Wrist temperature and cortisol awakening response in humans with social jetlag in the North

Associations between social jetlag trajectories and body mass index among young adults

STUDY OBJECTIVES

This study employed longitudinal data collected repeatedly from individuals over the course of several years to examine the trajectories of social jetlag from ages 11 to 22 years and their associations with subsequent body mass index (BMI). Potential sex differences were also investigated.

METHODS

Data were obtained from two longitudinal studies conducted in Taiwan (N = 4287). Social jetlag was defined as ≥ 2 hours of absolute difference in sleep midpoint between weekdays and weekends. BMI was calculated using weight (kg)/height(m)2 and categorized as underweight (<18 kg/m2), normal weight (18 kg/m2 ≤ BMI < 24 kg/m2), overweight (24 kg/m2 ≤ BMI < 27 kg/m2), and obese (≥27 kg/m2). Group-based trajectory modeling and multinomial logistic regression were applied to investigate study objectives.

RESULTS

Four distinct trajectories of social jetlag throughout the adolescent years were identified, with corresponding proportions as follows: low-stable (42%), moderate-decreasing (19%), low-increasing (22%), and chronic (17%) trajectories. Among males, the risk of being underweight (aOR, 1.96; 95% CI: 1.35 to 2.84) or obese (aOR, 1.40; 95% CI: 1.02 to 1.92) was higher in individuals with a low-increasing trajectory than in those with a low-stable trajectory. Among females, those with a low-increasing (aOR, 1.61; 95% CI: 1.02 to 2.54) or chronic (aOR, 2.04; 95% CI: 1.27 to 3.25) trajectory were at a higher risk of being obese relative to those with a low-stable trajectory.

CONCLUSIONS

Addressing the development of increasing or chronic social jetlag during adolescence can help prevent abnormal BMI in young adulthood. Practitioners should consider sex differences in treatment or consultation.

Social jetlag and trajectories of mood symptoms and reward responsiveness in individuals at low-risk, high-risk, and with bipolar spectrum disorders: An ecological momentary assessment study

A specific type of sleep disruption, social jetlag, involves an incongruence of sleep time between weekends and weekdays. This study investigated relationships between social jetlag and mood symptom lability and trajectories of daily reward responsiveness and mood symptoms. Participants (N = 130) from three groups (moderate reward sensitivity, high reward sensitivity, and high reward sensitivity with a diagnosed bipolar spectrum disorder [BSD]) were recruited from an ongoing longitudinal study based on their self-reported reward sensitivity and a diagnostic interview. For this study, they completed 20 days of ecological momentary assessment (EMA) of reward responsiveness and mood symptoms and a daily sleep diary. Social jetlag was significantly associated with differences in trajectories of depressive symptoms between groups. Specifically, greater social jetlag was associated with a greater increase in depressive symptoms over the 20 days for participants in the high reward sensitivity and BSD groups compared to the moderate reward sensitivity group. Social jetlag also was significantly associated with depressive symptom lability during the EMA period, but this finding was reduced to a trend toward significance when controlling for self-reported sleep duration. The study adds to the literature with methodological strengths including the EMA design and assessment of symptom and reward responsiveness trajectories.

Social jetlag longitudinally predicts internalizing and externalizing behavior for adolescent females, but not males

Biological changes contribute to preferences for later bed and wake times during adolescence, yet the social constraints of school start times necessitate early wake times. This often results in social jetlag (i.e. misalignment between preferred sleep timing on weekends and school days). We examined whether social jetlag predicts adolescent internalizing and externalizing behavior over time and/or whether associations differ based on sex. We used data from the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development Study (n = 767) to test whether social jetlag at 6th grade (ages 12-13 years) predicted internalizing and externalizing behavior at age 15 years and whether child sex moderated associations. Controlling for internalizing and externalizing behavior at 6th grade (ages 12-13 years), results were that social jetlag at 6th grade (ages 12-13 years) predicted more internalizing and externalizing behaviors at age 15 for females, but not males. These findings show that social jetlag during early adolescence confers risk for internalizing and externalizing behavior in females at mid-adolescence. Greater attention should be placed on identifying and addressing social jetlag in adolescent females.

