Working hours and health - key research topics in the past and future.

OBJECTIVE: This paper discusses the past and present highlights of working hours and health research and identifies key research needs for the future. METHOD: We analyzed over 220 original articles and reviews on working hours and health in the Scandinavian Journal of Work, Environment & Health published during the last 50 years. Key publications from other journals were also included. RESULTS: The majority of identified articles focussed on the effects of shift and night work, with fewer studying long and reduced working hours and work time control. We observed a transition from small-scale experimental and intensive field studies to large-scale epidemiological studies utilizing precise exposure assessment, reflecting the recent emergence of register-based datasets and the development of analytic methods and alternative study designs for randomized controlled designs. The cumulative findings provide convincing evidence that shift work and long working hours, which are often associated with night work and insufficient recovery, increase the risk of poor sleep and fatigue, sickness absence, occupational injuries, and several chronic health conditions such as cardiovascular diseases and cancer. The observed risks are strongly modified by individual and work-related factors. CONCLUSIONS: Although the observed health risks of shift work and long working hours are mostly low or moderate, the widespread prevalence of exposure and the hazardousness of the many associated potential outcomes makes such working time arrangements major occupational health risks. Further research is needed to identify exposure-response associations, especially in relation to the chronic health effects, and to elucidate underlying pathways and effective personalized intervention strategies.

Prospective effects of work-time control on overtime, work-life interference and exhaustion in female and male knowledge workers.

AIMS: Employee-based flexible working hours are increasing, particularly among knowledge workers. Research indicates that women and men use work-time control (WTC; control over time off and daily hours) differently: while men work longer paid hours, women use WTC to counteract work-life interference. In a knowledge-worker sample, we examined associations between WTC and overtime, work-life interference and exhaustion and tested whether gender moderates the mediating role of overtime. METHODS: The sample contained 2248 Swedish knowledge workers. Employing hierarchical regression modelling, we examined effects of control over time off/daily hours on subsequent overtime hours, work-life interference and exhaustion in general and in gender-stratified samples. Using conditional process analysis, we tested moderated mediation models. RESULTS: Control over time off was related to less work-life interference (ßmen= -0.117; 95% confidence interval (CI): -0.237 to 0.003; ßwomen= -0.253; 95% CI: -0.386 to -0.120) and lower exhaustion (ßmen= -0.199; 95% CI: -0.347 to -0.051; ßwomen= -0.271; 95% CI: -0.443 to -0.100). For control over daily hours, estimates were close to zero. While men worked more overtime (42 min/week), we could not confirm gender moderating the indirect effect of control over time off/daily hours on work-life interference/exhaustion via overtime. Independent of gender, effects of control over time off on work-life interference were partly explained by working fewer overtime hours. CONCLUSIONS: Control over time off was related to lower exhaustion and better work-life balance (in particular for women). We found no evidence for men's work-life interference increasing with higher WTC owing to working more overtime. Knowledge workers' control over time off may help prevent work-life interference and burnout.

Pros and cons of quick returns-a cross-sectional survey among Swedish nurses and nurse assistants.

Short rest (<11h) between evening and day shifts-known as quick returns (QRs)-impede recovery and may impair health. Nevertheless, QRs remain popular among some shift workers. This study explores nurses' and nurse assistants' perceptions of the merits and demerits of QRs from individual and organizational perspectives. Participants were recruited from eleven wards at two Swedish hospitals as part of a larger quasi-experimental intervention study. The majority (79%) had influence over their work schedules. Frequency distributions of responses are presented. Ninety six undertook a baseline survey regarding recovery, tolerance and work performance in relation to QRs. A majority experienced difficulties unwinding before bedtime (76%), insufficient sleep (80%), and daytime fatigue (72%). A third experienced an increased risk of errors and mistakes. However, QRs appeared to facilitate taking reports from patients and planning work, as this task was more often rated as 'very easy' following a QR compared to other shift combinations. Tolerance of QRs varied substantially. In conclusion, QRs seem to benefit continuity in work processes, but may do so at the expense of recovery and safety. Wards planning to reduce QRs-through participatory or fixed schedule models-should consider impacts on work processes.

Randomised control trial of a proactive intervention supporting recovery in relation to stress and irregular work hours: effects on sleep, burn-out, fatigue and somatic symptoms.

