Cross-sectional Internet-based survey of Japanese permanent daytime workers' sleep and daily rest periods

Sleep restriction alters the integration of multiple information sources in probabilistic decision-making

The detrimental effects of sleep loss on overall decision-making have been well described. Due to the complex nature of decisions, there remains a need for studies to identify specific mechanisms of decision-making vulnerable to sleep loss. Bayesian perspectives of decision-making posit judgement formation during decision-making occurs via a process of integrating knowledge gleaned from past experiences (priors) with new information from current observations (likelihoods). We investigated the effects of sleep loss on the ability to integrate multiple sources of information during decision-making by reporting results from two experiments: the first implementing both sleep restriction (SR) and total sleep deprivation (TSD) protocols, and the second implementing an SR protocol. In both experiments, participants were administered the Bayes Decisions Task on which optimal performance requires the integration of Bayesian prior and likelihood information. Participants in Experiment 1 showed reduced reliance on both information sources after SR, while no significant change was observed after TSD. Participants in Experiment 2 showed reduced reliance on likelihood after SR, especially during morning testing sessions. No accuracy-related impairments resulting from SR and TSD were observed in both experiments. Our findings show SR affects decision-making through altering the way individuals integrate available sources of information. Additionally, the ability to integrate information during SR may be influenced by time of day. Broadly, our findings carry implications for working professionals who are required to make high-stakes decisions on the job, yet consistently receive insufficient sleep due to work schedule demands.

The association between work interval regularity and sleep regularity: a 2-week observational study in daytime employees

OBJECTIVES

Several health issues are associated with irregular sleep patterns. However, it is unclear what causes workers to sleep irregularly. The work interval (WI) between the end of one day's working hours and the start of the next day's working hours contains sleep opportunities, and an irregular WI may result in irregular sleep. This study investigated this association among Japanese daytime workers.

METHODS

This study recruited 141 daytime workers without shiftwork for a 14-day observational study. Participants reported the WI duration, WI timing, time in bed (TIB: difference between bedtime and wake-up time), and bedtime timing every day before bedtime. The SD over 14 days was used to calculate the regularity scores. Logistic regression analysis was performed. The dependent variables were ≥60 minutes of TIB SD and bedtime timing SD, whereas the independent variables were WI duration and timing SD.

RESULTS

The odds ratios (ORs) (95% CIs) for ≥60 minutes of TIB SD across categories of WI duration SD were 1.000 (reference) for <30 minutes, 1.344 (0.337-5.360) for 30-60 minutes, and 4.743 (1.441-15.607) for ≥60 minutes. The ORs (95% CIs) for ≥60 min of bedtime timing SD across categories of WI timing SD were 1.000 for <30 minutes, 4.154 (1.574-10.965) for 30-60 minutes, and 7.714 (2.124-28.015) for ≥60 minutes.

CONCLUSIONS

Regularity of WI was associated with regularity of sleep. To ensure worker health, workers should have regular WI, and if they are exposed to irregular WI, they should make every effort to maintain regular sleep.

Effects of work-related electronic communication during non-working hours after work from home and office on fatigue, psychomotor vigilance performance and actigraphic sleep: observational study on information technology workers

OBJECTIVES

This study examined the effects of work-related electronic communication (WREC) during non-working hours in the work from home or office setting on health.

METHODS

The study recruited 98 information technology workers in a 9-day observational study. They recorded work-life events (eg, work style (working mostly from home or the office) and duration of WREC during non-working hours) and subjective ratings (eg, current fatigue, sleepiness and depression) and wore a sleep actigraph to measure objective sleep variables before bedtime every day. They completed the Brief Psychomotor Vigilance Test (PVT-B) before bedtime for 4 days.

RESULTS

The frequency of WREC was significantly higher when working mostly from home than in the office (p<0.01). In addition, the duration of WREC was longer when working mostly from home than in the office (p<0.001). Linear or generalised linear mixed model analysis for fatigue, depression and PVT lapse revealed significant interaction effects between work style and WREC (all p<0.05). Post hoc analysis showed that the longer the WREC, the worse the fatigue and depression and the lower the lapse on working mostly from the office (all p<0.05).

CONCLUSIONS

Longer WREC is associated with worse fatigue and depression and lower lapse of PVT (higher alertness) before bedtime for working mostly from the office. Workers, especially those working from the office, should minimise WREC during non-working hours to maintain good health. Therefore, companies, managers and other relevant stakeholders should refrain from contacting workers during non-working hours.