Quantifying teenagers' sleep patterns and sex differences in social jetlag using at-home sleep monitoring

Sleep plays an important role in the formative developmental processes occurring during the teenage years. At the same time, teenagers' changing bioregulatory mechanisms and psychosocial factors converge into the so-called social jetlag, a sleep timing misalignment between weekdays and weekends. The aim of this study was to quantify the course of day-to-day changes in sleep/wake patterns and sleep stage distributions, and the sex differences in social jetlag among teenagers. We observed the sleep of 156 teenagers (58.3% girls, 15-16 years) using a novel sleep monitor over the course of up to 10 consecutive days. 1323 nights of data were analyzed using multilevel modeling. On average, participants went to bed at 23:41, woke up at 07:48, slept for 7.7 h and had 85.5% sleep efficiency. Sleep stage distributions were in line with normative data. We found later sleep onset and offset, longer time in bed, sleep duration, and sleep onset latency (p = .001), greater proportion of light sleep and lower proportion of deep sleep, and poorer sleep efficiency (all p < .001) on weekend nights starting on Friday and Saturday. On Friday nights, girls had longer time awake after sleep onset (p = .020) than boys. On Friday and Saturday nights, girls fell asleep earlier (p < .001 and p = .006, respectively). On Saturday nights, girls had shorter sleep latency (p = .024), and better sleep efficiency (p = .019) than boys. In sum, teenagers' sleep patterns reflected healthy, albeit somewhat short sleep. There was convincing evidence of social jetlag, and girls exhibited less severe social jetlag than boys.

Functional connectivity from dorsolateral prefrontal cortex mediates the impact of social jetlag on depressive tendency in young adults

Social jetlag (SJL), a form of circadian rhythm disturbance, is linked to depressive symptoms; however, it is unclear what role the brain network, particularly the reward and cognitive control circuits, plays in this association. To address this issue, employing the ventral striatum (VS) and dorsolateral prefrontal cortex (DLPFC) as seeds, we used voxel-level whole-brain functional connectivity (FC) to determine the neural basis of the association between SJL and depressive tendency. Behavioral results indicated that SJL was positively associated with depression scores. Functional connection results showed that higher SJL was linked with decreased FC between the inferior orbitofrontal cortex and the VS. For DLPFC, we discovered changed FC in frontal, parietal, and occipital lobes related to SJL. More importantly, the mediation analysis revealed that the DLPFC-cuneus FC significantly mediated the relationship between SJL and depression scores. According to our study, higher SJL showed abnormal FC from the VS and DLPFC, which may involve attention impairments, cognitive control and reward function. Our results suggest that brain FC involving visual attention may explain the relationship between SJL and depressive tendency. This may offer new insights into the neural underpinnings of how circadian misalignment leads to mood issues.

The impact of sleep-corrected social jetlag on mental health, behavioral problems, and daytime sleepiness in adolescents

STUDY OBJECTIVES

This study aimed to examine the effect of sleep-corrected social jetlag (SJLsc) on mental health, behavioral problems, and daytime sleepiness in adolescents.

METHODS

This was a cross-sectional study which included 4787 adolescents (Mean age: 14.83±1.6y, 56.0% girls) recruited from 15 secondary schools in Hong Kong. SJLsc was defined as the absolute difference between sleep-corrected midsleep on weekdays and weekends, at which the sleep debt has been considered. It was classified into three groups: low-level ("LSJLsc", <1h), mid-level ("MSJLsc", ≥1h and <2h), and high-level of SJLsc ("HSJLsc", ≥2h). Adolescents' mental health, behavioral problems and daytime sleepiness were measured by the General Health Questionnaire (GHQ-12), the Strengths and Difficulties Questionnaire (SDQ) and the Pediatric Daytime Sleepiness Scale (PDSS). Logistic regression analysis and restricted cubic spline regression (RCS) analysis were applied with consideration of confounders including age, gender, puberty and sleep problems.

RESULTS

Nearly half (46.9%) of adolescents had SJLsc for at least 1 h. Greater SJLsc was associated with more behavioral difficulties (MSJLsc: OR: 1.20, p = 0.03; HSJLsc: OR: 1.34, p = 0.02) when controlling for age, sex, puberty, chronotype, insomnia, and time in bed. There was a dose-response relationship in which higher SJLsc had an increased risk of conduct problems and hyperactivity, while only high-level SJLsc was associated with a peer relationship problem. In RCS analysis, SJLsc was associated with a higher likelihood of behavioral difficulties (p = 0.03) but not poor mental health or daytime sleepiness.

CONCLUSIONS

Sleep-corrected social jetlag was a unique risk factor for behavioral problems in adolescents. Our findings highlighted the need for interventions to promote healthy sleep-wake patterns in school adolescents.

