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This cross-sectional study investigates the association between long working hours, short sleep duration, and mental health among Japanese physicians. We enrolled 232 Japanese physicians. We used the Brief Job Stress Questionnaire to assess high-stress status, and the Japanese version of the Center for Epidemiologic Studies Depression scale to assess depressive status. Daily sleep duration (DSD) and weekly working hours (WWHs) were collected using a self-administered questionnaire. Multivariable-adjusted logistic regression analysis was performed to examine the association of the combined categories of DSD and WWHs with high-stress and depressive status. Compared to physicians with WWHs <80 h and DSD ≥6 h, the multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of high-stress status for those with WWHs ≥80 and DSD ≥6, WWHs <80 and DSD <6, and WWHs ≥80 and DSD <6 were 2.76 (0.97-7.87), 3.36 (1.53-7.40), and 3.92 (1.52-10.14), respectively. The respective ORs (CIs) of depressive status were 1.82 (0.42-7.81), 4.03 (1.41-11.53), and 4.69 (1.33-16.62). The results showed that regardless of working long hours or not, physicians with DSD <6 h had significantly higher stress and depressive status, suggesting that not only regulating long working hours but also ensuring adequate sleep duration is important for preventing physicians' mental health.

This study was to investigate the impact of job satisfaction as the independent variable and the type of shift as the moderator variable on the sleep quality of female shift-working nurses. The Minnesota Satisfaction Questionnaire (MSQ) short form and the Pittsburgh Sleep Quality Index (PSQI) were used as evaluation tools. The subjects in the study were female shift-working nurses from teaching hospitals in northern Taiwan. A total of 178 valid questionnaires were recovered. A hierarchical multiple regression (HMR) was used to test for the moderating effect of shift type. The results demonstrated that there was a negative correlation between the total score for general job satisfaction and the Global PSQI scores. The Global PSQI scores were higher for nurses working night shifts than for those working day and evening shifts. HMR showed significant variances in the interaction between general job satisfaction of female shift-working nurses and the day/night shift as well as the evening/night shift. The type of shift had a moderating effect on the ways in which general job satisfaction impacts sleep quality. Furthermore, the moderating effect of night shift on the impact of job satisfaction on sleep quality was weaker in nurses working the night shift.

Potential effects of shift work on health are probably related to the misalignment between the light-dark cycle and the human activity-rest cycle. Light exposure at night mediates these effects, including social misalignment and leads to an inversion of activity and rest, which, in turn, is linked to changes in behaviours. This article reviews the epidemiological evidence on the association between shift work and health, and possible mechanisms underlying this association. First, evidence from findings of the meta-analyses and systematic reviews published in the last 10 yr is presented. In addition, it reports the larger single-occupation studies and recent large population-based studies of the general workforce. Koch's postulates were used to evaluate the evidence related to the development of disease as a result of exposure to shift work. Finally, we discussed limitations of the multiple pathways that link shift work with specific disorders and the methodological challenges facing shift work research. We concluded that the clearest indications of shift work being the cause of a disease are given when there is a substantial body of evidence from high quality field studies showing an association and there is good evidence from laboratory studies supporting a causal explanation of the link.

Working time arrangements that require shift work or other non-standard working hours have significant potential to encroach on time that is highly valued for family, social and leisure activity. This can often result in workers experiencing poorer work-family or work-life balance. Based on an extensive literature search and expert knowledge, primary risk factors were identified including shift work; long, irregular and unpredictable working hours; and work on evenings and weekends (in combination and independent of shift work). On the other hand, flexibility, in the form of adequate worker control over work schedules, may be a protective factor. In addition, workers experiencing excessive work-life conflict are likely to reduce their working hours, reflecting a reciprocal relationship between working hours and work-life balance. Workers' families are also affected by shift work and non-standard working hours. Parents' shift work is associated with poorer emotional and developmental outcomes for their children, and to a greater likelihood of risky behavior in adolescence. Additionally, the risk of separation or divorce is increased, especially for parents working night shifts. Due to relationships such as those above, the consequences of shiftwork and non-standard working hours on family and social life are largely dependent on a complex interaction between specific work schedules, other aspects of work organization, and family and individual worker characteristics. This article provides an overview of current evidence regarding the relationships between working time arrangements and various social and family variables, and concludes with shift scheduling and intervention recommendations to improve work-life balance and social well-being.

