Chronotype changes after sex hormone use: A prospective cohort study in transgender users of gender-affirming hormones

Chronotype, an individual's preferred sleep-wake timing, is influenced by sex and age. Men sometimes report a later chronotype than women and older age is associated with earlier chronotype. The sex-related changes in chronotype coincide with puberty and menopause. However, the effects of sex hormones on human chronotype remain unclear. To examine the impact of 3 months of gender-affirming hormone therapy (GAHT) on chronotype in transgender persons, this study used data from 93 participants from the prospective RESTED cohort, including 49 transmasculine (TM) participants starting testosterone and 44 transfeminine (TF) participants starting estrogens and antiandrogens. Midpoint of sleep and sleep duration were measured using the ultra-short Munich ChronoType Questionnaire (µMCTQ). After 3 months of GAHT, TM participants' midpoint of sleep increased by 24 minutes (95% CI: 3 to 45), whereas TF participants' midpoint of sleep decreased by 21 minutes (95% CI: -38 to -4). Total sleep duration did not change significantly in either group. This study provides the first prospective assessment of sex hormone use and chronotype in transgender persons, showing that GAHT can change chronotype in line with cisgender sex differences. These findings provide a basis for future studies on biological mechanisms and clinical consequences of chronotype changes.

The Association of Self-Reported Sleep and Circadian Measures with Glycemic Control and Diabetes Complications among Young Adults with Type 2 Diabetes

We aim to examine the association of sleep duration, sleep quality, late chronotype and circadian misalignment with glycemic control and risk of complications in young adults with youth-onset type 2 diabetes followed in the Treatment Options for Type 2 Diabetes in Adolescents and Youth (TODAY) study. Self-reported sleep duration, quality, timing, and circadian misalignment were assessed via a modified Pittsburgh Sleep Quality Index (PSQI) questionnaire, and chronotype was assessed via the Morningness-Eveningness Questionnaire (MEQ). We examined diabetes complications including loss of glycemic control (defined as hemoglobin A1c ≥8%), hypertension, dyslipidemia, albuminuria, and diabetic peripheral neuropathy. Multivariable logistic regression models were constructed to assess associations between sleep and circadian measures with outcomes of interest, such as loss of glycemic control and diabetes complications. A total of 421 participants (34.2% male), mean age 23.6±2.5 years, mean BMI of 36.10±8.26 kg/m2 and mean diabetes duration of 10.0±2.5 years were evaluated. Self-reported short sleep duration, daytime sleepiness, and sleep quality were not associated with loss of glycemic control or diabetes complications. Late self-reported bedtime (after midnight) on work/school nights, rather than self-expressed chronotype or circadian misalignment, was independently associated with loss of glycemic control. An association was seen between late bedtimes and albuminuria but was attenuated after adjusting for depression. In conclusion, late bedtime on work/school days, rather than short sleep duration, daytime sleepiness, or poor sleep quality, was independently associated with loss of glycemic control in this longitudinal cohort of young adults with youth-onset type 2 diabetes.

The effects of social jetlag and sleep variability on sleepiness in a population-based study: The mediating role of sleep debt

Sleepiness is a multicausal condition, and previous research has highlighted associations between this symptom and the circadian timing system, specifically concerning social jetlag and sleep variability. Recent inquiries have shown that the effects of social jetlag on sleepiness can be confounded with the consequences of sleep debt. In light of the current evidence, we aimed to assess the effects of social jetlag and sleep variability on sleepiness and the potential mediating role of sleep debt. We used data from the EPISONO study, a cross-sectional population-based study with a sample size of 1042 participants, representative of the city of Sao Paulo, Brazil. Participants completed the UNIFESP Sleep Questionnaire (self-reported bedtime and get-up time) and the Epworth Sleepiness Scale (subjective daytime sleepiness). Subsequently, sleep-corrected mid-sleep time (chronotype), total sleep time, social jetlag (absolute difference between the mid-sleep time on workdays and mid-sleep time on free days), sleep variability (standard deviation of mid-sleep time), and sleep debt (difference between total sleep time on workdays and free days) were calculated. Generalised linear models were used to test whether social jetlag and sleep variability affected sleepiness. Mediation models were used to determine if any observed significant effects were mediated by sleep debt. The prevalence of social jetlag was 23% for >1 h and 12% for >2 h. The mean sleep variability was 41 ± 30 min. Social jetlag had a significant effect on the Epworth Sleepiness Scale scores. This association was no longer statistically significant after controlling for age, sex, body mass index, work schedule, and chronotype. A significant indirect effect of social jetlag on sleep debt and subsequently on the Epworth Sleepiness Scale scores was found. No effect of sleep variability on sleepiness could be identified. In conclusion, the association between social jetlag and sleepiness was mediated by sleep debt but was not independent of demographic, work, and chronotype variables. This study provides new evidence on the importance of circadian misalignment and sleep debt for sleep health on a population level.

Social jetlag and body mass index among shift-working nurses in Korea: A cross-sectional study

PURPOSE

Shift-working nurses must function against their natural circadian system and are, thus, bound to be detrimentally affected by social jetlag. Circadian rhythms play a crucial role in regulating homeostasis, and social jetlag may increase one's risk for obesity. Therefore, this study aimed to identify associations between social jetlag and obesity among shift-working nurses.

METHODS

This cross-sectional study included 183 nurses working rotating shifts in South Korea. Chronotype and social jetlag were measured using the Morningness-Eveningness Questionnaire and the Munich Chronotype Questionnaire for Shift-Workers, respectively. Obesity was defined as a body mass index of 25.0 or higher, which was calculated using self-reported height and weight data. The associations between chronotype, social jetlag, and obesity were investigated using multiple logistic regression analysis.

FINDINGS

A total of 183 nurses were included in the analysis (81.4% women and 80.3% single, median age = 27.00 years). Majority of the participants' (95.1%) chronotypes were moderate evening or intermediate type. The mean overall social jetlag was 3 h and 31 min. The odds for obesity were 8.44 times higher among shift-working nurses whose social jetlag was over 3 h and 31 min (95% confidence interval: 1.66-42.99) while controlling for chronotype, exercise time, and eating habits.

CONCLUSIONS

Social jetlag may increase the likelihood of obesity among rotating shift-working nurses.

IMPLICATIONS FOR NURSING PRACTICE

To achieve positive outcomes for promoting nurses' health, upper nursing management should consider individual nurses' social jetlag when scheduling shifts. In addition, nursing managers should have the responsibility to educate nurses involved in shift work about the adverse effects of social jetlag.

Association of Meal Timing with Sleep Quality and Anxiety According to Chronotype: A Study of University Students

There are several determinants of mental health symptoms, ranging from individual characteristics to social factors. Consistent with patterns in the general population, students with evening characteristics tend to exhibit more anxiety symptoms and poorer sleep quality compared to morning students. Meal timing also appears to affect sleep and may be associated with mental health symptoms. In this context, the aim of the present study was to investigate the association of the timing of the main and last meals of the day with sleep quality and anxiety levels, according to the chronotype of university students. This study was conducted in colleges in São Paulo, Brazil, and involved application of a questionnaire to 162 university students. The questionnaire collected sociodemographic information meal and study times, and included scales assessing eveningness and morningness, sleep quality, and anxiety. Students demonstrating a phase delay in both chronotype and dinner timing exhibited higher levels of anxiety compared to morning-type students. Although no associations were observed between meal timing and sleep quality, sleeping later was associated with poorer sleep quality. The study suggests that evening students and those who eat late at night are more prone to presenting mental health symptoms. More studies are needed to further investigate this association.

Kairos study protocol: a multidisciplinary approach to the study of school timing and its effects on health, well-being and students' performance

Recent evidence from chronobiology, chssronomedicine and chronopsychology shows that the organisation of social time (e.g., school schedules) generally does not respect biological time. This raises concerns about the impact of the constant mismatch between students' social and internal body clocks on their health, well-being and academic performance. The present paper describes a protocol used to investigate the problem of (de) synchronisation of biological times (chronotypes) in childhood and youth in relation to school times. It studies the effects of student chronotype vs. school schedule matches/mismatches on health behaviours (e.g., how many hours students sleep, when they sleep, eat, do physical activity, spend time outdoors in daylight) and learning (verbal expression, spatial structuring, operations) and whether alert-fatigue levels mediate this effect alignments/misalignments on learning (verbal expression, spatial structuring, operations) and their mediation by alert-fatigue levels. The novelty of our protocol lies in its multidisciplinary and mixed methodology approach to a relevant and complex issue. It draws on up-to-date knowledge from the areas of biology, medicine, psychology, pedagogy and sociology. The methods employed include a varied repertoire of techniques from hormonal analysis (cortisol and melatonin), continuous activity and light monitoring, self-registration of food intake, sleep timings, exercise and exposure to screens, alongside with systematic application of cognitive performance tests (e.g., memory, reasoning, calculation, attention) and self-reported well-being. This comprehensive and interdisciplinary protocol should support evidence-based education policy measures related to school time organisation. Appropriate and healthier school timetables will contribute to social change, healthier students and with more efficient learning. The results of studies using a similar methodology in other countries would ensure replication and comparability of results and contribute to knowledge to support policy making.

Distribution of sleep components while working remotely

OBJECTIVES

The circadian system is the main regulator of almost all human physiological processes. The aim of this study was to assess sleep in the working population, in relation to the share of remote working.

MATERIAL AND METHODS

An online survey was conducted among students and staff representing 3 universities in Łódź, Poland (N = 1209). The participants were divided into 3 groups according to the percentage of time they worked remotely. Group I consisted of respondents performing tasks remotely for ≤45% of their working time; group II included respondents performing their duties remotely for >45-75% of their working time, and group III included those working >75% of their time remotely.