OBJECTIVES: To examine if a proactive recovery intervention for newly graduated registered nurses (RNs) could prevent the development of sleep problems, burn-out, fatigue or somatic symptoms. METHODS: The study was a randomised control trial with parallel design. Newly graduated RNs with less than 12 months' work experience were eligible to participate. 461 RNs from 8 hospitals in Sweden were invited, of which 207 signed up. These were randomised to either intervention or control groups. After adjustments, 99 RNs were included in the intervention group (mean age 27.5 years, 84.7% women) and 108 in the control group (mean age 27.0 years, 90.7% women). 82 RNs in the intervention group attended a group-administered recovery programme, involving three group sessions with 2 weeks between each session, focusing on proactive strategies for sleep and recovery in relation to work stress and shift work. Effects on sleep, burn-out, fatigue and somatic symptoms were measured by questionnaires at baseline, postintervention and at 6 months follow-up. RESULTS: Preventive effect was seen on somatic symptoms for the intervention group. Also, the intervention group showed less burn-out and fatigue symptoms at postintervention. However, these latter effects did not persist at follow-up. Participants used many of the strategies from the programme. CONCLUSIONS: A proactive, group-administered recovery programme could be helpful in strengthening recovery and preventing negative health consequences for newly graduated RNs. TRIAL REGISTRATION NUMBER: NCT04246736.

Psychosocial working conditions of shiftworking nurses: A long-term latent transition analysis.

AIM: This study aimed to identify profiles of working conditions to which nurses were exposed to over time and investigate how changes in working conditions relate to shiftworking and health. BACKGROUND: Previous studies rarely addressed the issue of working conditions development over long periods and the effects of such development on nurses' health. METHODS: Data from a national cohort of nurses in Sweden (N = 2936) were analysed using a person-centred analytical approach-latent profile and latent transition analysis. RESULTS: Nurses report better psychosocial working conditions as they progress into mid-career. Shiftworking nurses experience poorer working conditions than their dayworking counterparts and tend to move from shiftwork to daywork as they progress into mid-career. In mid-career, nurses in work environments characterized by low autonomy and support tend to report poorer health outcomes. CONCLUSION: Current analyses suggest that shiftworking nurses are particularly in need of interventions that address poor work environments. Not only do they experience more negative psychosocial working conditions than their dayworking counterparts, but they do so while having to contend with demanding schedules. IMPLICATIONS FOR NURSING MANAGEMENT: The findings highlight that organisational interventions should target different aspects of the work environment for nurses in diverse stages of their careers.

Association of rotating shift work schedules and the use of prescribed sleep medication: A prospective cohort study.

We examined whether working rotating shifts, with or without night work, is associated with the purchase of prescribed sleep medication, and whether the association is dependent on age. Data were obtained from a longitudinal cohort study of Finnish public sector employees who responded to questions on work schedule and background characteristics in 2000, 2004 and 2008. The data were linked to national register data on redeemed prescriptions of hypnotic and sedative medications, with up to 11 years of follow-up. Age stratified Cox proportional hazard regression models were computed to examine incident use of medication comparing two groups of rotating shift workers (those working shifts that included night shifts and those whose schedules did not include night shifts) with day workers who worked in a similar range of occupations. Shift work with night shifts was associated with increased use of sleep medication in all age groups, after adjustments for sex, occupational status, marital status, alcohol consumption, smoking and physical activity levels (hazard ratio [HR], [95% confidence interval, CI] 1.14 [1.01-1.28] for age group ≤39 years; 1.33 [1.19-1.48] for age group 40-49 years; 1.28 [1.13-1.44] for age group ≥50 years). Shift work without nights was associated with medication use in the two older age groups (HR [95% CI] 1.14 [1.01-1.29] and 1.17 [1.05-1.31] for age groups 40-49 years and >50 years, respectively). These findings suggest that circadian disruption and older age puts rotating shift workers, and especially those who work nights, at increased risk of developing clinically significant levels of sleep problems.

Intensive longitudinal study of newly graduated nurses' quick returns and self-rated stress.

OBJECTIVE: Little is known about the relationship between quick returns (QR) - shift combinations that result in inter-shift rest periods <11 hours) and stress. The current study examined whether variations in the frequency of QR, both between and within individuals, were associated with changes in self-rated stress. METHODS: A questionnaire was sent weekly to newly graduated nurses during the first 12 weeks of work. Stress was measured with four items from the Stress-Energy Questionnaire on a scale from 1 "not at all" to 5 "very much" [mean 2.65, standard deviation (SD) 1.08]. Shifts worked in the past week were reported and QR were identified by evening-morning shift combinations (mean 0.98, SD 0.90 per week). In total, 350 persons were included in the analysis (3556 observations). Data were analyzed with a multilevel residual dynamic structural equation model (RDSEM) using Bayesian estimation procedures. RESULTS: There was no between-person effect of QR on stress averaged across measurement occasions (0.181, 95% CI -0.060-0.415). However, there was a small within-person effect of QR (0.031, 95% CI 0.001-0.062), meaning that more QR during a given week, compared to that person's average, was associated with an increase in their level of stress during that week. CONCLUSIONS: Nurses were likely to report increased stress during weeks in which they worked more QR. Intervention studies are needed to determine whether the relationship is causal.

