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.

Irregular breakfast eating in type 2 diabetes mellitus is associated with greater social jetlag and poorer metabolic health.

Circadian disruption, arising from conflict between internal circadian time and behavioural sleep-wake and fasting-feeding rhythms, may contribute to the prevalence of type 2 diabetes mellitus and disease severity. Previous studies have demonstrated a link between irregular breakfast eating and poorer metabolic health. We aimed to further explore the relationships between breakfast habits, circadian misalignment (social jetlag), and metabolic parameters in a cohort of adult participants with type 2 diabetes mellitus. A total of 330 adult participants with type 2 diabetes mellitus attending for routine clinical review completed structured questionnaires to assess habitual sleep timing, chronotype, and social jetlag. Statistical analysis was via inferential groupwise approaches and path analysis to establish interdependencies of effects of social jetlag, chronotype, and breakfast eating regularity on HbA1c. 22.7% of the participants reported eating breakfast five times or fewer a week, and were categorised as irregular breakfast eaters. Compared with those who ate breakfast six or seven times a week, irregular breakfast eaters had significantly higher HbA1c and diastolic blood pressure, were younger and had greater social jetlag. In the path analysis, irregular breakfast eating exerted a direct effect on HbA1c, whilst social jetlag exerted only an indirect effect on HbA1c through breakfast eating regularity. Chronotype did not exert any effect on HbA1c, but did exert an indirect effect on breakfast eating regularity via social jetlag. Our results showed that adult participants with type 2 diabetes mellitus, who ate breakfast irregularly had poorer metabolic health and greater social jetlag. The relationship between social jetlag and glycaemic control appears to be mediated through breakfast eating habits.

Pressure Building Against the Clock: The Impact of Circadian Misalignment on Blood Pressure.

PURPOSE OF REVIEW: Misalignment between the endogenous biological timing system and behavioral activities (i.e., sleep/wake, eating, activity) contributes to adverse cardiovascular health. In this review, we discuss the effects of recurring circadian misalignment on blood pressure regulation and the implications for hypertension development. Additionally, we highlight emerging therapeutic approaches designed to mitigate the negative cardiovascular consequences elicited by circadian disruption. RECENT FINDINGS: Circadian misalignment elicited by work schedules that require individuals to be awake during the biological night (i.e., shift work) alters 24-h blood pressure rhythms. Mechanistically, circadian misalignment appears to alter blood pressure via changes in autonomic nervous system balance, variations to sodium retention, dysregulation of endothelial vasodilatory responsiveness, and activation of proinflammatory mechanisms. Recurring circadian misalignment produced by a mismatch in sleep timing on free days vs. work days (i.e., social jetlag) appears to have no direct effects on prevailing blood pressure levels in healthy adults; though, circadian disruptions resulting from social jetlag may increase the risk of hypertension through enhanced sympathetic activation and/or obesity. Furthermore, social jetlag assessment may be a useful metric in shift work populations where the magnitude of circadian misalignment may be greater than in the general population. Circadian misalignment promotes unfavorable changes to 24-h blood pressure rhythms, most notably in shift working populations. While light therapy, melatonin supplementation, and the timing of drug administration may improve cardiovascular outcomes, interventions designed to target the effects of circadian misalignment on blood pressure regulation are warranted.

Early morning sport scheduling is associated with poorer subjective sleep characteristics in British student-athletes.

This study presents the sleep characteristics of British student-athletes and examines the relationships between sport scheduling and time demands on sleep outcomes. Student-athletes (n = 157, 51% male) completed the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), and the Sleep Hygiene Index (SHI). Self-reported sleep characteristics on weekdays and weekends, weekly frequencies of early morning and late evening sport sessions, and academic-related and sport-related time demands were also collected. Questionnaires revealed a high prevalence of undesired sleep characteristics including poor sleep quality (global PSQI >5 in 49.0%) and low sleep durations on weekdays (25% reporting <7 h). Paired t-tests revealed significant differences in bedtime, waketime, sleep duration, and sleep onset latency between weekdays and weekends (all p < 0.01). Hierarchical regression analyses indicated that early morning sport frequency was a significant predictor of PSQI (ß = 0.30) and SHI (ß = 0.24) global scores, weekday waketimes (ß = -0.17), and weekday sleep durations (ß = -0.25; all p < 0.05) in models adjusted for participant characteristics. Late evening sport frequency, and academic-related and sport-related time demands, were not significant predictors of any sleep outcome. Adjusting sport scheduling to avoid early start times could provide a means to improve sleep outcomes and may improve sporting performance and academic attainment.

