Sleep-Wake Timings in Adolescence: Chronotype Development and Associations with Adjustment

No Earlier Than 9:45 A.M. A Qualitative Study of Adolescents' Experiences of Later School Start Times in Aotearoa New Zealand

OBJECTIVES

Many teenagers suffer chronic sleep loss, which could potentially be mitigated by later school start times to accommodate the natural shift in their circadian timekeeping system favoring later bedtimes. This study explored experiences of senior students from a school in Aotearoa New Zealand with later school start times.

METHOD

Semi-structured interviews were conducted with 14 students, purposively sampled for equivalent numbers starting later every day (9:45 A.M.), or on just one weekday (10:00 A.M.). Transcripts were analyzed using reflexive thematic analysis.

RESULTS

Four themes were identified that addressed the impact of later starts on sleep struggles, daily functioning, student autonomy, and routines and scheduling. Most perceived later starts as positively influencing their sleep quality, concentration, productivity, and personal well-being. The importance of autonomy over their learning, and impact of different start times on students' schedules was also emphasized. Major disadvantages were lack of free classes and potentially later finish times.

CONCLUSIONS

The experiences of later school start times for these adolescents were largely positive across a variety of life domains. Findings support the need for sleep health to be considered within school's health education and policy to address the unmet health concerns of chronic sleep loss in teens.

Caffeine, Daytime Sleepiness, and Conduct Problems Among Early Adolescents: A Longitudinal Analysis

PURPOSE

Recent research suggests that caffeine use may promote a range of adjustment difficulties among adolescents, particularly during the middle school years. The effects of caffeine are particularly concerning given the increased use of high-dosage caffeine products, such as energy drinks, among youth. We investigated the influence of caffeine use on trajectories of conduct problems among early adolescents. Daytime sleepiness was tested as mediator of caffeine's effect.

METHODS

Hypotheses were tested with longitudinal (4 waves) data from 2,633 middle school students beginning in the Fall of sixth grade and concluding in the spring of seventh grade. All students in a single class cohort at 20 West Virginia middle schools were invited to participate.

RESULTS

Controlling for family affluence and management practices and pubertal development, use of more than 100 mg of caffeine significantly predicted linear increases in conduct problems over time (Est. = 0.23, p = .015). Increases in daytime sleepiness partially mediated this effect (Est. = 0.22, p = .002).

DISCUSSION

Caffeine use and daytime sleepiness are important vulnerability factors for the emergence of conduct problems.

Temporal Tendencies: Exploring the Impact of Chronotype Timing on Youth Depression Risk

Developmental changes in youth sleep preferences (chronotype) and pubertal development are consequential for youth risk for depression. Previous research has identified individual differences in chronotype in risk for psychopathology. However, little is known regarding how the timing of chronotype may confer risk in youth. This study addressed this gap by examining associations between chronotypal timing and symptoms of depression in youth. Community youth (N = 155; M age =12.7) completed self-report measures of chronotype, pubertal status and depression every six months for a period of one year (three assessment points). Regression analyses showed that chronotypal timing predicted change in depressive symptoms across six months (b = -0.66, p = 0.019), but not across any other timeframe. Findings suggested that youth experiencing more of a morning preference compared to same-aged peers were at increased risk for later depression across six months. Chronotypal timing continued to predict changes in symptoms of depression controlling for gender (b = -0.63, p = 0.023) and pubertal timing (b = -0.72, p = 0.012). These findings suggest that chronotypal timing is prospectively related to changes in youth symptoms of depression. Results indicate that attention to the timing of normative changes in chronotype is warranted, in addition to mean-level differences.

Sex Differences in Circadian Timing and Biological Night in Adolescents

Circadian rhythms, intrinsic 24-h cycles that drive rhythmic changes in behavior and physiology, are important for normal physiology and health. Previous work in adults has identified sex differences in circadian rhythms of melatonin, temperature, and the intrinsic period of the human circadian timing system. However, less is known about sex differences in circadian rhythms at other developmental stages. To address this gap, we considered a secondary analysis of sleep and circadian data from two studies involving adolescent participants during the academic year: (n = 32, 15 females). We collected 1 week of in-home actigraphy data to calculate sleep-wake parameters and in-laboratory salivary melatonin data collection in dim-light conditions was used to compute dim-light melatonin onset (DLMO) and offset (DLMOff) using a threshold of 4 pg/mL. We found that DLMO was an average of 96 min earlier, the time between DLMO and bedtime was an average of 56 min greater, and the biological night (time between DLMO and DLMOff) was 60 min longer in females compared to males, even though bedtimes and waketimes were not statistically different between the groups. In addition, after accounting for differences in bedtime, sex was still a significant predictor of DLMO. Conversely, no evidence was found indicating a difference in DLMOff or the phase angle between DLMOff and waketime by sex. These findings suggest that sex differences in circadian rhythms are present in adolescents and may have implications for circadian health during this important developmental period.

The association of chronotype, sleep duration and trajectories of health-risk behaviors among college students: a cohort study

PURPOSE

To describe the trajectories of health-risk behaviors (HRBs) among college students through four consecutive surveys and explore the relationship between chronotype, sleep duration and different trajectories of HRBs.

METHODS

We used a data sample of 1,042 college students from the College Student Behavior and Health Cohort Study. Students reported sleep parameters, including chronotype (Morningness-Eveningness Questionnaire-5, MEQ-5) and sleep duration. The behavior scale was used to evaluate four HRBs (smoking, alcohol use, low physical activity, smartphone addiction). The latent class growth analysis (LCGA) was used to estimate the trajectory of self-reported HRBs. Multivariate logistic regression models were used to study whether sleep parameters (chronotype and sleep duration) correlated with HRBs' trajectories.

RESULTS

Four unique trajectories of behaviors were identified: unhealthy group (7.4%), increasing group (21.3%), decreasing group (10.3%) and healthy group (61.0%). Compared with the normal sleep, results from logistic regression analyses indicated that long sleep (> 9 h) was associated with the decreasing group and the unhealthy group (P < 0.05), while short sleep (< 7 h) was associated with the increasing group and the unhealthy group (P < 0.05). Compared with the M-type, the E-type were positively correlated with the unhealthy group, the increasing group, and the decreasing group (P < 0.05).

CONCLUSION

E-type, short sleep duration and long sleep duration were significantly associated with the trajectory of HRBs. Findings underscore the need for targeted screening and prevention of modifiable sleep behaviors with the aim of improving HRBs in college students.

Is Social Jetlag Associated With Physical Fitness Among Spanish Adolescents? Insights From the EHDLA Study

BACKGROUND

The misalignment of sleeping times during weekdays/weekends (i.e., social jetlag) is particularly common among adolescents and plausibly associated with their physical fitness. However, literature on this topic is scarce. Therefore, this study aimed to investigate the association between social jetlag and physical fitness in Spanish adolescents.