There is no standard definition of shift work universally, and no validated report of complete biological adjustment to shift work in workers. Similarly, the evidence for shift work tolerance is limited due to a small number of studies and a narrow range of outcome measures. This paper discusses evidence to date regarding individual differences in shift work tolerance and highlights areas for future research and recommendations for workplace practice. The few factors that are consistently associated with perceived or actual shift work tolerance are young age, low scores of morningness or being a late chronotype, low scores of languidity and neuroticism, high scores on extraversion, internal locus of control and flexibility and male sex. An important first step is to differentiate between factors that are potentially modifiable, such as those that are determined by lifestyle choices, and those factors specific to the working time arrangement. Identifying determinants of shift work tolerance and the ability to adjust to shift work, whether they are innate and/or acquired mechanisms, is important so workers who are less likely to tolerate shift work well can be self-identified and supported with appropriate harm/risk minimization strategies. This paper also identifies important areas for future research with the goal of increasing the evidence base on which we can develop evidence-based harm mitigation strategies for shift workers.

Although long work hours have been associated with various physical health problems, studies of their association with mental health have yielded inconsistent results, due to differences in study settings, study outcome and/or unmeasured background factors. In this study, we used a propensity score method to evaluate the association between work hours and depressive state. A total of 467 Japanese white-collar workers were surveyed and divided into long and regular work hour groups according to overtime work records. Propensity score matching was performed based on 32 individual background and workplace factors, yielding 74 pairs of propensity-matched subjects. CES-D score, an indicator of depressive state, did not differ significantly among the two groups (p=0.203). However, work motivation, work control, social support and emotional stability correlated with CES-D score. These findings suggest that work control and social support factors are more associated with depressive state than control of work hours. These results also suggest that it is possible to use propensity score matching to evaluate the association between work hours and mental health in occupational study settings. Further studies, in larger populations, are required to determine the association between work hours and mental health parameters.

Overwork-related disorders, such as cerebrovascular/cardiovascular diseases (CCVD) and mental disorders due to overwork, are a major occupational and public health issue worldwide, particularly in East Asian countries. This report discusses the recent trend of overwork-related disorders in Japan from the perspective of workers' compensated occupational diseases, as well as the development of a national policy for preventive measures against overwork-related disorders in Japan. Recently, the number of claimed and compensated cases of occupational mental disorders has increased substantially, particularly among young workers, as compared to those of occupational CCVD. In response to these situations and action from society, the Japanese Government passed the "Act on Promotion of Preventive Measures against Karoshi and Other Overwork-Related Health Disorders" in June 2014 to develop a national initiative towards the prevention of overwork-related disorders. Changes in the trend of overwork-related disorders in Japan under a legal foundation and an initiative by the central government should be closely monitored so that other countries can benefit from the experiences.

This study examined the association between long working hours and psychosocial stress responses. In total, 1,122 white-collar workers from a company in Korea completed self-administered questionnaires following a lecture about the study aim, procedures, and confidentiality. Psychosocial stress responses were evaluated using the Psychosocial Well-being Index - Short Form (PWI-SF), and psychosocial working conditions were evaluated with the Korean Occupational Stress Scale - Short Form (KOSS-SF). Multivariate logistic regression analysis was performed after adjusting for demographic variables and psychosocial working conditions to examine associations between long working hours and psychosocial stress responses. In comparison with the reference group, which worked 40-44 hours per week, the crude odds ratio (OR) of the respondents who worked 60 or more hours was 4.56 (95% confidence interval (CI), 2.55-8.15) in terms of psychosocial stress responses. After adjusting for demographic variables, the adjusted OR of those working ≥60 hours was 5.61 (95% CI, 3.01-10.47). After adjusting for both demographic variables and psychosocial working conditions, the adjusted OR of those working ≥60 hours was 3.25 (95% CI, 1.56-6.79). This study found that long working hours are significantly related to psychosocial stress responses among white-collar workers in one Korean company.

To examine the association between spouses' weekly working hours (SWWH) and psychological symptoms such as depressive symptom and suicidal ideation. We used data from the fourth and fifth Korean National Health and Nutrition Examination Survey (2007-2012). We collected information about general characteristics, depressive symptoms, suicidal ideation, and working hours. After inclusion and exclusion criteria were applied, a sample of 8,056 house units was used for analysis. A multiple logistic regression was conducted to investigate the association between SWWH and depressive symptoms, as well as suicidal ideation, to estimate the odds ratio (OR). The relationship between SWWH and psychological symptoms were linear in husbands, and J-shaped in wives. ORs for husbands' depressive symptoms and suicidal ideation increased according to increase in SWWH (p-values for trend were 0.0045 and <0.001, respectively). Crude ORs for wives' depressive symptoms and suicidal ideation decreased until SWWH of 40 to 49 hours, but increased after SWWH of 40 to 49 hours (all p-values were below 0.01). Similar trends were observed after adjustment for age, obesity, household income, and one's own weekly working hours, up to 1.33 and 1.57 in husbands, and 1.29 and 1.32 in wives, respectively. SWWH is negatively associated with mental health.