RESULTS

performing their duties remotely for >45-75% of their working time, and group III included those working >75% of their time remotely. Results: In the study, the authors found the association between the length of time spent on a computer, the percentage of time working remotely, and the occurrence of physical symptoms and the prevalence of sleep disorders. The most significant difference between working days and days off in terms of the mid-point of sleep (1.5 h) was observed in group I, where there was the greatest variability in the form of work performance. The participants who worked most of their time remotely (group III) shifted their bedtime to midnight, both on working days and on days off.

CONCLUSIONS

The study highlights that increased remote computer use leads to a shift in sleeping patterns towards midnight. The participants with later midpoint of sleep hours were found to have a higher incidence of sleep disorders. The prevalence of sleep disorders was significantly impacted by prolonged mobile phone use before bedtime and long hours of computer use. Thus, limiting both the time spent in front of a computer and the use of mobile phones before bedtime is recommended. Int J Occup Med Environ Health. 2024;37(1):34-44.

Routine regularity during a global pandemic: Impact on mental health outcomes and influence of chronotype

Among the public health recommendations for supporting mental health during the COVID-19 pandemic, many strategies had an impact on biological rhythms, like sleep hygiene, physical exercise and healthy eating habits. Considering the known relationship between circadian organization and mental health, our aim was to test the association between behavioral regularity and mental health, and its interaction with chronotype, in a large sample surveyed in Brazil. We collected longitudinal data using online questionnaires that assessed sociodemographic characteristics, behavioral routines, mental health (PHQ-9, GAD-7, WHO-5 scales), and chronotype estimation based on midpoint of sleep on free days - MSF (μMCTQ), in a sample of 1390 participants (81% females). We computed a Routine Regularity Score (RRS) that reflects regularity across four behaviors: sleep, eating, working, exercising. There was a strong negative association between RRS and the severity of anxiety and depressive symptoms (GAD-7 and PHQ-9 scores), which was weaker among participants with late MSF, and a strong positive association with well-being (WHO-5 scores). RRS was a mediator of the MSF-mental health association and a predictor of mental health states. This study provides empirical evidence that maintaining behavioral routines during times of hardship may serve as tools to alleviate the negative impact on mental health.

Relationship between Traumatic Experiences, Circadian Preference and ADHD Symptoms in Adolescents with ADHD Residing in Institutional Care: A Controlled Study

Circadian preference, describes biological and behavioural characteristics that influence the ability to plan daily activities according to optimal waking times. It is divided into three main categories: morning, evening and intermediate. In particular, the evening chronotype is associated with conditions such as Attention Deficit Hyperactivity Disorder (ADHD) and Post Traumatic Stress Disorder (PTSD). This study was conducted in three groups aged 14-18 years: The first group consisted of 34 adolescents diagnosed with ADHD who had been in institutional care for at least two years and had not used medication in the last six months. The second group included 29 adolescents with ADHD living with their families who had not used medication in the last six months. The third control group consisted of 32 healthy adolescents. The study utilized sociodemographic data forms, the Turgay DSM-IV Disruptive Behavior Disorders Rating Scale (T-DSM-IV-S) to measure ADHD symptoms, the Childhood Chronotype Questionnaire (CCQ), and the Childhood Trauma Questionnaire (CTQ). In institutionalized adolescents with diagnosed ADHD, ADHD and disruptive behavior symptoms were more severe. Increased trauma scores were associated with higher ADHD and disruptive behaviour symptom severity and evening chronotype. In the conducted mediation analysis, evening chronotype was identified as a full mediator in the relationship between trauma symptoms and ADHD symptoms, while it was determined as a partial mediator in the relationship between trauma symptoms and PTSD symptoms. In conclusion, traumatic experiences in institutionalized adolescents with diagnosed ADHD may exacerbate ADHD and disruptive behavior symptoms. Evening chronotype is associated with ADHD and disruptive behavior symptoms, and therefore, the chronotypes of these adolescents should be assessed. Chronotherapeutic interventions may assist in reducing inattention, hyperactivity, and behavioral problems.

Patterns in behavioural sleep variables and social jetlag in elderly people of Western Odisha

In humans, sleep is an essential physiological process for life and survival. The main objective of the current study is to determine the behavioural sleep patterns and social jetlag in elderly adults. The second objective is to define the relationship among subjective sleep quality, mid-sleep timings, social jetlag, and sunlight exposure. We recruited 945 female and 1047 male participants aged ≥ 60 years from 65 rural villages in the Sambalpur district of Odisha, India. The Munich Chrono Type Questionnaire (MCTQ) is a self-reported questionnaire that measures a person's behavioral sleep variables, including social jetlag and chronotype, whereas the Pittsburgh Sleep Quality Index (PSQI) measures the subjective sleep quality of an individual. We employed MCTQ and PSQI to obtain behavioral sleep variables and subjective sleep quality in the recruited subjects. The behavioral sleep variables were compared using a paired t-test on both work and work-free days. In addition, the behavioral sleep variables as a function of gender were compared using an independent Student's t-test. In the current study, most of the elderly individuals reported both midpoint of sleep on workdays (MSW) and midpoint of sleep on work-free days (MSF) between 00:01-03:00. The averages of mid-sleep timings between workdays and work-free days were not statistically significant. Data on MSFsc (midpoint of sleep on work-free days sleep corrected) indicated that most elderly adults (99.6%) are morning type; they go to bed early and wake up early. The elderly participants from the rural population of Sambalpur district in western Odisha had the least social jetlag and exhibited good subjective sleep quality. It would be worthwhile to find out the determinants of these positive features apropos social jetlag and behavioural sleep patterns.

Personality Risk Factors for Vape Use amongst Young Adults and Its Consequences for Sleep and Mental Health

(1) Background: The surge in vape (e-cigarette) use among young adults is concerning, as there is limited knowledge about risk factors and health consequences. This study explores the personality traits linked to vape use, and associations between vaping and chronotype, sleep quality, and mental health, among young adults. (2) Methods: 316 participants, aged 18-25, completed measurements of mindfulness, rumination, self-compassion, anxiety/depression, chronotype, and sleep quality. (3) Results: the vape user group scored significantly lower on mindfulness, higher on rumination, and lower on self-compassion. Vape users were more likely to be evening types and had significantly lower sleep quality and higher anxiety symptoms, as well as higher alcohol use and loneliness (at trend) (4) Conclusions: These novel findings enhance our understanding of what might predispose young adults to vaping and the potential impact on their mental health and sleep quality. Findings point to specific cognitive/personality traits as vaping risk factors, which could inform intervention strategies.

Chronotype and Affective Response to Sleep Restriction and Subsequent Sleep Deprivation

Prior research indicates that sleep restriction, sleep deprivation, and circadian misalignment diminish positive affect, whereas effects on negative affect are inconsistent. One potential factor that may influence an individual's affective response to sleep restriction, sleep deprivation, and circadian misalignment is chronotype. Later chronotypes generally report higher negative affect and lower positive affect under typical sleep conditions; however, there is mixed evidence for an influence of chronotype on affective responses to sleep restriction and sleep deprivation. The present study examined the effect of chronotype on positive and negative affect during sleep restriction and subsequent total sleep deprivation. Sixteen healthy adults (Mage = 28.2 years, SDage = 11.6 years) were classified as earlier or later chronotypes using multiple chronotype definitions: morningness-eveningness (MEQ), mid-sleep on free days corrected (MSFsc), habitual mid-sleep timing, dim light melatonin onset (DLMO), and phase relationship between DLMO and bedtime. Participants completed a 10-day protocol with one night of sleep restriction and subsequent 28 h total sleep deprivation. Affect was assessed hourly during scheduled wakefulness with the Positive and Negative Affect Schedule (PANAS). Data were analyzed with mixed-model analyses of variance (ANOVAs). During sleep restriction and subsequent sleep deprivation, positive affect decreased and negative affect increased. Across all chronotype measures, relatively later chronotypes demonstrated vulnerability to increased negative affect during sleep loss. The influence of chronotype on positive affect during sleep loss varied by chronotype measure. These findings suggest later chronotypes are more vulnerable to affective impairments during sleep loss and circadian misalignment, even when late chronotype is not extreme.

Comparison of actigraphy-measured and parent-reported sleep in association with weight status among preschool children

This study compared weekday and weekend actigraphy-measured and parent-reported sleep in relation to weight status among preschool-aged children. Participants were 3-6 years old preschoolers from the cross-sectional DAGIS-study with sleep data for ≥2 weekday and ≥2 weekend nights. Parents-reported sleep onset and wake-up times were gathered alongside 24 h hip-worn actigraphy. An unsupervised Hidden-Markov Model algorithm provided actigraphy-measured night time sleep without the guidance of reported sleep times. Waist-to-height ratio and age-and-sex-specific body mass index characterised weight status. Comparison of methods were assessed with consistency in quintile divisions and Spearman correlations. Associations between sleep and weight status were assessed with adjusted regression models. Participants included 638 children (49% girls) with a mean ± SD age of 4.76 ± 0.89. On weekdays, 98%-99% of actigraphy-measured and parent-reported sleep estimates were classified in the same or adjacent quintile and were strongly correlated (rs  = 0.79-0.85, p < 0.001). On weekends, 84%-98% of actigraphy-measured and parent-reported sleep estimates were respectively classified and correlations were moderate to strong (rs  = 0.62-0.86, p < 0.001). Compared with actigraphy-measured sleep, parent-reported sleep had consistently earlier onset, later wake-up, and greater duration. Earlier actigraphy-measured weekday sleep onset and midpoint were associated with a higher body mass index (respective β-estimates: -0.63, p < 0.01 and -0.75, p < 0.01) and waist-to-height ratio (-0.004, p = 0.03 and -0.01, p = 0.02). Though the sleep estimation methods were consistent and correlated, actigraphy measures should be favoured as they are more objective and sensitive to identifying associations between sleep timing and weight status compared with parent reports.

