Association of social jetlag with metabolic syndrome among Japanese working population: the Furukawa Nutrition and Health Study

The sleep paradox: The effect of weekend catch-up sleep on homeostasis and circadian misalignment

Weekend catch-up sleep involves not only changes in sleep duration between weekdays and weekends but also changes in sleep timing. When people sleep less during the weekdays, they accumulate sleep debt and extend their sleep duration on weekends to compensate, which is related with the homeostatic process. Thus, extend their sleep duration on weekends seems to be a protectively strategy of daytime function, mental and physical health. However, not all studies support this protective effect. Sleep duration changes with sleep timing. The difference in sleep timing between weekdays and weekends might bring social jet lag (SJL). Sleep duration changes with sleep timing. The difference in sleep timing between weekdays and weekends can lead to SJL, representing the discrepancy between the biological clock and the social clock. This makes SJL an indicator of circadian misalignment, which is associated with poor daytime function, reduced nighttime sleep quality, and an increased risk of depression, metabolic disturbances, and other diseases. Paradoxically, the protective effect of weekend catch-up sleep duration on the homeostatic process (compensating for sleep debt) and the potential impact of weekend catch-up sleep timing on the circadian process (circadian misalignment) contradict each other. A more comprehensive understanding of weekend catch-up sleep is essential to investigate its mechanisms using the two-process model and other influencing factors.

Relationship of Social Jetlag and Chronotype With the Risk of Diabetes Among Predominantly Male Japanese Daytime Workers: A Prospective Study

Greater social jetlag and late chronotypes have been linked to poor glucose metabolism, but their effects on diabetes risk in Asians remain unclear. This study investigated the prospective association between social jetlag, chronotype and diabetes risk among Japanese workers. We included 1681 workers (73% were daytime workers) aged 18-78 years who attended a nutritional survey in 2015 and 2016 and were followed for diabetes incidence until May 31, 2022. Social jetlag was defined as the absolute difference in the midpoint of sleep times between weekdays and weekends. Chronotype was estimated using the mid-sleep time on weekends that was corrected with sleep debt on weekdays. Following the American Diabetes Association criteria, diabetes onset was defined as the time when the participant first met any of the following conditions: HbA1c ≥ 6.5%, fasting plasma glucose ≥ 126 mg/dL, random plasma glucose ≥ 200 mg/dL or current use of antidiabetic medication. The Cox proportional hazards model was used to estimate hazard ratios (HRs) for diabetes incidence. Among the study participants, 88.8% were male, 5.0% experienced ≥ 2 h of social jetlag, and 7.6% were classified as having a late chronotype. During the 7-year follow-up, 107 individuals (6.4%) developed diabetes. Among daytime workers, social jetlag was not associated with diabetes risk: multivariable-adjusted HRs (95% CI) for diabetes were 1.00, 0.90 (0.52-1.55) and 1.08 (0.43-2.75) in participants with < 1.0, 1.0 to 1.9, and ≥ 2.0 h of social jetlag, respectively. Late chronotype was associated with higher diabetes risk, although not statistically significant, compared to early chronotype; multivariable-adjusted HRs (95% CI) were 1.32 (0.80-2.18) for intermediate chronotype and 1.98 (0.77-5.10) for late chronotype. In conclusion, this study suggests an association between late chronotypes and increased risk of diabetes among daytime workers and also highlights a mediating role of lifestyle-related behaviours on chronotype and their impact on metabolic health.

The relationship between chrononutrition profile, social jet lag and obesity: A cross-sectional study of Chinese college students

This study aimed to investigate the associations between chrononutrition profile, social jet lag (SJL) with obesity-related indicators (body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHTR), and percentage of body fat (PBF)). This cross-sectional study was conducted among college students in a university in Hunan Province, China, from 14 September 2023 to 8 June 2024. This study employed the Chrononutrition Profile - Questionnaire (CP-Q) along with physical examinations. SJL was defined as time difference of midpoint of sleep between the workdays and freedays. Sleep-corrected SJL (SJLsc) is the absolute difference between the sleep onset on free days and workdays. Average evening latency is the time between the last meal of the day and bedtime. Eating jet lag is the difference in the midpoint of the eating window between workdays and freedays. Logistic regression was utilized to assess the associations between chrononutrition profile, SJL, and obesity-related indicators among college students. A total of 805 participants were recruited, of which 695 have complete data after excluding those who did not meet the inclusion criteria. After adjusting for potential covariates, average evening latency <4 h was related with lower risk of high BMI, WC, and PBF [OR (95% CI) = 0.435 (0.285-0.663), 0.508 (0.305-0.848), 0.564 (0.402-0.792), respectively]. Average eating window >12 h was associated with a lower risk of high BMI, WC, and PBF [OR (95% CI) = 0.511 (0.327-0.800), 0.485 (0.277-0.851), 0.651 (0.456-0.930), respectively]. Last eating occasion jet lag >1 h was a higher risk of high PBF [OR (95% CI) = 1.554 (1.018-2.371)]. SJLsc > 1 h was associated with high PBF [OR (95% CI) = 1.527 (1.073-2.174)]. Circadian rhythm disruptions, including SJL and eating jet lag, are prevalent among college students. Long eating window, short evening latency, is associated with low risk of obesity, while short sleep duration, last eating occasion jet lag and larger SJLsc were associated with higher risk of obesity among youths.

Circadian Deregulation: Back Facing the Sun Toward Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) Development

Earth's rotation around its axis has pressured its inhabitants to adapt to 24 h cycles of day and night. Humans adapted their own circadian rhythms to the Earth's rhythms with a light-aligned awake-sleep cycle. As a consequence, metabolism undergoes drastic changes throughout the circadian cycle and needs plasticity to cope with opposing conditions in the day (when there is an increase in energy demands and food availability), and during the night (when prolonged fasting couples with cyclic changes in the energy demands across the sleep stages). In the last century, human behavior changed dramatically with a disregard for the natural circadian cycles. This misalignment in sleep and eating schedules strongly modulates the metabolism and energy homeostasis, favoring the development of obesity, metabolic syndrome, and metabolic dysfunction-associated steatotic liver disease (MASLD). This review summarizes the effects of circadian disruption, with a particular focus on the feeding and sleep cycles in the development of MASLD and hepatocellular carcinoma.