METHODS

A secondary analysis was conducted on cross-sectional data from the Eating Healthy and Daily Life Activities (EHDLA) study among 812 adolescents (54.9% girls) aged 12-17 years from the Valle de Ricote (Region of Murcia, Spain). Social jetlag was calculated from self-reported data on bedtimes and wake times for weekdays and weekends. Physical fitness was evaluated with the Assessing the Levels of PHysical Activity and Fitness (ALPHA-FIT) for children and adolescents and included cardiorespiratory fitness, muscular fitness, speed agility, and flexibility.

RESULTS

The analysis revealed significant negative associations between worse social jetlag and detrimental overall physical fitness (unstandardized beta coefficient [B] = -0.06, 95% confidence interval [CI]: -0.09, -0.02; p = 0.002), cardiorespiratory fitness (B = -1.28; 95% CI -2.22, -0.34; p = 0.008), and lower body muscular fitness (B = -2.01; 95% CI -3.90, -0.12; p = 0.038) after the adjustment for potential covariates (age, sex, socioeconomic status, physical activity level, sedentary behavior, nocturnal sleep duration, energy intake, and body mass index). In contrast with other fitness components, a significant positive association was identified between social jetlag and speed agility (B = 0.07; 95% CI 0.00, 0.14; p = 0.049).

CONCLUSIONS

In adolescents, social jetlag is significantly linked to poorer physical fitness, especially for cardiorespiratory fitness and lower-body muscular fitness. Maintaining regular and well-synchronized sleep could be crucial for optimizing physical health and preventing the decline of physical fitness during adolescence.

From Alert Child to Sleepy Adolescent: Age Trends in Chronotype, Social Jetlag, and Sleep Problems in Youth with Autism

PURPOSE

Developmental changes in sleep in youth with autism spectrum disorder (ASD) are understudied. In non-ASD youth, adolescents exhibit a "night owl chronotype" (i.e., later sleep/wake timing) and social jetlag (i.e., shifts in sleep timing across school nights and weekends), with corresponding sleep problems. The purpose of this study is to evaluate age trends in chronotype, social jetlag, and sleep problems in high-risk youth with ASD.

METHODS

Youth with ASD (N = 171), ages 5-21 years old, were enrolled at the time of admission to specialized psychiatric units. Caregivers reported children's demographic information, habitual sleep timing, and sleep problems. Multivariate analyses evaluated the effect of age on chronotype, social jetlag, and sleep problems and the effects of chronotype and social jetlag on sleep problems. Covariates and moderators included sex, race, verbal ability, autism symptom severity, supplemental melatonin, and pubertal status.

RESULTS

Older age was associated with later chronotype, more social jetlag, fewer sleep anxiety/co-sleeping problems, fewer night waking and parasomnia problems, and more daytime alertness problems. The effect of age on chronotype was stronger for youth with greater social affective symptom severity. Mediation analyses showed that later chronotype statistically mediated the association between age and daytime alertness problems.

CONCLUSIONS

Youth with ASD may exhibit night owl chronotype behavior and social jetlag as they enter adolescence. Shifts toward a later chronotype may be exacerbated by autism severity and may contribute to alertness problems and sleepiness during the day. Chronotype is modifiable and may be leveraged to improve daytime functioning in youth with ASD.

Using actigraphy to assess chronotype: Simpler is better

Actigraphy provides a unique method for objectively measuring sleep activity patterns, but confusion remains about how to use actigraphy data to determine chronotype. To determine the most suitable parameter, this study made a systematic comparison of actigraphy-derived parameters: the average midpoint of sleep of all record days (aMS-acti), cosine parameter (Bathyphase), and non-parametric parameter (L5-mid) in terms of the consistency with subjective chronotype parameters, test-retest reliability, and external validity. More importantly, we proposed multiple Munich Chronotype Questionnaire (MCTQ)-based actigraphy parameters: considering the difference between weekday (MSW-acti) with weekends (MSF-acti) and the sleep debt (MSFsc-acti). The study collected 5 days of actigraphy and scale data from 1,055 young adults, 138 of whom participated in the retest 2 years later. The results showed that, in terms of consistency with subjective chronotype, aMS-acti generally performed better than other actigraphy parameters. In addition, aMS-acti had the highest test-retest reliability and was more closely related to the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), and Self-Rating Depression Scale (SDS). The results suggest that the simplest parameter (aMS-acti) is superior to traditional cosine and non-parametric parameters and MCTQ-derived parameters for short-term assessment of chronotype.

Sleep Matters in Chronotype and Mental Health Association: Evidence from the UK and Germany

BACKGROUND

There is considerable evidence supporting the elevated risk of mental health problems in individuals with evening chronotype relative to those with morning or intermediate chronotypes. Recent data, however, suggest that this risk may be explained, at least partially, by poor sleep quality.

METHODS

This study aimed to further clarify the roles of chronotype and sleep quality in mental health outcomes (depression, anxiety, stress) in young individuals (18-40 years) living in the UK (n = 185) or Germany (n = 209).

RESULTS

Consistent with our recent observations in a comparable North Indian sample, we found that poor quality of sleep had significantly positive associations with adverse mental health outcomes both in the UK and Germany-based samples. Significant associations between evening chronotype and poor mental health were also evident, but these associations were fully mediated by poor quality of sleep in both samples.

CONCLUSIONS

These observations suggest that efforts to identify sleep disruption in a timely manner and promotion of good sleep may prevent mental health problems, especially in individuals with evening chronotype and other known risks for mental disorders.

Probable sleep and awake bruxism in adolescents: A path analysis

BACKGROUND

Bruxism has a multifactorial etiology, including the influence of sleep characteristics and chronotypes.

AIM

To identify the pathways that influence the occurrence of probable sleep bruxism (PSB) and probable awake bruxism (PAB) in adolescents.

DESIGN

A total of 403 adolescents, aged 12-19 years, participated in the study. Parents/caregivers filled out a questionnaire about sociodemographic issues and the adolescent's health conditions, and the adolescents about sleep characteristics, occurrence of bruxism (based on previous study and the International Consensus of Bruxism), and chronotype (Circadian Energy Scale). Clinical examinations were performed. Statistical analysis included descriptive analysis and path analysis.

RESULTS

PSB and PAB are related to each other, with moderate and positive correlation (β = .390). Poor sleep quality and higher household income had a direct effect on both PSB (β = -.138; β = .123, respectively) and PAB (β = -.155; β = .116, respectively). Chronotype had a direct effect on PSB, in such a way that adolescents with a morningness chronotype tend to have PSB (β = -.102). Adolescents that drool on the pillow (β = .184) and/or have agitated sleep (β = .104) tend to have PSB.

CONCLUSION

Poor sleep quality, household income, morningness chronotype profile, drooling on the pillow, and agitated sleep influence the paths taken by PSB. PAB was influenced by the quality of sleep and family income.

