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.

Sleep in everyday life - relationship to mood and performance in young and older adults: a study protocol.

Laboratory based sleep deprivation studies demonstrate that lack of sleep impairs well-being and performance ability, but suggest that these effects are mitigated in older adults. Yet, much less is known whether day-to-day variations of sleep have similar consequences in the context of everyday life. This project uses an intensive longitudinal design to investigate the occurrence of day-to-day variations in sleep and their impact on mood and performance in everyday life and to examine whether effects differ between young and older adults. We aim to include 160 young (18-30 years) and 160 older adults (55-75 years) to complete a 21-day experience sampling method (ESM) protocol. During the ESM period, participants are asked to fill in (i) a brief morning questionnaire, (ii) 8 short daytime questionnaires addressing momentary well-being, sleepiness, stress, and mind wandering, followed by a 1 min cognitive task and (iii) a brief evening questionnaire, all delivered via a mobile phone application. Sleep will be measured using self-reports (daily questions) and objectively with wrist actigraphy. The impact of adult age on mean levels and intraindividual variability of sleep will be analyzed using mixed-effects location scale models. The impact of sleep on daily cognitive performance will be analyzed using multilevel linear mixed models. The relationship of sleep to mean values and variability of positive and negative affect in young and older adults will be analyzed using mixed-effects location scale modeling. The overarching purpose of the project is improving the current knowledge on the occurrence of day-to-day variations in sleep and their relationship to performance as well as positive and negative affect in young and older adults.

Workplace Psychosocial Resources and Risk of Sleep Disturbances Among Employees.

Importance: Workplace psychosocial resources naturally tend to cluster in some work teams. To inform work-related sleep health promotion interventions, it is important to determine the associations between clustering of workplace resources and sleep disturbances when some resources are high while others are low and to mimic an actual intervention using observational data. Objective: To examine whether clustering of and changes in workplace psychosocial resources are associated with sleep disturbances among workers. Design, Setting, and Participants: This population-based cohort study used data from the Swedish Longitudinal Occupational Survey of Health (2012-2018), the Work Environment and Health in Denmark study (2012-2018), and the Finnish Public Sector Study (2008-2014), collected biennially. Statistical analysis was conducted from November 2020 to June 2022. Exposure: Questionnaires were distributed measuring leadership quality and procedural justice (ie, vertical resources) as well as collaboration culture and coworker support (ie, horizontal resources). Resources were divided into clusters of general low, intermediate vertical and low horizontal, low vertical and high horizontal, intermediate vertical and high horizontal, and general high. Main Outcomes and Measures: Odds ratios (ORs) and 95% CIs were reported from logistic regression models for the associations between the clustering of resources and concurrent and long-term sleep disturbances. Sleep disturbances were measured by self-administered questionnaires. Results: The study identified 114 971 participants with 219 982 participant-observations (151 021 [69%] women; mean [SD] age, 48 [10] years). Compared with participants with general low resources, other groups showed a lower prevalence of sleep disturbances, with the lowest observed in the general high group concurrently (OR, 0.38; 95% CI, 0.37-0.40) and longitudinally after 6 years (OR, 0.52; 95% CI, 0.48-0.57). Approximately half of the participants (27 167 participants [53%]) experienced changes in resource clusters within 2 years. Improvements in vertical or horizontal dimensions were associated with reduced odds of persistent sleep disturbances, and the lowest odds of sleep disturbances was found in the group with improvements in both vertical and horizontal dimensions (OR, 0.53; 95% CI, 0.46-0.62). A corresponding dose-response association with sleep disturbances was observed for decline in resources (eg, decline in both dimensions: OR, 1.74; 95% CI, 1.54-1.97). Conclusions and Relevance: In this cohort study of workplace psychosocial resources and sleep disturbances, clustering of favorable resources was associated with a lower risk of sleep disturbances.

Disturbed sleep and its attribution to stress and other causes: A population-based survey.