Association of Social Jetlag with the Dietary Quality Among Korean Workers: Findings from a Nationwide Survey

Background/Objectives: Social jetlag, which refers to the misalignment between biological rhythms and social schedule, is linked to an increased risk of metabolic diseases. This cross-sectional study investigated the relationship between social jetlag and workers' dietary quality. Methods: This secondary data analysis included a sample of workers from the Korea National Health and Nutrition Examination Survey (n = 11,430). Social jetlag was determined by calculating the difference in the sleep midpoint between free days and workdays, based on sleep onset and offset times. The Korean Health Eating Index (KHEI) was calculated based on 24-h recalls, with higher scores indicating superior dietary qualities (range: 0-100). Poor dietary quality was defined as a KHEI below the lowest quartile (<51.6). Linear or logistic regressions were utilized to estimate β or odds ratio (OR), respectively. Results: Among study participants, 12.1% of workers experienced ≥120 min of social jetlag. ≥120 min of social jetlag was associated with a reduced KHEI score compared with 0-59 min (β: -1.23, 95% confidence interval [CI]: -2.16, -0.30). Those with ≥120 min of social jetlag were more likely to have poor dietary quality than those with 0-59 min (OR: 1.27, 95% CI: 1.08, 1.50). Conclusions: Workers experiencing ≥120 min of social jetlag had poorer dietary quality compared with workers with 0-59 min of social jetlag. Therefore, this study suggests that policy efforts are needed to reduce social jetlag among workers in Korea.

Night shift-induced circadian disruption: links to initiation of non-alcoholic fatty liver disease/non-alcoholic steatohepatitis and risk of hepatic cancer

The circadian system plays a crucial role in regulating metabolic homeostasis at both systemic and tissue levels by synchronizing the central and peripheral clocks with exogenous time cues, known as zeitgebers (such as the light/dark cycle). Our body's behavioral rhythms, including sleep-wake cycles and feeding-fasting patterns, align with these extrinsic time cues. The body cannot effectively rest and repair itself when circadian rhythms are frequently disrupted. In many shift workers, the internal rhythms fail to fully synchronize with the end and start times of their shifts. Additionally, exposure to artificial light at night (LAN), irregular eating patterns, and sleep deprivation contribute to circadian disruption and misalignment. Shift work and jet lag disrupt the normal circadian rhythm of liver activity, resulting in a condition known as "circadian disruption". This disturbance adversely affects the metabolism and homeostasis of the liver, contributing to excessive fat accumulation and abnormal liver function. Additionally, extended working hours, such as prolonged night shifts, may worsen the progression of non-alcoholic fatty liver disease (NAFLD) toward non-alcoholic steatohepatitis (NASH) and increase disease severity. Studies have demonstrated a positive correlation between night shift work (NSW) and elevated liver enzymes, indicative of hepatic metabolic dysfunction, potentially increasing the risk of hepatocellular carcinoma (HCC) related to NAFLD. This review consolidates research findings on circadian disruption caused by NSW, late chronotype, jet lag, and social jet lag, drawing insights from studies involving both humans and animal models that investigate the effects of these factors on circadian rhythms in liver metabolism.

Associations between habitual sleep characteristics and cardiometabolic disease risk in corporate executives

OBJECTIVES

Corporate executive job demands may lead to poor sleep habits, increasing their risk for cardiometabolic disease. This study aimed to describe and explore associations between objectively measured habitual sleep characteristics and cardiometabolic disease risk of corporate executives, while accounting for occupational, psychological, and lifestyle factors.

METHODS

Habitual sleep was measured using wrist-worn actigraphy and a sleep diary over seven consecutive days in 61 (68.3% men) corporate executives aged 46.4 ± 8.7years. A composite cardiometabolic disease risk score was determined using body mass index, waist circumference, blood pressure and fasting glucose and lipid concentrations. Prediction models were built using a backward stepwise selection approach to explore associations between sleep characteristics and cardiometabolic disease risk factors adjusting for occupational, psychological, and lifestyle covariates.

RESULTS

Average total sleep time was 6.60 ± 0.75 hours, with 51.7% of participants reporting poor sleep quality and 26.2% extending their weekend sleep. Adjusted models showed that lower sleep efficiency (β = -0.25, 95%CI: -0.43; -0.08, P = .006), shorter weekday total sleep time (β = -1.37, 95% CI: -2.41, -0.32; P = .011) and catch-up sleep (β = 0.84, 95%CI: 0.08, 1.60, P = .002) were associated with higher cardiometabolic disease risk scores. Adjusted models also found that shorter average time-in-bed (ß=-2.00, 95%CI: -3.76; -0.18, P = .031), average total sleep time (ß=1.98, 95%CI: -3.70; -0.25, P = .025) and weekday total sleep time (β = -2.13, 95%CI: -3.56; -0.69, P = .025) as well as catch-up sleep (β = 1.67, 95% CI: 0.52; 2.83; P = .012) were all associated with a higher body mass index.

CONCLUSION

Corporate executives who compromise sleep duration during the working week may increase their risk for obesity and future cardiometabolic disease.

Association Between Social Jetlag and Components of Metabolic Syndrome: A Systematic Review and Meta-Analysis

BACKGROUND

A mismatch between biological and social time, often referred to as social jetlag (SJL), can lead to inadequate sleep and activities or taking meals at times that do not align with our biological rhythms, increasing the risk of metabolic abnormalities. Although the association between sleep and metabolic syndrome (MetS) is well established, the effects of SJL on MetS and the components of MetS in adults remain unclear.

PURPOSE

This study was designed to explore the relationship between SJL and MetS components in adults.

METHODS

A systematic review and meta-analysis was conducted on studies registered in PubMed, Cochrane, Web of Science, and Embase between the inception of each database until November 15, 2023. We focused on studies designed to evaluate the relationship between SJL and either MetS or its components. Only studies using cross-sectional, prospective, or retrospective designs were considered for inclusion. The relationship between SJL and MetS was depicted as an odds ratio with a corresponding 95% confidence interval (CI). We determined the mean differences and 95% CIs to estimate the associations between SJL and MetS components. The Joanna Briggs Institute Critical Appraisal Checklist was used to evaluate the methodological rigor of the selected studies. Data were analyzed using RevMan software Version 5.4.

RESULTS

The systematic review included 16 studies, with five analyzed via a meta-analysis covering four outcomes, each based on two to three studies. When comparing SJL of less than 1 hour with SJL of 2 hours or more, the latter showed a higher likelihood of MetS (pooled odds ratio: 1.52). Although a significant decrease in systolic blood pressure (pooled mean differences = -3.52 mmHg, 95% CI [-6.41, -0.64]) and a significant increase in waist circumference (pooled mean differences = 2.17 cm, 95% CI [0.61, 3.73]) were observed, the correlation between SJL and diastolic blood pressure failed to reach statistical significance.

