Social jetlag and obesity: A systematic review and meta-analysis.

Social jetlag, the weekly variation in sleep timing, is proposed to contribute to increased obesity risk, potentially because of the misalignment of behavioral cycles relative to the endogenous circadian timing system. This systematic review and meta-analysis aim to determine the association between social jetlag and adiposity-related measures using observational studies. We reviewed 477 references, of which 43 studies met inclusion criteria with a total sample size of 231,648. There was a positive association between social jetlag and body mass index (correlation coefficient [r]: 0.12; 95%CI, 0.07, 0.17; P < 0.001; I2  = 94.99%), fat mass (r: 0.10; 95%CI, 0.05, 0.15; P < 0.001; I2  = 0.00%), fat mass index (fat mass divided by height in meter squared, ß: 0.14 kg/m2 ; 95%CI, 0.05, 0.23; P < 0.001; I2  = 56.50%), percent of body fat (r: 0.37; 95%CI, 0.33, 0.41; P < 0.001; I2  = 96.17%), waist circumference (r: 0.15; 95%CI, 0.06, 0.24; P = 0.001; I2  = 90.83%), and the risk of having overweight/obesity (odds ratio: 1.20; 95%CI, 1.02, 1.140; P = 0.039; I2  = 98.25%). Social jetlag is positively and consistently associated with multiple obesity-related anthropometric measures. Further studies are needed to test causality, underlying mechanisms, and whether obesity interventions based on increasing regularity of the sleep/wake cycle can aid in the battle against the obesity pandemic.

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

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

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.

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.

Cardiometabolic risk factors and social jetlag in university professors.

Chronic stress leads to circadian disruption, with variability in sleep time and duration. This scenario increases the prevalence and incidence of cardiometabolic abnormalities. Social jetlag (SJL), a proxy of circadian disruption, has been associated with increased vulnerability to the development of metabolic syndrome, obesity, and type 2 diabetes. This research aimed to evaluate how variables associated with cardiometabolic risk are related to SJL and poor sleep among university professors. From 2018 to 2019, full-time university professors (n=103) with a mean age of 44±5.4 years were assessed for sleep quality, chronotype, SJL, metabolic components, sociodemographic characteristics, and physical evaluation. Sleep quality and weekday sleep duration were associated with stress (r=0.44 and r=-0.34) and anxiety (r=0.40), respectively. Mean sleep duration (n=65) was 7.0±1.1 h and all professors with poor sleep (41.2%; n=28) worked 40 h/week. Professors who slept less were significantly (r=-0.25) older, and teaching time (years) was positively correlated with blood glucose (r=0.42). Mean SJL was 59.8 ±4.5 min (n=68) and 48.5% of these professors had values ≤1 h and 51.4% ≥1 h. SJL and blood glucose concentration were associated (r=0.35), which reinforced that challenges to the circadian system reverberate on metabolism. In this study, professors at the Federal University of Rio Grande do Norte had cardiometabolic risks related to anxiety, stress, and sleep quality.

Social jetlag is associated with adverse cardiometabolic latent traits in early adolescence: an observational study.

Introduction: Adolescence is marked by physiological and social changes, such as puberty, increased responsibilities and earlier school start times. This often leads to insufficient sleep on school nights and the need to compensate for lost sleep on weekends, causing a misalignment between biological and social times, which has been termed social jetlag (SJL). SJL triggers stress responses and is associated with several negative health outcomes, including higher cardiometabolic risk in adults. In adolescence, however, SJL has only been consistently related to increases in adiposity but its association with other cardiometabolic indicators are unclear. Method: In a sample of 278 healthy early adolescents (9-15 years of age; 168 girls) we investigated: 1) whether self-reported SJL is associated (using path analyses) with a cardiometabolic status latent factor obtained by testing the best fitting model via confirmatory factor analyses from an initial set of eight indicators [body mass index (BMI), waist/height ratio, triglyceride concentration, diastolic and systolic blood pressure, glycated hemoglobin, total cholesterol/high-density lipoprotein ratio (chol/HDL), and % body fat]; and 2) whether age and/or pubertal status influence the association between SJL and cardiometabolic status. Result: We found that, for girls, higher SJL was associated with more adverse cardiometabolic latent scores (the shared variance of BMI, waist/height ratio, chol/HDL and systolic blood pressure, which had acceptable model fit indices). However, the role of age and pubertal status in this association was unclear for both sexes. Discussion: SJL was associated with adverse cardiometabolic latent traits beyond increases in adiposity in this observational study in early female adolescents. Because disruptions of circadian rhythms are believed to lead to dysregulated energy homeostasis and not vice-versa, our findings highlight the need for sleep interventions in adolescence to help reduce the global burden of cardiometabolic ill health, especially in girls.