Can psychosocial working conditions help to explain the impact of shiftwork on health in male- and female-dominated occupations? A prospective cohort study.

Occupational factors are sometimes invoked to explain gender differences in the associations between shiftwork and health. We examined prospective associations between shiftwork and health, and between shiftwork and sick leave, separately for workers in female-dominated (FD) and male-dominated (MD) occupations; and whether the associations remained after controlling for psychosocial working conditions. Data from six waves of the Swedish Longitudinal Occupational Survey of Health were used to examine prospective associations with a four-year time lag between work schedule (daywork versus shiftwork involving nightwork; and daywork versus shiftwork not involving nightwork) and self-reports of depressive symptoms; incidents of short- and long-term sick leave; self-rated health; and sleep disturbance. Dynamic panel models with fixed effects were applied, using structural equation modeling. The analyses included adjustments for personal circumstances and employment conditions; and additional adjustments for psychosocial working conditions (psychological and emotional job demands; job control; worktime control; social support at work; persecution at work; and threats or violence at work). Within FD occupations, shiftwork that included night work (as compared to daytime work) predicted higher incidence of short-term sick leave (<1 week); within MD occupations, shiftwork that included nightwork predicted greater symptoms of mild depression. Despite notable differences in psychosocial working conditions between dayworkers and shiftworkers, both associations remained significant after adjustments. Thus, it was not confirmed that the associations between shiftwork and health reflected poorer working conditions of shiftworkers in either FD or MD occupations, although the possibility remains that the associations were due to other unmeasured aspects of the working environment.

Sleep and fatigue in newly graduated nurses-Experiences and strategies for handling shiftwork.

AIMS AND OBJECTIVES: To explore newly graduated nurses' strategies for, and experiences of, sleep problems and fatigue when starting shiftwork. A more comprehensive insight into nurses' strategies, sleep problems, fatigue experiences and contributing factors is needed to understand what support should be provided. BACKGROUND: For graduate nurses, the first years of practice are often stressful, with many reporting high levels of burnout symptoms. Usually, starting working as a nurse also means an introduction to shiftwork, which is related to sleep problems. Sleep problems may impair stress management and, at the same time, stress may cause sleep problems. Previously, sleep problems and fatigue have been associated with burnout, poor health and increased accident risk. DESIGN AND METHODS: Semi-structured interviews were conducted with nurses (N = 11) from four different Swedish hospitals, and qualitative inductive content analysis was used. The study was approved by the Regional Ethical Review Board in Stockholm. The COREQ checklist was followed. RESULTS: Many nurses lacked effective strategies for managing sleep and fatigue in relation to shiftwork. Various strategies were used, of which some might interfere with factors regulating and promoting sleep such as the homeostatic drive. Sleep problems were common during quick returns, often due to difficulties unwinding before sleep, and high workloads exacerbated the problems. The described consequences of fatigue in a clinical work context indicated impaired executive and nonexecutive cognitive function. CONCLUSION: The findings indicate that supporting strategies and behaviours for sleep and fatigue in an intervention for newly graduated nurses starting shiftwork may be of importance to improve well-being among nurses and increase patient safety. RELEVANCE TO CLINICAL PRACTICE: This study highlights the importance of addressing sleep and fatigue issues in nursing education and work introduction programmes to increase patient safety and improve well-being among nurses.

Associations between shift work and use of prescribed medications for the treatment of hypertension, diabetes, and dyslipidemia: a prospective cohort study.

Objective This study examined the associations between shift work and use of antihypertensive, lipid-lowering, and antidiabetic medications. Methods Survey data from two cohorts of Finnish men (N=11 998) and women (N=49 944) working in multiple occupations where shift work was used were linked to national Drug Prescription Register data, with up to 11 years of follow-up. In each cohort, age-stratified Cox proportional hazard regression models were computed to examine any incident use of prescription medication for each of the three medical conditions, separately comparing each of two groups of rotating shift workers (those whose schedules included night shifts, and those whose schedules did not include night shifts) with day workers who worked in a similar range of occupations. Results In the larger cohort, among participants aged 40-49 at baseline, shift work without night shifts was associated with increased use of type-2 diabetes medication after adjustments for sex, occupational status, marital status, alcohol consumption, smoking, and physical activity [hazard ratio (HR) 1.28, 95% confidence interval (CI) 1.01-1.62], while shift work with night shifts was associated with increased use of dyslipidemia medication after adjustments (HR 1.33, 95% CI 1.12-1.57). There were no such associations among younger and older shift workers. Also in the larger cohort, among those aged <50 years at baseline, both types of shift work were associated with increased use of hypertension medication after adjustments [up to HR 1.20 (95% CI 1.05-1.37)]. There were no positive associations in the smaller cohort. Conclusions There was mixed evidence regarding the use of medications for cardiovascular risk factors by shift workers. Selection effects may have affected the associations.