CONCLUSIONS/IMPLICATIONS FOR PRACTICE

The meta-analysis conducted in this study found an association between SJL and MetS. Healthcare practitioners should prioritize the management of sleep quality and duration, especially for individuals exhibiting substantial SJL. Improving sleep can aid in controlling blood pressure and managing weight and should form part of MetS management strategies.

Circadian Disruption as a Risk Factor for Development of Cardiovascular and Metabolic Disorders - From Animal Models to Human Population

The lifestyle of human society is drifting apart from the natural environmental cycles that have influenced it since its inception. These cycles were fundamental in structuring the daily lives of people in the pre-industrial era, whether they were seasonal or daily. Factors that disrupt the regularity of human behaviour and its alignment with solar cycles, such as late night activities accompanied with food intake, greatly disturb the internal temporal organization in the body. This is believed to contribute to the rise of the so-called diseases of civilization. In this review, we discuss the connection between misalignment in daily (circadian) regulation and its impact on health, with a focus on cardiovascular and metabolic disorders. Our aim is to review selected relevant research findings from laboratory and human studies to assess the extent of evidence for causality between circadian clock disruption and pathology. Keywords: Circadian clock, Chronodisruption, Metabolism, Cardiovascular disorders, Spontaneously hypertensive rat, Human, Social jetlag, Chronotype.

The relationship between chronotype and food addiction: Serial mediation of social jetlag and psychological pain

This study evaluates how food addiction is related to chronotype, social jetlag, and psychological pain. Of the participants (n = 1,035 university students), 16.6% had a morning chronotype, 25.1% had an evening chronotype, and 25.1% were clinically addicted to eating. The mean sleep durations for participants were 7.41 ± 2.18 h and 8.95 ± 3.0 h on weekdays and weekends, respectively. The mean misalignment time for social jetlag was 1.45 ± 1.5 h. Food addiction, psychological pain, and social jetlag levels were high among participants with the evening chronotype. The risk factors for food addiction included being female, having an evening chronotype, and having high body mass index levels and psychological pain. The total indirect effect of psychological pain and social jetlag on the relationship between chronotype and food addiction was 20.6%. However, the social jetlag effect is relatively minor compared to psychological pain. The significant conclusions of this study are as follows. Clinical food addiction is prevalent among students, and a strong direct correlation between chronotype and food addiction was observed. The study emphasizes the importance of being aware of chronotype and mental status in establishing a healthy diet and lifestyle.

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, β: 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.

Relationship between Telework Jetlag and Perceived Psychological Distress among Japanese Hybrid Workers

Social jetlag is associated with physical and mental health problems. With the increased popularity of telework, we investigated a specific form of social jetlag that we termed "telework jetlag". This study aimed to clarify the relationship between telework jetlag-the difference in sleep and wake-up times between in-office and telework days-and mental health problems among Japanese hybrid workers. A cross-sectional study was conducted with 1789 participants from October to December 2021 using an online-based questionnaire. Telework jetlag, defined as the difference in the midsleep point between in-office and telework days, was investigated using two groups according to telework jetlag-those lagging <1 h versus ≥1 h. We used the six-item Kessler Scale as a nonspecific psychological distress scale for the outcome. Telework jetlag was significantly associated with psychological distress, and the ≥1 h group had a higher risk (odds ratio: 1.80) of developing high psychological distress (HPD) than the <1 h group in the multivariate analysis. Since most teleworkers are forced to have a hybrid work style that mixes going to work and teleworking, telework jetlag must be addressed to maintain the health of teleworkers.

Effects of Chronotype and Social Jet-Lag on Neurocognitive Functioning

The chronotype, which reflects the circadian rhythm preferences of individuals in their daily activities and sleep-wake cycles, can be considered on a dimension of extreme morningism and extreme eveningism. Individuals with extreme morning and extreme evening chronotypes face many physical and psychological dangers due to accumulated sleep debt, short total sleep time and insufficient sleep efficiency. In extreme chronotypes, especially in extreme evening people, the social jet-lag effect due to the mismatch between social and circadian clocks is thought to exacerbate these dangers. More recent studies have suggested that social jet-lag and chronotype have many negative effects on cognitive functioning. The aim of this article is to review the impact of social jet-lag and chronotype on cognitive functioning.

Acute social jetlag augments morning blood pressure surge: a randomized crossover trial

Although social jetlag (SJL) is generally considered a chronic condition, even acute SJL may have unfavorable effects on the cardiovascular system. We focused on the acute effects of SJL on morning blood pressure (BP) surge. This randomized crossover trial recruited 20 healthy men. In the SJL trial, participants delayed their bedtime by three hours on Friday and Saturday nights. Participants in the control (CON) trial implemented the same sleep-wake timing as on weekdays. Pre- and post-intervention measurements were performed to evaluate resting cardiovascular variables on Friday and Monday mornings, respectively. The ambulatory BP was automatically measured during the sleep and awake periods for 2 h after the participant woke up at night before pre- and post-intervention measurements. SJL (average mid-sleep time on weekends - average mid-sleep time on weekdays) occurred only in the SJL trial (SJL: 181 ± 24 min vs. CON: 8 ± 47 min). Carotid-femoral pulse wave velocity (cfPWV) and morning BP surge on Monday in the SJL trial were significantly higher than those on Friday in the SJL trial (cfPWV: P = 0.001, morning BP surge: P < 0.001), and those on Monday in the CON trial (cfPWV: P = 0.007; morning BP surge: P < 0.001). Furthermore, a significant positive correlation was found between ΔcfPWV and Δmorning BP surge (R = 0.587, P = 0.004). These results suggest that even acute SJL augments morning BP surge. This phenomenon may correspond to increased central arterial stiffness.State the details of Clinical Trials: Name: Effect of acute social jetlag on risk factors of lifestyle-related diseases. URL: https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000053204 . Unique identifier: UMIN000046639. Registration date: 17/01/2022.

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.