Circadian misalignment proxies, BMI, and chronic conditions: the role for weekday to weekend sleep differences.

OBJECTIVE: To evaluate whether social jet lag (SJL) and weekend catch-up sleep (CUS), proxies of circadian misalignment, were associated with BMI and chronic conditions. METHODS: Participants (n = 2,050,18-65y) were part of a virtual cross-sectional and population-based research. We examined CUS and SJL as continuous and categorical (< 1 h,1-2 h, > 2 h). Linear regression analyses were performed to assess the differences in BMI (outcome) associated with CUS and SJL. Restricted cubic splines were performed to explore the shape of the relationship between weekday-to-weekend variability in sleep duration, midpoint, wake time, and bedtime. Logistic regression models were used to estimate ORs(95%CIs) for chronic conditions and overweight related to CUS and SJL. Analyses were adjusted for sleep duration, biological and behavior-related variables. RESULTS: We found a positive association of SJL and CUS with BMI. The effects remained even after adjustment for weekly sleep duration and demonstrated a proportional increase with the magnitude of sleep variability. Among participants with SJL > 2 h, BMI increased by 2.29 kg/m2 (95%CI:0.84;3.74,p:0.002). They also had 129% higher odds of chronic conditions (95%CI:1.16;4.52, p:0.01) and 119% higher odds of overweight (95%CI: 1.20;3.98,p:0.01). Individuals with CUS > 2 h presented 78% higher odds of overweight (95%CI:1.27;2.50,p:0.001) and an increase of 1.61 kg/m2 in BMI (95%CI: 0.81; 2.40,p < 0.001). CONCLUSIONS: Our findings, which demonstrate that even a slight weekend sleep extension and variability of just 1 h is associated with higher values of BMI, suggest incorporating measures for sleep consistency and regularity into clinical protocols and public health guidelines to prevent and treat obesity and related diseases.

Mismatch of Biological and Social Time in Cocaine-Addicted Men.

INTRODUCTION: Chronotype describes a person's preferential activity pattern during a 24-hour period, which may not be in line with their social lifestyle. A mismatch between biological and social time is known as "social jetlag," which has negative effects on wellbeing. Cocaine influences a person's activity levels, but very little is known about possible changes in chronotype of patients with cocaine use disorder (CUD). Here, we aimed to shed light on self-reported changes in chronotype in patients with CUD and the clinical implications. METHODS: A total of 90 men from the local community were recruited; about half of the sample met the criteria for CUD, while the other half were healthy without a personal history of substance use disorder. Participants completed the Munich Chronotype Questionnaire along with questionnaires about mental health, daily fatigue, and drug/alcohol use. RESULTS: Half of the CUD patients fell into the category of late chronotype - a significantly larger proportion than their healthy peers. Late "night owls" tended to have started using cocaine at an earlier age than other chronotypes; a finding that was not observed with tobacco, cannabis, or alcohol. Drug use severity in CUD patients did not differ across chronotypes. CUD patients (52%) did not have a preferred time of day to use cocaine. The mismatch between social and biological time was significantly greater in CUD patients and unrelated to drug use or mental health status. CONCLUSION: CUD appears to be associated with disruptions in chronotype which are, contrary to a widely held view, not reflected by using patterns or addiction severity.

[Overview of chronobiological and sleep medical aspects of depression in adolescents]. / Überblick zu chronobiologischen und schlafmedizinischen Aspekten bei Depressionen im Jugendalter.

Changes in sleep are reported in adolescents with depression with a frequency of up to 71%. Aspects of chronobiology and sleep based on the current scientific literature are illustrated and summarized in this narrative review. The circadian clock synchronizes organisms to the light-dark structure of the environment. The individual synchronization is called "chronotype." Chronotype changes according to age, among other factors, and adolescents experience the latest chronotypes overall. The potential discrepancy between internal and external time is called "social jetlag." Social jetlag is especially pronounced during adolescence. It is associated with numerous health risks, such as depression. Changes in sleep behavior in affective disorders and its comorbidity to depression have also been well described in the literature. In this article, underlying concepts from chronobiology and sleep medicine are initially summarized. Then, health risks of disrupted sleep-wake behavior are described, and connections to depression specifically during adolescence are drawn. The article concludes with clinical recommendations for sleep disorders and depression during adolescence as well as suggestions for further research.