What Is the Relationship between Chronotype and Disordered Eating in Adolescents? The EHDLA Study

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.

Social Jetlag on Obesity-Related Outcomes in Spanish Adolescents: Cross-Sectional Evidence from the EHDLA Study

PURPOSE

This study aimed to investigate the association between social jetlag (SJL) and obesity-related outcomes among adolescents from Valle de Ricote (Region of Murcia, Spain). We explored the relationship between SJL and body mass index (BMI) z-score, waist circumference, and body fat percentage, as well as the odds of having excess weight, obesity, and abdominal obesity in a sample of Spanish adolescents.

METHODS

A cross-sectional study was conducted using data from the Eating Healthy and Daily Life Activities (EHDLA) project, which included 847 Spanish adolescents aged 12-17 years. SJL was assessed based on the differences in sleep patterns between weekdays and weekends. Obesity-related indicators such as BMI z-score, waist circumference, body fat percentage, excess weight, obesity, and abdominal obesity were measured. Generalized linear models with a Gaussian or binomial distribution were used to analyze the associations between SJL and obesity-related outcomes, adjusting for potential confounders.

RESULTS

The analysis revealed significant associations between SJL and BMI z-score (unstandardized beta coefficient [B] = 0.15, 95% CI: 0.05 to 0.25, p = 0.003), waist circumference (B = 1.03, 95% CI: 0.39 to 1.67, p = 0.002), and body fat percentage (B = 0.83, 95% CI: 0.31 to 1.43, p = 0.008). Additionally, the odds ratios (ORs) for excess weight (OR = 1.35, 95% CI: 1.16 to 1.57; p < 0.001), obesity (OR = 1.59, 95% CI: 1.26 to 2.00; p < 0.001), and abdominal obesity (OR = 1.46, 95% CI: 1.23 to 1.72; p < 0.001) increased significantly with each 60 min increment in SJL.

CONCLUSIONS

This study pointed out that the misalignment of sleeping times during weekdays and weekends (SJL) is significantly associated with higher BMI z-scores, waist circumference, body fat percentage, and higher odds of excess weight, obesity, and abdominal obesity among adolescents, being more significant in boys than in girls. These findings highlight the importance of addressing circadian misalignment in the prevention and management of obesity and its related metabolic disorders in this population.

Sleep and lucid dreaming in adolescent athletes and non-athletes

During lucid dreaming (LD), dreamers are aware of experiencing a dream and may consciously influence its content. This study used an online questionnaire to investigate the LD frequency and applications in 193 adolescent athletes and non-athletes (17.40 ± 2.09 years; 46% athletes, 54% controls). Given the critical role that sleep plays in adolescent health, development, and performance, associations of LD with various sleep parameters were also explored. LD is prominent in adolescents (67.4% experienced it at least once, 30.0% once a month or more, 12.9% at least once a week), but similar in terms of frequency and uses between athletes and non-athletes. A higher proportion of those who practiced sports/dance during LD reported improved waking self-efficacy (57.1%) over sport performance (42.9%). There was no indication that chronotype preference may influence LD nor that LD may be detrimental to adolescent sleep. Athletes and controls had similar sleep durations, daytime sleepiness, and sleep disturbances frequency, but athletes reported higher sleep quality. Despite, on average, meeting the minimum sleep recommendation guidelines for their age, a relatively large proportion of adolescents did not attain sufficient sleep, particularly on weeknights (47.4% 14-17 years; 20.0% 18-21 years), suggesting that restricted sleep remains prevalent in adolescent populations.

Randomized Controlled Feasibility Trial of Late 8-Hour Time-Restricted Eating for Adolescents With Type 2 Diabetes

Background

No trial to date has tested the effects of late time-restricted eating (lTRE) on glycemic control or body composition in adolescents with type 2 diabetes (T2D).

Objective

The objective of the current study was to examine the feasibility, acceptability, and preliminary efficacy of lTRE compared to a prolonged eating window in adolescents with T2D.

Design

A 12-week, randomized, controlled, feasibility study of lTRE compared to control in adolescents with obesity and new onset T2D was conducted.

Participants/setting

Eligible participants were 13-21 years old; with a diagnosis of T2D, on metformin monotherapy, recruited from Children's Hospital Los Angeles, between January 2021 and December of 2022. From 36 eligible participants, 27 were enrolled (75% recruitment rate; age: 16.5 ± 1.7 years, HbA1c: 6.6 ± 0.9%, 22/27 [81%] Hispanic, 17/27 [63%] female, 23/27 [85%] public insurance; all p-values >.05), and 23 of 27 completed the protocol.

Intervention

Participants wore a continuous glucose monitor (CGM) daily and were randomized to one of two meal-timing schedules for 12-weeks: (1) lTRE (eating all food between 12:00 PM and 20:00 PM without calorie counting or recommended daily caloric intake) or (2) Control (eating over a period of 12 or more hours per day).

Main outcome measures

Study recruitment, retention and adherence to intervention arms were captured to operationalize feasibility. Glucose control (HbA1c), weight loss (%BMIp95), total body fat mass on DEXA, sleep, and dietary intake were explored as secondary outcomes.

Statistical Analysis

Analyses were based on the intention to treat (ITT) population. Between-group differences in clinical outcomes were assessed using mixed-effects longitudinal regression models.

Results

Overall adherence to the 8-hr lTRE was 6.2 ± 1.1 d/wk and Control was 5.9 ± 0.9 d/wk. Participants assigned to lTRE indicated that limiting their eating window did not negatively affect their daily functioning and no adverse events were reported. In this pilot study, lTRE led to a reduction in %BMIp95 (-3.4%-95%CI: -6.1, -0.7, p = 0.02), HbA1c (-0.4%, 95%CI: -0.9, -0.01, p = .06), and ALT (-31.1 U/L, 95%CI: -60, -2, p = .05) within the group. There was no significant difference observed between lTRE and control across these measures (all p > .05). The lTRE group had a -271.4 (95% CI, -565.2, 5.2) kcal/day energy reduction compared to a +293.2 (95% CI: 30.4, 552.7) kcal/day increase in Control (p = .01). There were no significant changes observed in sleep or eating behaviors over the study period between groups.

Conclusions

Recruitment and retention rates suggest a trial of lTRE in adolescents with T2D was feasible. lTRE was seen as acceptable by participants and adherence was high. A revised intervention, building on the successful elements of this pilot alongside adapting implementations strategies to augment adherence and engagement, should therefore be considered.

Causal dynamics of sleep, circadian rhythm, and mood symptoms in patients with major depression and bipolar disorder: insights from longitudinal wearable device data

BACKGROUND

Sleep and circadian rhythm disruptions are common in patients with mood disorders. The intricate relationship between these disruptions and mood has been investigated, but their causal dynamics remain unknown.