Associations of social jetlag with physical activity and sedentary behaviour in children and adolescents: A systematic review and meta-analysis

Sleep and daytime movement behaviours occur co-dependently with each other within a finite 24 h day. Sleep parameters other than sleep duration, such as social jetlag and chronotype, have been linked to health problems and unhealthy behaviours among children and adolescents. Given the increasing number of studies examining sleep timing/chronotype and weight-related behaviours, including physical activity and sedentary behaviour, in the past decade, this systematic review and meta-analysis collated and evaluated the evidence on the relationships of social jetlag and chronotype with physical activity and sedentary behaviour among children and adolescents aged 3-17 years. Seven databases were searched on 16 March 2022, and 52 studies were identified as eligible for inclusion, 47 of which were suitable for the meta-analysis. A positive association was found between social jetlag and screen media use (r = 0.14, 95% CI: 0.04-0.24; I2  = 96%; p = 0.008). The morning chronotype was associated with a higher level of physical activity and a lower level of sedentary behaviour than the evening chronotype. No relationship was found between social jetlag and physical activity. The magnitude of heterogeneity among the included studies was high. Further experimental studies are urgently required to understand how circadian preference or misalignment affects activity behaviours. Interventions to promote an active lifestyle in young populations should consider their circadian preference, especially among individuals with the evening chronotype.

Hemodialysis-induced chronodisruption and chronotype distribution in patients with chronic kidney disease

Changes in circadian rhythms have been observed in patients with chronic kidney disease (CKD), and evidence suggests that these changes can have a negative impact on health. This study aimed to investigate the existence of hemodialysis-induced chronodisruption, the chronotype distribution, and their association with sleep quality and quality of life (QoL). This was a cross-sectional study that enrolled 165 patients (mean age: 51.1 ± 12.5 y, 60.6% male) undergoing hemodialysis from three local units. The following instruments were used: the Morning-Eveningness Questionnaire (MEQ); a modified version of the Munich Chronotype Questionnaire (MCQT) to estimate hemodialysis-induced chronodisruption (HIC); the Kidney Disease QoL Short Form (KDQOL-SF); the Epworth Sleepiness Scale (ESS); the Pittsburgh Sleep Quality Index (PSQI) and the 10-Cognitive Screener (10-CS). HIC was present in 40.6% of CKD patients. Morning chronotype was prevalent in CKD patients (69%) compared to evening-type (17.1%) and significantly different from a paired sample from the general population (p < 0.001). HIC and chronotype were associated with different domains of QoL but not with sleep quality. This study suggests that there is a HIC and that morning chronotype is associated with CKD patients undergoing hemodialysis, with implications for QoL.

Neuropsychiatric disorders, chronotype and sleep: A narrative review of GWAS findings and the application of Mendelian randomization to investigate causal relationships

Genome-wide association studies (GWAS) have been important for characterizing the genetic component and enhancing our understanding of the biological aetiology of both neuropsychiatric disorders and sleep-related phenotypes such as chronotype, which is our preference for morning or evening time. Mendelian randomization (MR) is a post-GWAS analysis that is used to infer causal relationships between potential risk factors and outcomes. MR uses genetic variants as instrumental variants for exposures to study the effect on outcomes. This review details the main results from GWAS of neuropsychiatric disorders and sleep-related phenotypes, and the application of MR to investigate their bidirectional relationship. The main results from MR studies of neuropsychiatric disorders and sleep-related phenotypes are summarized. These MR studies have identified 37 causal relationships between neuropsychiatric disorders and sleep-related phenotypes. MR studies identified evidence of a causal role for five neuropsychiatric disorders and symptoms (attention deficit hyperactivity disorder, bipolar disorder, depressive symptoms, major depressive disorder and schizophrenia) on sleep-related phenotypes and evidence of a causal role for five sleep-related phenotypes (daytime napping, insomnia, morning person, long sleep duration and sleep duration) on risk for neuropsychiatric disorders. These MR results show a bidirectional relationship between neuropsychiatric disorders and sleep-related phenotypes and identify potential risk factors for follow-up studies.

Shift work and evening chronotype are associated with hepatic fat fraction and non-alcoholic fatty liver disease in 282,303 UK biobank participants

Background and aims

Non-alcoholic fatty liver disease (NAFLD) has rapidly become the most common liver disease worldwide. Modern lifestyles have been linked to this rise in prevalence with changes in rhythmic human behaviour emerging as a possible mechanism. We investigated how shift working patterns and chronotype were associated with hepatic fat fraction and NAFLD in 282,303 UK Biobank participants.

Methods

We stratified participants into day, irregular-shift, and permanent night-shift workers. We then utilised multiple methods of disease identification including (i) Dallas steatosis index (DSI), (ii) ICD10 codes, and (iii) hepatic proton density fat fraction (PDFF) and examined how shift work exposure impacted these variables. We further assessed the relationship of baseline chronotype with liver phenotypes using these same outcome measures.

Results

Compared to day workers, irregular-shift workers were more likely to have a high DSI (OR 1.29 (1.2-1.4)) after adjusting for major covariates with some attenuation after additional adjustment for BMI (OR 1.12 (1.03-1.22)). Likelihood of high DSI was also increased in permanent night-shift workers (OR 1.08 (0.9-1.29)) in the fully adjusted model. Mediator analysis revealed that BMI was a significant mediator of the shift work effect. Compared to participants with intermediate chronotype, those with extreme late chronotype had a higher likelihood of high DSI defined NAFLD (OR 1.45 (1.34-1.56)) and a higher likelihood of NAFLD/NASH by ICD10 code (OR 1.23 (1.09-1.39)). Hepatic PDFF was elevated in irregular shift workers, but not permanent night-shift workers.

Conclusions

Irregular-shift work and extreme late chronotype are associated with pathological liver fat accumulation, suggesting circadian misalignment may have an underlying pathogenic role. These findings have implications for health interventions to mitigate the detrimental effect of shift work.

Circadian rhythm in sportspersons and athletic performance: A mini review

Circadian rhythms in the physiological and behavioral processes of humans play a crucial role in the quality of living and also in the magnitude of success and failure in various endeavors including competitive sports. The rhythmic activities of the body and performance in sportspersons do have a massive impact on their every cutthroat competition. It is essential to schedule sports activities and training of players according to their circadian typology and time of peak performance for improved performance and achievement. In this review, the focus is on circadian rhythms and diurnal variations in peak athletic performance in sportspersons. Accuracy and temporal variability in peak performance in an individual could be attributed to various factors, namely chronotype, time of the day, body temperature, jetlag, hormones, and prior light exposure. Circadian rhythm of mood, alertness, T-core, and ultimately athletic performance is not only affected by sleep but also by circadian variations in hormones, such as cortisol, testosterone, and melatonin. There are, however, a few reports that are not consistent with the conclusions drawn in this review. Nevertheless, circadian rhythm and performance among sportspersons and athletes are important areas of research. This review might be useful to the managers and policymakers associated with competitive sports and athletic events.

ADHD, chronotype, and circadian preference in a multi-site sample of college students

Attention-deficit/hyperactivity disorder and an evening chronotype are both common among college students, and there is growing interest in understanding the possible link between attention-deficit/hyperactivity disorder and circadian function. However, mixed findings have been reported, and many of the existing studies have used small samples that were unable to examine chronotype across attention-deficit/hyperactivity disorder presentations. Participants were 4751 students (73% female; 80% White), aged 18-29 years (M = 19.28, SD = 1.50), from five universities who completed measures assessing attention-deficit/hyperactivity disorder, depressive and anxiety symptoms, as well as the Morningness-Eveningness Questionnaire to assess chronotype (categorical) and circadian preference (dimensional). Participants with either attention-deficit/hyperactivity disorder predominantly inattentive presentation or attention-deficit/hyperactivity disorder combined presentation had higher rates of being an evening type (47.2% and 41.5%, respectively) than participants without elevated attention-deficit/hyperactivity disorder (28.5%), and participants with attention-deficit/hyperactivity disorder predominantly inattentive presentation also had higher rates of being an evening type than participants with attention-deficit/hyperactivity disorder predominantly hyperactive-impulsive presentation (30.7%). Dimensional analyses indicated that attention-deficit/hyperactivity disorder inattentive symptoms were more strongly associated than hyperactive-impulsive symptoms with eveningness preference. Finally, greater eveningness preference strengthened the association between attention-deficit/hyperactivity disorder inattention and depressive symptoms but not anxiety symptoms. This is the largest study to document that college students with elevated attention-deficit/hyperactivity disorder symptoms are more likely to be evening types than other college students, and inattentive symptoms in particular are associated with later circadian preference.