This study explores the prevalence of attributed causes of disturbed sleep and the association between stress-disturbed sleep and age, sex, and sleep duration on weekdays as well as weekends in a representative sample. A nationally representative sample (n = 1,128, response rate 72.8%), stratified for sex and age, completed a computer-assisted phone survey that included questions about sleep disturbances and attributed causes. Stress was the main attributed cause of sleep disturbance (35.1%), most frequently attributed by younger women (χ2 = 26.5, p < 0.001). Prevalence of stress-disturbed sleep was higher with lower age (B = -0.05, odds ratio (OR) = 0.94, CI = 0.91, 0.98). There was a trend, however, toward a significant interaction between age and sex, with women in the older age-groups more frequently reporting stress-disturbed sleep than older men (B = -0.02, OR = 1.022, CI = 1.003, 1.042). Weekday sleep duration decreased with increased stress-disturbed sleep, with an inverse relationship on weekends except for those reporting stress-disturbed sleep more than 5 days per week (F = 10.5, p < 0.001), who also had the shortest weekend sleep duration. Sleep disturbances were commonly attributed to stress, and more strongly so in women younger than 46 years. Stress-disturbed sleep during weekdays seems to be potentially compensated for with extended sleep on weekends, except for those with continuous stress-disturbed sleep.

Development and performance of a sleep estimation algorithm using a single accelerometer placed on the thigh: an evaluation against polysomnography.

Accelerometers placed on the thigh provide accurate measures of daily physical activity types, postures and sedentary behaviours, over 24 h and across consecutive days. However, the ability to estimate sleep duration or quality from thigh-worn accelerometers is uncertain and has not been evaluated in comparison with the 'gold-standard' measurement of sleep polysomnography. This study aimed to develop an algorithm for sleep estimation using the raw data from a thigh-worn accelerometer and to evaluate it in comparison with polysomnography. The algorithm was developed and optimised on a dataset consisting of 23 single-night polysomnography recordings, collected in a laboratory, from 15 asymptomatic adults. This optimised algorithm was then applied to a separate evaluation dataset, in which, 71 adult males (mean [SD] age 57 [11] years, height 181 [6] cm, weight 82 [13] kg) wore ambulatory polysomnography equipment and a thigh-worn accelerometer, simultaneously, whilst sleeping at home. Compared with polysomnography, the algorithm had a sensitivity of 0.84 and a specificity of 0.55 when estimating sleep periods. Sleep intervals were underestimated by 21 min (130 min, Limits of Agreement Range [LoAR]). Total sleep time was underestimated by 32 min (233 min LoAR). Our results evaluate the performance of a new algorithm for estimating sleep and outline the limitations. Based on these results, we conclude that a single device can provide estimates of the sleep interval and total sleep time with sufficient accuracy for the measurement of daily physical activity, sedentary behaviour, and sleep, on a group level in free-living settings.

Behavioral factors predict all-cause mortality in female coronary patients and healthy controls over 26 years - a prospective secondary analysis of the Stockholm Female Coronary Risk Study.

OBJECTIVE: The prognosis of coronary artery disease (CAD) is related to its severity and cardiovascular risk factors in both sexes. In women, social isolation, marital stress, sedentary lifestyle and depression predicted CAD progression and outcome within 3 to 5 years. We hypothesised that these behavioral factors would still be associated with all-cause mortality in female patients after 26 years. METHODS: We examined 292 patients with CAD and 300 healthy controls (mean age of 56 ± 7 y) within the Fem-Cor-Risk-Study at baseline. Their cardiac, behavioral, and psychosocial risk profiles, exercise, smoking, and dietary habits were assessed using standardized procedures. Physiological characteristics included a full lipid profile, the coagulation cascade and autonomic dysfunction (heart rate variability, HRV). A new exploratory analysis using machine-learning algorithms compared the effects of social and behavioral mechanisms with standard risk factors. Results: All-cause mortality records were completed in 286 (97.9%) patients and 299 (99.7%) healthy women. During a median follow-up of 26 years, 158 (55.2%) patients and 101 (33.9%) matched healthy controls died. The annualized mortality rate was 2.1% and 1.3%, respectively. After controlling for all available confounders, behavioral predictors of survival in patients were social integration (HR 0.99, 95% CI 0.99-1.0) and physical activity (HR 0.54, 95% CI 0.37-0.79). Smoking acted as a predictor of all-cause mortality (HR 1.56, 95% CI 1.03-2.36). Among healthy women, moderate physical activity (HR 0.42, 95% CI 0.24-0.74) and complete HRV recordings (≥50%) were found to be significant predictors of survival. CONCLUSIONS: CAD patients with adequate social integration, who do not smoke and are physically active, have a favorable long-term prognosis. The exact survival times confirm that behavioral risk factors are associated with all-cause mortality in female CAD patients and healthy controls.