The association between social jetlag and parameters of metabolic syndrome and type 2 diabetes: a systematic review and meta-analysis.

This study aims to determine the association between social jetlag and parameters of metabolic syndrome and type 2 diabetes (T2D) in a systematic review and meta-analysis. A systematic literature search was conducted in PubMed/Embase/Scopus until May 2022. Included studies described an association between social jetlag and parameters of the metabolic syndrome and/or T2D, were available full text and written in English or Dutch. Data extraction and quality assessment were performed on pre-piloted forms independently by two reviewers. Results were meta-analysed using random-effects analysis. A total of 6,290 titles/abstracts were screened, 176 papers were read full-text, 68 studies were included. Three studies were rated as low quality, 27 were moderate, and 38 were high quality. High quality studies showed that having social jetlag compared to no social jetlag was significantly associated with higher body mass index in 20 studies (0.49 kg/m2 , 95% confidence interval [CI] 0.21-0.77; I2  = 100%), higher waist circumference in seven studies (1.11 cm, 95% CI 0.42-1.80; I2  = 25%), higher systolic blood pressure in 10 studies (0.37 mmHg, 95% CI 0.00-0.74; I2  = 94%) and higher glycated haemoglobin in 12 studies (0.42%, 95% CI 0.12- 0.72; I2  = 100%). No statistically significant associations were found for obesity, abdominal obesity, high- and low-density lipoprotein levels, cholesterol, triglycerides, diastolic blood pressure, hypertension, fasting glucose, homeostatic model assessment for insulin resistance, metabolic syndrome or T2D. Sensitivity analyses did not reduce heterogeneity. Despite substantial heterogeneity, social jetlag is associated with certain parameters of the metabolic syndrome and T2D, but not with prevalent metabolic syndrome or T2D. These findings should be interpreted with caution as the level of evidence is low and mostly based on cross-sectional data. Longitudinal studies are needed to further assess the direction of causality.

Association of social jetlag and eating patterns with sleep quality and daytime sleepiness in Japanese high school students.

A high prevalence of excessive daytime sleepiness and poor sleep quality has been reported in adolescents, but the effects of social jetlag on sleep quality and daytime sleepiness are unclear. Therefore, we assessed the association of sleep and eating patterns with daytime sleepiness and sleep quality among a total of 756 Japanese high school students. Participants completed the Pittsburgh Sleep Quality Index to evaluate sleep quality, the Pediatric Daytime Sleepiness Scale to evaluate daytime sleepiness, and an 8-day sleep diary. Data on average sleep duration, social jetlag, midsleep on free days sleep corrected, and the differences in the first and last meal timing between school days and non-school days were obtained from participants' sleep diaries. The results reveal that social jetlag is associated with differences in the first meal timing between school days and non-school days, and that social jetlag of more than 2 hr is associated with extremely poor sleep quality and excessive daytime sleepiness in Japanese high school students. Our findings suggest that reducing social jetlag to within a 2-hr window is important to prevent poor sleep quality and excessive daytime sleepiness for this population.

Solar clock and school start time effects on adolescents' chronotype and sleep: A review of a gap in the literature.

Circadian rhythms are entrained by external factors such as sunlight and social cues, but also depend on internal factors such as age. Adolescents exhibit late chronotypes, but worldwide school starts early in the morning leading to unhealthy sleep habits. Several studies reported that adolescents benefit from later school start times. However, the effect of later school start time on different outcomes varies between studies, and most previous literature only takes into consideration the social clock (i.e. local time of school starting time) but not the solar clock (e.g. the distance between school start time and sunrise). Thus, there is an important gap in the literature: when assessing the effect of a school start time on chronotype and sleep of adolescents at different locations and/or seasons, the solar clock might differ and, consistently, the obtained results. For example, the earliest school start time for adolescents has been suggested to be 08:30 hours, but this school start time might correspond to different solar times at different times of the year, longitudes and latitudes. Here, we describe the available literature comparing different school start times, considering important factors such as geographic position, nationality, and the local school start time and its distance to sunrise. Then, we described and contrasted the relative role of both social and solar clocks on the chronotype and sleep of adolescents. As a whole, we point and discuss a gap in literature, suggesting that both clocks are relevant when addressing the effect of school start time on adolescents' chronotype and sleep.