The impact of a mobile app-based corporate sleep health improvement program on productivity: Validation through a randomized controlled trial

Based on a randomized controlled trial applied to employees of a manufacturing company, this study examines the extent to which a corporate sleep program improves workers' sleep health and productivity. In the three-month sleep improvement program, applicants were randomly divided into a treatment group and a control group, and the treatment group was provided with a noncontact sensing device to visualize their sleep. A smartphone app linked to the device notified them of their sleep data every morning and presented them with advice on behavioral changes to improve their sleep on a weekly basis. The results of the analysis revealed the following. First, even after controlling for factors that may cause sleep disturbances and nocturnal awakenings, such as increased workload and the number of days spent working from home during the measurement period, the treatment group showed improved sleep after the program compared to the control group. Second, the treatment group showed statistically significant improvement in presenteeism (productivity). The effect size on presenteeism through sleep improvement was similar regardless of the estimation method used (i.e., ANCOVA estimator of ATT and two 2SLS methods were performed). In particular, we confirmed that productivity was restored through sleep improvement for the participants who diligently engaged in the program. These results suggest that promoting sleep health using information technology can improve sleep deficiency and restore productivity.

The Joint Association of Daily Rest Periods and Sleep Duration with Worker Health and Productivity: A Cross-Sectional Web Survey of Japanese Daytime Workers

A daily rest period (DRP) is a daily inter-work interval that contains sleep opportunity. This study investigates the joint association of DRP and sleep duration with worker health and productivity. A total of 13,306 Japanese daytime workers participated in this web-based cross-sectional survey. Participants reported on their DRPs and sleep duration; moreover, sleep difficulties, mental health, and presenteeism were assessed by the standardized questionnaires. The participants were divided into 10 groups based on their DRPs and sleep duration. Logistic regression analyses showed that the combination of quick return (QR: DRP of <11 h) and short sleep duration (<6 h) was found to be significantly associated with sleep difficulties (odds ratio [OR] = 4.45, 95% confidence interval [CI] = 2.83-7.01), poor mental health (OR = 3.04, 95% CI = 1.79-5.15), and presenteeism (OR = 2.35, 95% CI = 1.47-3.77) compared with the reference group (the combination of adequate DRP [15 h] and a normal sleep duration [≥6 h]). The combination of QR and normal sleep duration or adequate DRP and short sleep duration was significantly associated with high ORs for the outcomes. QR, short sleep duration, or both negatively affect worker health and productivity.

Effect of occupation on sleep duration among daytime Japanese workers: A cross-sectional study

Occupation is one of the factors contributing to the loss of sleep. Although many studies have investigated sleep loss due to irregular and nighttime shifts, the causes of sleep loss in daytime workers remain unknown. The aims of the present study were to determine whether occupation is a dependent factor for sleep duration and whether working status and lifestyle are related to sleep duration.We examined the health check results of 17,519 (9028 men and 8491 women) workers who had at least 1 health check between the fiscal years 2013 and 2019. We asked about the workers' occupation, bedtime, dinner time, overtime work, and commuting time, using a self-administered questionnaire at their health check. The occupations were classified into 4 categories: high white-collar, low white-collar, pink-collar, and blue-collar. We conducted a linear regression model and analysis of covariance to investigate the effect of occupation on sleep duration.As a result of linear regression analysis, bedtime, overtime work and occupation were significantly associated with decreased sleep duration in males, and bedtime, age, and occupation were significantly associated with decreased sleep duration in females. Analysis of covariance revealed that both male and female blue-collar tended to sleep for significantly shorter durations than those in the other occupations.The results of the current study indicate that sleep duration is affected by occupation. When determining the cause of loss of sleep, medical personnel should consider their patient's lifestyles and how they have been affected by their occupation.

Overtime working patterns and adverse events in work-related suicide cases: hierarchical cluster analysis of national compensation data in Japan (fiscal year 2015-2016)

Background

Although various work-related adverse events affect workers’ mental health, the association between long working hours and mental disorders remains unclear. We investigated the characteristics of overtime work and work-related adverse events among all cases of compensated work-related suicide in Japan to empirically reveal the context of the serious consequences.

Methods

We analysed all 167 cases of mental disorders resulting in suicide that were compensated in fiscal year 2015–2016. Hierarchical clustering was applied to the overtime working history. Work-related adverse events were also evaluated as the qualitative aspects of their jobs.

Results

More than half of the cases committed suicide within a month of developing a mental disorder. The Administrative and professional or engineering workers had a higher suicide rate. The clustering analysis revealed chronic long working hours (19%), gradual increase (27%), or rapid increase (25%) in working hours before the onset of a mental disorder. A group of cases with less overwork experienced more interpersonal conflicts.

Conclusion

This is the first study to employ a clustering technique to objectively reveal the actual working patterns behind suicide. The patterns of working overtime before the onset of mental disorders varied considerably among the cases. Taking the transition of working overtime into account may provide clearer insight into the relationship between long working hours and workers’ mental health. These results highlight the need for countermeasures especially for causes of chronic overworking, drastic increases in working hours, and interpersonal conflicts to prevent work-related suicide.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00420-021-01760-5.