The aim of this field study is to describe night shift resting and napping strategies and to examine their beneficial effects on sleepiness and quality of work. The study was carried out with 16 nurses working in an intensive care unit. Data collected during 20 night shifts were related to job demands (systematic observations), to the duration and timing of rests and naps taken by nurses (systematic observations, sleep diaries), to sleepiness (Karolinska Sleepiness Scale), and to quality of work scores (visual analog scale). The results showed that the number of rests and naps depended on the job demands. Resting and napping lowered the levels of sleepiness at the end of the shift. There was no direct relationship between sleepiness and the quality of work score. Discussions about the choice of indicators for the quality of work are necessary. Suggestions for implementing regulations for prescribed napping during night shifts are presented.

The objective of the present study was to investigate if satisfaction of the basic needs of autonomy, competence, and relatedness is related to shift work tolerance, specifically physical and mental fatigue, insomnia, and digestive troubles in a sample of shift workers. This is a cross-sectional pilot questionnaire study, including 252 shift workers employed in a municipality in Norway. Autonomy was negatively related to physical fatigue and digestive troubles, while competence was negatively related to mental fatigue. Relatedness showed significant correlations with insomnia and mental fatigue, but did not reach significance in the regression model controlling for the two other basic needs as well as work scheduling, night work exposure, and sleep medication. Sleep medication was significant in the final regression model for insomnia, but unrelated to fatigue and digestive troubles. The demographic variables, work hours per week, work schedule, and night work exposure were unrelated to all four measures of shift work tolerance. Autonomy and competence may be more important for fatigue and digestive troubles among shift workers than work arrangement variables, night work exposure, and sleep medication use.

The purpose of the present study was to answer the following research questions: (1) Do workers in different shift schedules differ in mental distress? (2) Do workers in different shift schedules differ in neuroticism? (3) Do shift schedules differ in psychosocial work exposures? (4) Do psychosocial work exposures contribute to mental distress among onshore- and offshore workers? (5) Does neuroticism confound the association between work exposures and mental distress? Workers on six shift-schedules answered a questionnaire (1,471 of 2,628 employees). Psychological and social work factors were measured by QPSNordic, mental distress was measured by HADS and neuroticism was measured by EPQ. The results showed 1) No differences in mental distress between workers in different shift schedules, 2) Revolving-shift workers reported higher neuroticism compared to day workers, 3) Swing-shift workers and revolving-shift workers reported lower job control compared to permanent-night and -day workers, 4) Job demands and role conflict were associated with more mental distress. Job control, role clarity, support, and leadership were associated with lower mental distress, 5) Neuroticism influenced the relationship between psychosocial work factors and mental distress. The present study did not find differences in mental distress between shift schedules. Job characteristics may be contributing factors when determining health effects of shift work.

The aim of the present study was to define the nature of individual differences in shift work tolerance (SWT). This was investigated by an exploratory factor analysis of scores from a wide range of established instruments designed to measure sleep, sleepiness, fatigue, social functioning, as well as physical and mental health. Data were collected from a representative sample of 1,529 Norwegian nurses engaged in rotating shift work. The analyses yielded two factors that seemed to be especially relevant for SWT, namely "Well-being" and "Physical health". Both factors were related to several demographic and personality variables. In addition, both factors were related to job satisfaction, social support and negative acts, while Well-being was also related to coping. These results support the construct and concurrent validity of the Well-being and Physical factors of SWT. Our findings represent a step towards answering calls from previous research concerning the establishment of a wider definition of individual differences in SWT.

This study describes an ecological study that evaluated the combined effects of working hours, income, and leisure time on suicide in all 47 prefectures of Japan. In men, the age-adjusted rate of suicide (per 100,000 population) was significantly correlated with working hours (r=0.587, p<0.0001) as well as significantly and negatively correlated with income (r=-0.517, p=0.0002) and times for the leisure activities of self-education (r=-0.447, p=0.0016) and hobbies (r=-0.511, p=0.0002). In addition, a stepwise multiple regression analysis identified time for leisure social activities as a determining factor in suicide rate, even after adjusting for working hours and income. However, the impact of time for leisure social activities on suicide rate was smaller than that of working hours and income. In contrast, none of these factors affected suicide rate in women. These results suggest that increasing leisure time may be useful for preventing suicide among men in Japan.