Social jet lag and (changes in) glycemic and metabolic control in people with type 2 diabetes.

OBJECTIVE: Social jet lag, i.e., the discordance among social and biological rhythms, is associated with poor metabolic control. This study aimed to assess cross-sectional and longitudinal associations among social jet lag and glycemic and metabolic control in people with type 2 diabetes. METHODS: In a prospective cohort (N = 990) with type 2 diabetes, social jet lag was measured at baseline using daily diaries and was categorized (high, moderate, or low). Metabolic outcomes were assessed at baseline and at 1 and 2 years of follow-up. Associations among social jet lag and glycemic and metabolic control were analyzed using linear regression and linear mixed models adjusted for confounding factors. Analyses were stratified for work status (retired vs. working; p value for interaction = 0.007 for glycated hemoglobin [HbA1c]). RESULTS: In working people, a cross-sectional association between high social jet lag and HbA1c (1.87 mmol/mol [95% CI: 0.75 to 2.99]) and blood pressure (5.81 mm Hg [95% CI: 4.04 to 7.59]) was observed. For retired people, high social jet lag was negatively associated with HbA1c (-1.58 mmol/mol [95% CI: -2.54 to -0.62]), glucose (-0.19 mmoL/L [95% CI:-0.36 to -0.01]), and blood pressure (-3.70 mm Hg [95% CI: -5.36 to -2.04]), and the association with BMI was positive (1.12 kg/m2 [95% CI: 0.74 to 1.51]). Prospective associations had the same direction as cross-sectional findings but were nonsignificant for working or retired people. CONCLUSIONS: Social jet lag was cross-sectionally, but not prospectively, associated with glycemic and metabolic markers. Interaction with work status was present, and directions of the associations were generally detrimental in the working population, whereas higher social jet lag was associated with improved glycemic and metabolic control for retired people.

Associations of social jetlag and insomnia symptoms with depressive symptoms among Chinese adolescents: A large population-based study.

OBJECTIVE: This study aimed to evaluate the associations of social jetlag and insomnia symptoms with depressive symptoms among adolescents. METHODS: A total of 37,871 junior high students completed an online survey between May 24th and Jun 5th, 2022. Insomnia symptoms were assessed by three items based on the Diagnostic and Statistical Manual of Mental Disorders criteria. Social jetlag and depressive symptoms were evaluated by the Munich Chronotype Questionnaire and the Patient Health Questionnaire, respectively. Restricted cubic splines were used to explore the relationship between social jetlag and depressive symptoms. Joint effects of social jetlag and insomnia symptoms on depressive symptoms were estimated using additive interaction models. RESULTS: The prevalence of depressive symptoms was 13.1%. Depressive symptoms were more common in adolescents with social jetlag ≥2 h (OR: 1.51, 95% CI: 1.39-1.65) and insomnia symptoms (OR: 6.91, 95% CI: 6.41-7.44). There was a J-shaped relationship between social jetlag and depressive symptoms when we took social jetlag as a continuous variable. Moreover, a positive additive interaction of social jetlag ≥2 h and insomnia symptoms on depressive symptoms was found in female adolescents (RERI: 2.30, 95% CI: 0.11-4.49). CONCLUSIONS: Our findings suggested that social jetlag ≥2 h and insomnia are related to the occurrence of depressive symptoms in adolescents. Their coexistence additively enhances the strength of the association with depressive symptoms. Early screening and intervention for insomnia, as well as methods to reduce social jetlag, should be comprised as part of preventive strategies for depression in adolescents.

Association of smartphone use with abnormal social jetlag among adolescents in Korea before and after COVID-19.