Associations of social jetlag with depressive symptoms among adults in Southern China: a cross-sectional study

To investigate the associations between social jetlag and depressive symptoms and further analyze the interaction of social jetlag and chronic diseases on depressive symptoms among adults. Data were derived from a cross-sectional survey. Information on social jetlag, depressive symptoms, demographic characteristics, lifestyles, and health situations were collected via a structured self-administered questionnaire. The multivariable logistic regression analyses and restricted cubic splines regression were performed to test the association between social jetlag and depressive symptoms. The multiplicative model was applied to analyze the interaction of social jetlag and chronic disease on depressive symptoms. A total of 5818 adults were included and the prevalence of social jetlag was 22.95%. After multivariable adjustment, adults who experienced more than 2 hours of social jetlag had a significantly greater risk of depressive symptoms (OR = 1.43,95%CI:1.00-2.05, P = 0.049). Compared with participants having<1 hour of social jetlag and no chronic disease, participants having chronic disease were more likely to report depressive symptoms(OR = 3.22,95%CI = 2.59-4.00, P < 0.001). Moreover, among those who have chronic disease, the greater the social jetlag they reported, the greater risk of depressive symptoms they have (OR = 3.81,95%CI = 2.77-5.33, P < 0.001; OR = 4.08,95%CI = 2.24-7.43, P < 0.001). Social jetlag was linearly associated the with risk of depressive symptoms, according to restricted cubic splines. This study shows that 22.95% adults experience more than 1 hour of social jetlag. Social jetlag was positively associated with an increased risk of depressive symptoms. Among those who have chronic disease, the greater the social jetlag they reported, the greater risk of depressive symptoms they have.

Shift Work and Metabolic Syndrome Updates: A Systematic Review

Shift work can cause circadian cycles disturbances and misaligns the endogenous rhythms. The physiological variables are driven by the circadian system and, its misalignment, can impair the metabolic functions. Thus, the main objective of this study was to evaluate the metabolic alterations as a result of shift work and night work reported in articles published in the last 5 years, using the eligibility criteria both gender and indexed articles in English language. In order to execute this work, we perform a systematic review according to PRISMA guidelines and searched about Chronobiology Disorders and Night Work, both related to metabolism, in Medline, Lilacs, ScienceDirect and Cochrane. Cross-sectional, cohort and experimental studies with low risk of bias were included. We found a total of 132 articles, and, after the selection process, 16 articles remained to be analyzed. It was observed that shift work can cause circadian misalignment and, consequently, some metabolic parameters alterations such as an impaired glycemic control and insulin functioning, cortisol phase release, cholesterol fractions imbalance, changes in morphological indexes and melatonin secretion. There are some limitations, such as heterogenicity in used databases and the 5 years restriction period, because the effects of sleep disturbance may have been reported earlier. In conclusion, we suggest that shift work interferes with the sleep-wake cycle and eating patterns, which cause crucial physiological alterations that, together, can lead to metabolic syndrome.

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.

Association of Eating Pattern, Chronotype, and Social Jetlag: A Cross-Sectional Study Using Data Accumulated in a Japanese Food-Logging Mobile Health Application

Chronotype (morningness-eveningness) and social jetlag (SJL; discrepancy in the sleep pattern between the weekday and weekend) are related to eating behavior and health. The association between sleep behavior and the daily macro- and micronutrient eating pattern of each meal (breakfast, lunch, and dinner) have not been discussed well and need more evidence. Here, meal pattern datasets of Japanese participants aged 20-59 years were obtained as averages over 1 month from the data stored in the food-logging app "Asken". We allocated three groups for each chronotype and SJL. Multiple regression analyses revealed that morning chronotype and small SJL were associated with higher total daily intake of potassium, fiber, magnesium, phosphorus, and vitamin K. Breakfast energy intake and consumption of nutrients, including protein, lipid, carbohydrate, and minerals, were higher in the morning chronotype or small SJL. Lunch intake of potassium, cholesterol, fiber, magnesium, and vitamin K was also higher in the morning chronotype or small SJL. Dinner energy intake and nutrient intake of proteins, lipids, carbohydrates, sodium, and saturated fatty acids were lower in the morning chronotype or small SJL. The current data would help to establish a detailed reference for dietary intake which considers eating patterns over a day.

Effects of Irregular Mealtimes on Social and Eating Jet Lags among Japanese College Students

College students' social and eating jet lags and chronotypes may be related to irregular eating habits. Therefore, we examined the relationship between social and eating jet lags, chronotypes, variability in first and last mealtimes, and non-eating duration, as well as the effects of snacking between dinner and bedtime on social and eating jet lags, chronotypes, and mealtime variation. A total of 1900 Japanese male college students were recruited in this study. Mean wake-up time, bedtime, sleeping time, first and last mealtimes, snacks between meals, non-eating duration, the midpoint of non-eating duration, social and eating jet lags, and chronotype were calculated. Standard deviations in first and last mealtimes, the midpoint of non-eating duration, and the coefficient of variation in non-eating duration were used to evaluate mealtime variations. Mealtime variations were significantly associated with social and eating jet lags, chronotype, the midpoint of non-eating duration, and the difference in first and last mealtime between school holidays and class days. Chronotype and the midpoint of non-eating duration were significantly delayed with increased snacking after dinner. Mealtime variations were significantly lower in those who avoided snacking than in those who did not. Thus, social and eating jet lags and chronotypes are associated with sleep habits and mealtime irregularities.

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.

Irregular sleep and cardiometabolic risk: Clinical evidence and mechanisms

Sleep regularity is an essential part of the multidimensional sleep health framework. The phenomenon of irregular sleep patterns is widespread in contemporary lifestyles. This review synthesizes clinical evidence to summarize the measures of sleep regularity and discusses the role of different sleep regularity indicators in developing cardiometabolic diseases (coronary heart disease, hypertension, obesity, and diabetes). Existing literature has proposed several measurements to assess sleep regularity, mainly including the standard deviation (SD) of sleep duration and timing, sleep regularity index (SRI), interdaily stability (IS), and social jetlag (SJL). Evidence on associations between sleep variability and cardiometabolic diseases varies depending on the measure used to characterize variability in sleep. Current studies have identified a robust association between SRI and cardiometabolic diseases. In comparison, the association between other metrics of sleep regularity and cardiometabolic diseases was mixed. Meanwhile, the associations of sleep variability with cardiometabolic diseases differ across the population. SD of sleep characteristics or IS may be more consistently associated with HbA1c in patients with diabetes compared with the general population. The association between SJL and hypertension for patients with diabetes was more accordant than in the general population. Interestingly, the age-stratified association between SJL and metabolic factors was observed in the present studies. Furthermore, the relevant literature was reviewed to generalize the potential mechanisms through which irregular sleep increases cardiometabolic risk, including circadian dysfunction, inflammation, autonomic dysfunction, hypothalamic-pituitary-adrenal (HPA) axis disorder, and gut dysbiosis. Health-related practitioners should give more attention to the role of sleep regularity on human cardiometabolic in the future.