The purpose of this study was to examine the effects of two 15-min naps on nurses who work at night in a three-shift system. Of the 15 nurses who were included as study subjects on a night shift, eight took two short naps (the Nap condition), and seven worked without taking a nap (the No-nap condition) during the night shift. We measured sublingual temperature and the bispectral index (BIS), obtained heart rate and heart rate variability measures from an electrocardiogram (ECG), and evaluated sleepiness and fatigue levels every hour using the Visual Analog Scale (VAS). Both subjective sleepiness and fatigue increased between 4:00 and 5:00, with no significant differences observed between the two groups. However, the low- to high-frequency ratio (LF/HF) in the Nap condition group was found to be significantly lower than in the No-nap condition group. Furthermore, a sudden, brief increase in HF values was observed in the No-nap condition group in the morning. The results of this study suggest that taking two short naps may effectively reduce tension and prevent a brief increase in HF values by suppressing sympathetic nervous activity in the morning.

This study aims to assess the interactive effect of marital status and shift work on family function. A population-based sample of 1,438 nurses between the ages of 20-45 yr was recruited from Taiwan during the period from July 2005 to April 2006 using a mailed questionnaire. The self-administered questionnaire contained information about demographic data, work status, shift work schedule, and the Family APGAR (Adaptation, Partnership, Growth, Affection, and Resolve) Scale, to evaluate family function. Compared to day shift nurses, non-night and rotation shift nurses had 1.53- and 1.38-fold (95% CI=1.09-2.14 and 1.01-1.88) risk to have poor family function after adjusting for other covariates. Married nurses, by contrast, had a 0.44-fold (95% CI=0.29-0.66) risk to have poor family function compared to single nurses. In addition, married nurses who worked non-night or rotation shifts had a significantly higher percent of poor family function than those married nurses working day shifts; however, similar results were not replicated in single nurses. We concluded that shift work and marital status could influence family function.

Shift and night work are associated with several negative outcomes. The aim of this study was to make a systematic review of all studies which examine effects of shift and night work in the offshore petroleum industry, to synthesize the knowledge of how shift work offshore may affect the workers. Searches for studies concerning effects on health, sleep, adaptation, safety, working conditions, family- and social life and turnover were conducted via the databases Web of Knowledge, PsycINFO and PubMed. Search was also conducted through inspection of reference lists of relevant literature. We identified studies describing effects of shift work in terms of sleep, adaptation and re-adaptation of circadian rhythms, health outcomes, safety and accidents, family and social life, and work perceptions. Twenty-nine studies were included. In conclusion, the longitudinal studies were generally consistent in showing that adaptation to night work was complete within one to two weeks of work, while re-adaptation to a daytime schedule was slower. Shift workers reported more sleep problems than day workers. The data regarding mental and physical health, family and social life, and accidents yielded inconsistent results, and were insufficient as a base for drawing general conclusions. More research in the field is warranted.

This study investigated associations between individual and work-related factors and perceived mastery of work among offshore shift workers. 2,406 employees of a Norwegian petroleum company were invited to participate. A web-based survey was used and 1336 completed questionnaires were returned (56%). Mastery of work was assessed using QPS Nordic Mastery Scale and the results were compared with a sample from the QPS Nordic study. Individual factors adjusted for were age, gender, marital status and personality. The following work-related factors were included: demands, control, support, night work and shift work home interference. Female offshore shift workers reported higher levels of perceived mastery of work compared with women in the comparison sample. The following variables were independently associated with perceived mastery of work: female gender (β=0.10, p=0.008), decisional demands (β=0.13, p<0.001), control (β=0.05, p=0.009), social support (β=0.07, p<0.001), shift-work locus of control (β=0.04, p=0.005) and neuroticism (β=-0.29, p<0.001). Post hoc analyses showed no sex differences in perceived mastery in two separate work positions on the platforms. Work-related variables and personality explained 55% and 45% respectively of the total variance (R(2)=0.22) explained by the final model. Female petroleum offshore workers reported somewhat higher levels of mastery of work than their male colleagues, however, this may be due to different work positions. Work-related factors accounted for about half of the explained variance and decisional demands, control and support remained statistically significant after controlling for personality.

Long working hours adversely affect workers' safety and health. In 2004, Korea passed legislation limiting the working week to 40 h, to improve quality-of-life and to increase business competitiveness. In the present study, we explored the characteristics of work in Korea and compared our data of the second Korean Working Conditions Survey (KWCS) with those of the first KWCS. We found that the average number of hours worked weekly has been reduced but the proportions of workers who work for more than 48 h per week has increased over the 4 yr between the two Korean surveys in all categories studied (male, female, employee, self-employed, and employer). We also found that self-employed and employers work much longer hours than do employees, who are protected by the Labor Standards Act. This was particularly true in the accommodation and food service sectors. In conclusion, Korean workers work longer than do workers of EU countries. The use of average figures masks differences in the numbers of working hours among those engaged in various types of employment, or in certain work sectors. Therefore, the Korean government should not simply monitor reductions in average weekly working hours, but should identify employees working for over 60 h weekly, and reduce their working time.