PURPOSE: This study aimed to use social jetlag to determine how smartphone overuse by adolescents before and after the COVID-19 pandemic might be associated with their circadian rhythm. METHODS: We used 2017 and 2020 Korea Youth Risk Behavior web-based Survey data and conducted a survey analysis on 100,976 adolescents. The dependent variable was abnormal social jetlag. Based on the times recorded by the survey, we calculated the weekday midpoint and weekend sleep time. The main independent variable was smartphone usage time (<2h/day, 2-3.9 h/day, 4-5.9 h/day, and ≥ 6 h/day). Multiple logistic regression and relative excess risk due to interaction (RERI) were performed. RESULTS: Abnormal social jetlag was most prevalent in male and female adolescents who used smartphones ≥ 6 h/day (adjusted odds ratio [AOR] = 2.60, 95 % confidence interval [CI] = 2.47-2.74). The longer the smartphone usage time, the higher the association with abnormal social jetlag. This association was more prominent in female adolescents. The additive interaction between longer smartphone usage time and post-COVID-19 year was statistically significant (total: RERI = 0.92, 95 % CI = 0.90-0.95; males: RERI = 0.83, 95 % CI = 0.80-0.87; females: RERI = 1.13, 95 % CI = 1.08-1.18). CONCLUSION: Our results clearly indicated that increased smartphone usage time tended to result in greater social jetlag, an association that was more pronounced in female. Moreover, the COVID-19 pandemic significantly strengthened this relationship. Further research is needed regarding the proper use of smartphones to ensure good sleep-in adolescents after the COVID-19 pandemic.

Examination of sleep factors affecting social jetlag in Japanese male college students.

We hypothesized that social jetlag would be associated with prolonged sleep duration on weekends and irregularities in wake-up time and/or bedtime on weekdays. In total, 1,200 Japanese male college students were included in this study. Participants completed an eight-day sleep diary in which they recorded their wake-up time, bedtime, and sleep duration every day for a week. Mean wake-up time, bedtime, and sleep duration, standard deviations in wake-up time and bedtime, the coefficient of variation in sleep duration, social jetlag, and chronotype were calculated over seven nights. Multiple regression was used to explore the factors influencing social jetlag. Stepwise selection analysis was performed to analyze the parameters identified on multiple regression analysis. The mean chronotype of the included participants was 5.3 ± 1.5; their mean social jetlag value was 1.1 ± 1.0. The mean wake-up time, bedtime, and sleep duration values were 8.5 ± 1.1, 25.0 ± 1.1, and 7.5 ± 1.1 h, respectively. Multiple regression analysis showed five indicators exerting a statistically significant influence on social jetlag. The standard deviation in wake-up time was adopted as the first factor in the stepwise selection analysis. These results show that social jetlag is associated with not only prolonged sleep duration on weekends but also irregularities in wake-up time during the week.

Influence of social jetlag on daytime sleepiness in obstructive sleep apnea.

Social jetlag is the discrepancy between socially determined sleep timing on workdays and biologically determined sleep timing on days free of social obligation. Poor circadian timing of sleep may worsen sleep quality and increase daytime sleepiness in obstructive sleep apnea (OSA). We analysed de-identified data from 2,061 participants (75.2% male, mean [SD] age 48.6 [13.4] years) who completed Sleep Apnea Global Interdisciplinary Consortium (SAGIC) research questionnaires and underwent polysomnography at 11 international sleep clinic sites. Social jetlag was calculated as the absolute difference in the midpoints of sleep between weekdays and weekends. Daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS). Linear regression analyses were performed to estimate the association between social jetlag and daytime sleepiness, with consideration of age, sex, body mass index, ethnicity, insomnia, alcohol consumption, and habitual sleep duration as confounders. Of the participants, 61.5% had <1 h of social jetlag, 27.5% had 1 to <2 h, and 11.1% had ≥2 h. Compared to those with <1 h of social jetlag, those with ≥2 h of social jetlag had 2.07 points higher ESS (95% confidence interval [CI] 0.77-3.38, p = 0.002), and those with 1 to <2 h of social jetlag had 0.80 points higher ESS (95% CI 0.04-1.55, p = 0.04) after adjustment for potential confounding. Interaction with OSA severity was observed; social jetlag appeared to have the greatest effect on daytime sleepiness in mild OSA. As social jetlag exacerbates daytime sleepiness in OSA, improving sleep timing may be a simple but novel therapeutic target for reducing the impact of OSA.

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.

Persistent, High Levels of Social Jetlag Predict Poor Weight Outcomes in a Weight Gain Prevention Study for Young adults.