Pressure Pain Sensitivity and Chronotype: A Population-based Study of Middle-aged Finns

Evening chronotype individuals experience pain more often than morning chronotypes, but relationships with pain sensitivity have rarely been studied. We examined whether chronotype is associated with pressure pain sensitivity, with special reference to mental health disorders, insomnia, and chronic musculoskeletal (MSK) pain as potential moderating factors. The study sample consisted of members of the Northern Finland Birth Cohort 1966 aged 46. Pressure pain threshold and tolerance were measured via the standardized protocol, categorized as lowest quartile versus others. Chronotype (morning [M; the reference], intermediate [I], and evening [E]) was defined using the Short Morningness-Eveningness questionnaire. Sex-stratified binary logistic regression models were separately adjusted for education, body mass index, long-term diseases (fully adjusted model), and for mental health disorders, insomnia, and chronic MSK pain (a residual confounding analysis). Interaction terms (Chronotype × Mental health/insomnia/chronic MSK pain) were tested. The study had 2,132 males and 2,830 females. The E-type males had 1.5-fold odds of having a low pain threshold (fully adjusted odds ratio [OR] 1.45, 95% confidence interval 1.05-2.00) and pressure pain tolerance (fully adjusted OR 1.47, 1.07-2.02), in comparison to M-types. Having a mental health disorder intensified the association with low pain threshold fourfold (4.06, 1.56-10.6). Being an E-type female was also associated with a low pain threshold, but the association was statistically nonsignificant (fully adjusted OR 1.18, .90-1.53). No statistically significant interactions were found among females. These results emphasize the role of chronotype in pain sensitivity and add an understanding of pain experience in light of innate circadian types. PERSPECTIVE: Male evening chronotypes are more sensitive to pain than morning chronotypes. Diagnosed mental health disorders in particular indicate a low pain threshold for evening chronotype males.

Disruption of circadian rhythms promotes alcohol use: a systematic review

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

Circadian Rhythms, Chrononutrition, Physical Training, and Redox Homeostasis-Molecular Mechanisms in Human Health

A multitude of physiological processes, human behavioral patterns, and social interactions are intricately governed by the complex interplay between external circumstances and endogenous circadian rhythms. This multidimensional regulatory framework is susceptible to disruptions, and in contemporary society, there is a prevalent occurrence of misalignments between the circadian system and environmental cues, a phenomenon frequently associated with adverse health consequences. The onset of most prevalent current chronic diseases is intimately connected with alterations in human lifestyle practices under various facets, including the following: reduced physical activity, the exposure to artificial light, also acknowledged as light pollution, sedentary behavior coupled with consuming energy-dense nutriments, irregular eating frameworks, disruptions in sleep patterns (inadequate quality and duration), engagement in shift work, and the phenomenon known as social jetlag. The rapid evolution of contemporary life and domestic routines has significantly outpaced the rate of genetic adaptation. Consequently, the underlying circadian rhythms are exposed to multiple shifts, thereby elevating the susceptibility to disease predisposition. This comprehensive review endeavors to synthesize existing empirical evidence that substantiates the conceptual integration of the circadian clock, biochemical molecular homeostasis, oxidative stress, and the stimuli imparted by physical exercise, sleep, and nutrition.

The association between chronotype profile and temporomandibular disorders among college students

BACKGROUND

Temporomandibular joint disorders (TMDs) are common in young adults, and the link between chronotype profile and TMDs is unclear.

OBJECTIVE

This study examined TMD prevalence and chronotype distribution and explored the relationship between chronotype and TMDs in young adults.

MATERIALS AND METHODS

A total of 663 students from Sichuan University completed questionnaires. Chronotype profiles were assessed using the Morningness-Eveningness Questionnaire, and TMDs were screened using the Fonseca Memory Index. To validate the findings, 68 TMD patients and 136 controls were enrolled.

RESULTS

The prevalence of TMDs was 69.7%, with significant differences among chronotype profiles. The intermediate profile was the most common chronotype. Eveningness profile was associated with higher TMDs prevalence and severity. Muscle pain and side movement difficulty scores were higher in eveningness and intermediate profiles. Female gender (OR 2.345; 95% CI 1.668-3.297) was a TMD risk factor, while morningness profile (OR 0.537; 95% CI 0.297-0.970) was protective. Validation with TMD patients and controls supported these findings, showing higher eveningness profile prevalence in the TMD groups.

CONCLUSIONS

TMDs have a high prevalence in college students, chronotype profiles shown to be associated with TMDs. Morningness is the protection factor in TMDs and PT, eveningness is a risk factor for IT.

Circadian epidemiology: Structuring circadian causes of disease and practical implications

That disruptions of the body's internal clockwork can lead to negative health consequences, including cancer, is a plausible hypothesis. Yet, despite strong mechanistic and animal support, the International Agency for Research on Cancer (IARC) experts considered epidemiological evidence as limited regarding the carcinogenicity of "shift-work involving circadian disruption" (2007) and "night shift work" (2019). We use directed acyclic graphs (DAGs) to outline a concept of circadian causes that discloses challenges when choosing appropriate exposure variables. On this basis, we propose to move beyond shift-work alone as a direct cause of disease. Instead, quantifying chronodisruption as individual doses can lead to interpretable circadian epidemiology. The hypothesis is that doses of chronodisruption cause disrupted circadian organisation by leading to desynchronization of circadian rhythms. Chronodisruption can be conceptualized as the split physiological nexus of internal and external times. Biological (or internal) night - an individual's intrinsically favoured sleep time window - could be the backbone of circadian epidemiology. In practice, individual doses that cause disrupted circadian organisation are derived from the intersection of time intervals of being awake and an individual's biological night. After numerous studies counted work shifts, chronobiology may now advance circadian epidemiology with more specific dose estimation - albeit with greater challenges in measurement (time-dependent individual data) and analysis (time-dependent confounding).

Effects of aerobic exercise on ambulatory blood pressure responses to acute partial sleep deprivation: impact of chronotype and sleep quality

Blood pressure (BP) follows a circadian rhythm intertwined with the sleep-wake cycle. Acute partial sleep deprivation (PSD; sleep ≤ 6 h) can increase BP, associated with increased cardiovascular risk. Acute exercise can reduce BP for up to 24 h, a phenomenon termed postexercise hypotension. The present study tested whether aerobic exercise could mitigate the augmented 24-h ambulatory BP caused by acute PSD. Twenty-four young otherwise healthy adults (22 ± 3 yr; 14 females; self-reported chronotypes: 6 early/10 intermediate/8 late; Pittsburgh sleep quality index: 17 good/7 poor sleepers) completed a randomized crossover trial in which, on different days, they slept normally (2300-0700), restricted sleep [0330-0700 (PSD)], and cycled for 50 min (70-80% predicted heart rate maximum) before PSD. Ambulatory BP was assessed every 30 min until 2100 the next day. Acute PSD increased 24-h systolic BP (control 117 ± 9 mmHg, PSD 122 ± 9 mmHg; P < 0.001) and prior exercise attenuated (exercise + PSD 120 ± 9 mmHg; P = 0.04 vs. PSD) but did not fully reverse this response (exercise + PSD, P = 0.02 vs. control). Subgroup analysis revealed that the 24-h systolic BP reduction following exercise was specific to late types (PSD 119 ± 7 vs. exercise + PSD 116 ± 6 mmHg; P < 0.05). Overall, habitual sleep quality was negatively correlated with the change in daytime systolic BP following PSD (r = -0.56, P < 0.01). These findings suggest that the ability of aerobic cycling exercise to counteract the hemodynamic effects of acute PSD in young adults may be dependent on chronotype and that habitual sleep quality can predict the daytime BP response to acute PSD.NEW & NOTEWORTHY We demonstrate that cycling exercise attenuates, but does not fully reverse, the augmented 24-h ambulatory blood pressure (BP) response caused by acute partial sleep deprivation (PSD). This response was primarily observed in late chronotypes. Furthermore, daytime BP after acute PSD is related to habitual sleep quality, with better sleepers being more prone to BP elevations. This suggests that habitual sleeping habits can influence BP responses to acute PSD and their interactions with prior cycling exercise.

Associations between cardiorespiratory fitness and lifestyle-related factors with DNA methylation-based ageing clocks in older men: WASEDA'S Health Study

DNA methylation-based age estimators (DNAm ageing clocks) are currently one of the most promising biomarkers for predicting biological age. However, the relationships between cardiorespiratory fitness (CRF), measured directly by expiratory gas analysis, and DNAm ageing clocks are largely unknown. We investigated the relationships between CRF and the age-adjusted value from the residuals of the regression of DNAm ageing clock to chronological age (DNAmAgeAcceleration: DNAmAgeAccel) and attempted to determine the relative contribution of CRF to DNAmAgeAccel in the presence of other lifestyle factors. DNA samples from 144 Japanese men aged 65-72 years were used to appraise first- (i.e., DNAmHorvath and DNAmHannum) and second- (i.e., DNAmPhenoAge, DNAmGrimAge, and DNAmFitAge) generation DNAm ageing clocks. Various surveys and measurements were conducted, including physical fitness, body composition, blood biochemical parameters, nutrient intake, smoking, alcohol consumption, disease status, sleep status, and chronotype. Both oxygen uptake at ventilatory threshold (VO2 /kg at VT) and peak oxygen uptake (VO2 /kg at Peak) showed a significant negative correlation with GrimAgeAccel, even after adjustments for chronological age and smoking and drinking status. Notably, VO2 /kg at VT and VO2 /kg at Peak above the reference value were also associated with delayed GrimAgeAccel. Multiple regression analysis showed that calf circumference, serum triglyceride, carbohydrate intake, and smoking status, rather than CRF, contributed more to GrimAgeAccel and FitAgeAccel. In conclusion, although the contribution of CRF to GrimAgeAccel and FitAgeAccel is relatively low compared to lifestyle-related factors such as smoking, the results suggest that the maintenance of CRF is associated with delayed biological ageing in older men.