A questionnaire survey was conducted among 3,233 workers (2,442 males and 791 females) from 17 medium-sized business establishments in northern Japan with respect to GHQ-12 score, suicidal ideation, sociodemographic characteristics, work-associated factors, and attitude toward mental health resources. Sex differences were assessed for each questionnaire item, and logistic regression analyses were performed separately for males and females. Significant correlations between common mental disorder (CMD: GHQ-12 score≥3) and the following factors were found for both sexes: short sleep, irregular working schedule, working in specific businesses, and attitude toward mental health resources. Associations between CMD and excess workload were significant only in male workers. While correlations between suicidal ideation and demand for mental health resources were observed in both sexes, significant correlations were observed between suicidal ideation and use of mental health resources for female workers alone. These results suggest that screening of a high-risk population and provision of mental health resources contribute to suicide prevention as a part of mental health promotion measures in medium-sized business establishments. They also suggest the need for identification of business/job type-specific stressors while considering sex differences in lifestyle factors, working environment, and help-seeking behavior.

Seasonal variation in circulating 25-hydroxyvitamin D (25OHD) levels related to seasonal and inter-day fluctuation in sunlight ultraviolet irradiation, may lead to misjudgments concerning 25OHD status in individual workers around threshold levels. Here, to examine seasonal and inter-day variations in plasma 25OHD, we conducted a longitudinal study involving indoor daytime workers. Subjects were four male indoor daytime workers aged 32-57 yr working in Kawasaki City, Japan. Blood samples were obtained on six days within two two-week periods in February and October, 2008. Plasma 25OHD, serum intact parathyroid hormone (PTH) and 1α,25-dihydroxyvitamin D [1α,25(OH)(2)D] were measured. Individual monthly mean 25OHD levels were 16-56% higher in October than in February (p=0.03), while individual monthly mean intact PTH levels were 15-41% lower in October (p=0.09). No seasonal change was observed in 1α,25(OH)(2)D (p=0.62). Notably, nearly all measured 25OHD levels in February were lower than the reference value of 20 ng/ml. Our study identified the occurrence of seasonal variation in circulating 25OHD and intact PTH levels, even after accounting for inter-day variability, and hypovitaminosis D in wintertime in indoor daytime male workers in Japan. Due to this variability, single spot measurements of 25OHD may lead to misjudgment of workers' vitamin D status.

The purpose of this study was to examine the correlation of medical incidents and errors among nurses with factors describing their lifestyle, health, and work environment. We analyzed questionnaires completed by 6,445 female hospital nurses engaged in shift work in Japanese hospitals with general wards of more than 200 beds. Logistic regression analysis indicated that the risk for medical incidents/errors was predicted by being under treatment, absence due to sickness in the past 6 months, workplace, break times during night shift, bodily pain, and role (emotional). These results indicate that to prevent the occurrence of medical incidents/errors, it is necessary to regard current/recent illness, bodily pain, and role (emotional) as a nurse's personal problems and break times during the night shift and workplace as administrative problems.

The aim of the present study was to examine the relation of insomnia with job stress factors, stress response, and social support. A self-completed questionnaire survey was conducted in 212 male Japanese workers at a synthetic fiber plant. With regard to insomnia, subjects were asked the first 5 of the 8 questions on the Athens Insomnia Scale (AIS). Job stress factors, stress response and social support were assessed using the Job Stress Questionnaire. Multiple regression analyses showed that psychological job stress factors of poor appropriateness of work and high qualitative workload were associated with insomnia. The psychological stress response of depression and physical stress responses were also related with insomnia. Depression was also related to appropriateness of work. The present results showed that insomnia was closely related with the psychological job stress factor of appropriateness of work and the psychological response of depression. These mutual relationships between insomnia and poor mental health need be investigated further.