Associations of social jetlag and emotional and behavioral problems among Chinese preschoolers

To describe the prevalence of social jetlag among preschoolers and explore its association with emotional and behavioral problems, we conducted a cross-sectional survey of healthy development among preschool children in 11 cities in October and November 2017. The study included 27 200 children aged 3-6 years and the questionnaires were completed exclusively by their parents or main caregivers. Social jetlag was calculated by difference of sleep midpoint between weekdays and weekends. Emotional and behavioral problems (emotional symptoms, conduct problems, hyperactivity, peer interaction, and prosocial behavior) among preschoolers were assessed by the Strengths and Difficulties Questionnaire (SDQ). The binary logistic regression model was used to examine the association between social jetlag and emotional/behavioral problems in preschool children. The social jetlag was 0.60 hours in boys and 0.64 hours in girls. After adjusting for confounding factors as children' s gender, age, only child, living area, family economic status, mother's age and education, father's education, screen time and full-day sleep time, we found that longer social jetlag (≥1 h/d) was positively associated with overall emotional and behavioral problems (OR = 1.20, 95%CI: 1.10-1.32; P < .001), emotional symptoms (OR = 1.23, 95% CI: 1.11-1.15, P < .001), hyperactivity (OR = 1.20, 95%CI: 1.11-1.30, P < .001) and conduct problems (OR = 1.18, 95%CI: 1.07-1.31, P < .01). We found that social jetlag is prevalent among Chinese preschool children and is positively associated with emotional and behavioral problems.

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

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

The association between metabolic parameters and evening chronotype and social jetlag in non-shift workers: A meta-analysis

AIMS

The aim of the study was to evaluate the association between evening chronotype and social jetlag (SJL) with obesity, blood glucose and lipid levels in non-shift working adults.

METHODS

The databases of MEDLINE, EMBASE and Cochrane Reviews were searched for studies analyzing the metabolic parameters among groups of different chronotypes or SJL until Feb 2022. Weighted mean difference (WMD) and 95% confidence intervals (CI) were used to analyze the association between these parameters and chronotypes or SJL.

RESULTS

A total of 27 studies were included in this meta-analysis. Compared with morning chronotype, the participants with evening chronotype had higher body mass index (BMI) (WMD= 0.44 kg/m², 95%CI, 0.30 to 0.57 kg/m², p<0.001), higher fasting blood glucose level (WMD= 5.83mg/dl, 95%CI, 3.27to 8.38 mg/dl, p<0.001), higher total cholesterol level (WMD= 6.63mg/dl, 95%CI, 0.69 to 12.56 mg/dl, p=0.03), and lower high density lipoprotein cholesterol (HDL-C) level (WMD= -1.80mg/dl, 95%CI, -2.30 to -1.31 mg/dl, p<0.001). Compared with the participants with small SJL, the participants with large SJL had larger waist circumference (WMD= 0.80cm, 95%CI, 0.77 to 0.83cm, p<0.001).

CONCLUSIONS

Evening chronotype and SJL were associated with obesity and unfavorable metabolic parameters of glucose and lipid metabolism.

SYSTEMATIC REVIEW REGISTRATION

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42022303401.

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

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

Adolescent Development of Biological Rhythms in Female Rats: Estradiol Dependence and Effects of Combined Contraceptives

Adolescence is a period of continuous development, including the maturation of endogenous rhythms across systems and timescales. Although, these dynamic changes are well-recognized, their continuous structure and hormonal dependence have not been systematically characterized. Given the well-established link between core body temperature (CBT) and reproductive hormones in adults, we hypothesized that high-resolution CBT can be applied to passively monitor pubertal development and disruption with high fidelity. To examine this possibility, we used signal processing to investigate the trajectory of CBT rhythms at the within-day (ultradian), daily (circadian), and ovulatory timescales, their dependence on estradiol (E2), and the effects of hormonal contraceptives. Puberty onset was marked by a rise in fecal estradiol (fE2), followed by an elevation in CBT and circadian power. This time period marked the commencement of 4-day rhythmicity in fE2, CBT, and ultradian power marking the onset of the estrous cycle. The rise in circadian amplitude was accelerated by E2 treatment, indicating a role for this hormone in rhythmic development. Contraceptive administration in later adolescence reduced CBT and circadian power and resulted in disruption to 4-day cycles that persisted after discontinuation. Our data reveal with precise temporal resolution how biological rhythms change across adolescence and demonstrate a role for E2 in the emergence and preservation of multiscale rhythmicity. These findings also demonstrate how hormones delivered exogenously in a non-rhythmic pattern can disrupt rhythmic development. These data lay the groundwork for a future in which temperature metrics provide an inexpensive, convenient method for monitoring pubertal maturation and support the development of hormone therapies that better mimic and support human chronobiology.