Stability of social jetlag and sleep timing into the second year of the Covid-19 pandemic: Results from a longitudinal study of a nationally representative adult sample in Ireland

The early phase of the COVID-19 pandemic has previously been associated with marked changes in sleep/wake timing arising from the imposition of society-wide infection mitigation measures. Such observations are considered of broader significance as they reveal the social pressures that sleep timing normally operates under. In order to assess how persistent such changes were as the COVID-19 pandemic developed, we assessed sleep timing and quality in a longitudinal study of a nationally-representative sample of Irish adults with data collected at two time-points (December 2021 and March 2021). Data on social jetlag and chronotype was derived from the micro Munich Chronotype Questionnaire from 830 and 843 participants who provided data in December 2020 and March 2021 respectively, of which 338 contributed data to both timepoints. Demographics and measures of insomnia symptoms, anxiety, depression and loneliness were also collected, and data was analysed both within-subjects and cross-sectionally within data waves. Social jetlag (the mismatch between sleep timing on "work" and "free" days) and other measures of sleep timing were stable across the two time-points, although insomnia symptoms improved slightly from December 2020 to March 2021. The mean social jetlag at both timepoints was ~ 30 minutes, considerably lesser than reported pre-pandemic levels in similar populations. Multiple regression analysis of cross-sectional data reveals that the timing of midsleep on "free" days was only a weak-to-moderate predictor of social jetlag, whilst hours worked per week was the strongest predictor of social jetlag. Requirement for "face-to-face" contact with the public at work and urban location of residence also emerged as predictors of social jetlag, although insomnia, anxiety and depression symptoms and loneliness rating did not. We conclude that sleep timing changes that occurred during the initial phase of the COVID-19 pandemic persisted into the second year of the pandemic, and these results further illustrate the key roles working practices and other social factors have in shaping social jetlag.

Relationship between mid-sleep time and depression, health-related quality of life, and sleep deprivation in the 2018 Korea Community Health Survey

This cross-sectional study examined the relationship of mid-sleep time (MST) with depression, quality of life, and sleep deprivation. This study included 173 284 adults aged ≥ 19 years who participated in the 2018 Korea Community Health Survey. The Patient Health Questionnaire-9 for depression, EuroQol-5 dimension for health-related quality of life, and the Pittsburgh Sleep Quality Index for MST, daytime sleepiness, and sleep quality were used. Regression and logistic regression analysis was used for complex sample analysis. The results showed that individuals with later MST had a higher risk of depression, poor quality of life, poor sleep quality, and excessive daytime sleepiness than intermediate-type individuals, whereas earlier MST was associated with good sleep quality in the total population. This association was significant in both men and women. The later type was associated with all items of health-related quality of life in both men and women. These findings suggest that the later type is a significant predictor of mental health, quality of life, sleep quality, and daytime sleepiness. Identifying an individual's mid-sleep time may help tailor interventions and treatment strategies that optimize sleep, mental health outcomes, and quality of life.

Evening Chronotype and Suicide: Exploring Neuroinflammation and Psychopathological Dimensions as Possible Bridging Factors-A Narrative Review

A chronotype is generally defined as the variability of the phase angle of entrainment, while the latter reflects the relationship between the timing of a certain rhythm (e.g., the sleep-wake cycle) and the timing of an external temporal cue. Individuals can be placed on a spectrum from "morning types" (M types) to "evening types" (E types). E-chronotype has been proposed as a transdiagnostic risk factor for psychiatric conditions, and it has been associated with psychopathological dimensions. Eveningness seems to be correlated with both suicidal ideation (SI) and suicidal behavior (SB) through several possible mediating factors. Immunological alterations have also been linked to later chronotypes and SI/SB. This narrative review aims to summarize the evidence supporting the possible association between chronotypes and suicide and the eventual mediating role of neuroinflammation and several psychopathological dimensions. A search of the literature (2003-2023) was conducted using various databases: PUBMED, EMBASE, Scopus, UpToDate, PsycINFO, and Cochrane Library. English-language articles were collected and screened for eligibility. Despite the apparent absence of a direct correlation between E-chronotype and suicidality, E-chronotype promotes a chain of effects that could be involved in an increased risk of SB, in which with neuroinflammation possibly plays an intriguing role and some psychopathological dimensions may stand out.

Behavioural Parameters of Circadian Rhythm Are Not Correlated with Dim Light Melatonin Onset: An Observational Study on Healthy Volunteers

Dim light melatonin onset (DLMO) is considered the most reliable marker of the circadian rhythm phase in humans. DLMO may moderately correlate with sleep onset and sleep offset time. There are no sufficient data about the correlations between DLMO and clinical scales assessing sleep quality and daytime symptoms of poor night sleep. The aim of the study was to determine the association between DLMO and basic sleep parameters from actigraphy and sleep diaries, as well as the association between DLMO and the following insomnia clinical scales: the Athens Insomnia Scale (AIS), Insomnia Severity Index (ISI), Epworth Sleepiness Scale (ESS), and chronotype questionnaires: Morningness-Eveningness Questionnaire (MEQ) and Composite Scale of Morningness (CSM). Participants of the study were healthy volunteers. Sleep parameters were measured by sleep diaries and actigraphy, and the following clinical scales: the AIS, ISI, and ESS, and chronotype questionnaires: MEQ and CSM. DLMO was calculated based on plasma melatonin concentration. The blood samples were collected hourly at five time points between 20:00 and 00:00 during the session in dim red light (<50 lux). Melatonin concertation was determined by LC-MS/MS. Twenty-one volunteers participated in the study. DLMO was calculated in 12 participants. There was a significant correlation between DLMO and ISI (r = 0.60, p = 0.038) and ESS (r = 0.61, p = 0.034). The correlation coefficient between the DLMO and the AIS was also high, however insignificant (r = 0.57, p = 0.054). There were no significant correlations between DLMO and chronotype scales MEQ and CSM. DLMO did not correlate with sleep onset and sleep offset; however, DLMO correlated with the Sleep Fragmentation Index (SFI) (r = 0.67, p = 0.017). DLMO is associated with poorer sleep maintenance, a stronger feeling of insomnia, and sleepiness during the day. Simultaneously, chronotype pattern and circadian rhythm parameters do not correlate with DLMO. Biological circadian rhythm does not reflect the real-life sleep-wake rhythm, indicating that the lifestyle is more often disconnected from the biological clock.

Functional Connectivity Between Default Mode and Ventral Attention Networks Mediates the Effects of Chronotype on Daily Physical Activity

Daily physical activity (dPA) is closely related to circadian rhythm and chronotype. The functional connectivity (FC) within or between the default mode (DMN) and ventral attention network (vAN) were associated with dPA and chronotype. DMN-vAN FC was investigated for its role in chronotype and dPA. 153 participants completed the reduced version of the Morningness-Eveningness Questionnaire (rMEQ), dPA was measured via actigraphy (5-day), and then resting-state fMRI scans were performed. rMEQ scores and steps recorded by the actigraphic devices (with each hour as the time window to calculate steps for five consecutive days per hour, subsequently yielding the maximum number of steps and its corresponding time, ie, SM and SMT) represent chronotype and dPA respectively. The results found that the rMEQ scores were significantly negatively correlated with SMT. The positive correlation between the rMEQ scores and the DMN-vAN FC was significant. There were also significant positive correlations between SMT and DMN-vAN FC. Further analysis revealed that DMN-vAN mediates the relationship between chronotype and SMT. The FC of DMN-vAN may be the underlying neural mechanism through which chronotype influences dPA. These findings could support the development of reasonable activity schedules or specific intervention programs to improve physical health.

Evaluation of chronotype and sleep quality in infertile population and comparison with fertile population: a cross-sectional study

PURPOSE

Infertility is a stressful condition for couples and can affect patients' circadian rhythm and sleep quality. The goal of this study is to assess differences in chronotype and sleep quality between infertile and fertile people.

METHODS

A cross-sectional study was conducted. The infertile patient population consisted study group. Primiparous patients without any known gynecological disease who presented for routine cervical cancer screening follow-up were included in the control group. The Turkish version of the Morningness-Eveningness Questionnaire (MEQ) and Pittsburg Sleep Quality Index (PSQI) scores were evaluated between groups.

RESULTS

A total of 227 patients were assessed. There were 110 patients in the study (infertile) group and 117 patients in the control (fertile) group. The evening chronotype proportion (23.6 vs. 0.9%, p < 0.001) was higher in the infertile group. The median of MEQ score was significantly higher in the fertile patients (50, IQR = 43 - 55 vs. 56, IQR = 51 - 59; p < 0.001), and the median of PSQI score was significantly higher in the infertile patients (5, IQR = 4 - 6, vs. 4, IQR = 3 - 5; p < 0.001).

CONCLUSIONS

In this study, we found significantly worse sleep quality, and more evening chronotype in the patients with infertility.

To Sleep Dreaming Medals: Sleep Characteristics, Napping Behavior, and Sleep-Hygiene Strategies in Elite Track-and-Field Athletes Facing the Olympic Games of Tokyo 2021

PURPOSE

Few data are available on sleep characteristics of elite track-and-field athletes. Our study aimed to assess (1) differences in sleep between sexes and among different track-and-field disciplines, (2) the effect of individualized sleep-hygiene strategies on athletes' sleep parameters, and (3) daytime nap characteristics in track-and-field athletes.

METHODS

Sleep characteristics of 16 elite Olympic-level track-and-field athletes (male: n = 8; female: n = 8) were assessed during the preseason period, at baseline (T0), and during the in-season period, after the adoption of individualized sleep-hygiene strategies (T1). Sleep parameters were objectively monitored by actigraphy for a minimum of 10 days, for each athlete, at both T0 and T1. A total of 702 nights were analyzed (T0 = 425; T1 = 277).