Investigations of mood and workload in health care settings have focussed primarily on nurses and junior doctors. Given the critical shortfall in the Australian midwifery workforce, and the specialised nature of midwifery as an occupation, it is important to understand how mood and workload are experienced by midwives. Twenty midwives (18F, 2M) in an Australian metropolitan hospital completed logbooks assessing daily fluctuations in subjective mood and workload. Participants also provided information about history of psychopathology and sleep quality. Results revealed that midwives were relatively stable in terms of mood but did experience increased fear and decreased happiness when at work. Further, workload factors significantly predicted mood at work. Specifically, when participants felt that their work was more demanding and frustrating and required more effort, or when they felt that they could not accomplish all that was expected, mood was negatively influenced. This supports the connection between workload and negative mood change in healthcare. Given the potential for mood to influence a multitude of functions relevant to safety, performance and psychosocial wellbeing it is important to understand the factors which influence mood, particularly in light of the current shortfall in the Australian healthcare workforce.

Medical error involving nurses is a critical issue since nurses' actions will have a direct and often significant effect on the prognosis of their patients. To investigate the significance of nurse health in Japan and its potential impact on patient services, a questionnaire-based survey amongst nurses working in hospitals was conducted, with the specific purpose of examining the relationship between shift work, mental health and self-reported medical errors. Multivariate analysis revealed significant associations between the shift work system, General Health Questionnaire (GHQ) scores and nurse errors: the odds ratios for shift system and GHQ were 2.1 and 1.1, respectively. It was confirmed that both sleep and mental health status among hospital nurses were relatively poor, and that shift work and poor mental health were significant factors contributing to medical errors.

The present study examined the association between workaholism, the tendency to work excessively hard in a compulsive fashion, and sleep problems among Japanese nurses. A cross-sectional survey was conducted among 600 nurses from 2 university hospitals in Japan using a self-reported questionnaire on workaholism, sleep, job-related variables (i.e., job demands, job control, and worksite support), and demographic variables. A total of 394 nurses returned the questionnaire (response rate=65.7%) and complete data from 312 female nurses were used for analyses (final coverage rate=52.0%). Workaholics, as measured using the Japanese version of the Dutch Workaholism Scale, were defined as those having high scores on both the "work excessively" and "work compulsively" subscales. Logistic regression analyses revealed that workaholics had higher risks for sleep problems in terms of subjective sleep insufficiency, excessive daytime sleepiness at work, difficulty awakening in the morning, and feeling tired when waking up in the morning (odds ratios [OR] of 4.40, 3.18, 3.48, and 4.61, respectively, p<0.05). These remained significant even after adjusting for demographic and job-related variables (OR 3.41, 5.36, 2.56, and 2.77, respectively). However, no significant associations were found between workaholism and insomnia symptoms. These results suggest that workaholic nurses had higher risks for impaired awakening, insufficient sleep, and workplace sleepiness.

The aim of this study was to investigate self-reported health effects of extended work hours (10 h on/14 h off) for 21 d at work/21 d off, for 40 male tunnel workers in an Arctic area. A questionnaire obtaining information about demographics and subjective health complaints (SHC), including musculoskeletal, pseudoneurological, gastrointestinal, allergic, and flu-like complaints the last thirty days was distributed on day 14 of a work period. In addition questions on coping, psychological job demands, control, and social support were asked. The questionnaire was repeated three times during a nine months observation period. Twenty-six workers completed all three questionnaires. The prevalence of subjective health complaints did not change during the observation period. The prevalence of subjective health complaints was the same or lower than in a control group. There was a slight increase in self-reported job demands during the observation period. Coping, job control, and social support from colleagues and management were reported high and did not change. No association between this type of long work hours and changes in self-reported health was found in this study. However, this might have been a selected group of workers, and the same results may not be found in another population.

This study examined the relationship between coping skills, working hours, and psychological health among Japanese daytime workers. Self-administered questionnaires were mailed to a randomly selected sample of 2,000 workers who were members of a pre-recruited market research panel. A total of 1,821 participants responded (response rate=91.1%). Participants completed a questionnaire regarding working hours, coping skills, and psychological health (negative emotions, fatigue, and concentration/activity levels). Analyses of covariance were conducted to determine the relations of number of working hours, coping skills, and their interactions to psychological health with control for sex, age, drinking, job type, and employment type. Results revealed that working hours were significantly associated with fatigue and concentration/activity levels. High levels of instrumental support and positive reframing were significantly associated with low levels of negative emotions, fatigue, and concentration/activity levels. High levels of self-blame, denial, substance use, venting, self-distraction, religion, and behavioral disengagement were significantly associated with high levels of negative emotions, fatigue, and concentration/activity levels. This study suggests that improving coping skills such as using instrumental support or positive reframing may reduce the adverse health effects of long working hours.