Evaluation of truck driver rest locations and sleep quality.

Objectives: Truck drivers' work organization requires that rest and sleep be taken in various locations, where sleep quality might be affected by the discomfort of these environments. The purpose of this study was to evaluate truck drivers' rest locations and their association with sleep quality utilizing an ergonomic approach. Material and Methods: The sleep quality of 81 truck drivers was assessed using the Pittsburgh sleep quality index (PSQI). An adapted version of the ergonomics workplace analysis (EWA) instrument was used to evaluate 44 rest locations. Results: Half of the workers preferred sleeper berths (51.2%) as a rest place. Sleep was classified as poor by 71.6% of the drivers. Dorms were rated more positively (p<0.001) by truck drivers (2.0±1.1) than by the analyst (2.6±0.6). Sleeper berths and dorms were rated statistically different by truck drivers (p=0.002), as well as by the analyst (p=0.003). No correlation was found between EWA evaluations and total score for sleep quality. Separate analyses of dorms and truck berths showed very few correlations. The higher the noise of roommates in dorms, the worse the sleep quality. Conversely, noise in corridors or outside the room positively impacted sleep quality. Conclusion: Noise in the rest place may affect sleep in both directions, negatively or positively. Sleep was classified as poor regardless of resting place. The quality of resting places seemed to have little effect on sleep quality of truck drivers. Factors other than rest place, such as work scheduling, are probably more important for promoting good sleep quality.

Shiftworkers' attitude to their work hours, positive or negative, and why?

OBJECTIVE: Shift work is associated with impaired health and safety but there is a lack of systematic knowledge of shift workers attitude to their shift systems. This may be important for the ability to retain valuable personnel in the company/organization, and to attract new employees. The purpose of the present study was to investigate: the prevalence of shift characteristics (nights, long shifts, short rest, etc.) in traditional shift systems, the workers' attitude to their shift systems, if combinations of problematic shift characteristics are associated with the workers' attitude, and if work stress and poor sleep, fatigue, or social difficulties are associated with attitudes to shift systems. METHODS: A representative sample of 3,500 individuals with non-day work in the general population of Sweden were asked to participate in the study. A total of 1965 workers remained after drop-outs. The material was analyzed by Chi2 analysis and hierarchical multiple regression. RESULTS: The results showed that traditional shift systems included many more shift characteristics than those constituting the core of the systems. All included day work, for example. 90.2% of those with roster work had shifts > 10 h at least once a month. 66.9% of those with roster work without nights had < 11 h rest between shifts at least once a month. Less than 25% of the respondents had a rather or very negative attitude to their shift system, with the lowest level for those who work either fixed days or nights (7.6 and 5.7%, respectively) and highest for three-shift work (21.2%) and roster work without night work (24.4%). Shiftwork or roster work with nights had highest levels (> 50%) of sleep problems and fatigue. The difference across shift systems was significant at p < .001 in all cases. Combinations of the most problematic shift characteristics were associated with some increase in negative attitude to the shift schedule. Among schedule characteristics, only long weeks turned out significant in the multivariable regression. The strongest predictor of negative attitude to work hours were social difficulties due to work schedule [ß = 4.98 (95% Confidence interval (Ci) = 3.41, 7.27; p < .001], fatigue caused by schedule (ß = 3.20 Ci = 2.03, 5.05; p < .001), sleep problems caused by schedule (ß = 2.10 Ci = 1.46, 3.01; p = .01), and stressful work (ß = 1.52 Ci = 1.10, 2.11; p < .05). CONCLUSION: It was concluded that shift systems often included many different shift characteristics, that night shift systems had a large proportion of long shifts, and that split shifts mainly occurred in roster day work. Furthermore, it was concluded that the attitude to the worker's present shift systems seems to be positive for the majority, with the highest level for those who work either fixed days or nights, compared to those who work alternating shifts (including night shifts). Negative attitude to shift systems was more linked to social difficulties, fatigue or sleep problems due to the shift schedule, than to schedule characteristics per se.