RESULTS

Female athletes displayed better sleep efficiency (88.69 [87.69-89.68] vs 91.72 [90.99-92.45]; P = .003, effect size [ES]: 0.44), lower sleep latency (18.99 [15.97-22.00] vs 6.99 [5.65-8.32]; P < .001, ES: 0.65), higher total sleep time (07:03 [06:56-07:11] vs 07:18 [07:10-07:26]; P = .030, ES: 0.26), earlier bedtime (00:24 [00:16-00:32] vs 00:13 [00:04-00:22]; P = .027, ES: 0.18), and lower nap frequency (P < .001) than male athletes. Long-distance runners had earlier bedtime (00:10 [00:03-00:38] vs 00:36 [00:26-00:46]; P < .001, ES: 0.41) and wake-up time (07:41 [07:36-07:46] vs 08:18 [08:07-08:30]; P < .001, ES: 0.61), higher nap frequency, but lower sleep efficiency (88.79 [87.80-89.77] vs 91.67 [90.95-92.38]; P = .013, ES: 0.44), and longer sleep latency (18.89 [15.94-21.84] vs 6.69 [5.33-8.06]; P < .001, ES: 0.67) than athletes of short-term disciplines. Furthermore, sleep-hygiene strategies had a positive impact on athletes' total sleep time (429.2 [423.5-434.8] vs 451.4 [444.2-458.6]; P < .001, ES: 0.37) and sleep latency (14.33 [12.34-16.32] vs 10.67 [8.66-12.68]; P = .017, ES: 0.19).

CONCLUSIONS

Sleep quality and quantity were suboptimal at baseline in Olympic-level track-and-field athletes. Large differences were observed in sleep characteristics between sexes and among different track-and-field disciplines. Given the positive effect of individualized sleep-hygiene strategies on athlete's sleep, coaches should implement sleep education sessions in the daily routine of top-level athletes.

Archaic Introgression Shaped Human Circadian Traits

When the ancestors of modern Eurasians migrated out of Africa and interbred with Eurasian archaic hominins, namely, Neanderthals and Denisovans, DNA of archaic ancestry integrated into the genomes of anatomically modern humans. This process potentially accelerated adaptation to Eurasian environmental factors, including reduced ultraviolet radiation and increased variation in seasonal dynamics. However, whether these groups differed substantially in circadian biology and whether archaic introgression adaptively contributed to human chronotypes remain unknown. Here, we traced the evolution of chronotype based on genomes from archaic hominins and present-day humans. First, we inferred differences in circadian gene sequences, splicing, and regulation between archaic hominins and modern humans. We identified 28 circadian genes containing variants with potential to alter splicing in archaics (e.g., CLOCK, PER2, RORB, and RORC) and 16 circadian genes likely divergently regulated between present-day humans and archaic hominins, including RORA. These differences suggest the potential for introgression to modify circadian gene expression. Testing this hypothesis, we found that introgressed variants are enriched among expression quantitative trait loci for circadian genes. Supporting the functional relevance of these regulatory effects, we found that many introgressed alleles have associations with chronotype. Strikingly, the strongest introgressed effects on chronotype increase morningness, consistent with adaptations to high latitude in other species. Finally, we identified several circadian loci with evidence of adaptive introgression or latitudinal clines in allele frequency. These findings identify differences in circadian gene regulation between modern humans and archaic hominins and support the contribution of introgression via coordinated effects on variation in human chronotype.

Impact of Sleep Duration, Quality, and Chronotype on Learning and Academic Performance: A Cross-Sectional Study Among First Year Medical Students of a Tertiary Care Institute

Introduction The link between sleep and cognitive processes, such as memory and learning, continues to be one of the most intriguing and perplexing theories. Undergraduate medical students in their first year are particularly vulnerable to sleep disturbances. Academic achievement and learning have been linked to sleep patterns, which include not only the quantity and quality of sleep but also the timing of sleep in relation to the natural sleep onsets, or chronotypes. There have been conflicting reports on the outcomes of sleep and relatively fewer researches focused on the impact of chronotypes on learning and academic achievement among medical students. The current study thus sought to determine the chronotypes of medical students, evaluate the quantity and quality of sleep, and determine the impact of these factors on learning and academic performance. Methods The study was conducted in the Department of Physiology, All India Institute of Medical Sciences (AIIMS) Gorakhpur, India. Sleep health was assessed in 167 first-year medical students using the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), morningness-eveningness questionnaire (MEQ), and sleep log books. Learning and memory assessment was performed using Raven's progressive matrices test. Grade point average (GPA) was used to assess their academic performance. The relationship of sleep scores with GPA and RPM scores were obtained by linear regression analysis. One-way analysis of variance (ANOVA) and unpaired t-test were used to investigate other comparisons among categories of chronotypes and those of mean GPA. A p-value of <0.05 was considered as significant. Results The mean GPA and RPM scores obtained in the groups with PSQI ≥ 5 (2.67 ± 1.1, 49.51 ± 6.24, respectively) and PSQI < 5 (3.15 ± 0.59, 54.73 ± 4.01, respectively) and those in the group with ESS ≥ 10 (2.72 ± 1.17, 50.97 ± 5.92, respectively) and ESS < 10 (3.15 ± 0.6, 54.18 ± 3.91, respectively) varied with statistically significant differences (p < 0.05). Statistically significant R-squared values for the relationship of PSQI and ESS scores with RPM and GPA scores were obtained. No correlation between academic grades and chronotype was found. Poor GPA scores were found to be associated with reduced mean sleep duration for one week before the exams. Conclusion Learning and academic performance are negatively impacted by poor sleep quality and daytime sleep dysfunction. No definite evidence for the association of sleep chronotypes with the learning and memory could be attained. Higher test performance is more closely linked to the average sleep length over a duration of time preceding the exams.

The effect of sleep disorders, school jet lag, and anxiety in students 8-10 years of age on traumatic dental injuries

BACKGROUND/AIM

Traumatic dental injuries (TDI) constitute a public health problem. The aim of the present study was to investigate whether sleep disorders, school jet lag, and anxiety are associated with TDI in schoolchildren 8-10 years of age.

METHODS

An analytical, cross-sectional study was conducted with 739 pairs of parents/guardians and children enrolled in public and private schools. The parents/guardians answered a socioeconomic questionnaire, the Sleep Disturbance Scale for Children, Circadian Energy Scale, and Revised Children's Manifest Anxiety Scale. Four examiners underwent calibration exercises for the diagnosis of TDI (K > 0.80) using the criteria proposed by Andreasen (2007). A directed acyclic graph was used for the formulation of the theoretical model and statistical adjustments. Unadjusted and adjusted robust binary logistic regression analyses were performed (α = 5%).

RESULTS

The prevalence of TDI was 16.2%. The following variables remained associated with the outcome in the final model: family income less than or equal to the minimum monthly wage (OR = 1.77; 95% CI: 1.09-2.88; p = .02), child's height >137.6 cm (OR = 1.68; 95% CI: 1.06-2.64; p = .02), the occurrence of school jet lag (OR = 2.12; 95% CI: 1.27-3.53; p = .004), anxiety (OR = 1.77; 95% CI: 1.04-3.00; p = .04) and sleep disorders (OR = 1.63; 95% CI: 1.38-1.93; p = .05).

CONCLUSION

Children from families with a lower income, taller children, those with school jet lag, those with anxiety and those with sleep disorders had a greater occurrence of TDI.

Why do owls have it worse? Mediating role of self-perceptions in the links between diurnal preference and features of mental health

Recent research provides evidence for the negative social perceptions of evening chronotypes and their consequences on mental health. However, there is a lack of studies indicating whether these negative, socially shared beliefs may become internalized in negative self-perceptions of evening-types (E-types). The present article provides a seminal empirical analysis of the role of self-liking and self-competence in the associations between chronotype and both depressiveness and well-being. In the first part of the study, the participants completed the Composite Scale of Morningness. On the basis of the chronotype cut-off criteria for Composite Scale of Morningness distribution, 100 individuals were classified as morning-types (M-types) and 66 individuals as E-types. Therefore, 166 participants (80 women and 86 men) aged 18-36 years (M ± SD: 29.27 ± 4.81 years) took part in the second part of the study, and completed questionnaires measuring self-liking, self-competence, life satisfaction, positive and negative affect, and depressiveness. Results show that E-types scored lower in self-liking, self-competence and subjective well-being, and higher in depressive symptoms than M-types. Controlling for age and gender, we obtained significant mediation effects, showing that the relationship between chronotype and subjective well-being might stem from the lower levels of self-liking and self-competence among E-types, and that the relationship between chronotype and depressive symptoms might stem from the lower level of self-liking among E-types. Our results suggest that self-liking and self-competence are important antecedents of lower well-being and higher depressiveness reported by E-types. Socially shared stereotypes of M-types and E-types can be internalized by the extreme chronotypes, which may significantly affect their psychological health.

Investigating Chronotype and Sleep Quality in Psoriatic Patients: Results from an Observational, Web-Based Survey

BACKGROUND

Psoriasis is an inflammatory disease for which the implications and repercussions go far beyond the skin. Psoriasis patients suffer not only due to its skin manifestations and related symptoms but also because of comorbidities and a huge emotional impact.

OBJECTIVE

The objective of this study was to investigate chronotype and sleep quality in a group of Italian psoriatic patients.

MATERIALS AND METHODS

An observational, cross-sectional, web-based study was set up by the Dermatology and Clinical Medicine Sections of the Department of Medical Sciences, University of Ferrara, Italy. The web questionnaire was sent to an email list of an Italian association of psoriatic patients with the aim of recording their main demographic, social, historical, and clinical data. The survey included two questionnaires: the Morningness-Eveningness Questionnaire (MEQ) and the Pittsburg Sleep Quality Index (PSQI).