METHODS

We analysed data from 139 patients (76 female, mean age = 23.5 ± 3.64 years) with mood disorders who participated in a prospective observational study in South Korea. The patients wore wearable devices to monitor sleep and engaged in smartphone-delivered ecological momentary assessment of mood symptoms. Using a mathematical model, we estimated their daily circadian phase based on sleep data. Subsequently, we obtained daily time series for sleep/circadian phase estimates and mood symptoms spanning >40,000 days. We analysed the causal relationship between the time series using transfer entropy, a non-linear causal inference method.

FINDINGS

The transfer entropy analysis suggested causality from circadian phase disturbance to mood symptoms in both patients with MDD (n = 45) and BD type I (n = 35), as 66.7% and 85.7% of the patients with a large dataset (>600 days) showed causality, but not in patients with BD type II (n = 59). Surprisingly, no causal relationship was suggested between sleep phase disturbances and mood symptoms.

INTERPRETATION

Our findings suggest that in patients with mood disorders, circadian phase disturbances directly precede mood symptoms. This underscores the potential of targeting circadian rhythms in digital medicine, such as sleep or light exposure interventions, to restore circadian phase and thereby manage mood disorders effectively.

FUNDING

Institute for Basic Science, the Human Frontiers Science Program Organization, the National Research Foundation of Korea, and the Ministry of Health & Welfare of South Korea.

Morning compared to afternoon school-based exercise on cognitive function in adolescents

PURPOSE

Adolescents may be less ready to learn in the mornings due to a propensity for waking up later. High-intensity interval exercise (HIIE) has been shown to acutely improve cognitive functioning in teenagers. This within-measures study explored whether the benefit of HIIE differs when delivered in the morning or afternoon.

METHODS

37 teenagers (19 boys, 13.7 ± 0.4 years) each completed 3 trials in school; morning HIIE (MORN), afternoon HIIE (AFTER) and a no-exercise control trial (CON). The HIIE involved 10x10 second sprints, interspersed by 50 s of walking. Cognitive function was assessed using a battery of computerised tasks four times over the course of the day.

RESULTS

Z scores for reaction time, but not proportion of correct responses, were improved 45 min post exercise in the MORN trial (P < 0.01, d = 0.47), and this improvement persisted until the third (P = 0.04, d = 0.34), but not final (P = 0.93, d = 0.01), time point. Global reaction time was not improved 45 min post exercise in the AFTER trial (P = 0.17, d = 0.20). Global reaction time was quicker 45 min post morning exercise compared to the same time point in CON (P = 0.02, d = 0.56) and AFTER (P = 0.01, d = 0.72).

CONCLUSION

HIIE may be more effectual in improving cognitive functioning when delivered in the morning.

Sleep, Nutrition, and Injury Risk in Adolescent Athletes: A Narrative Review

This narrative review explores the impact of sleep and nutrition on injury risk in adolescent athletes. Sleep is viewed as essential to the recuperation process and is distinguished as an active participant in recovery through its involvement in growth, repair, regeneration, and immunity. Furthermore, the literature has shown that the sleep of athletes impacts elements of athletic performance including both physical and cognitive performance, recovery, injury risk, and mental well-being. For sleep to have a restorative effect on the body, it must meet an individual's sleep needs whilst also lasting for an adequate duration and being of adequate quality, which is age-dependent. The literature has suggested that athletes have increased sleep needs compared to those of the general population and thus the standard recommendations may not be sufficient for athletic populations. Therefore, a more individualised approach accounting for overall sleep health may be more appropriate for addressing sleep needs in individuals including athletes. The literature has demonstrated that adolescent athletes achieve, on average, ~6.3 h of sleep, demonstrating a discrepancy between sleep recommendations (8-10 h) and actual sleep achieved. Sleep-wake cycles undergo development during adolescence whereby adaptation occurs in sleep regulation during this phase. These adaptations increase sleep pressure tolerance and are driven by the maturation of physiological, psychological, and cognitive functioning along with delays in circadian rhythmicity, thus creating an environment for inadequate sleep during adolescence. As such, the adolescent period is a phase of rapid growth and maturation that presents multiple challenges to both sleep and nutrition; consequently, this places a significant burden on an adolescent athletes' ability to recover, thus increasing the likelihood of injury. Therefore, this article aims to provide a comprehensive review of the available literature on the importance of sleep and nutrition interactions in injury risk in adolescent athletes. Furthermore, it provides foundations for informing further investigations exploring the relation of sleep and nutrition interactions to recovery during adolescence.

Circadian preference and mental health outcomes in youth: A systematic review and meta-analysis

Youth is a vulnerable developmental period associated with an increased preference for eveningness and risk for developing psychopathology. Growing evidence suggests a link between eveningness and poorer mental health outcomes, but the findings in the current literature are inconsistent, and a comprehensive synthesis of evidence in this area remains lacking. This meta-analysis aimed to 1) synthesise the existing evidence on the association between circadian preference and mental health outcomes in youths and 2) explore potential sleep-related factors that may moderate the relationship between circadian preference and mental health outcomes. A systematic search of five electronic databases resulted in 81 observational studies included in the review. Eveningness was found to be significantly associated with general mental health (r = 0.20), mood-related disturbances (r = 0.17), and anxiety problems (r = 0.13). The qualitative review also identified that eveningness was associated with greater risks for psychotic symptoms and maladaptive eating behaviours. These findings highlighted the need to consider circadian preference in the clinical management of youth mental health problems. Further research is needed to examine the efficacy of a circadian-focused intervention in the context of youth mental health.

Is chronotype linked with adherence to the Mediterranean diet among adolescents? The EHDLA study

BACKGROUND

No previous study has evaluated the relationship between chronotype and adherence to the Mediterranean diet among adolescents. The aim of the present study was to assess the association between chronotype and adherence to the Mediterranean diet in a sample of Spanish adolescents aged 12-17 years.

METHODS

This study examined secondary data from 820 adolescents (55.5% girls) from the Eating Healthy and Daily Life Activities (EHDLA) study, which included a representative sample of adolescents aged 12-17 years from the Valle de Ricote (Region of Murcia, Spain). Adolescents' chronotype was evaluated with the Morningness/Eveningness Scale in Children. Adherence to the Mediterranean diet was determined through the Mediterranean Diet Quality Index for Children and Teenagers.

RESULTS

The proportion of adolescents with an optimal Mediterranean diet was 37.6%. In relation to chronotype, we found that 24.5%, 69.4%, and 6.1% of the adolescents were classified as morning, intermediate, and evening types, respectively. After adjusting for several covariates, both evening- and intermediate-type adolescents showed lower odds of having optimal adherence to the Mediterranean diet (evening-type: odds ratio [OR] = 0.30, confidence interval [CI] 95% 0.12-0.72; intermediate-type: OR = 0.62, CI 95% 0.44-0.87) than morning-type adolescents.

