years of high school and college. 71 adolescents participated in the study (45 girls and 26 boys), 44 enrolled in high school morning classes (G1 - 15.5±0.7 years), from a private school, and 27 college students enrolled in morning classes (G2 - 18.8±1.04 years), from biosciences courses from a public institution. The groups did not differ in bedtime, get up time, time in bed and sleep irregularity. However, both groups showed differences according to the day of the week, bedtime and get up time became later and time in bed extended on weekends. G1 presented worse sleep quality and regarding attention, showed higher percentage of omissions in all components and worse performance in sustained attention (ANOVA, p<0.05). The poorer sleep quality of high school adolescents and reduced attention may have a negative effect on school performance. Additional studies are needed to investigate the causes of these differences between these two educational levels.

On the influence of the day of the week on objective and self-rated sleep quality of adults

Background and objective

The extent to which adult sleep varies depending on the day of the week has not yet been systematically investigated with electroencephalography (EEG) data. Whether such effects exist and whether they are related to age, gender, and employment status was retrospectively analyzed based on data from an experimental double-blind cross-over study in which effects of electromagnetic fields of a cell phone base station on the sleep of a general rural population had been examined.

Methods

The sleep of 397 adults (age 45.0 ± 14.2 years, range 18–81 years; 50.9% women) from ten different rural German villages was recorded for 12 nights with ambulatory devices. Self-reported sleep quality was recorded in morning and evening protocols. Friedman tests were used for statistical analysis of the comparison between the days, and the Kruskal–Wallis and Mann–Whitney U tests were used for pairwise comparisons of independent parameters between groups.

Results

For the present analysis, data from 335 participants were considered. Overall, the differences between nights were small and the quality of sleep was good. Three of the five objective and all six self-rated sleep parameters differed significantly between the days of the week. While the objective and the self-estimated total sleep time were longest on Sunday nights, the qualitatively poorest values occurred on Monday nights. People who worked fulltime had the longest sleep latencies on Sunday nights. Friday nights were rated the best.

Conclusion

The objective and self-rated sleep quality varied relatively little in a rural adult population over the course of the week, being worst on Monday nights and best on Friday nights.