RESULTS

Two hundred and forty-three psoriatic patients (mean age 52.9 ± 12.8 yrs., 32.5% males and 67.5% females) filled out the questionnaire. A good 63.8% of them were affected with psoriasis for more than 10 years, 25.9% reported having a diffuse psoriasis, and 66.7% were on treatment at the time they completed the questionnaire. With reference to chronotype, the mean MEQ score was 55.2 ± 10.7; furthermore, 44% of the patients were "morning-oriented types", M-types, or "larks", 44.5% were "intermediate-types" or I-types, and 11.5% were "evening-oriented types", E-types, or "owls". No correlations were found between chronotype and psoriasis extension. Based on the PSQI results, 72.8% of the study population was judged to have a low sleep quality. Sleep disturbance was significantly related to female sex, living alone, and the presence of comorbidities.

CONCLUSIONS

Sleep disturbance is very common in psoriatic patients, especially in those with comorbidities, in females, and in patients who live alone. The chronotype in psoriatic patients does not appear different when compared to the general population, nor does it seem to have any link with psoriasis severity.

Blame it on the "night owls": Perceived discrimination partly mediates the effects of morningness-eveningness on positive and negative affect

The well-established effects of evening preference on diminished well-being and poorer mental health are usually explained in terms of common genetic bases of eveningness and negative emotionality and/or the discrepancy between biological and social clocks, experienced far more frequently by the Evening-types. However, recent studies provide evidence for the negative stereotyping of evening chronotypes which may lead to unexpectedly pronounced social stigma and its consequences. The present article provides a seminal empirical analysis of the role of perceived chronotype-related discrimination in the association between morningness-eveningness and both positive affect and negative affect. The study was conducted on a gender-balanced sample of 768 individuals aged between 18 and 56 years who filled measures of morningness-eveningness, positive and negative affect, as well as a modified version of the Perceived Devaluation Discrimination scale, tentatively labeled Perceived Chronotype-Related Discrimination scale (https://osf.io/urs8x/), developed to measure the sense of chronotype-based discrimination. Conducted analyses provided evidence for a positive association between eveningness and perceived discrimination. Moreover, perceived discrimination partly mediated the associations between morningness-eveningness and both positive affect and negative affect, explaining 18% and 29% of these effects, respectively. Hence, our results provide initial evidence for yet another mechanism through which chronotype may impact emotional functioning, namely the experience of chronotype-based stigmatisation.

Is evening chronotype associated with higher alcohol consumption? A systematic review and meta-analysis

A broader understanding of whether and to what extent chronotype should be considered a risk factor for alcohol consumption is needed. The aim of this systematic review was to summarize the evidence on the association between evening chronotype and alcohol consumption. A systematic search of observational studies on this association was conducted in the PubMed, Scopus, Web of Science, Cochrane Library and PsycINFO databases up to April 30th, 2023. Random-effect models estimated the pooled odds ratio (OR) of alcohol consumption according to chronotype. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and Quality Assessment tool for Observational Cohorts and Cross-sectional Studies from the National Heart, Lung and Blood Institute were followed. A total of 33 studies involving 28 207 individuals (age range: 18-93 years) were included in this review. Overall, most studies indicated a higher volume and frequency of alcohol consumption in evening-type individuals than in individuals with different chronotypes. Additionally, a meta-analysis including 13 studies showed that evening-type individuals were 41% more likely to consume alcohol than those with other chronotypes (OR = 1.41, 95% confidence interval: 1.16-1.66; I2 = 38.0%). Limitations of the present findings are the predominance of cross-sectional studies and varied definitions of alcohol consumption. The available evidence supports an association between the evening chronotype and alcohol consumption. The evening-type population, especially young adults, is a specific target for educational interventions for preventing or reducing alcohol consumption.PROSPERO number: CRD42022343778.

Evaluation of social jetlag and chronotypes in Indian school-going adolescents

Background

School-going students' school time acts as a zeitgeber during the weekdays, and in the weekends, due to the absence of the zeitgeber, they show free run and wake up late in the morning. This may result in poor health hazards in adolescents.

Objective

The aim of this study was to assess the prevalence of social jetlag along with the distribution of their chronotype in school-going adolescents.

Materials and Methods

This is a cross-sectional study conducted between May and June 2019 with the help of the MCTQ (Munich Chronotype Questionnaire) and MEQ (Morningness and Eveningness Questionnaire) in the adolescent population (N = 1154).

Statistical Analysis

The study was performed using the Mann-Whitney U test to compare continuous variables of sleep parameters between workdays and free days. The significance was taken at P < 0.05.

Results

The results showed that out of the total population, 81% were morning type and 67% of adolescents were socially jetlagged. There was a significant delay in the time to bed on free days by 1.88 hours and a significant delay in the wake-up time by 2.46 hours. The total sleep duration was also significantly higher on free days by 1.88 hours in the population.

Conclusion

This is our first study in the Indian population to show that morning-type individuals showed irregular sleep timings and were more socially jetlagged. This needs to be focused on by the school authorities and government to keep a flexible school timing for the students on the basis of their chronotype for their better academic performance.

For Whom (and When) the Time Bell Tolls: Chronotypes and the Synchrony Effect

Circadian rhythms are powerful timekeepers that drive physiological and intellectual functioning throughout the day. These rhythms vary across individuals, with morning chronotypes rising and peaking early in the day and evening chronotypes showing a later rise in arousal, with peaks in the afternoon or evening. Chronotype also varies with age from childhood to adolescence to old age. As a result of these differences, the time of day at which people are best at attending, learning, solving analytical problems, making complex decisions, and even behaving ethically varies. Across studies of attention and memory and a range of allied areas, including academic achievement, judgment and decision-making, and neuropsychological assessment, optimal outcomes are found when performance times align with peaks in circadian arousal, a finding known as the synchrony effect. The benefits of performing in synchrony with one's chronotype (and the costs of not doing so) are most robust for individuals with strong morning or evening chronotypes and for tasks that require effortful, analytical processing or the suppression of distracting information. Failure to take the synchrony effect into consideration may be a factor in issues ranging from replication difficulties to school timing to assessing intellectual disabilities and apparent cognitive decline in aging.

Sleeping Difficulties, Sleep Duration, and Risk of Hypertension in Women

BACKGROUND

Rates of poor sleep and hypertension are alarming worldwide. In this study, we investigate the association between sleeping difficulties and sleep duration with hypertension risk in women.

METHODS

Sixty-six thousand one hundred twenty-two participants of the Nurses' Health Study 2, who were free of hypertension at baseline (2001), were followed prospectively for 16 years and incident hypertension assessed every 2 years. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for hypertension incidence associated with sleeping difficulties and sleep duration.

RESULTS

During follow-up, we documented 25 987 incident cases of hypertension. After controlling for demographic and lifestyle risk factors, compared with women who slept 7 to 8 hours, women with shorter sleep duration had a significantly higher risk of hypertension (≤5 hours: HR, 1.10 [95% CI, 1.05-1.16]; 6 hours: HR, 1.07 [95% CI, 1.03-1.10]), whereas the risk for women with longer sleep duration was not statistically significant (9 hours: HR, 1.03 [95% CI, 0.97-1.10]; >9 hours: HR, 1.08 [95% CI, 0.94-1.23]). Compared with women rarely having difficulty falling or staying asleep, women sometimes or usually having these sleep difficulties had significantly higher risk of developing hypertension (HR, 1.14 [95% CI, 1.11-1.17] and 1.28 [95% CI, 1.22-1.35]; Ptrend<0.001). Early morning awakening was not associated with hypertension risk (Ptrend=0.722). There was no effect modification by night work or chronotype.

CONCLUSIONS

Difficulty falling or staying asleep and short sleep duration were associated with higher risk of hypertension among women in our study. Screening for poor sleep could be useful in identifying people at higher risk for hypertension.

Sex Differences in the Relationship between Chronotype and Eating Behaviour: A Focus on Binge Eating and Food Addiction

BACKGROUND

Men are more likely than women to have subthreshold overeating disorders. Lifestyle plays a role as a determinant, while chronotype is an emerging factor. Chronotype explains the natural preferences of wakefulness and activity throughout the day: evening chronotypes (E-Types), those most productive in the evening, have been linked with unhealthy dietary patterns and a higher propensity to substance addiction than morning types (M-Types).

METHODS

We carried out a cross-sectional study on 750 overweight or obese adults (70% females, 48 ± 10 years, BMI 31.7 ± 5.8 kg/m2). The Binge-Eating Scale, the Yale Food Addiction Scale 2.0 (YFAS 2.0), the reduced Morningness-Eveningness Questionnaire (rMEQ), and the MEDAS questionnaire were used to assess binge eating, food addiction, chronotype, and adherence to the Mediterranean diet, respectively.

RESULTS

No differences in BES binge-eating and FA food-addiction scores occurred between chronotypes, but we found significant interactions between sex × rMEQ score. While women showed the same prevalence for binge eating and food addiction across all chronotypes, binge eating and food addiction risk increased with reducing rMEQ score in men, indicating that being male and E-Type increases the risk association of binge eating and/or food addiction prevalence.

CONCLUSIONS

chronotype is associated with binge eating and food addiction in men, emphasizing the link between chronobiology and sex differences as determinants in appetite and eating behaviour dysregulation and in overweight and obesity.

Chronotype-Dependent Sleep Loss Is Associated with a Lower Amplitude in Circadian Rhythm and a Higher Fragmentation of REM Sleep in Young Healthy Adults

In modern society, the time and duration of sleep on workdays are primarily determined by external factors, e.g., the alarm clock. This can lead to a misalignment of the intrinsically determined sleep timing, which is dependent on the individual chronotype, resulting in reduced sleep quality. Although this is highly relevant given the high incidence of sleep disorders, little is known about the effect of this misalignment on sleep architecture. Using Fitbit trackers and questionnaire surveys, our study aims to elucidate sleep timing, sleep architecture, and subjective sleep quality in young healthy adults (n = 59) under real-life conditions (average of 82.4 ± 9.7 days). Correlations between variables were calculated to identify the direction of relationships. On workdays, the midpoint of sleep was earlier, the sleep duration was shorter, and tiredness upon waking was higher than on free days. A higher discrepancy between sleep duration on workdays and free days was associated with a lower stability of the circadian rhythm of REM sleep and also with a higher fragmentation of REM sleep. Similarly, a higher tiredness upon waking on free days, thus under intrinsically determined sleep timing conditions, was associated with a lower proportion and a higher fragmentation of REM sleep. This suggests that the misalignment between extrinsically and intrinsically determined sleep timing affects the architecture of sleep stages, particularly REM sleep, which is closely connected to sleep quality.