CONCLUSIONS

Chronotype could affect adherence to the Mediterranean Diet in adolescents, so it should be a factor to be considered in future studies assessing eating habits.

IMPACT

No previous study has evaluated the relationship between chronotype and adherence to the Mediterranean diet among adolescents. Both evening- and intermediate-type adolescents showed lower odds of having optimal Mediterranean diet adherence than morning-type adolescents. These findings may indicate a need to promote eating healthy habits based on a more holistic approach, not only on the total energy expenditure or in specific food groups but also on the chronotype.

Chronotype characteristics of professional athletes in China: a comprehensive descriptive study

BACKGROUND

Chronotype has gained recognition as a significant factor in enhancing athletic performance. This study aimed to deepen our understanding of athletes' sleep chronotypes and provide a foundation for developing evidence-based training and competition programs. By comprehensively describing and analyzing the chronotype characteristics of Chinese professional athletes, considering individual and sports factors, sleep quality and habits, and mental energy, this research aimed to contribute valuable insights to the field.

METHODS

A sample of 1069 professional athletes from sports teams in Shanghai completed the Athlete Sleep Screening Questionnaire and the Athlete Mental Energy Scale to assess chronotype, sleep quality, sleep-influencing habits, and mental energy.

RESULTS

Among athletes, sleep typology fell within the intermediate range, slightly leaning toward morningness. Male athletes and those who engaged in static sports displayed a greater propensity for morningness. Age correlated with a preference for eveningness. High-level athletes exhibited a stronger inclination toward eveningness. Sleep quality issues were associated with an inclination toward eveningness. Daily caffeine intake and the habit of using electronic devices before bedtime are also linked to eveningness. Chronotype demonstrated the ability to predict various dimensions of athletes' mental energy. It was the strongest predictor of vigor, but the loadings were smaller than those of sleep quality.

CONCLUSION

Chinese athletes' chronotypes primarily exhibit distinct characteristics related to individual factors such as gender, sports discipline, and ranking, as well as habits like caffeine consumption and electronic device use. Moreover, these sleep patterns demonstrate predictive capabilities across all dimensions of athletes' mental energy. This study sheds light on Chinese athletes' unique sleep chronotype attributes, enriching our understanding of sleep patterns among professional athletes under various systems. These insights offer an initial basis for enhancing the effectiveness of athlete scheduling and training management.

Impact of 8-hour time-limited eating on sleep in adolescents with obesity

STUDY OBJECTIVES

The relationship between time-limited eating (TLE) and sleep quality is a topic of growing interest in the field of chronobiology. Data in adult cohorts shows that TLE may improve sleep quality, but this has not been evaluated in adolescents. The aim of this secondary analysis was to (1) examine the impact of 8-hour TLE on sleep parameters in youth with obesity and (2) explore if there was any association between sleep patterns and glycemic profiles.

METHODS

Adolescents with obesity were randomized into one of three groups: 8-hour TLE (participants self-selected their eating window) + real-time continuous glucose monitor, 8-hour TLE + blinded continuous glucose monitor, or a prolonged eating window. In the primary analysis, it was found that participants in the real-time continuous glucose monitor group + 8-hour TLE group did not access their continuous glucose monitor data and thus for this analysis the two TLE groups were combined and only completers who had available Pittsburgh Sleep Quality Index (PSQI) data at all three time points were included. Participants completed the PSQI at baseline, week 4, and week 12. Mixed-effects generalized linear regression models were utilized to examine the change in PSQI score and assess association between glycemic variability and PSQI total score overtime by intervention arm.

RESULTS

The median PSQI total score for the TLE groups (n = 27) was 6 at week 0 (interquartile range = 5 to 10) and 5 at week 12 (interquartile range = 2 to 7). There was no significant difference in the change in total PSQI score or sleep latency between TLE and control over the study period (P > .05). There was no association between PSQI score and change in weight or glycemic profile between groups (all P values > 0.05).

CONCLUSIONS

These results suggest that in adolescents with obesity, an 8-hour TLE approach did not negatively impact sleep quality or efficiency when compared to a prolonged eating window. The potential effects of TLE on sleep should be further investigated in larger randomized trials.

CITATION

Jayakumr A, Gillett ES, Wee CP, Kim A, Vidmar AP. Impact of 8-hour time-limited eating on sleep in adolescents with obesity. J Clin Sleep Med. 2023;19(11):1941-1949.

Stride-to-Stride Fluctuations of Human Gait Are Affected By Chronobiology: An Exploratory Study

Physiological processes present daily oscillations of ≈24 h, called circadian rhythms. Motor performance, for example, reaches its peak in the afternoon, although this can be affected by chronotype. Certain motor activities, for example, walking, can also be affected by circadian rhythms. Healthy walking exhibits stride-to-stride fluctuations with a fractal-like structure that enables adaptability. While pathology and aging are shown to lead to random-like fluctuations; and, therefore, decreased adaptability; the influence of circadian rhythms remains unknown. This study investigates how these fluctuations present in healthy gait are affected by the time of day and chronotype. Eighteen young adults walk for 10 min every 2 h, from 8 a.m. to 6 p.m. Footswitches are used to determine heel-strike and calculate stride time. Then, detrended fluctuation analysis is used to calculate fractal scaling. A mixed-model Analysis of Variance is used and followed by a backward stepwise elimination process. Tukey's tests are used for pairwise comparisons. The statistical model shows the effect of time during the day (12 p.m. exhibits a higher fractal scaling compared to 8 a.m.); and chronotype (evening-types exhibit higher fractal scaling compared to morning-types). This study reveals the influence of chronobiology on stride-to-stride fluctuations. These findings open new perspectives to integrate circadian medicine in biomechanics.

Obesogenic sleep patterns among Chinese preschool children: A latent profile and transition analysis of the association sleep patterns and obesity risk

OBJECTIVE

This paper utilized a person-centered approach to examine whether sleep patterns on school and free days are associated with obesity risk in preschool children aged 3-6 years.

METHODS

The cross-sectional analysis included 204 children from the Wuhan Healthy Start Project with valid sleep data in at least four consecutive days gathered via Actigraph GT3X+. Based on three domains of sleep duration, sleep onset, and sleep offset, we used latent profile analysis to identify distinct sleep patterns on school and free days separately. Additionally, we conducted latent transition analysis to explore the probabilities of sleep patterns transitions between school and free days. The multivariate logistic regression model investigated the associations of sleep patterns with overweight/obesity (OWO) (BMI ≥ age- and sex-specific 85th percentile) and abdominal obesity (AO) (WC ≥ age- and sex-specific 75th percentile).