Working Time Society consensus statements: Evidence-based effects of shift work on physical and mental health.

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.

Effect of work schedule on prospective antidepressant prescriptions in Sweden: a 2-year sex-stratified analysis using national drug registry data.

INTRODUCTION: Depression-related mood disorders affect millions of people worldwide and contribute to substantial morbidity and disability, yet little is known about the effects of work scheduling on depression. This study used a large Swedish survey to prospectively examine the effects of work schedule on registry-based antidepressant prescriptions in females and males over a 2-year period. METHODS: The study was based on an approximately representative sample (n=3980 males, 4663 females) of gainfully employed participants in the Swedish Longitudinal Occupational Survey of Health. Sex-stratified analyses were conducted using logistic regression. For exposure, eight categories described work schedule in 2008: 'regular days' (three categories of night work history: none, ≤3 years, 4+ years), 'night shift work', 'regular shift work (no nights)', 'rostered work (no nights)', 'flexible/non-regulated hours' and 'other'. For the primary outcome measure, all prescriptions coded N06A according to the Anatomical Therapeutic Chemical System were obtained from the Swedish National Prescribed Drug Register and dichotomised into 'any' or 'no' prescriptions between 2008 and 2010. Estimates were adjusted for potential sociodemographic, health and work confounders, and for prior depressive symptoms. RESULTS: In 2008, 22% of females versus 19% of males worked outside of regular daytime schedule. Registered antidepressant prescription rates in the postsurvey period were 11.4% for females versus 5.8% for males. In fully adjusted models, females in 'flexible/non-regulated' schedules showed an increased OR for prospective antidepressant prescriptions (OR=2.01, 95% CI=1.08 to 3.76). In males, odds ratios were most increased in those working 'other' schedules (OR=1.72, 95% CI=0.75 to 3.94) and 'Regular days with four or more years' history of night work' (OR=1.54, 95% CI=0.93 to 2.56). CONCLUSIONS: This study's findings support a relationship between work schedule and prospective antidepressant prescriptions in the Swedish workforce. Future research should continue to assess sex-stratified relationships, using detailed shift work exposure categories and objective registry data where possible.

Quick returns and night work as predictors of sleep quality, fatigue, work-family balance and satisfaction with work hours.

Quick returns (intervals of <11 h between the end of one shift and the start of the next) are associated with short sleeps and fatigue on the subsequent shift. Recent evidence suggests that shift workers regard quick returns as being more problematic than night work. The current study explored quick returns and night work in terms of their impact on sleep, unwinding, recovery, exhaustion, satisfaction with work hours and work-family interference. Data from the 2006 cohort of Swedish nursing students within the national Longitudinal Analysis of Nursing Education (LANE) study were analysed (N = 1459). Respondents completed a questionnaire prior to graduation (response rate 69.2%) and 3 years after graduation (65.9%). The analyses examined associations between frequency of quick returns and night work and measures taken in year three, while adjusting for confounding factors (in year three and prior graduation). Frequency of quick returns was a significant predictor of poor sleep quality, short sleeps, unwinding, exhaustion, satisfaction with work hours and work-to-family interference, with higher frequency predicting more negative outcomes. Quick returns did not predict recovery after rest days. Frequency of night work did not predict any of the outcomes. In conclusion, quick returns were an important determinant of sleep, recovery and wellbeing, whereas night work did not show such an association.

Work time control, sleep & accident risk: A prospective cohort study.