Rise and shine for eating right: the link between healthy nutrition and chronotype among young adults

Aim

Many studies have examined the relationship between chronotype and general health. Because healthy eating is the basis of health aim of this study is to evaluate the relationship between healthy nutrition attitudes and chronotype in young adults. Methods: This cross-sectional study was conducted with 1,400 young adults (936 females and 464 males). Chronotype was assessed by the Turkish version of the Morningness-Eveningness Questionnaire (MEQ) and the Attitude Scale for Healthy Nutrition (ASHN) was applied by face-to-face interview. Furthermore, 24-h dietary recall was collected. The scores of nutrient adequacy ratio (NAR) and mean adequacy ratio (MAR) were calculated. The anthropometric measurements including body weight and height were taken.

Results

The chronotype distribution of participants according to the MEQ score and MAR score were not significantly different between females and males (p > 0.05). The percentage of participants with high healthy eating attitude was lowest in the evening chronotype and highest in the morning chronotype (49.7, 37.7 and 25.4% in morning-, intermediate-, evening-types, respectively; p = 0.000 for all groups according to the reciprocal comparisons). There was a positive correlation of the MEQ scores with the scores of ASHN (r = 0.282, p < 0.01). ASHN score was shown to be a predictor for MEQ score (β = 0.280, p = 0.000). Moreover, the score of "poor eating habits" was shown to be highest in the evening chronotype and lowest in the morning chronotype (14.9 ± 3.0 and 13.1 ± 3.0, respectively; p < 0.01).

Conclusion

The results of this study indicate that individuals with the evening chronotype are more deficient in terms of healthy nutrition attitudes. Further studies with larger populations will potentially guide the development of health promotion strategies to prevent and treat chronic diseases based on an individual's chronotype.

Nocturnal selective pressures on the evolution of human musicality as a missing piece of the adaptationist puzzle

Human musicality exhibits the necessary hallmarks for biological adaptations. Evolutionary explanations focus on recurrent adaptive problems that human musicality possibly solved in ancestral environments, such as mate selection and competition, social bonding/cohesion and social grooming, perceptual and motor skill development, conflict reduction, safe time-passing, transgenerational communication, mood regulation and synchronization, and credible signaling of coalition and territorial/predator defense. Although not mutually exclusive, these different hypotheses are still not conceptually integrated nor clearly derived from independent principles. I propose The Nocturnal Evolution of Human Musicality and Performativity Theory in which the night-time is the missing piece of the adaptationist puzzle of human musicality and performing arts. The expansion of nocturnal activities throughout human evolution, which is tied to tree-to-ground sleep transition and habitual use of fire, might help (i) explain the evolution of musicality from independent principles, (ii) explain various seemingly unrelated music features and functions, and (iii) integrate many ancestral adaptive values proposed. The expansion into the nocturnal niche posed recurrent ancestral adaptive challenges/opportunities: lack of luminosity, regrouping to cook before sleep, imminent dangerousness, low temperatures, peak tiredness, and concealment of identity. These crucial night-time features might have selected evening-oriented individuals who were prone to acoustic communication, more alert and imaginative, gregarious, risk-taking and novelty-seeking, prone to anxiety modulation, hedonistic, promiscuous, and disinhibited. Those night-time selected dispositions may have converged and enhanced protomusicality into human musicality by facilitating it to assume many survival- and reproduction-enhancing roles (social cohesion and coordination, signaling of coalitions, territorial defense, antipredatorial defense, knowledge transference, safe passage of time, children lullabies, and sexual selection) that are correspondent to the co-occurring night-time adaptive challenges/opportunities. The nocturnal dynamic may help explain musical features (sound, loudness, repetitiveness, call and response, song, elaboration/virtuosity, and duetting/chorusing). Across vertebrates, acoustic communication mostly occurs in nocturnal species. The eveningness chronotype is common among musicians and composers. Adolescents, who are the most evening-oriented humans, enjoy more music. Contemporary tribal nocturnal activities around the campfire involve eating, singing/dancing, storytelling, and rituals. I discuss the nocturnal integration of musicality's many roles and conclude that musicality is probably a multifunctional mental adaptation that evolved along with the night-time adaptive landscape.

Better alignment between circadian preference and sleep and work timings during COVID-19 did not benefit work engagement at home

Modern society is structured around early routines which cause evening types to suffer from health and performance detriments associated with sleep times being misaligned with biological needs (circadian preference). Given that COVID-19 lockdowns were less constrained by social schedules, the current study explores whether temporal behaviours became better aligned with biological needs, and whether these changes benefited work engagement. 406 UK participants reported circadian preference and pre-lockdown and lockdown sleep times, work times, and work engagement. Results found that sleep health improved under lockdown measures in terms of increased sleep duration and reduced social jetlag, and sleep and work times became better aligned with circadian preferences. The most circadian-misaligned participants - students and young adults - exhibited the largest changes to sleep and work habits. However, work engagement decreased more in participants with improved social jetlag and delayed work habits, which is surprising given that these temporal changes reflect improved circadian alignment. We discuss potential moderators including poor sleep quality, non-engaging work-from-home environments, and mental health. These findings have implications for encouraging flexible educational and employment schedules post-COVID-19 to satisfy the common drive to improve circadian alignment, but future work must determine the moderating factors that impair work engagement during remote work.

Chronotype and time-of-day effects on spatial working memory in preschool children

STUDY OBJECTIVES

Spatial working memory (SWM) capacity subserves complex cognitive functions, yet it is unclear whether individual diurnal preferences and time-of-day influence SWM in preschool children. The main and interaction effects of chronotype and time-of-day on SWM and SWM differences in preschoolers with different chronotypes within each time-of-day group will be examined.

METHODS

We studied a subset of typically developing 4.5-year-olds taking part in a birth cohort study (n = 359). The Children's Chronotype Questionnaire categorized children into morning-, intermediate-, and evening-types. Using a computerized neuropsychological test (Cambridge Neuropsychological Test Automated Battery), SWM was determined from the total number of between-search errors (ie, between search-total errors) and Strategy scores. Higher between search-total errors or lower Strategy scores indicated worse SWM. Time-of-day was categorized into late morning (10:00 am to 11:59 am), afternoon (12:00 pm to 3:59 pm), and late afternoon (4:00 pm to 6:30 pm). In a subsample (n = 199), caregiver-reported chronotype was validated using actigraphy-measured sleep midpoint.

RESULTS

After controlling for ethnicity, no significant main and interaction effects of chronotype and time-of-day on between search-total errors and Strategy scores were seen (all P > .05). However, evening-types outperformed morning-types (ie, lower mean between search-total errors) in the late afternoon (P = .013) but not in the late morning and afternoon (all P > .05). Actigraphy data in the subsample confirmed that evening-types had later sleep midpoints during weekdays and weekends (P < .001).

CONCLUSIONS

Since evening-type preschoolers had better SWM in the late afternoon compared to morning-type preschoolers, this gives insights into optimal learning opportunities in early childhood education.

CITATION

Abdul Jafar NK, Tham EKH, Eng DZH, et al. Chronotype and time-of-day effects on spatial working memory in preschool children. J Clin Sleep Med. 2023;19(10):1717-1726.

Impact of chronotype, insomnia symptoms, sleep duration, and electronic devices on nonrestorative sleep and daytime sleepiness among Japanese adolescents

OBJECTIVES

Nonrestorative sleep (NRS) and excessive daytime sleepiness (EDS) are important indicators of daytime dysfunction. Electronic media use before bedtime greatly affects adolescent sleep quality. However, few studies have examined factors associated with these symptoms. Therefore, we aimed to investigate the impact of chronotype, electronic device use before bedtime, and insomnia symptoms on NRS and EDS in Japanese adolescents.

METHODS

A web-based cross-sectional survey of 2067 adolescents was conducted in 2022 to mainly assess sleep-related issues (sleep duration, chronotype, insomnia symptoms, NRS, and EDS), time spent using electronic devices, physical activity, and mental health.

RESULTS

We analyzed data of 1880 adolescents (age, 16.4 ± 0.8 years; males, 56.7%). NRS and EDS prevalence rates were 54.9% and 39.4%, respectively. In multivariate analysis, evening chronotype [odds ratio (OR): 2.14, 95% confidence interval (CI): 1.58-2.89], difficulty initiating sleep (OR: 1.94, 95% CI: 1.43-2.64), <5 h sleep (OR: 1.77, 95% CI: 1.24-2.54), 5-6 h sleep (OR: 1.52, 95% CI: 1.20-1.93), and using electronic devices just before bedtime (OR: 1.48, 95% CI: 1.08-2.04) were associated with NRS. Evening chronotype (OR: 1.40, 95% CI: 1.07-1.82), early morning awakening (OR: 1.60, 95% CI: 1.02-2.50), using electronic devices just before bedtime (OR: 2.08, 95% CI: 1.48-2.93), and using electronic devices 30 min before bedtime (OR: 1.57, 95% CI: 1.07-2.29) were associated with EDS.

CONCLUSION

Chronotype may be an important factor influencing NRS and EDS. Discontinuing electronic device use at least 30 min before bedtime could benefit affected adolescents.