RESULTS

Two sleep patterns were identified for school days: "EL-sc" (early-to-sleep/longer-duration) (n = 119; 58.3%) and "LS-sc" (late-to-sleep/shorter-duration) (n = 85; 41.7%). Similarly, "LES-fr" (late-to-sleep/early-to-wake/shorter-duration) (n = 118; 57.8%) and "ELL-fr" (early-to-sleep/late-to-wake/longer-duration) (n = 86; 42.2%) patterns were identified for free days. LTA categorized the participants into four distinct transition groups, i.e., "EL-sc→ELL-fr" (32.9%), "EL-sc→LES-fr" (24.0%), "LS-sc→LES-fr" (33.8%), and "LS-sc→ELL-fr" (9.3%). Compared with the "ELsc→ELL-fr", the "LS-sc→LES-fr" had a higher risk of OWO (AOR 4.76; 95% CI: 1.39-20.33) and AO (AOR, 2.78; 95% CI, 1.21-6.62), respectively. Neither "EL-sc→LES-fr" (AOR, 1.11; 95% CI, 0.14-6.67) nor "LS-sc→ELL-fr" (AOR, 0.74; 95% CI, 0.03-6.14) was significantly associated with OWO. Likewise, no significant association was observed for "EL-sc→LES-fr" (AOR, 0.96; 95% CI, 0.35-2.62) and "LS-sc→ELL-fr" (AOR, 0.56; 95% CI, 0.11-2.18) with AO.

CONCLUSIONS

"LS-sc→LES-fr" pattern is significantly associated with an increased risk of general and abdominal obesity, indicating its obesogenic nature. Furthermore, although not statistically associated with obesity outcomes, "LS-sc→ELL-fr" and "EL-sc→LES-fr" patterns exhibit a semi-obesogenic characteristic. In addition, we identified a concerning trend that preschool children are at risk of transitioning to and persisting in sleep patterns characterized by delayed and shorter sleep. These findings underscore the importance of implementing interventions and strategies to address sleep patterns as a crucial step to minimize the risk of obesity.

Circadian preference and physical and cognitive performance in adolescence: A scoping review

Adolescence is a crucial period of development which coincides with changes in circadian rhythmicity. This may augment the impact of circadian preference on performance in this group. We aimed to scope the literature available on chronotypes and their effect on physical and mental aspects of performance in adolescents. Studies were identified by systematically searching bibliographical databases and grey literature. The Morningness-Eveningness Questionnaire was the most frequently reported tool for circadian preference assessment. Academic achievement was the most prevailing outcome, with evidence suggesting that morning type adolescents tend to outperform evening types, yet the results vary depending on multiple factors. Performance in tests of intelligence and executive functions was generally better at optimal times of the day (synchrony effect). Physical performance was examined in 8 studies, with very heterogeneous outcomes. Although the associations between circadian preference and performance in adolescents are evident in some areas, there are many factors that may be involved in the relationship and require further investigation. This review highlights the assessment of physical performance in relation to chronotypes, the multidimensional assessment of circadian preference, and the need for longitudinal studies as priorities for further research.Protocol: OSF Registration - Public registration, DOI: 10.17605/OSF.IO/UCA3Z.

Light Therapy for Adolescent Depression: A Scoping Review

PURPOSE

Depressive disorders in adolescents are a major health concern associated with developmental, social, and educational impairment. Bright Light Therapy (BLT) is a feasible and effective treatment for depressive disorders in adults, but few controlled trials have been conducted with children or adolescents. This scoping review focuses on the current state of knowledge for BLT in the treatment of adolescent depression. We reviewed the literature for novel data and methodologic approaches using BLT and pediatric and young adult populations.

RECENT FINDINGS

BLT is a tolerable treatment with few side effects. However, there is a marked lack of well-powered studies to support BLT as a treatment for depressive disorders in adolescent populations. Given evidence of tolerability and positive treatment effect on depression in the adult literature, research is needed to establish the efficacy, feasibility, and acceptability of BLT in adolescents.

Association between Chronotype and Physical Behaviours in Adolescent Girls

The aim of this study was to (1) describe accelerometer-assessed physical behaviours by chronotype, and (2) examine the association between chronotype and accelerometer-assessed physical behaviours in a cohort of adolescent girls. Chronotype (single question) and physical behaviours (GENEActiv accelerometer on the non-dominant wrist) were assessed in 965 adolescent girls (13.9 ± 0.8 years). Linear mixed-effects models examined the relationships among chronotype and physical behaviours (time in bed, total sleep time, sleep efficiency, sedentary time, overall, light and moderate-to-vigorous physical activity) on weekdays and weekend days. Over the 24 h day, participants spent 46% sedentary, 20% in light activity, 3% in moderate-to-vigorous physical activity, and 31% in 'time in bed'. Seventy percent of participants identified as 'evening' chronotypes. Compared to evening chronotypes, morning chronotypes engaged in less sedentary time (10 min/day) and had higher overall physical activity (1.3 mg/day, ~30 min of slow walking) on weekdays. Most girls identified as evening chronotypes with a large proportion of their day spent sedentary and a small amount in physical activities which may be exacerbated in evening chronotypes on weekdays. The results maybe be important for programmes aiming to promote physical activity in adolescent girls.

Factors Underpinning the Shift to Eveningness during Early Adolescence: Pubertal Development and Family Conflicts

Biological and psychosocial factors have been related to the shift to eveningness during early adolescence but it is necessary to study them from a longitudinal perspective. This longitudinal study examined the contribution of these factors to the onset of a shift towards eveningness in early adolescence. A sample of 440 (49.9% boys) Spanish adolescents were assessed for pubertal development, family conflicts, and morningness/eveningness. The same measures were taken twice at the age of 12 and one year later (T1: M = 12.47, SD = 0.75 and T2: M = 13.64, SD = 0.78). Pubertal development and family conflicts were considered predictors of morningness/eveningness in a mixed-effects multilevel model. The developmental shift towards eveningness appeared in girls but not in boys. The shift was related to more advanced pubertal development and more conflicts in the family. This study has implications for shaping healthy sleep habits in adolescents and possible interventions focused on family dynamics.

Development of morning-eveningness in adolescence: implications for brain development and psychopathology

BACKGROUND

Morning-evening preference is defined as an individual's preference for a morning- or evening-oriented rhythm. Across adolescence, a preference for eveningness becomes more predominant. Although eveningness is cross-sectionally associated with internalizing and externalizing psychopathology, few studies have examined developmental changes in eveningness and its potential biological substrates. Here, we investigated the longitudinal relationships among the trajectory of eveningness preference, internalizing and externalizing psychopathology and white matter development, across adolescence.

METHODS

Two-hundred and nine adolescents (49% male) were assessed longitudinally at four separate time points between 12 and 19 years of age. Morning-evening preference and internalizing and externalizing symptoms were assessed at each time point. Diffusion-weighted images were acquired on a subset of participants at the final two time points to estimate changes in global mean fractional anisotropy (FA). Linear mixed models were performed to estimate the change in eveningness over time. A series of linear regression models assessed the influence of change in eveningness on psychopathology and white matter development at age 19.