Day-to-day variability in sleep parameters and depression risk: a prospective cohort study of training physicians

While 24-h total sleep time (TST) is established as a critical driver of major depression, the relationships between sleep timing and regularity and mental health remain poorly characterized because most studies have relied on either self-report assessments or traditional objective sleep measurements restricted to cross-sectional time frames and small cohorts. To address this gap, we assessed sleep with a wearable device, daily mood with a smartphone application and depression through the 9-item Patient Health Questionnaire (PHQ-9) over the demanding first year of physician training (internship). In 2115 interns, reduced TST (b = -0.11, p < 0.001), later bedtime (b = 0.068, p = 0.015), along with increased variability in TST (b = 0.4, p = 0.0012) and in wake time (b = 0.081, p = 0.005) were associated with more depressive symptoms. Overall, the aggregated impact of sleep variability parameters and of mean sleep parameters on PHQ-9 were similar in magnitude (both r² = 0.01). Within individuals, increased TST (b = 0.06, p < 0.001), later wake time (b = 0.09, p < 0.001), earlier bedtime (b = - 0.07, p < 0.001), as well as lower day-to-day shifts in TST (b = -0.011, p < 0.001) and in wake time (b = -0.004, p < 0.001) were associated with improved next-day mood. Variability in sleep parameters substantially impacted mood and depression, similar in magnitude to the mean levels of sleep parameters. Interventions that target sleep consistency, along with sleep duration, hold promise to improve mental health.

Coupled network of the circadian clocks: a driving force of rhythmic physiology

The circadian system is composed of coupled endogenous oscillators that allow living beings, including humans, to anticipate and adapt to daily changes in their environment. In mammals, circadian clocks form a hierarchically organized network with a 'master clock' located in the suprachiasmatic nucleus of the hypothalamus, which ensures entrainment of subsidiary oscillators to environmental cycles. Robust rhythmicity of body clocks is indispensable for temporally coordinating organ functions, and the disruption or misalignment of circadian rhythms caused for instance by modern lifestyle is strongly associated with various widespread diseases. This review aims to provide a comprehensive overview of our current knowledge about the molecular architecture and system-level organization of mammalian circadian oscillators. Furthermore, we discuss the regulatory roles of peripheral clocks for cell and organ physiology and their implication in the temporal coordination of metabolism in human health and disease. Finally, we summarize methods for assessing circadian rhythmicity in humans.

Differential associations between chronotype, anxiety, and negative affect: A structural equation modeling approach

BACKGROUND

Increasing evidence implicates circadian rhythms, including chronotype, in anxiety symptoms and disorders. However, it remains unclear whether this relation is accounted for by sleep disturbance. Likewise, given overlap between anxiety and negative affect, a unique link between chronotype and anxiety remains to be established. The present study addressed these questions using a multimethod approach to determine whether there is a unique relation between chronotype and anxiety symptoms, controlling for sleep disturbance.

METHODS

Indicators of chronotype, sleep disturbance, anxiety, and negative affect were collected in a sample of adults (N = 151) using a combination of subjective and behavioral measures both within and outside the laboratory over a 9-day period. Structural equation modeling was used to examine associations between latent constructs.

RESULTS

Results revealed significant associations between sleep disturbance and both anxiety and negative affect. A significant association was found between chronotype and anxiety, over and above the effect of sleep disturbance. In contrast, the relation between chronotype and negative affect was nonsignificant after controlling for sleep disturbance.

LIMITATIONS

Unselected sample, lack of experimental manipulation, cross-sectional design.

CONCLUSIONS

These findings suggest a unique role of chronotype in anxiety and point to circadian disruption as a potential biological mechanism in anxiety-related disorders.

Chronotype and Social Jetlag: A (Self-) Critical Review

The Munich ChronoType Questionnaire (MCTQ) has now been available for more than 15 years and its original publication has been cited 1240 times (Google Scholar, May 2019). Additionally, its online version, which was available until July 2017, produced almost 300,000 entries from all over the world (MCTQ database). The MCTQ has gone through several versions, has been translated into 13 languages, and has been validated against other more objective measures of daily timing in several independent studies. Besides being used as a method to correlate circadian features of human biology with other factors-ranging from health issues to geographical factors-the MCTQ gave rise to the quantification of old wisdoms, like "teenagers are late", and has produced new concepts, like social jetlag. Some like the MCTQ's simplicity and some view it critically. Therefore, it is time to present a self-critical view on the MCTQ, to address some misunderstandings, and give some definitions of the MCTQ-derived chronotype and the concept of social jetlag.