Delayed bedtime on non-school days associates with higher weight and waist circumference in children: Cross-sectional and longitudinal analyses with Mendelian randomisation.

Sleep duration has been linked with obesity in population-based studies. Less is known about bedtimes and, especially, if discrepancy between bedtimes on school and non-school days associate with adiposity in children. The associations of self-reported bedtimes with the body mass index z-score (BMIz) and waist-to-height ratio (WtHr) were examined among children with a mean (SD) age of 11.2 (0.85) years in cross-sectional (n = 10,245) and longitudinal (n = 5085) study settings. The causal relationship of whether BMIz contributes to bedtimes, was further examined in a subset of 1064 participants by exploiting Mendelian randomisation (MR). After adjusting for sleep duration and other confounders, every 0.5 h later bedtime on non-school nights and a delay in bedtime in non-school nights compared with school nights associated with 0.048 (95% CI 0.027; 0.069) and 0.08 (95% CI 0.056; 0.105) higher BMIz as well as 0.001 (95% CI 0; 0.002) and 0.004 (95% CI 0.003; 0.005) with higher WtHr, respectively. Moreover, every 0.5-h delay in bedtime in non-school nights compared with school nights associated with 0.001 (95% CI 0; 0.002) greater increase in WtHr in the 2.5 years follow-up. Thus, a 2-h delay in bedtime at the age of 11 years corresponds with a 0.6 cm increase in waist circumference. The MR analysis did not indicate an opposite causal relationship: higher BMIz was not causing delayed bedtimes. Later bedtime on non-school days and discrepancy in bedtimes associated with increased BMIz and WtHr, while longitudinally these predicted higher WtHr, independently of sleep duration. Promoting early bedtimes, especially on weekends, should be considered in obesity prevention among school-aged children.

Fetal and infant growth patterns, sleep, and 24-h activity rhythms: a population-based prospective cohort study in school-age children.

The study objective was to explore associations of fetal and infant weight patterns and preterm birth with sleep and 24-h activity rhythm parameters at school-age. In our prospective population-based study, 1327 children were followed from birth to age 10-15 years. Fetal weight was estimated using ultrasound in the second and third trimester of pregnancy. Birth weight and gestational age were available from midwife registries. Infant weight was measured at 6, 12 and 24 months. Fetal and infant weight acceleration or deceleration were defined as a change of >0.67 standard deviation between the corresponding age intervals. At school-age, sleep duration, sleep efficiency, wake after sleep onset, social jetlag, inter-daily stability, and intra-daily variability were assessed using tri-axial wrist actigraphy for 9 consecutive nights. We observed that low birth weight (<2500 g) was associated with 0.24 standard deviation (95% confidence interval [CI] 0.04; 0.43) longer sleep duration compared to normal weight. Compared to normal growth, growth deceleration in fetal life and infancy was associated with 0.40 standard deviation (95% CI 0.07; 0.73) longer sleep duration, 0.44 standard deviation (95% CI 0.14; 0.73) higher sleep efficiency, and -0.41 standard deviation (95% CI -0.76; -0.07) shorter wake after sleep onset. A pattern of normal fetal growth followed by infant growth acceleration was associated with -0.40 standard deviation (95% CI -0.61; -0.19) lower inter-daily stability. Preterm birth was not associated with any sleep or 24-h rhythm parameters. Our findings showed that children with fetal and infant growth restriction had longer and more efficient sleep at school-age, which may be indicative of an increased need for sleep for maturational processes and development after a difficult start in life.

Variable Eating Patterns: A Potential Novel Risk Factor for Systemic Inflammation in Women.