RESULTS

Across the sample, a preference for eveningness became more predominant by 19 years of age. Greater individual-level change towards eveningness significantly predicted greater severity in externalizing, but not internalizing, symptoms at 19 years of age. In contrast, change in psychopathology from 12 to 19 years of age was not associated with morning-eveningness at age 19. A change towards eveningness predicted an attenuated increase in FA between 17 and 19 years of age.

CONCLUSIONS

This study suggests that developmental changes in morning-evening preference may predict both neurodevelopmental and psychological outcomes in adolescents.

Approach to a sleepy child: Diagnosis and treatment of excessive daytime sleepiness in children and adolescents

The aim of this review is to give updated information to pediatric neurologists on the correct diagnostic approach and treatment of excessive daytime sleepiness (EDS) in children and adolescents. Due to the change in the society habits, EDS is becoming an emerging problem for the health system. At the present there are few articles specifically devoted to the evaluation of EDS. EDS is often reported in several manuscripts as a side effect of other sleep disorders (obstructive sleep apnea, circadian disorders, etc.) or of the use of drugs or of the substance abuse or as a consequence of bad sleep habits and poor sleep hygiene. EDS, especially in children, may manifest with paradoxical symptoms like hyperactivity, inattention, and impulsiveness. However, common sign of EDS in children are the propensity to sleep longer than usual, the difficulty waking up in the morning, and falling asleep frequently during the day in monotonous situation. The diagnosis should include subjective (sleep diaries, questionnaires) and objective (polysomnography, multiple sleep latency test, etc.) instruments to avoid misdiagnosis. Narcolepsy is the most studied central disorder of hypersomnolence, and it is a predominantly pediatric disease with a peak age of onset in prepuberty but the diagnosis is often delayed especially in mild forms. The early and correct treatment of narcolepsy and of other form of EDS is extremely important since late and inappropriate treatments can affect the psychosocial development of the children and adolescents.

Sleep Reactivity and Related Factors in Adolescence: An Increased Risk for Insomnia? A Longitudinal Assessment

Purpose

The individual vulnerability for stress-related sleep difficulties (eg, sleep reactivity) is known as a predisposing factor of insomnia in adults, yet relatively little is known about sleep reactivity in adolescence. The study goal is to determine factors related to sleep reactivity and to investigate whether sleep reactivity and related factors predict current and new incidents of insomnia in adolescents.

Patients and Methods

At baseline, 11-to-17-year-olds (N = 185, M_age = 14.3 years, SD = 1.8, 54% female) answered an age-appropriate version of the Ford Insomnia Response to Stress Test, questionnaires about sleep, stress, psychological symptoms, and resources, filled out a sleep diary and used actigraphy. Insomnia diagnoses according to ISCD-3 criteria were assessed at baseline, after 9 months and after one and a half years.

Results

Adolescents with high compared to low sleep reactivity had increased pre-sleep arousal, negative sleep-related cognitions, pre-sleep mobile phone use, stress experience, stress vulnerability, internalizing and externalizing symptoms, less social resources, and a later midpoint of bedtime. High sleep reactivity increased the likelihood for currently having insomnia, but not for the development of insomnia at subsequent assessments.

Conclusion

The findings suggest that high sleep reactivity is related to poor sleep health and mental health but cast doubt on sleep reactivity as a pivotal predisposing factor for the development of insomnia in adolescence.

Prospective association between evening circadian preference and academic functioning in adolescents: the role of daytime sleepiness

BACKGROUND

There is growing evidence for the role of circadian factors in adolescents' sleep and academic adjustment, with greater evening preference being linked to poorer academic functioning. However, studies have yet to evaluate this association prospectively in adolescence, nor have studies examined daytime sleepiness as a putative mechanism linking evening preference to poor academic functioning. The current study used a multi-informant design to test the prospective association of evening circadian preference, daytime sleepiness, and academic functioning (e.g., global academic impairment and grades) across 2 years in adolescence. As evening circadian preference, sleepiness, and academic problems are elevated in adolescents with ADHD, we used a sample enriched for adolescents with ADHD and explored whether ADHD moderated effects.

METHOD

Participants were 302 adolescents (M_age  = 13.17 years; 44.7% female; 81.8% White; 52% with ADHD). In the fall of eighth grade, adolescents reported on their circadian preference, and in the fall of ninth grade, adolescents and parents completed ratings of daytime sleepiness. In the middle of 10th grade, parents and teachers reported on adolescents' academic impairment and at the end of 10th grade, adolescents' grade point average (GPA) was obtained from school records.

RESULTS

Above and beyond covariates (e.g., adolescent sex, ADHD status, medication, sleep duration) and baseline academic impairment, greater self-reported evening preference in 8th grade predicted increased parent ratings of academic impairment in 10th grade indirectly via adolescent and parent ratings of daytime sleepiness in 9th grade. Furthermore, evening preference in 8th grade predicted greater teacher ratings of academic impairment and lower average GPA in 10th grade via parent ratings of daytime sleepiness in 9th grade, controlling for covariates and baseline GPA. ADHD status did not moderate indirect effects.

CONCLUSION

Findings underscore daytime sleepiness as a possible intervening mechanism linking evening preference to poor academic functioning across adolescence. Intervention studies are needed to evaluate whether targeting circadian preference and sleepiness improves academic functioning in adolescents.

Gender differences in the interference of sleep difficulties and daytime sleepiness on school and social activities in adolescents

OBJECTIVES

During adolescence, changes in the circadian and homeostatic systems, combined with psychosocial factors, create a phase delay in the sleep of adolescents. These changes in sleep are associated with increased sleep difficulties and a shortened sleep duration, which has a negative impact on daytime functioning of adolescents. Some studies showed that teenage girls report worse sleep quality and shorter sleep duration than boys during adolescence. The objective of this study was to investigate gender differences in the impact of sleep difficulties and sleepiness on daytime functioning in adolescents and to measure which aspect of sleep may interfere with daytime functioning in boys and girls.

METHOD

A total of 731 adolescents (311 boys, 420 girls; age 13 to 17,5 years) completed questionnaires on sleep and daytime functioning.

RESULTS

Compared to boys, teenage girls reported a significantly greater impact of short sleep duration and sleep difficulties on their school and social activities. Furthermore, our results suggest that the factors predicting the negative interference on daytime functioning seem to be more complex and multifactorial for girls than for boys.

CONCLUSIONS

This study further emphasizes the importance of monitoring insufficient and poor sleep quality in adolescents, as these sleep variables seem to have a significant impact on their daytime functioning. Clinicians should also take into account gender when considering sleep issues in adolescents, as teenage girls and boys have different vulnerabilities and needs.