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.

Associations between sleep variability and cardiometabolic health: A systematic review

This review explored the associations between sleep variability and cardiometabolic health. It was performed following PRISMA guidelines. We identified 63 studies. Forty-one studies examined the association between sleep variability and body composition, with 29 examined body mass index (BMI). Thirteen studies used social jet lag (SJL), n = 30,519, with nine reporting a null association. Eight studies used variability in sleep duration (n = 33,029), with five reporting a correlation with BMI. Fourteen studies (n = 133,403) focused on overweight/obesity; significant associations with sleep variability were found in 11 (n = 120,168). Sleep variability was associated with weight gain (seven studies; n = 79,522). Twenty-three studies examined glucose outcomes. The association with hemoglobin A1c (16 studies, n = 11,755) differed depending on populations, while associations with diabetes or glucose were mixed, and none were seen with insulin resistance (five studies; n = 6416). Sixteen studies examined cardiovascular-related outcomes, with inconsistent results. Overall significant associations were found in five studies focusing on metabolic syndrome (n = 7413). In summary, sleep variability was likely associated with obesity, weight gain, and metabolic syndrome. It might be associated with hemoglobin A1c in people with type 1 diabetes. The associations with other outcomes were mixed. This review highlighted the possible association between sleep variability and cardiometabolic health.

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.

Social jetlag and depression in female rotating-shift nurses: A secondary analysis

PURPOSE

This study aimed to identify the predictors of depression among female rotating-shift nurses.

DESIGN AND METHODS

This secondary data analysis used data of 190 Korean female rotating-shift nurses from the parent study conducted in 2018. A multiple logistic regression analysis was performed to identify the predictors of depression.

FINDINGS

Young age, poor sleep quality, and greater morning-shift social jetlag predicted depression among female nurses working a three-shift schedule.

PRACTICE IMPLICATIONS

Nursing management should consider scheduling shifts to minimize nurses' social jetlag and develop interventions for improving sleep quality to prevent depression among female rotating-shift nurses.

Association between irregular daily routine and risk of incident stroke and coronary heart disease in a large Japanese population

Circadian misalignments have been linked to adverse cardiometabolic outcomes. However, the association between irregular daily routine and the risk of cardiovascular disease (CVD) remains unknown. We examined this association in a prospective study in Japan. The study included 78,115 Japanese participants aged 45–74 years. The self-reported daily routine was evaluated using the question, ‘Is your daily routine or activity schedule regular?’ The response (yes/no) was obtained as a binary variable. Cox proportional hazard regression analysis was used to estimate the hazard ratios and 95% confidence intervals for the association between an irregular daily routine and CVD incidence risk. Among the participants, 23.7% reported an irregular daily routine. During the mean follow-up period of 13.3 years, we observed 4641 CVD events. An irregular daily routine was significantly associated with increased risks of CVD and total stroke in women, but not in men. This positive association between an irregular daily routine and the risk of CVD was weak in the high vegetable and fruit consuming population. An irregular daily routine is positively associated with the risk of incident CVD, especially in women. These associations may be weak in populations that consume a diet rich in vegetables and fruits.

Direction and magnitude of social jetlag are associated with obesity: Results from a sample of hospital employees

Social jetlag, the discrepancy between social and biological timing, has been suggested to disturb metabolic functions. However, the relationship between social jetlag and obesity has been inconsistent in other studies. In this study we examined the association between social jetlag and obesity among day and shift workers. We invited 2508 day workers and 1383 shift workers from a hospital worker health cohort to participate in a 2018-2019 survey on their sleep behaviors. Shift-specific social jetlag was quantified using the Munich ChronoType Questionnaire, and body mass index was measured during annual physical examinations. The distributions of shift-specific social jetlag were illustrated, and logistic regression analysis was used to examine the association between social jetlag and obesity. We found that high level of social jetlag (odds ratio [OR] = 1.26, 95% confidence interval [CI] = 1.08-1.47) and positive social jetlag (OR = 2.25, 95% CI = 1.30-3.90) during evening shifts were associated with obesity after adjustment for age, sex, health behaviors, and sleep quality. During night shift periods, sleep time varied greatly on free days, but the participants slept at similar times, namely 16:00, on workdays. In conclusion, phase advance on workdays and high levels of social jetlag were associated with obesity. Sleep timing should therefore be recommended according to the relative phase of individuals' preferred sleep time and work time.

Relationship of chronotype and social jetlag with adherence to the Japanese dietary guidelines among workers

While late chronotype and greater social jetlag have been associated with poor dietary behavior among the general population, these associations have not been investigated among workers, who struggle to align their sleep timings with work schedules. We aimed to explore the cross-sectional association of social jetlag and a late chronotype with adherence to a healthy diet among Japanese workers. Participants were 1,435 non-shift workers (18-78 years) who attended a nutritional survey. Social jetlag was defined as the difference in the midpoint of sleep times between weekdays and weekends, while chronotype was estimated using the mid-sleep time on weekends that was corrected with sleep debt on weekdays. We calculated the adherence score of the Japanese Food Guide Spinning Top (JFGST) - healthy diet guidelines for Japanese. Multivariable linear regression analyses were used to calculate the adjusted means and 95% confidence intervals (CI) for adherence scores of social jetlag and chronotype. We found that greater social jetlag was associated with a lower JFGST score. The multivariable-adjusted mean (95% CI) of JFGST scores were 39.7 (39.1-40.2), 38.7 (37.9-39.6), and 38.1 (36.6-39.7) for <1 hour, 1 to <2 hours, and ≥2 hours of social jetlag, respectively (P-trend = 0.02). Workers with late chronotypes had significantly lower adherence scores on JFGST [36.3 (34.7-37.8); P-trend = 0.002]. Results suggest that a late chronotype and social jetlag are inversely associated with adherence to a healthy diet among Japanese workers.

Association of sleep duration and sleep quality with overweight/obesity among adolescents of Bangladesh: a multilevel analysis

Background

Sleep deprivation is widely recognized as a potential contributor to childhood obesity. However, few studies have addressed this issue in low-income settings. The aim of this study was to determine the association of both sleep duration and sleep quality with overweight/obesity among adolescents of Bangladesh.