BACKGROUND: The timing and regularity of eating patterns could play a role in systemic inflammation, as circadian clocks responsible for daily rhythms of inflammatory signaling are entrained by food intake. PURPOSE: To evaluate associations of intra-weekly and weekday-weekend differences in eating timing patterns with high-sensitivity C-reactive protein (hsCRP). METHODS: A community-based sample of 103 U.S. women from the American Heart Association Go Red for Women Strategically Focused Research Network completed a meal-timing questionnaire and provided a blood sample for measurement of hsCRP. Differences in weekday versus weekend eating start time, eating end time, and nightly fasting duration were calculated as eating jetlag metrics. Intra-weekly variability in eating timing patterns was defined by the standard deviation (SD) of these variables. Multivariable linear regression models were used to evaluate cross-sectional associations of eating timing variability metrics with hsCRP. RESULTS: Each additional 30-min difference in weekday-weekend eating end time was related to 13% higher hsCRP (p = .023). Similarly, every 30-min increase in eating end time SD, reflecting greater variability in timing of last eating occasion, was associated with 29% higher hsCRP. Per 1-hr weekday-weekend difference in nightly fasting duration, there was a 45% elevation in hsCRP (p = .003). Every 30-min increase in nightly fasting duration SD, representing greater variability in span of the daily fasting/eating periods, was associated with 46% higher hsCRP. CONCLUSIONS: Variable eating timing patterns were associated with higher hsCRP. Intervention studies are needed to determine whether stabilizing the timing of eating occasions may represent a novel strategy to reduce chronic inflammation.

The relationship between pain and sleep in pediatric sickle cell disease.

BACKGROUND: Pain and sleep disturbances are prevalent complications experienced by pediatric patients with sickle cell disease (SCD). This study aims to identify associations between pain and sleep, and to characterize sleep chronotype and social jetlag in children and adolescent patients with SCD. METHODS: We performed a cross-sectional survey of 105 pediatric patients with SCD aged 8-17 years using PROMIS (Patient Reported Outcomes Measurement System) pain interference, sleep disturbance, and sleep-related impairment item banks. The µMCTQ (Ultra-short Munich Chronotype Questionnaire) assessed chronotype and social jetlag. Analyses were performed to assess associations between PROMIS measures, sleep patterns, and clinical variables. RESULTS: Female participants reported higher T-scores for sleep-related impairment than males (females: 56.7 ± 10 vs. males 50.2 ± 9.4, p = .0009). Patients with one or more emergency department (ED) visits for pain in the last 12 months reported greater sleep disturbance (55.0 ± 8.5 vs. 50.7 ± 10, p = .046) and sleep-related impairment (57.1 ± 9.3 vs. 52.1 ± 10.2, p = .03) than patients without any ED visits for pain in the last 12 months. Pain interference was significantly associated with both sleep disturbance (r = .49, p < .0001) and sleep-related impairment (r = .46, p < .0001). The average mid-sleep time was 4:14 ± 1:44 a.m. and the average social jetlag (hh:mm) was 2:32 ± 1:35. CONCLUSION: Our study demonstrates that pain interference is associated with both sleep disturbance and sleep-related impairment. PROMIS measures can identify patients that suffer from pain and sleep disturbances and highlights the need to conduct longitudinal prospective studies to define the directionality of pain and sleep in SCD.

Exploring the relationship between social jetlag with gut microbial composition, diet and cardiometabolic health, in the ZOE PREDICT 1 cohort.

PURPOSE: In this study, we explore the relationship between social jetlag (SJL), a parameter of circadian misalignment, and gut microbial composition, diet and cardiometabolic health in the ZOE PREDICT 1 cohort (NCT03479866). METHODS: We assessed demographic, diet, cardiometabolic, stool metagenomics and postprandial metabolic measures (n = 1002). We used self-reported habitual sleep (n = 934) to calculate SJL (difference in mid-sleep time point of ≥ 1.5 h on week versus weekend days). We tested group differences (SJL vs no-SJL) in cardiometabolic markers and diet (ANCOVA) adjusting for sex, age, BMI, ethnicity, and socio-economic status. We performed comparisons of gut microbial composition using machine learning and association analyses on the species level genome bins present in at least 20% of the samples. RESULTS: The SJL group (16%, n = 145) had a greater proportion of males (39% vs 25%), shorter sleepers (average sleep < 7 h; 5% vs 3%), and were younger (38.4 ± 11.3y vs 46.8 ± 11.7y) compared to the no-SJL group. SJL was associated with a higher relative abundance of 9 gut bacteria and lower abundance of 8 gut bacteria (q < 0.2 and absolute Cohen's effect size > 0.2), in part mediated by diet. SJL was associated with unfavourable diet quality (less healthful Plant-based Diet Index), higher intakes of potatoes and sugar-sweetened beverages, and lower intakes of fruits, and nuts, and slightly higher markers of inflammation (GlycA and IL-6) compared with no-SJL (P < 0.05 adjusted for covariates); rendered non-significant after multiple testing adjustments. CONCLUSIONS: Novel associations between SJL and a more disadvantageous gut microbiome in a cohort of predominantly adequate sleepers highlight the potential implications of SJL for health.