Integration of Time-Based Recommendations with Current Pediatric Health Behavior Guidelines: Implications for Obesity Prevention and Treatment in Youth

PURPOSE OF REVIEW

Youth-onset obesity is associated with negative health outcomes across the lifespan including cardiovascular diseases, type 2 diabetes, obstructive sleep apnea, dyslipidemias, asthma, and several cancers. Pediatric health guidelines have traditionally focused on the quality and quantity of dietary intake, physical activity, and sleep.

RECENT FINDINGS

Emerging evidence suggests that the timing (time of day when behavior occurs) and composition (proportion of time spent allocated to behavior) of food intake, movement (i.e., physical activity, sedentary time), and sleep may independently predict health trajectories and disease risks. Several theoretically driven interventions and conceptual frameworks feature behavior timing and composition (e.g., 24 h movement continuum, circadian science and chronobiology, intermittent fasting regimens, structured day hypothesis). These literatures are, however, disparate, with little crosstalk across disciplines. In this review, we examine dietary, sleep, and movement guidelines and recommendations for youths ages 0-18 in the context of theoretical models and empirical findings in support of time-based approaches. The review aims to inform a unifying framework of health behaviors and guide future research on the integration of time-based recommendations into current quantity and quality-based health guidelines for children and adolescents.

The Effect of Chronotype on Oppositional Behaviour and Psychomotor Agitation of School-Age Children: A Cross-Sectional Study

The aim of this study is to examine the relationship between chronotype, classroom behaviour and school performance in 140 healthy school-age children attending various levels of education during the 1st cycle during 2021 in Portugal. In this cross-sectional and quantitative study, the Chronotype Questionnaire for Children (to assess the chronotype) and the Conners Scale-a reduced version was presented to the teachers (to assess behaviours such as excessive movement, inattention and oppositional behaviours)-were used. The methodology of this study followed a comparative method since the independent variables were not controlled, and therefore, it was still possible to compare the differences between the morning and evening groups. Statistical methods were used such as multivariate analyses, inter-item correlations and reliability tests, and descriptive tests were used for the percentile analysis. The sample was divided into three groups based on the identification of the chronotype-morning, intermediate and evening types-to further study the relationship between these chronotypes, their academic performance and classroom behaviour were studied. A multivariate analysis of variance revealed that there was a higher rate of oppositional behaviour in the morning type and no differences in the school performance during the two semesters (covering all of the school periods) regarding the chronotype effect, even with the analysis of regression parameters and covariates. On the other hand, the morning-type children showed a greater amount of motor agitation and impulsivity after controlling for the gender covariate. Age had an effect on the chronotype, after controlling for the covariate parental education. This study highlights the need for further research on the chronotype of the morning children in order to regulate their behaviour. The data that were obtained raise questions that have not been yet considered in the literature in the area of education and infant development.

Sleep to Internalizing Pathway in Young Adolescents (SIPYA): A proposed neurodevelopmental model

The prevalence of internalizing disorders, i.e., anxiety and depressive disorders, spikes in adolescence and has been increasing amongst adolescents despite the existence of evidence-based treatments, highlighting the need for advancing theories on how internalizing disorders emerge. The current review presents a theoretical model, called the Sleep to Internalizing Pathway in Young Adolescents (SIPYA) Model, to explain how risk factors, namely sleep-related problems (SRPs), are prospectively associated with internalizing disorders in adolescence. Specifically, SRPs during late childhood and early adolescence, around the initiation of pubertal development, contribute to the interruption of intrinsic brain networks dynamics, both within the default mode network and between the default mode network and other networks in the brain. This interruption leaves adolescents vulnerable to repetitive negative thought, such as worry or rumination, which then increases vulnerability to internalizing symptoms and disorders later in adolescence. Sleep-related behaviors are observable, modifiable, low-stigma, and beneficial beyond treating internalizing psychopathology, highlighting the intervention potential associated with understanding the neurodevelopmental impact of SRPs around the transition to adolescence. This review details support for the SIPYA Model, as well as gaps in the literature and future directions.

Sleep loss and addiction

Reducing sleep hours is a risk factor for developing cardiovascular, metabolic, and psychiatric disorders. Furthermore, previous studies have shown that reduction in sleep time is a factor that favors relapse in addicted patients. Additionally, animal models have demonstrated that both sleep restriction and sleep deprivation increase the preference for alcohol, methylphenidate, and the self-administration of cocaine. Therefore, the present review discusses current knowledge about the influence of sleep hours reduction on addictivebehaviors; likewise, we discuss the neuronal basis underlying the sleep reduction-addiction relationship, like the role of the orexin and dopaminergic system and neuronal plasticity (i.e., delta FosB expression). Potentially, chronic sleep restriction could increase brain vulnerability and promote addictive behavior.

Strategies and foundations for scientific discovery in longitudinal studies of bipolar disorder

Bipolar disorder (BD) is a complex and dynamic condition with a typical onset in late adolescence or early adulthood followed by an episodic course with intervening periods of subthreshold symptoms or euthymia. It is complicated by the accumulation of comorbid medical and psychiatric disorders. The etiology of BD remains unknown and no reliable biological markers have yet been identified. This is likely due to lack of comprehensive ontological framework and, most importantly, the fact that most studies have been based on small nonrepresentative clinical samples with cross-sectional designs. We propose to establish large, global longitudinal cohorts of BD studied consistently in a multidimensional and multidisciplinary manner to determine etiology and help improve treatment. Herein we propose collection of a broad range of data that reflect the heterogenic phenotypic manifestations of BD that include dimensional and categorical measures of mood, neurocognitive, personality, behavior, sleep and circadian, life-story, and outcomes domains. In combination with genetic and biological information such an approach promotes the integrating and harmonizing of data within and across current ontology systems while supporting a paradigm shift that will facilitate discovery and become the basis for novel hypotheses.

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.

The multiplicative effect of stress and sleep on academic cognitions in Latino college students

Latino students are increasingly represented in higher education within the United States, but remain one of the groups least likely to graduate from a four-year institution. Stress and sleep are factors that have been implicated in students' academic success. This study examined concurrent and longitudinal interactive effects of stress and sleep on academic cognitions in a sample of 196 Latino students (M_age = 18.95; 64.4% female) in their second and third semester of college. Stress and actigraphy-measured sleep (duration, efficiency, midpoint, midpoint-variability) were measured in the second semester and academic cognitions (engagement, motivation, self-efficacy) were measured in the second and third semesters. Structural equation modeling revealed that higher stress was concurrently related to lower academic cognitions for students with consistently delayed sleep timings (e.g., later average midpoints) and longitudinally related to reduced academic functioning for students with lower sleep efficiency. These findings can inform programs that target stress-reduction and sleep hygiene among incoming college students.