Methods

A cross-sectional study was conducted in four randomly selected schools in Gazipur, Bangladesh, from May to August 2019. Using a self-administered semi-structured questionnaire, data on sleep duration and sleep quality were collected from 1,044 adolescents between 13 and 17 years of age. The body mass indices of the study participants were evaluated using their objectively-assessed anthropometric measurements (weight and height). Multilevel logistic regression was used for data analysis.

Results

The prevalence of underweight, overweight and obesity in adolescents in this study were 14.9, 18 and 7.1%, respectively. More than 15% of the students reported sleep disturbance and poor sleep quality. After adjusting for confounders, reduced (<7 h/day) total sleep duration (OR=1.73, 95% CI=1.21-2.47), weekend sleep duration (OR=1.46, 95% CI=1.00-2.12), and night sleep duration (OR=1.55, 95% CI=1.06-2.28) were found to be significantly associated with overweight or obesity in Bangladeshi adolescents. Similarly, significant positive associations were evident between short duration of total sleep (OR=0.33, 95% CI=0.20-0.54), weekday sleep (OR=0.55, 95% CI=0.35-0.84), weekend sleep (OR=0.53, 95% CI=0.31-0.89), and night sleep (OR=0.56, 95% CI=0.36-0.87), and underweight in study participants. Adolescents with short sleep duration were found less likely to be underweight and more likely to be overweight/obese.

Conclusions

Study findings denoted short sleep duration to be associated with overweight/obesity and underweight among adolescents of Bangladesh. Adequate sleep may therefore serve as an effective obesity prevention strategy in the growing stages.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-12774-0.

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 Cardiometabolic Risk in Preadolescent Children

Objective: Childhood cardiometabolic disease risk (CMD) has been associated with short sleep duration. Its relationship with other aspects of sleep should also be considered, including social jetlag (SJL) which represents the difference between a person's social rhythms and circadian clock. This study investigated whether childhood CMD risk is associated with sleep duration, sleep disturbances, and SJL.

Study Design: The observational study included 332 children aged 8–10 years (48.5% female). The three independent variables were sleep duration, sleep disturbances, and SJL. SJL was calculated as the variation in hours between the midpoint of sleep during free (weekend) days and work/school days. Eleven cardiometabolic biomarkers were measured, including central blood pressure, lipids, glycated hemoglobin, arterial wave reflection, and glucose. Underlying CMD risk factors were identified using factor analysis.

Results: Four underlying CMD risk factors were identified using factor analysis: blood pressure, cholesterol, vascular health, and carbohydrate metabolism. Neither sleep disturbances nor sleep duration were significantly associated with any of the four CMD factors following adjustments to potential confounders. However, SJL was significantly linked to vascular health (p = 0.027) and cholesterol (p = 0.025).

Conclusion: These findings suggest that SJL may be a significant and measurable public health target for offsetting negative CMD trajectories in children. Further studies are required to determine biological plausibility.

Weekend catch-up sleep and depression: results from a nationally representative sample in Korea

BACKGROUND

There is limited information on the association between weekend catch-up sleep (CUS), which has beneficial effects on health, and depression. This study aimed to investigate the association between CUS and depression in adults.

METHODS

We used the data of the Seventh Korea National Health and Nutrition Examination Survey, 2016. Depression was defined as Patient Health Questionnaire-9 score ≥10. We categorized CUS duration as ≤0, 0 < to 1, 1 < to 2, and >2 h.

RESULTS

Of 5550 eligible participants, 3286 (54.9%), 1033 (19.5%), 723 (14.7%) and 508 (10.9%) had CUS duration ≤0, 0 < to 1, 1 < to 2, and >2 h, respectively; of these, the prevalence of depression was 7.0%, 4.2%, 2.9%, and 6.0%, respectively. Multivariable regression analyses including covariates revealed that individuals with CUS duration 1 < to 2 h had a significantly decreased risk of depression compared to individuals with CUS duration ≤0 h (odds ratio [OR] = 0.517, 95% CI = 0.309-0.865). Individuals with CUS duration 0 < to 1 h (OR = 0.731, 95% CI = 0.505-1.060) and >2 h (OR = 1.164, 95% CI = 0.718-1.886) showed no significantly different risk of depression.

CONCLUSIONS

The risk of depression in individuals with CUS duration 1 < to 2 h was lower than for those with CUS duration ≤0 h. This finding provides a better understanding on the association between CUS and depression; and can be a basis for better management of depression.

Association of sleep duration on workdays or free days and social jetlag with job stress

AIM

The aim of this study was to investigate the impact of sleep problems on job stress in office workers.

METHODS

This study included 4645 office workers from 29 companies who completed the study questionnaires between April 2017 and April 2019 in Japan. Sleep duration was assessed based on the participants' subjective sleep schedule on workdays and free days. The midpoint of sleep on free days (sleep-corrected) and social jetlag were calculated in accordance with the Munich Chronotype Questionnaire. To assess job stress, we used the 57-item Brief Job Stress Questionnaire.

RESULTS

Multivariate logistic regression analysis revealed that the following factors were significantly associated with high job stress in office workers: a sleep duration <6 h on workdays (OR = 1.77, 95% CI = 1.46-2.15, P < 0.001), a sleep duration <6 h on free days (OR = 1.40, 95% CI = 1.05-1.87, P = 0.022), a sleep duration of at least 8 h on free days (OR = 1.31, 95% CI = 1.06-1.60, P = 0.011), and more than 2 h of social jetlag (OR = 1.33, 95% CI = 1.04-1.70, P = 0.022).

CONCLUSION

This study suggests that insufficient sleep, long sleep durations on free days, and social jetlag may be associated with high job stress in office workers.

Association of weekday-to-weekend sleep differences and stress response among a Japanese working population: a cross-sectional study

OBJECTIVES

To investigate the relationship between differences in weekday-to-weekend sleep habits and stress responses in a working population.

METHODS

This cross-sectional study used data from university workers on sleep habits, differences in sleep duration between weekdays and weekends, and each midpoint of the sleep phase on weekdays and weekends. Social jetlag was defined as the difference in the midpoint of the sleep phase between weekdays and weekends. In addition, the Brief Job Stress Questionnaire assessed stress responses and stress-related factors. To examine sleep-related factors affecting stress responses, regression analysis was performed with adjustments for age, sex, and stress-related factors.