The number of female doctors in Japan has been increasing, but the relationship between their work environment and their mental health is not clear. This study aimed to determine factors in the work environment influencing mental health status among female doctors. We mailed an anonymous survey questionnaire to 587 female doctors, and 367 (62.5%) responded. The survey included questions about age, marital status, work-related information including their specialty, affiliated medical facility, position, type of employment, working time, and night duty. The thirty-item version of the General Health Questionnaire (GHQ-30) was used to examine psychological distress. For the purposes of analysis, subjects with a GHQ-30 score greater than or equal to eight were considered to have psychological distress. The mean age of the subjects was 45.1 yr (SD 15.1). A total of 152 [corrected] (41.6% [corrected]) of subjects met criteria for having psychological distress. Bivariate analysis showed that age (p=0.0009), marital status (p=0.0038), medical facility (p=0.0476), position (p=0.0180), working time (p=0.0337), and working at night (p<0.0001) were associated with the GHQ-30 score. Multiple logistic regression analysis showed that younger age (p=0.0030), engaging in night duty (p=0.0049), and being divorced (p=0.0093) were independently associated with psychological distress. These results suggest that work environment factors, particularly night duty, play important roles in modulating psychological distress among female doctors.

The present study examined the relationship of work duration or physical symptoms to the mental health of visual display terminal (VDT) workers in Japan. The mental health status of 2,327 VDT users at an administrative office was investigated using the 12-item General Health Questionnaire (GHQ-12). Subjects were asked about their age, sex, hours of daily VDT use, rest and breaks during VDT work, eyestrain, and musculoskeletal pain. Logistic regression analysis was used to evaluate the associations with mental health status (GHQ-12 scores). The mean age of subjects was 39.5 yr (SD=10.3). Among all subjects, 36.7% could rest during VDT work and 66.9% received breaks during VDT work. The proportion of subjects who reported eyestrain and musculoskeletal pain were 19.6% and 25.7%, respectively. Eighteen percent of subjects were classified into a GHQ-12 high score group. Logistic regression analysis showed that age less than 40 yr, not receiving breaks during VDT work, and the presence of eyestrain and musculoskeletal pain were significantly associated with poor mental health status (high GHQ-12 scores). Using a VDT for more than 5 h/d and being female were also marginally associated with high GHQ scores (p<0.1). In conclusion, the management of physical health as well as work duration is important for good mental health status among VDT users.

The aim of the study was to study the effects of a flexible shift system (based on self-determined work hours) with respect to sleep/wake complaints and subjective health. The comparison group was a rapidly rotating shift system, with frequently occurring quick returns. A secondary aim was to examine the relation between work hour characteristics indicating compressed or difficult rosters (e.g. number of workdays in a row, frequency of quick returns and long work shifts) and subjective sleep and sleepiness, within the flexible shift system group. The sample of the analysis included 533 randomly selected police officers, of which 26% were females. The participants answered a questionnaire. The results showed that the flexible shift system group did not differ with respect to sleep/wake complaints and subjective health. However, the flexible shift group obtained more sleep in connection with the shifts, probably because of longer rest time between shifts. Thus, they worked less quick returns and long work shifts. The association between work hour characteristics and sleep/wake complaints was weak in the flexible shift group. Instead, sleep/wake problems were mainly associated with the attitude to work hours.

To ascertain the usefulness of a 21-item checklist that assesses accumulated fatigue due to overwork, we examined (1) the associations between overtime work, job stressors, or the quantity of sleep/rest and subjective symptoms of fatigue, and (2) whether sleeping hours and monthly days off are associated with the accumulated fatigue parameter using the checklist. Questionnaire surveys were administered twice to Japanese workers at a plant of a manufacturing company. Among the 390 registered workers, 383 workers (284 males and 99 females) in the first survey and 350 workers (260 males and 90 females) in the second survey responded. The subjective symptoms score significantly increased according to the order of grade of overtime work, other job stressors, and sleep/rest subscales in both sexes by ANOVA. The subjective symptoms grade was significantly associated with the other job stressors grade and sleep/rest grade, but not with overtime work. The accumulated fatigue parameter was negatively correlated with daily sleeping hours (significant Spearman's correlation coefficient (r(s)) =-0.318 and -0.340 in the 1st and 2nd surveys) and with monthly days off (r(s)=-0.250 and -0.151) among all of the subjects. It may be possible to assess overwork by the accumulated fatigue parameter.

A literature review of 105 studies on the effects of extended daily working hours was conducted. Potential negative effects of extended working hours are discussed: More accidents on the job; more accidents off the job; reduced duration and quality of sleep due to moonlighting; sleepiness; reduced alertness; fatigue; adverse effects on performance; prolonged toxic exposure; adverse effects on health; increased absenteeism; problems communicating with managers; and problems while driving home. Potential positive effects of extended working hours are discussed: Less travel time and costs; more time for the family, social life, and domestic duties; increased satisfaction with working hours; fewer handovers; and less overtime. No firm conclusions can be drawn because of the partly contradictory results and the methodological problems of many studies. However, caution is advised when considering the introduction of extended work shifts, particularly where public safety is at stake. A checklist is provided (concerning work load, breaks, staffing level, systematic assessments of health and safety factors) to support decisions for or against the use of extended work shifts.