Social Jetlag and Chronotypes in the Chinese Population: Analysis of Data Recorded by Wearable Devices

Background

Chronotype is the propensity for a person to sleep at a particular time during 24 hours. It is largely regulated by the circadian clock but constrained by work obligations to a specific sleep schedule. The discrepancy between biological and social time can be described as social jetlag (SJL), which is highly prevalent in modern society and associated with health problems. SJL and chronotypes have been widely studied in Western countries but have never been described in China.

Objective

We characterized the chronotypes and SJL in mainland China objectively by analyzing a database of Chinese sleep-wake pattern recorded by up-to-date wearable devices.

Methods

We analyzed 71,176 anonymous Chinese people who were continuously recorded by wearable devices for at least one week between April and July in 2017. Chronotypes were assessed (N=49,573) by the adjusted mid-point of sleep on free days (MSFsc). Early, intermediate, and late chronotypes were defined by arbitrary cut-offs of MSFsc <3 hours, between 3-5 hours, and >5 hours. In all subjects, SJL was calculated as the difference between mid-points of sleep on free days and work days. The correlations between SJL and age/body mass index/MSFsc were assessed by Pearson correlation. Random forest was used to characterize which factors (ie, age, body mass index, sex, nocturnal and daytime sleep durations, and exercise) mostly contribute to SJL and MSFsc.

Results

The mean total sleep duration of this Chinese sample is about 7 hours, with females sleeping on average 17 minutes longer than males. People taking longer naps sleep less during the night, but they have longer total 24-hour sleep durations. MSFsc follows a normal distribution, and the percentages of early, intermediate, and late chronotypes are approximately 26.76% (13,266/49,573), 58.59% (29,045/49,573), and 14.64% (7257/49,573). Adolescents are later types compared to adults. Age is the most important predictor of MSFsc suggested by our random forest model (relative feature importance: 0.772). No gender differences are found in chronotypes. We found that SJL follows a normal distribution and 17.07% (12,151/71,176) of Chinese have SJL longer than 1 hour. Nearly a third (22,442/71,176, 31.53%) of Chinese have SJL<0. The results showed that 53.72% (7127/13,266), 25.46% (7396/29,045), and 12.71% (922/7257) of the early, intermediate, and late chronotypes have SJL<0, respectively. SJL correlates with MSFsc (r=0.54, P<.001) but not with body mass index (r=0.004, P=.30). Random forest model suggests that age, nocturnal sleep, and daytime nap durations are the features contributing to SJL (their relative feature importance is 0.441, 0.349, and 0.204, respectively).

Conclusions

Our data suggest a higher proportion of early compared to late chronotypes in Chinese. Chinese have less SJL than the results reported in European populations, and more than half of the early chronotypes have negative SJL. In the Chinese population, SJL is not associated with body mass index. People of later chronotypes and long sleepers suffer more from SJL.

Social jetlag and quality of life among nursing students: A cross-sectional study

AIMS

To investigate chronotype categories and social jetlag among nursing students and to identify associations between rhythm asynchrony and participants' physical and psychological health, academic performance and quality of life.

BACKGROUND

Social jetlag refers to the asynchrony between chronotypes and social working hours, resulting in a misalignment of biological and social time. Recent studies have reported possible changes in psychosocial functioning owing to social jetlag. Therefore, the present study investigated chronotypes and the extent of social jetlag among nursing students.

DESIGN

A cross-sectional study was conducted in 2015 with a sample of 346 nursing students in two universities in Korea.

METHODS

Social jetlag and quality of life were measured with the Munich Chronotype Questionnaire and the abbreviated version of the World Health Organization Quality of Life Scale, respectively, in the year 2015. Data analysis was mainly based on a multiple regression to identify social jetlag's influence on students' quality of life.

RESULTS

Average social jetlag was 1 hr - 36 min. Social jetlag was negatively correlated with chronotype, academic performance and quality of life. A multiple regression analysis revealed that social jetlag, a positive emotional state, recovery resilience and depressive symptoms affected students' quality of life. These variables accounted for 41.7% of the variance in quality of life.