How does work impact daily sleep quality? A within-individual study using actigraphy and self-reports over the retirement transition.

This study examined how the cessation of work at retirement affects daily measures of actigraphy-measured and self-rated sleep quality. Time in bed or asleep and stress at bedtime were examined as potential mechanisms. In total 117 employed participants who were aged 60-72 years and planned to retire soon were recruited to the Swedish Retirement Study. Sleep quality was measured in a baseline week using accelerometers, diaries, and questionnaires. Subjective sleep measures were sleep quality, restless sleep, restorative sleep, getting enough sleep, estimated wake after sleep onset, difficulties falling asleep, too early final awakening, and difficulties waking up. Actigraphy measures were sleep efficiency, wake after sleep onset, and average awakening length. After 1 and 2 years, the measurements were repeated for the now retired participants. Daily variations in sleep quality before and after retirement were analysed using multilevel modelling, with time in bed or asleep and stress at bedtime as potential mediators. We found that several self-reports of sleep improved (e.g., +0.2 standard deviations for sleep quality and +0.5 standard deviations for restorative sleep) while objective sleep quality remained unchanged or decreased slightly with retirement (e.g., -0.8% for sleep efficiency). Increased time in bed or asleep and stress at bedtime accounted partially for the improvements in self-rated sleep quality at retirement. In conclusion, actigraph-measured and self-reported sleep quality do not change in concert at retirement, highlighting the interest of studying both outcomes. The main effects of retirement from work concern subjective experiences of recovery more than sleep quality per se.

Sleepy drivers on a slippery road: A pilot study using a driving simulator.

Sleepy drivers have problems with keeping the vehicle within the lines, and might often need to apply a sudden or hard corrective steering wheel movement. Such movements, if they occur while driving on a slippery road, might increase the risk of ending off road due to the unforgiving nature of slippery roads. We tested this hypothesis. Twelve young men participated in a driving simulator experiment with two counterbalanced conditions; dry versus slippery road × day (alert) versus night (sleepy) driving. The participants drove 52.5 km on a monotonous two-lane highway and rated their sleepiness seven times using the Karolinska Sleepiness Scale. Blink durations were extracted from an electrooculogram. The standard deviation of lateral position and the smoothness of steering events were measures of driving performance. Each outcome variable was analysed with mixed-effect models with road condition, time-of-day and time-on-task as predictors. The Karolinska Sleepiness Scale increased with time-on-task (p < 0.001) and was higher during night drives (p < 0.001), with a three-way interaction suggesting a small increased sleepiness with driving time at night with slippery road conditions (p = 0.012). Blink durations increased with time-on-task (p < 0.01) with an interaction between time-of-day and road condition (p = 0.040) such that physiological sleepiness was lower for sleep-deprived participants in demanding road conditions. The standard deviation of lateral position increased with time-on-task (p = 0.026); however, during night driving it was lower on a slippery road (p = 0.025). The results indicate that driving in demanding road condition (i.e. slippery road) might further exhaust already sleepy drivers, although this is not clearly reflected in driving performance.

How does cessation of work affect sleep? Prospective analyses of sleep duration, timing and efficiency from the Swedish Retirement Study.

Several strands of research indicate that work competes for time with sleep, but to what extent the timing and duration of sleep is affected by work is not known. Retirement offers a quasi-experimental life transition to study this in a within-individual study design. The few existing studies report that people sleep longer and later after retirement but mainly rely on self-reported data or between-individual analyses. We recruited 100 participants aged 61-72 years who were in paid work but would soon retire and measured them in a baseline week with accelerometers, diaries and questionnaires. After 1 and 2 years, the measurements were repeated for the now retired participants. Changes in sleep duration, timing, efficiency, chronotype and social jetlag were analysed using multilevel modelling. Gender, chronotype at baseline and partner's working status were analysed as potential effect modifiers. Sleep duration increased by 21 min, whereas sleep efficiency remained similar. Time of sleep onset and final awakening were postponed by 26 and 52 min, respectively, pushing midsleep forward from 03:17 to 03:37 hours. Changes in duration and timing of sleep were driven by weekday sleep, whereas weekend sleep stayed about the same. Social jetlag decreased but still occurred after retirement. Changes at retirement in sleep duration and timing were smaller for participants with a later chronotype and who had full-time working partners. These findings indicate that paid work generates sleep loss and hinders people from sleeping in line with their biological time.