We examined whether the beneficial impact of work time control (WTC) on sleep leads to lower accident risk, using data from a nationally representative survey conducted in Sweden. Logistic regressions examined WTC in 2010 and 2012 as predictors of accidents occurring in the subsequent 2 years (N = 4840 and 4337, respectively). Sleep disturbance and frequency of short sleeps in 2012 were examined as potential mediators of the associations between WTC in 2010 and subsequent accidents as reported in 2014 (N = 3636). All analyses adjusted for age, sex, education, occupational category, weekly work hours, shift work status, job control and perceived accident risk at work. In both waves, overall WTC was inversely associated with accidents (p = 0.048 and p = 0.038, respectively). Analyses of the sub-dimensions of WTC indicated that Control over Daily Hours (influence over start and finish times, and over length of shift) did not predict accidents in either wave, while Control over Time-off (CoT; influence over taking breaks, running private errands during work and taking paid leave) predicted fewer accidents in both waves (p = 0.013 and p = 0.010). Sleep disturbance in 2012 mediated associations between WTC/CoT in 2010 and accidents in 2014, although effects' sizes were small (effectWTC = -0.006, 95% confidence interval [CI] = -0.018 to -0.001; effectCoT = -0.009, 95%CI = -0.022 to -0.001; unstandardized coefficients), with the indirect effects of sleep disturbance accounting for less than 5% of the total direct and indirect effects. Frequency of short sleeps was not a significant mediator. WTC reduces the risk of subsequently being involved in an accident, although sleep may not be a strong component of the mechanism underlying this association.

Investigating the factorial structure and availability of work time control in a representative sample of the Swedish working population.

AIMS: Past research has often neglected the sub-dimensions of work time control (WTC). Moreover, differences in levels of WTC with respect to work and demographic characteristics have not yet been examined in a representative sample. We investigated these matters in a recent sample of the Swedish working population. METHODS: The study was based on the 2014 data collection of the Swedish Longitudinal Occupational Survey of Health. We assessed the structure of the WTC measure using exploratory and confirmatory factor analysis. Differences in WTC by work and demographic characteristics were examined with independent samplet-tests, one-way ANOVAs and gender-stratified logistic regressions. RESULTS: Best model fit was found for a two-factor structure that distinguished between control over daily hours and control over time off (root mean square error of approximation = 0.06; 95% CI 0.04 to 0.09; Comparative Fit Index (CFI) = 0.99). Women, shift and public-sector workers reported lower control in relation to both factors. Age showed small associations with WTC, while a stronger link was suggested for civil status and family situation. Night, roster and rotating shift work seemed to be the most influential factors on reporting low control over daily hours and time off. CONCLUSIONS: Our data confirm the two-dimensional structure underlying WTC, namely the components 'control over daily hours' and 'control over time off'. Women, public-sector and shift workers reported lower levels of control. Future research should examine the public health implications of WTC, in particular whether increased control over daily hours and time off can reduce health problems associated with difficult working-time arrangements.

Systematic review of the relationship between quick returns in rotating shift work and health-related outcomes.

A systematic literature search was carried out to investigate the relationship between quick returns (i.e., 11.0 hours or less between two consecutive shifts) and outcome measures of health, sleep, functional ability and work-life balance. A total of 22 studies published in 21 articles were included. Three types of quick returns were differentiated (from evening to morning/day, night to evening, morning/day to night shifts) where sleep duration and sleepiness appeared to be differently affected depending on which shifts the quick returns occurred between. There were some indications of detrimental effects of quick returns on proximate problems (e.g., sleep, sleepiness and fatigue), although the evidence of associations with more chronic outcome measures (physical and mental health and work-life balance) was inconclusive. PRACTITIONER SUMMARY: Modern societies are dependent on people working shifts. This study systematically reviews literature on the consequences of quick returns (11.0 hours or less between two shifts). Quick returns have detrimental effects on acute health problems. However, the evidence regarding effects on chronic health is inconclusive.

Chronic effects of shift work on cognition: findings from the VISAT longitudinal study.

OBJECTIVES: Shift work, like chronic jet lag, is known to disrupt workers' normal circadian rhythms and social life, and to be associated with increased health problems (eg, ulcers, cardiovascular disease, metabolic syndrome, breast cancer, reproductive difficulties) and with acute effects on safety and productivity. However, very little is known about the long-term consequences of shift work on cognitive abilities. The aim of this study was to assess the chronicity and reversibility of the effects of shift work on cognition. METHODS: We conducted a prospective cohort study of 3232 employed and retired workers (participation rate: 76%) who were 32, 42, 52 and 62 years old at the time of the first measurement (t1, 1996), and who were seen again 5 (t2) and 10 (t3) years later. 1484 of them had shift work experience at baseline (current or past) and 1635 had not. The main outcome measures were tests of speed and memory, assessed at all three measurement times. RESULTS: Shift work was associated with impaired cognition. The association was stronger for exposure durations exceeding 10 years (dose effect; cognitive loss equivalent to 6.5 years of age-related decline in the current cohort). The recovery of cognitive functioning after having left shift work took at least 5 years (reversibility). CONCLUSIONS: Shift work chronically impairs cognition, with potentially important safety consequences not only for the individuals concerned, but also for society.