A number of situational and behavioural individual differences moderate the impact of shift and night work. The aims of this study were to identify individual differences correlates of sleep and fatigue-related shiftwork outcomes and examine their potential relative causal impact. Power company shiftworkers completed a questionnaire that measured age/experience, number of dependents, shiftwork locus of control, morningness-eveningness, workload and sleep/health-related behaviours. Shiftwork sleep and fatigue outcome variables were also measured. Hierarchical multiple regression was used to examine predictive contributions of the individual difference variables and to generate path coefficients from situational and psychological predictors through behavioural variables to the outcome variables. Shiftwork-specific internality showed the most systematic significant causal relationships with sleep and fatigue outcomes. While not having as strong a direct causal influence on sleep and fatigue outcomes as internality, the other predictors did show more significant causal effects upon sleep-related behaviours than did internality. Behavioural variables made little contribution to the total causal effects of the predictors on the outcome variables. The results suggest control beliefs to be a moderating factor in shiftwork exposure and the potential utility of this construct in aiding more effective targeting of interventions.

This study examined the relationship between perceived adaptation to shift work and shift-related problems. A total of 608 male operators at nuclear power plants completed a set of validated questionnaires including a modified version of the Standard Shiftwork Index, which covered adaptation to shift work, fit to job content, chronotypes, chronic fatigue, sleep, naps, shift work locus of control (SHLOC), psychological health, social/family life, daytime sleepiness, workload, alertness on the job, and lifestyle factors. Participants were divided into two groups according to their perceived level of adaptation to shift work. The good adaptation group showed better outcomes than the poor adaptation group in terms of fit to job content, chronic fatigue, daytime sleep before night shifts, social and family disruption, SHLOC, psychological health, and alertness during night shifts (ps<0.001). Operators who reported good adaptation also took a more frequent, longer nap and more cigarettes during night shifts (ps<0.05). The cross-sectional study design cannot determine a causal relationship between perceived adaptation and shift work problems, yet the present results suggest that the effects of working shifts may be modified by perceptions of shift work adaptation.

We compared the shift work-related problems between 16-h night shift and 8-h evening/night shifts among nurses in a university hospital with respect to subjective symptoms, physical activity, heart rate (HR), and sleep. The nurses of one group (n = 20) worked a 16-h night shift under a rotating two-shift system, while those of the other group (n = 20) worked an 8-h evening or night shift under a rotating three-shift system. The 16-h night shift was staffed by three or four nurses who alternately took a 2-h nap during the shift, and had at least one day off after each shift. Subjective symptoms and daily behavior were measured every 30 min by the nurses before, during, after each shift as well as during days off using a time-budget method. Also, physical activity, heart rate (HR), and posture were recorded during shifts. The results showed similar or lower levels of sleepiness, difficulty in concentration, fatigue, physical activity, and HR during the 16-h shift compared to the 8-h shifts. No differences in subjective symptoms between the two shift schedules were observed before or after the shifts or during days off. The main sleep was longer after the shifts and during days off in the 16-h shift group than in the 8-h shift group. Our results suggest that the work-related problems in 16-h night shift nurses may not be excessively greater than those in 8-h evening/night shift nurses, as long as appropriate countermeasures are taken during and after the extended shift.

To assess the shift work-related problems associated with a 16-h night shift in a two-shift system, we took the following important factors into consideration; the interaction between circadian rhythms and the longer night shift, the type of morningness and eveningness experienced, the subjective sleep feeling, the subjects' daily behavior, the effectiveness of taking a nap during the long night shift, and finally the effectiveness of using several different kinds of measuring devices. Included among the measuring devices used were a standard questionnaire, repetitive self-assessment of subjective symptoms and daily behavior at short intervals, and a continuous recording of such objective indices as physical activity and heart rate. A potential problem lies in the fact that field studies that use such measures tend to produce a mass of data, and are thus faced with the accompanying technical problem of analyzing such a large amount of data (time, effort and cost). To solve the data analysis problem, we developed an automated data processing system. Through the use of an image scanner with a paper feeder, standard paper, an optical character recognition function and common application software, we were able to analyze a mass of data continuously and automatically within a short time. Our system should prove useful for field studies that produce a large amount of data collected with several different kinds of measuring devices.