Workplace violence and health in human service industries: a systematic review of prospective and longitudinal studies.

OBJECTIVES: To provide systematically evaluated evidence of prospective associations between exposure to physical, psychological and gender-based violence and health among healthcare, social care and education workers. METHODS: The guidelines on Preferred Reporting Items for Systematic Reviews and Meta-Analyses were followed. Medline, Cinahl, Web of Science and PsycInfo were searched for population: human service workers; exposure: workplace violence; and study type: prospective or longitudinal in articles published 1990-August 2019. Quality assessment was performed based on a modified version of the Cochrane's 'Tool to Assess Risk of Bias in Cohort Studies'. RESULTS: After deduplication, 3566 studies remained, of which 132 articles were selected for full-text screening and 28 were included in the systematic review. A majority of the studies focused on healthcare personnel, were from the Nordic countries and were assessed to have medium quality. Nine of 11 associations between physical violence and poor mental health were statistically significant, and 3 of 4 associations between physical violence and sickness absence. Ten of 13 associations between psychological violence and poor mental health were statistically significant and 6 of 6 associations between psychological violence and sickness absence. The only study on gender-based violence and health reported a statistically non-significant association. CONCLUSION: There is consistent evidence mainly in medium quality studies of prospective associations between psychological violence and poor mental health and sickness absence, and between physical violence and poor mental health in human service workers. More research using objective outcomes, improved exposure assessment and that focus on gender-based violence is needed.

Association of work-time control with sickness absence due to musculoskeletal and mental disorders: An occupational cohort study.

OBJECTIVES: Work-time control is associated with lower sickness absence rates, but it remains unclear whether this association differs by type of diagnosis and sub-dimension of work-time control (control over daily hours and control over time off) and whether certain vulnerable groups benefit more from higher levels of work-time control. METHODS: Survey data from the Finnish 10-town study in 2004 were used to examine if baseline levels of work-time control were associated with register data on diagnose-specific sickness absence for 7 consecutive years (n = 22 599). Cox proportional hazard models were conducted, adjusted for age, sex, education, occupational status, shift work including nights, and physical/mental workload. RESULTS: During follow-up, 2,818 individuals were on sick leave (≥10 days) due to musculoskeletal disorders and 1724 due to mental disorders. Employees with high (HR = 0.80, 95% CI 0.74-0.87; HR = 0.76, 95% CI 0.70-0.82, respectively) and moderate (HR = 0.83, 95% CI 0.77-0.90; HR = 0.85, 95% CI 0.79-0.91, respectively) levels of control over daily hours/control over time off had a decreased risk of sickness absence due to musculoskeletal disorders. Sub-group analyses revealed that especially workers who were older benefitted the most from higher levels of work-time control. Neither sub-dimension of work-time control was related to sickness absence due to mental disorders. CONCLUSIONS: Over a 7-year period of follow-up, high and moderate levels of work-time control were related to lower rates of sickness absence due to musculoskeletal disorders, but not due to mental disorders.

A combined fMRI and EMG study of emotional contagion following partial sleep deprivation in young and older humans.

Sleep deprivation is proposed to inhibit top-down-control in emotion processing, but it is unclear whether sleep deprivation affects emotional mimicry and contagion. Here, we aimed to investigate effects of partial sleep deprivation on emotional contagion and mimicry in young and older humans. Participants underwent partial sleep deprivation (3 h sleep opportunity at the end of night), crossed-over with a full sleep condition in a balanced order, followed by a functional magnetic resonance imaging and electromyography (EMG) experiment with viewing of emotional and neutral faces and ratings of emotional responses. The final sample for main analyses was n = 69 (n = 36 aged 20-30 years, n = 33 aged 65-75 years). Partial sleep deprivation caused decreased activation in fusiform gyri for angry faces and decreased ratings of happiness for all stimuli, but no significant effect on the amygdala. Older participants reported more anger compared to younger participants, but no age differences were seen in brain responses to emotional faces or sensitivity to partial sleep deprivation. No effect of the sleep manipulation was seen on EMG. In conclusion, emotional contagion, but not mimicry, was affected by sleep deprivation. Our results are consistent with the previously reported increased negativity bias after insufficient sleep.The Stockholm sleepy brain study: effects of sleep deprivation on cognitive and emotional processing in young and old. https://clinicaltrials.gov/ct2/show/NCT02000076 .