INTRODUCTION: Social jetlag (SJL), the discrepancy in sleep timing between weekdays and weekends, is associated with higher BMI and cardiometabolic risk and is common in young adults. We examined whether chronic SJL impacts weight gain in young adults participating in a weight gain prevention trial. METHODS: Young adults (n = 599, age 18-35; BMI: 21.0-30.9 kg/m2) completed assessments at 0, 4, 12, and 24 months. Multilevel mixed growth models were used to examine (1) associations between demographics and longitudinal SJL and (2) longitudinal SJL as a predictor of weight change and cardiometabolic outcomes. SJL was assessed as a continuous and clinically-significant dichotomous (< vs. ≥2 h) variable. RESULTS: 38% of participants had clinically-significant SJL at ≥ 1 timepoints (Baseline M ± SD = 1.3±0.89). Younger (b=-0.05, p < 0.001), female (b = 0.18, p = 0.037) and Black (compared to White, b = 0.23, p = 0.045) participants were more likely to have greater SJL. Individuals with high SJL (≥ 2 h; between-person effect) were more likely to have greater weight gain over 2 years (b = 0.05, p = 0.028). High SJL did not affect the rate of change in waist circumference or cardiometabolic markers over time. CONCLUSIONS: High SJL is associated with greater weight gain over time. Reducing SJL may positively impact weight status in young adults.

Association of social jetlag with gestational diabetes: Qazvin Maternal and Neonatal Metabolic Study.

The association of social jetlag (SJL), as a quantitative measure of circadian misalignment, with insulin resistance and metabolic syndrome has been reported. The present study was designed to investigate the association of SJL with gestational diabetes mellitus (GDM). Pregnant women with gestational age ≤14 weeks were enrolled in this longitudinal study. The participants with pre-GDM, shift workers and those who used alarms for waking up on free days were excluded from the study. SJL as well as behavioral and psychological parameters were evaluated at enrollment. The participants were categorized based on each 1-h increment of SJL. The association of SJL with the occurrence of GDM in the late second trimester was evaluated using univariate and multivariate methods. In total, 821 pregnant women entered the study, and after omitting individuals with excluding criteria, analyses were performed on 557 participants. The frequencies of SJL < 1 h,1 ≤ SJL < 2 h and SJL ≥ 2 h were 44.7%, 37.2% and 18.1%, respectively. Average sleep duration was higher in SJL < 1 h compared with the two other groups (p < 0.001). During follow-up, 90 (16.1%) women with GDM were identified. SJL ≥ 2 h was associated with a 4.4-5.6 times higher risk of GDM in different models of adjustment (p < 0.05). Pregnant women with high SJL are at a higher risk of GDM. Further studies for evaluating the mechanisms by which SJL affects GDM are warranted.

Associations among social jetlag, sleep-related characteristics, premenstrual symptoms, depression, and body mass index of female nursing students.

PURPOSE: This study aimed to identify the predictors of female nursing students' body mass index (BMI), including social jetlag. DESIGN AND METHODS: This secondary data analysis of a cross-sectional survey conducted in 2015 included data of 304 female undergraduate nursing students. A hierarchical regression analysis was performed to identify the predictors of BMI. FINDINGS: Social jetlag was the most potent predictor of BMI, followed by premenstrual symptoms and sleep quality. PRACTICE IMPLICATIONS: This study presents foundational data for developing interventions for social jetlag management as a strategy to prevent obesity in female nursing students by identifying factors predicting BMI.

Adverse Effect of Circadian Rhythm Disorder on Reparative Angiogenesis in Hind Limb Ischemia.

Background Circadian rhythm disorders, often seen in modern lifestyles, are a major social health concern. The aim of this study was to examine whether circadian rhythm disorders would influence angiogenesis and blood perfusion recovery in a mouse model of hind limb ischemia. Methods and Results A jet-lag model was established in C57BL/6J mice using a light-controlled isolation box. Control mice were kept at a light/dark 12:12 (12-hour light and 12-hour dark) condition. Concentrations of plasma vascular endothelial growth factor and circulating endothelial progenitor cells in control mice formed a circadian rhythm, which was diminished in the jet-lag model (P<0.05). The jet-lag condition deteriorated tissue capillary formation (P<0.001) and tissue blood perfusion recovery (P<0.01) in hind limb ischemia, which was associated with downregulation of vascular endothelial growth factor expression in local ischemic tissue and in the plasma. Although the expression of clock genes (ie, Clock, Bmal1, and Cry) in local tissues was upregulated after ischemic injury, the expression levels of cryptochrome (Cry) 1 and Cry2 were inhibited by the jet-lag condition. Next, Cry1 and Cry2 double-knockout mice were examined for blood perfusion recoveries and a reparative angiogenesis. Cry1 and Cry2 double-knockout mice revealed suppressed capillary density (P<0.001) and suppressed tissue blood perfusion recovery (P<0.05) in the hind limb ischemia model. Moreover, knockdown of CRY1/2 in human umbilical vein endothelial cells was accompanied by increased expression of WEE1 and decreased expression of HOXC5. This was associated with decreased proliferative capacity, migration ability, and tube formation ability of human umbilical vein endothelial cells, respectively, leading to impairment of angiogenesis. Conclusions Our data suggest that circadian rhythm disorder deteriorates reparative ischemia-induced angiogenesis and that maintenance of circadian rhythm plays an important role in angiogenesis.