RESULTS

Analyzed were 2,739 participants. Sleep duration differences obtained by subtracting sleep duration on weekdays from that on weekends, social jetlag, and weekday sleep duration were significantly associated with an increased risk of stress responses in a univariate linear regression model. Adjusting for age, sex, job stressors, and stressor buffering factors did not change this trend. However, when additionally adjusting for all sleep parameters, only sleep duration differences and weekday sleep duration were significantly associated with stress responses (β 0.67 [95% CI 0.24, 1.10], p = 0.002), (-0.66 [-1.20, -0.13], p = 0.015).

CONCLUSIONS

This study provided further evidence that weekday sleep duration and weekday-to-weekend sleep duration differences were independently associated with stress responses even when considering stress-related factors. However, social jetlag was not clearly associated with stress responses. Our findings highlighted the necessity of securing sufficient sleep for stress management and mental health promotion in a working population.

[Association between social jetlag and presenteeism in Japanese industry: A cross-sectional study]

OBJECTIVES

Research suggests that misalignment of the biological clock and social time, referred to as social jetlag (SJL),can induce physical and mental disorders. SJL may also be associated with presenteeism (i.e., a state in which workers are unable to perform sufficiently due to mental and physical health problems, even though they are going to work). However, the association between SJL and presenteeism among workers in Japan remains unclear. This study aimed to verify the following hypotheses in a sample of workers in an industrial setting in Japan: "Workers exhibiting SJL have a high degree of work functioning impairment due to presenteeism" and "An association between SJL and presenteeism exists, even when taking work style and sleep-related factor into consideration."

METHODS

A self-administered questionnaire survey was conducted with 1,573 workers in the manufacturing industry. Of these, 1,501 participants responded (response rate: 95.4%). Individuals who provided invalid answers or used alarm clocks to wake on work-free days were excluded, according to the Munich Chronotype Questionnaire (MCTQ) guidelines. The final sample comprised 980 participants (80.7% male; average age: 44.4 [SD 11.3] years). SJL was assessed using the MCTQ. Presenteeism was measured using the work functioning impairment scale. Using presenteeism as the dependent variable, we conducted hierarchical multiple regression analyses to compare the explanatory power of the different models. Independent variables were SJL, daily rest period between workdays, weekday sleep duration, and subjective insomnia. Models 2 and 3 were adjusted for age, sex, employment position, occupation, employment status, and working regulations.

RESULTS

Multiple regression analyses indicated that SJL was significantly and individually associated with presenteeism (β = .066, p = .038). After adjusting for work- and sleep-related variables (Models 2 and 3), SJL no longer contributed significantly to presenteeism. In the final model, daily rest periods (β = .076, p = .017) and subjective insomnia (β = .470, p < .001) remained significantly associated with presenteeism (adjusted R² = .239).

CONCLUSIONS

The hypothesis "Workers experiencing SJL have a high degree of work functioning impairment due to presenteeism" was supported in our univariate analysis. However, after considering the influence of subjective insomnia and daily rest periods, the association disappeared. Therefore, a direct relationship between SJL and presenteeism is not supported. Thus, the risk of presenteeism should be considered in two stages, first confirming the perception of insomnia among workers who experience SJL, and then considering the possibility of presenteeism occurring.

Sleep Debt and Social Jetlag Associated with Sleepiness, Mood, and Work Performance among Workers in Japan

Although sleep debt and social jetlag (SJL) influence daytime dysfunctions, the effects of both sleep debt and SJL on them have not been analyzed. The aim of this study was to examine the mutual relationship between sleep debt and SJL on daytime sleepiness, mood, and work performance. This study was a cross-sectional study on sleep health conducted on the Japanese general population. A total of 4505 general workers (30% female, aged 43.57 ± 11.63 years) were selected and analyzed. Sleep debt was defined by sleep debt index (SDI), which is the discrepancy between desired and real sleep duration. SJL and SDI scores exhibited a positive but weak coefficient (r = 0.19). In a 4 (SJL) × 3 (SDI) two-way ANOVA, the interaction effects were notable for sleepiness and depression scores, while the group effects were notable for the work performance score. For sleepiness and depression scores, SDI >2 h was not significantly different from SJL. In addition, the impact of SDI was higher than that of SJL on sleepiness (β = 0.17), depression (β = 0.16), and work performance (β = -0.10). The impact of sleep debt was more pronounced than SJL on daytime dysfunctions, although both sleep debt and SJL have negative impacts on them.

Association between social jet lag, quality of diet and obesity by diurnal preference in Finnish adult population

The evening type has been associated with unhealthy behaviors and adverse health outcomes, such as unhealthy dietary habits and obesity. Misalignment between biological and social rhythms, referred to as social jet lag (SJL), has been considered to explain these outcomes, because evening types are more prone to SJL. However, the existing evidence has been inconsistent and SJL by diurnal preference has hardly been examined. We examined the associations between SJL, the quality of the diet, and the prevalence of obesity by diurnal preference. This dataset included 6779 Finns (55% women, aged 25-74 years) from the National FINRISK 2012 and DILGOM 2014 studies. Diurnal preference was assessed with a shortened version of the Morningness-Eveningness Questionnaire (MEQ). SJL was calculated with the sleep-corrected formula (SJL_sc). SJL was divided into three groups by the degree of SJL (<1h, ≥1h but <2h and ≥2h). The dietary intake was assessed with a validated food frequency questionnaire (FFQ) and the quality of the diet with the Baltic Sea Diet Score. Body weight, height, and waist circumference (WC) were measured, and the body mass index (BMI) was calculated (kg/m²). Analysis of covariance (ANCOVA) followed by Bonferroni multiple comparison post-hoc tests and logistic regression models were used to analyze the differences between the lowest and the highest SJL groups by diurnal preference. In the highest SJL group (≥2h), there were more evening types than morning types (7%-points, p < .001). Overall, those in the highest SJL_sc group were on average younger than those in the lowest SJL_sc group (p< .001). Also, those in the highest SJL_sc group tended to have lower adherence to the Baltic Sea Diet compared to the participants in the lowest SJL_sc group, but this difference reached significance only in morning types (p = .006). Furthermore, morning types in the highest SJL_sc group had higher BMI and WC compared to the morning types in the lowest SJL_sc group (BMI, p = .016; WC, p = .012). In conclusion, evening types had on average more SJL than morning types, but the degree of SJL was associated with the quality of the diet and obesity only in the morning types.

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.

Circadian Misalignment Is Negatively Associated with the Anthropometric, Metabolic and Food Intake Outcomes of Bariatric Patients 6 Months After Surgery

PURPOSE

Circadian misalignment has been associated with an increased risk of overweight and obesity, as well as changes in metabolic parameters. This study evaluated the association between social jet lag (SJL), a measure of circadian misalignment, and anthropometric, metabolic and food intake outcomes 6 months after bariatric surgery.