Chronobiological changes due to school closures during the COVID-19 pandemic among adolescents in the DOrtmund Nutritional and Anthropometric Longitudinally Designed cohort study.

Due to the lockdown of schools as one of the COVID-19 control measures, adolescents have had the opportunity to re-organise their daily lives; e.g. some of them have adapted their bedtimes to the new situation during the lockdown in favour of their own chronotype. Hence, we investigated differences in chronobiological characteristics (e.g., the midpoint of sleep, sleep duration or social jetlag (SJL); i.e., a discrepancy between biological and social timing) before and during the pandemic lockdown to examine potential changes. We asked participants from the ongoing open cohort Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study to fill out the Munich Chronotype Questionnaire during the COVID-19 lockdown and received the information of participants (n = 66) during the pandemic. A reference group matched for age, season, and sex was randomly selected from the DONALD study to assess participants' chronobiological characteristics prior to (n = 132) the pandemic. Analyses of covariance were applied to examine differences between the two groups reflecting the situation before and during the COVID-19 pandemic. Participants were aged 9-18 years (52% males). In the current examination, average sleep duration across the week was higher among adolescents during the pandemic (ß = 00:30; p = 0.0006) and social jetlag was significantly lower (ß = -00:39; p < 0.0001). CONCLUSION: Our results showed that the COVID-19 lockdown enabled adolescents to adapt their sleeping habits according to their naturally late chronotype, which led to a significant reduction in SJL. These observations are likely to be explained by the effect of school closure. WHAT IS KNOWN: • Under 'normal conditions' without pandemic lockdowns, adolescents accumulate a lack of sleep due to social obligations such as school starts, resulting in social jetlag. • A late chronotype or exposure to social jetlag is a known risk factor for the development of chronic diseases. WHAT IS NEW: • The COVID-19 lockdown represents a 'natural experiment' that enables adolescents to adhere to their internal biological clock. Without the usual social obligations, social jetlag can be significantly reduced.

Influence of the practice of sports, sleep disorders, and habits on probable sleep bruxism in children with mixed dentition.

OBJECTIVE: Investigate the association between sleep disorders and probable sleep bruxism (SB) in children eight to ten years of age. METHODS: A cross-sectional study was conducted with 739 schoolchildren in Brazil. Parents/guardians answered a sociodemographic questionnaire, the sleep disturbance scale for children, and the Circadian Energy Scale. Parafunctional habits were evaluated using the Nordic Orofacial Test-Screening. Multivariate logistic regression was performed (α = 5%), and a directed acyclic graph was used in the statistical model. RESULTS: The prevalence of probable SB was 9.1% and 58.6% of the children had sleep disorders. In the final model, having unmarried parents/guardians (OR = 1.98; 95% CI: 1.07-3.65), exhibiting parafunctional habits (OR = 2.02; CI: 1.01-4.06), not practicing sports (OR = 1.92; CI: 1.04-3.54), sleep-wake transition disorders (SWTD) (OR = 2.01; 95%CI: 1.12-3.62), and excessive daytime sleepiness (EDS) (OR = 2.17; 95%CI: 1.11-4.29) were significant associated with probable SB. CONCLUSION: The occurrence of probable sleep bruxism was influenced by the marital status of the parents/guardians, parafunctional habits, the non-practice of sports, and sleep disturbance (SWTD and EDS). This research contributes to the planning of public policies that include educational regimens at school to prevent sleep disorders and favor the reduction in sleep bruxism prevalence.