CONCLUSIONS

Results suggest that decreases in social jetlag and depressive symptoms, as well as increases in the positive emotional state and recovery resilience, enhance students' quality of life.

Sleep duration and social jetlag are independently associated with anxious symptoms in adolescents

Although short total sleep time (TST) is associated with increased anxious symptoms in adolescents, it is unknown whether social jetlag, a misalignment between sleep timing on the weekend and school week, is independently associated with anxious symptoms. In the current study, sleep timing, anxious symptoms, and demographic information were assessed from 3097 adolescents (48% female, mean ± SD age 15.59 ± .77 years) from the age 15 wave of the Fragile Families and Child Wellbeing Study. Social jetlag was calculated as the absolute value of the midpoint of sleep on the weekend minus the midpoint of sleep during the school week. Anxious symptoms were measured through the 6-item anxiety subscale of the Brief Symptom Inventory 18. We assessed associations between sleep variables and anxious symptoms using multiple linear regression. Adjusted analyses controlled for sex, race/ethnicity, age in years, body mass index percentile, number of other children below the age of 18 in the household, and primary caregiver (PCG) married/cohabiting with youth's biological parent, PCG employment status, PCG household income and PCG education level. In fully adjusted models (R² = .034), school night TST (b = -.04, ∆R² = .005, p < .001) was negatively associated with anxiety symptoms, while social jetlag (b = .04, ∆R² = .009, p < .001) was positively and independently associated with anxiety symptoms. Findings indicate small associations of school night TST and social jetlag with anxious symptoms. Thus, maintenance of optimal emotional health in adolescents may require both sufficient sleep duration and regularity of sleep timing across the week.

Sex Moderates Relationships Among School Night Sleep Duration, Social Jetlag, and Depressive Symptoms in Adolescents

Social jetlag, a misalignment between sleep timing on the weekend and during the work week, is associated with depressive symptoms among adults across both sexes. A previous study found that later sleep timing was associated with depressive symptoms in women but not men. To date, however, no research has investigated whether the association between social jetlag and depression varies by sex among adolescents. The current study assessed self-reported sleep, depressive symptoms, and demographic information from 3058 adolescents (48% female, mean [SD] age 15.59 [0.77] years) from the age 15 wave of the Fragile Families and Child Wellbeing Study (FFCWS). Social jetlag was calculated as the absolute value of the midpoint of sleep on the weekend minus the midpoint of sleep during the school week. Depressive symptoms were measured through a modified 5-item version of the Center for Epidemiologic Studies Depression Scale (CES-D). We assessed whether the associations among sleep duration on school nights, social jetlag, and depressive symptoms were similar between male and female adolescents using multiple linear regression. In fully adjusted models, sex moderated the association between school night total sleep time and depressive symptoms ( p < 0.001) and between social jetlag and depressive symptoms ( p = 0.037). In females, but not in males, school night total sleep time was negatively associated with depressive symptoms ( p < 0.001), whereas social jetlag ( p < 0.001) was positively and independently associated with depressive symptoms. The results indicate the importance of regular sleep timing across the week and adequate sleep duration for the maintenance of optimal emotional health among female adolescents.

Chronotype is associated with psychological well-being depending on the composition of the study sample

Past studies examining the effect of chronotype and social jetlag on psychological well-being have been inconsistent so far. Here, we recruited participants from the general population and enquired about their natural sleeping behavior, sleep quality, depressive symptoms, and perceived stress. Partial correlations were computed between sleep variables and indicators of psychological well-being, controlling for age and sex. Less sleep during work days was found a good indicator for impairments in psychological well-being. In exploratory follow-up analyses, the same correlations were calculated within groups of early, intermediate, and late chronotype. We observed that the composition of the sample in terms of chronotype influenced whether associations between sleep variables and psychological well-being could be observed, a finding that is advised to be taken into account in future studies.

Social jet lag: Sleep-corrected formula

Social jet lag is a term describing misalignment between social and biological times. In this article, it is argued that the currently used formula for social jet lag captures not only this misalignment, but also sleep debt resulting from sleep deprivation during workdays. It is proposed to adopt the sleep-corrected formula for social jet lag, which takes the form of the difference between the sleep onset on free days and workdays in the case of subjects with longer sleep and later (or equal) sleep onset on free days compared to workdays; it takes the form of the difference between the sleep offset on free days and workdays for subjects with longer sleep and earlier (or equal) sleep offset on workdays compared to free days.