Prospective changes in sleep problems in response to the daily rest period among Japanese daytime workers: A longitudinal web survey

The daily rest period (DRP) is the daily inter‐work interval and can include a sleep opportunity, leisure time, and other non‐work time. A longer DRP may allow workers to increase time in bed (TIB) and adjust sleep timing, and that may reduce sleep problems such as short sleep duration, sleep debt, social jetlag, and poor sleep quality. The present study examined the longitudinal association between the DRP and these sleep problems among Japanese daytime workers. The DRP, TIB on workdays, sleep quality (Pittsburgh Sleep Quality Index [PSQI]), sleep debt and social jetlag were measured in November 2016 (n = 10,000) and February 2019 (n = 3,098). Of these, 955 permanent daytime workers were divided into five groups based on the change in the DRP duration: shortened ≥2 hr, shortened ≥1 hr, no change (<1 hr), extended ≥1 hr and extended ≥2 hr. Linear mixed‐model analysis revealed significant interaction (group × time) effects on the TIB, PSQI score and sleep debt (all p < 0.001), but not on social jetlag (p = 0.476). Post hoc comparisons revealed that the TIB was decreased, and the sleep debt was increased in the shortened ≥2 hr group, whereas the TIB was increased and PSQI score was improved in the extended ≥2 hr group (all p < 0.01). These findings suggest that an extension of the DRP improves sleep quantity and quality but not sleep debt and social jetlag. Aside from extending the DRP, ensuring a sufficient sleep duration and adjusting sleep timing during the DRP may also be needed to prevent sleep problems.

[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.

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.

Sociomedical problems of overwork-related deaths and disorders in Japan

Objectives

Cerebrovascular and cardiovascular diseases (CCVDs) and mental disorders, including suicide, are prevalent among overworked individuals in Japan. The 2014 legislation regarding the prevention of overwork‐related deaths and disorders has accelerated the research in this field and ultimately the implementation of preventive actions.

Methods

To understand the current problematic situations, the Research Center for Overwork‐Related Disorders of the National Institute of Occupational Safety and Health, Japan, conducted analyses of compensated claims for overwork‐related CCVDs and mental disorders that were recognized from January 2010 to March 2015.

Results

The majority of CCVD cases were the men in their 50s. Transport and postal activities was the highest risk industry. Cerebrovascular cases were higher than cardiovascular ones. Long working hours was the principal factor for CCVDs. The mental disorder cases comprised approximately 70% men and affected younger age groups (peak in the third decade) with various industries at risk. In men, there was an almost equal number of F3 (Mood [affective] disorders) and F4 (Neurotic, stress‐related, and somatoform disorders) diagnoses according to the 10th revision of the International Classification of Diseases and Related Health Problems. A larger number of women were diagnosed to have F4. The mental disorder cases were associated not only with long working hours, but also with injuries and disasters as well as interpersonal conflict at work.

Conclusions

Multiple, simultaneous actions need to be made by employees, employers, researchers, and the authorities to achieve the goal of reducing the number of workers suffering from the overwork‐related CCVDs and mental disorders.

Day-to-day variations in daily rest periods between working days and recovery from fatigue among information technology workers: One-month observational study using a fatigue app

BACKGROUND

The European Union's Working Time Directive stipulates recovery periods as "Eleven consecutive hour daily rest periods (DRPs) between working days." In Japan, adopting this regulation has been discussed.

OBJECTIVE

To examine the association between weekday DRPs and recovery from fatigue by conducting a one-month observational study using a fatigue monitoring application (fatigue app) on a smart tablet.

METHODS

Fifty-five daytime employees working at an information technology company participated in this study. Visual analogue scales (VAS) regarding fatigue, psychological detachment from work, a psychomotor vigilance task (PVT), and sleep-wake logs were repeatedly measured using a fatigue app that we developed for this study. Sleep was measured by a wrist actigraph.

RESULTS

The average and SD of weekday DRPs was 13.1 ± 2.3 h. However, 54.5% of employees experienced less than the minimum 11-hour DRP at least once a month. Sleep duration was significantly changed with weekday DRPs, though no significant difference was found in sleep efficiency. Linear mixed effects models showed that sleep duration increased by approximately 15 minutes for each hour of weekday DRPs (β = 0.24, 95% CI; 0.17, 0.32, p <.001). VAS-measured fatigue and psychological detachment from work significantly improved as DRPs increased (β = -3.4, 95% CI; -4.7, -2.1, p <.001; β = 2.6, 95% CI; 1.2, 4.0, p <.001, respectively). However, PVT performance did not significantly change with weekday DRPs.

CONCLUSIONS

Ensuring weekday DRPs plays an essential role in protecting the opportunities to sleep, with better recovery from fatigue and stress among information technology workers.