Circadian disruption in mice through chronic jet lag-like conditions modulates molecular profiles of cancer in nucleus accumbens and prefrontal cortex.

Biological rhythms regulate physiological activities. Shiftwork disrupts normal circadian rhythms and may increase the risk of cancer through unknown mechanisms. To mimic environmental light/dark changes encountered by shift workers, a protocol called 'chronic jet lag (CJL)' induced by repeatedly shifting light-dark cycles has been used. Here, we subjected mice to CJL by advancing light-dark cycle by 6 h every 2 days, and conducted RNA sequencing to analyze the expression profile and molecular signature in the brain areas of prefrontal cortex and nucleus accumbens. We also performed positron emission tomography (PET) imaging to monitor changes related to glucose metabolism in brain. Our results reveal systematic reprogramming of gene expression associated with cancer-related pathways and metabolic pathways in prefrontal cortex and nucleus accumbens. PET imaging indicates that glucose uptake level was significantly reduced in whole brain as well as the individual brain regions. Moreover, qPCR analysis describes that the expression levels of cancer-related genes were altered in prefrontal cortex and nucleus accumbens. Overall, these results suggest a molecular and metabolic link with CJL-mediated cancer risk, and generate hypotheses on how CJL increases the susceptibility to cancer.

Daytime Workers with Longer Daily Rest Periods Have Smaller Sleep Debt and Social Jetlag: A Cross-Sectional Web Survey.

Objectives: The work interval duration between the end of one workday and the start of the following workday is referred to as the daily rest period (DRP). The present study examined whether DRP - a proxy for sleep opportunity between work shifts - is associated with indicators of sleep debt and social jetlag among daytime workers. Methods: We used a web-based survey to gather data on demographics, average DRP in the previous month, time in bed (TIB), bedtime, wake-up time, and sleep timing on workdays and non-workdays. The Japanese daytime workers (n = 3,914) were divided into seven DRP groups (hours) as follows: <11, 11, 12, 13, 14, 15, and ≥16. Results: The two-way analyses of covariance (DRP group x day) for TIB, mid-sleep as sleep timing, bedtime, and wake-up time showed significant interactions (all p < .001). Specifically, TIB was significantly shorter, and mid-sleep and wake-up time were significantly earlier on workdays than on non-workdays, across all DRP groups (all p < .001). Additionally, the different values for TIB (sleep debt), sleep timing (social jetlag), bedtime, and wake-up time were calculated by subtracting workdays from non-workdays. The trend analysis showed that workers with longer DRP (sleep opportunity) had smaller differences in TIB, sleep timing, and wake-up time between workdays and non-workdays (all p < .001). Conclusions: Overall, daytime workers reported significant sleep debt and misalignment between work and free sleep-wake periods. However, workers with shorter DRPs (less sleep opportunity between shifts) reported significantly greater amounts of sleep debt and social jetlag than did workers with longer DRPs.

The Impact of Social Jetlag on Sleep Quality among Nurses: A Cross-Sectional Survey.

Social jetlag (SJL) refers to an asynchrony between one's chronotype and social working hours, which can be detrimental to health. The current SJL situation in shift nurses who work in dysregulation is poorly understood. Therefore, this study aimed to investigate SJL during night shifts and identify the predictors of sleep quality in rotating shift nurses. A cross-sectional study was conducted in 2018 on a sample of 132 shift-working nurses from two general hospitals in South Korea (the response rate was 88.8%). The SJL was measured with the Munich Chronotype Questionnaire, and sleep quality was measured with the Pittsburgh Sleep Quality Index and the Verran and Snyder-Halpern Sleep Scale. Data analysis was mainly based on a multiple regression, to identify SJL's influence on nurses' sleep quality. The average SJL during night shifts was 2 h and 3 min, and the average sleep duration during night shifts was 6 h 10 min. Multiple regression analysis revealed that SJL, day-shift fatigue, and sleep quality during night shifts affected nurses' sleep quality. These variables accounted for 24.7% of the variance in overall sleep quality. The study concluded that overall sleep quality can increase with decreasing day-shift fatigue, decreasing SJL, and increasing sleep quality on night shifts.