MATERIALS AND METHODS

A total of 122 bariatric patients were included (77% female, aged 33 years (range 28-41); 79.5% underwent Roux-en-Y gastric bypass). Anthropometric, food consumption and SJL were evaluated in the preoperative evaluation and in the third and sixth months after surgery. SJL was calculated based on the absolute difference between the mid-sleep time on weekends and weekdays. Generalised estimating equations and linear regression were performed to evaluate the associations between mean SJL exposure and the outcomes.

RESULTS

The interaction between SJL and follow-up time negatively influenced the evolution of weight (p = 0.01), BMI (p = 0.04) and insulin levels (p = 0.01). SJL had an effect on intake of calories (p = 0.001), carbohydrate (p = 0.005) and total (p = 0.007), monounsaturated (p = 0.03) and polyunsaturated fat (p < 0.001). Linear regression showed a negative association between mean SJL exposure over the 6 months and the percentage of weight loss (coefficient = - 0.30, p = 0.006), body weight loss (kg) (coefficient = - 0.17, p = 0.03) and the reduction of BMI (coefficient = - 0.24, p = 0.007).

CONCLUSIONS

SJL was negatively associated with anthropometric, metabolic and food consumption outcomes 6 months after bariatric surgery. Future studies with longer follow-up are needed to confirm these findings.

TRIAL REGISTRATION

Clinical Trials.gov : NCT03485352.

Sleep Regularity and Cardiometabolic Heath: Is Variability in Sleep Patterns a Risk Factor for Excess Adiposity and Glycemic Dysregulation?

PURPOSE OF REVIEW

Night-to-night variability in sleep patterns leads to circadian disruption and, consequently, could increase cardiometabolic risk. The purpose of this review is to summarize findings from studies published between 2015 and 2020 examining various measures of night-to-night variability in sleep in relation to metabolic syndrome (MetS), type 2 diabetes (T2D), and their risk factors. We illustrate a potential causal pathway between irregular sleep patterns and T2D, highlighting knowledge gaps along the way.

RECENT FINDINGS

Across different measures of sleep variability, irregular sleep patterns were associated with poorer cardiometabolic outcomes. Higher standard deviations (SD) across nights of sleep duration and onset or midpoint of sleep were associated with increased odds of having MetS and clusters of metabolic abnormalities as well as greater adiposity and poorer glycemic control. Conversely, greater regularity of rest-activity patterns related to lower risk for T2D. Social jetlag was associated with glycemic dysregulation, adiposity, T2D, and MetS. These associations are often observed in both metabolically healthy and unhealthy individuals; both higher SD of sleep duration and social jetlag relate to poorer glucose regulation in individuals with diabetes. There is consistent evidence of associations of sleep variability with increased risk for adiposity, glucose dysregulation, T2D, and MetS. Although experimental evidence is needed to determine causation, there is support to recommend stabilizing sleep patterns for cardiometabolic risk prevention.

Social jetlag, eating behaviours and BMI among adolescents in the USA

There is a lack of research on associations of social jetlag with eating behaviours and obesity among adolescents. We examined the associations of social jetlag with eating behaviours and BMI in adolescents before and after adjustment for potential confounders. Self-report data were collected from 3060 adolescents (48·1 % female, mean age 15·59 (sd 0·77) years) from the Fragile Families and Child Wellbeing Study. In regression models, social jetlag predicted odds of consumption of breakfast, fruits/vegetables, fast food and sweetened drinks and BMI percentile. Primary models adjusted for school night sleep duration, sex, age, household income and youth living arrangements; secondary models further adjusted for race/ethnicity. In fully adjusted models, greater social jetlag was associated with lower odds of consumption of breakfast (OR = 0·92, P = 0·003) and fruits/vegetables (OR = 0·92, P = 0·009) and higher odds of consumption of fast food (OR = 1·18, P < 0·001) and sweetened drinks (OR = 1·18, P < 0·001). Social jetlag was positively associated with BMI percentile after additional adjustment for eating behaviours (b = 0·84, P = 0·037), but this relationship was attenuated after adjustment for race/ethnicity (b = 0·72, P = 0·072). Ethnoracial differences in social jetlag may attenuate the association of social jetlag with BMI and should be considered in future studies of circadian misalignment, eating behaviours and obesity markers.

Weight loss in conservative treatment of obesity in women is associated with physical activity and circadian phenotype: a longitudinal observational study

Introduction

The study investigates the association between circadian phenotype (CP), its stability (interdaily stability - IS) and physical activity (PA) in a weight loss (WL) programme.

Methods

Seventy-five women in WL conservative treatment (BMI ≥ 25 kg/m2) were measured (for about 3 months in between 2016 and 2018) by actigraphy.

Results

We observed a difference in time of acrophase (p = 0.049), but no difference in IS (p = 0.533) between women who lost and did not lose weight. There was a difference in PA (mesor) between groups of women who lost weight compared to those who gained weight (p = 0.007). There was a relationship between IS and PA parametres mesor: p0.001; and the most active 10 h of a day (M10): p < 0.001 - the more stable were women in their rhythm, the more PA they have. Besides confirming a relationship between PA and WL, we also found a relation between WL and CP based on acrophase. Although no direct relationship was found for the indicators of rhythm stability (IS), they can be considered very important variables because of their close connection to PA – a main factor that contributes to the success of the WL programme.

Discussion

According to the results of the study, screening of the CP and its stability may be beneficial in the creation of an individualized WL plan.

At the Interface of Lifestyle, Behavior, and Circadian Rhythms: Metabolic Implications

Nutrient metabolism is under circadian regulation. Disruption of circadian rhythms by lifestyle and behavioral choices such as work schedules, eating patterns, and social jetlag, seriously impacts metabolic homeostasis. Metabolic dysfunction due to chronic misalignment of an organism's endogenous rhythms is detrimental to health, increasing the risk of obesity, metabolic and cardiovascular disease, diabetes, and cancer. In this paper, we review literature on recent findings on the mechanisms that communicate metabolic signals to circadian clocks and vice versa, and how human behavioral changes imposed by societal and occupational demands affect the physiological networks integrating peripheral clocks and metabolism. Finally, we discuss factors possibly contributing to inter-individual variability in response to circadian changes in the context of metabolic (dys)function.

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.