The association between social jetlag and depression is independent of sleep debt.

OBJECTIVES: To investigate whether the association between SJLsc (sleep-corrected social jetlag) and depressive mood is significant and independent of sleep debt. METHODS: Participants from the general adult population were interviewed using structured questionnaires on sleep duration, weekday/weekend sleep schedules, and depressive mood (Patient Health Questionnaire-9). Social jetlag (SJL) was measured by SJLsc and standard SJL (SJLs). SJLs was the absolute difference between mid-sleep time on free days (MSF) and workdays (MSW). For SJLsc, both MSF and MSW were adjusted for average sleep duration across the week according to the direction of sleep debt. Sleep debt was defined by sleep extension on free days. The association of SJL with depression was investigated, and covariates included age, sex, sociodemographic factors, insomnia symptoms, sleep duration, and sleep debt. RESULTS: A total of 1982 individuals (1089 men; age 43.1 ± 14.4 years) were analyzed. SJL was present in 24.6% measured by SJLsc and 51.0% by SJLs. SJLsc and SJLs were significantly associated with depressive mood (r = 0.06, P = 0.02; r = 0.06, P = 0.01, respectively), independent of sleep debt. Sleep debt was also associated with depression (r = 0.07, P < 0.01). CONCLUSIONS: By adopting sleep-corrected formula for SJL, this study found that misaligned and insufficient sleep, at levels occurring in routine social life, can negatively affect mood. Minimizing social jetlag and sleep deprivation may promote individual psychological well-being.

Associations of chronotype and social jetlag with eating jetlag and their changes among German students during the first COVID-19 lockdown. The Chronotype and Nutrition study.

Due to their biologically later chronotype, young students are vulnerable to a discrepant sleeping pattern between work- and free days, coined social jetlag (SJL). This study examined whether a later chronotype and/or a larger SJL are related to an analogous discrepancy in meal timing defined as eating jetlag (EJL) and whether chronotype and/or changes in SJL during the first COVID-19 related lockdown in Germany associated with changes in EJL. Baseline data were collected from September 2019-January 2020 among 317 students (58% females) aged 18-25 years of which a total of 156 students (67% females) completed an online follow-up survey in June-July 2020 (1st lockdown). Data were collected on daily routines, timing of meals/snacks, and physical activity. Chronotype was determined using the Munich ChronoType Questionnaire; SJL and EJL correspond to the difference in the daily midpoint of sleep/eating duration between work- and free days. Multivariable linear regression revealed that students with a later chronotype or a larger SJL experienced a larger EJL (padjusted = 0.0124 and padjusted<0.0001). A later chronotype at baseline and reductions in SJL during lockdown associated with concurrent reductions in EJL (padjusted = 0.027 and padjusted<0.0001). In conclusion, students with a later chronotype exhibit a more erratic meal pattern, which associates with SJL. During lockdown, flexible daily schedules allowed students to align the meal timing with their inner clock.

Sleep habits and problems across gestational progress in Japanese women.

BACKGROUND: Pregnancy-related anatomic, physiologic, and hormonal factors can occur at different stages of pregnancy and affect sleep disturbances. Sleep problems and habits among Japanese women across gestational stages have not been described. This study aimed to elucidate sleep problems, including a high risk of sleep-disordered breathing and sleep habits, among Japanese women across gestational progress, including postpartum. METHODS: A questionnaire survey using the Pittsburgh Sleep Quality Index (PSQI) and Berlin Questionnaire was conducted for 683 pregnant women (223 in the second trimester, 453 in the third trimester) and 386 postpartum (within 1 week after delivery). RESULTS: The total PSQI score was 5.3 [2.6] in the second trimester, 6.1 [2.8] in the third trimester, and 6.8 [3.1] in the first week postpartum. The percentage of those at high risk for sleep-disordered breathing, as determined by the Berlin Questionnaire, was 11.8% in the second trimester, 21.3% in the third trimester, and 19.2% in the first week postpartum, with the highest percentage of those at high risk in the third trimester of pregnancy. CONCLUSION: The PSQI total score exceeded the cut-off value in the third trimester and the first week postpartum, suggesting sleep deterioration. Therefore, it is necessary to understand and support sleep in pregnant women to ensure safe delivery, postpartum recovery, and health.