How to schedule night shift work in order to reduce health and safety risks.

Objectives This discussion paper aims to provide scientifically based recommendations on night shift schedules, including consecutive shifts, shift intervals and duration of shifts, which may reduce health and safety risks. Short-term physiological effects in terms of circadian disruption, inadequate sleep duration and quality, and fatigue were considered as possible links between night shift work and selected health and safety risks, namely, cancer, cardio-metabolic disease, injuries, and pregnancy-related outcomes. Method In early 2020, 15 experienced shift work researchers participated in a workshop where they identified relevant scientific literature within their main research area. Results Knowledge gaps and possible recommendations were discussed based on the current evidence. The consensus was that schedules which reduce circadian disruption may reduce cancer risk, particularly for breast cancer, and schedules that optimize sleep and reduce fatigue may reduce the occurrence of injuries. This is generally achieved with fewer consecutive night shifts, sufficient shift intervals, and shorter night shift duration. Conclusions Based on the limited, existing literature, we recommend that in order to reduce the risk of injuries and possibly breast cancer, night shift schedules have: (i) ≤3 consecutive night shifts; (ii) shift intervals of ≥11 hours; and (iii) ≤9 hours shift duration. In special cases - eg, oil rigs and other isolated workplaces with better possibilities to adapt to daytime sleep - additional or other recommendations may apply. Finally, to reduce risk of miscarriage, pregnant women should not work more than one night shift in a week.

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.

Sleepiness, sleep duration, and human social activity: An investigation into bidirectionality using longitudinal time-use data.

Daytime sleepiness impairs cognitive ability, but recent evidence suggests it is also an important driver of human motivation and behavior. We aimed to investigate the relationship between sleepiness and a behavior strongly associated with better health: social activity. We additionally aimed to investigate whether a key driver of sleepiness, sleep duration, had a similar relationship with social activity. For these questions, we considered bidirectionality, time of day, and differences between workdays and days off. Over 3 wk, 641 working adults logged their behavior every 30 min, completed a sleepiness scale every 3 h, and filled a sleep diary every morning (rendering >292,000 activity and >70,000 sleepiness datapoints). Using generalized additive mixed-effect models, we analyzed potential nonlinear relationships between sleepiness/sleep duration and social activity. Greater sleepiness predicted a substantial decrease in the probability of social activity (odds ratio 95% CI = 0.34 to 0.35 for days off), as well as a decreased duration of such activity when it did occur. These associations appear especially robust on days off and in the evenings. Social duration moderated the typical time-of-day pattern of sleepiness, with, for example, extended evening socializing associated with lower sleepiness. Sleep duration did not robustly predict next-day social activity. However, extensive social activity (>5 h) predicted up to 30 min shorter subsequent sleep duration. These results indicate that sleepiness is a strong predictor of voluntary decreases in social contact. It is possible that bouts of sleepiness lead to social withdrawal and loneliness, both risk factors for mental and physical ill health.

Gray Matter Volume Correlates of Sleepiness: A Voxel-Based Morphometry Study in Younger and Older Adults.

BACKGROUND: Subjectively experienced sleepiness is a problem in society, possibly linked with gray matter (GM) volume. Given a different sleep pattern, aging may affect such associations, possibly due to shrinking brain volume. PURPOSE: The purpose of the present study was to investigate the association between subjectively rated sleepiness and GM volume in thalamus, insula, hippocampus, and orbitofrontal cortex of young and older adults, after a normal night's sleep. METHODS: Eighty-four healthy individuals participated (46 aged 20-30 years, and 38 aged 65-75 years). Morphological brain data were collected in a 3T magnetic resonance imaging (MRI) scanner. Sleepiness was rated multiple times during the imaging sessions. RESULTS: In older, relative to younger, adults, clusters within bilateral mid-anterior insular cortex and right thalamus were negatively associated with sleepiness. Adjustment for the immediately preceding total sleep time eliminated the significant associations. CONCLUSION: Self-rated momentary sleepiness in a monotonous situation appears to be negatively associated with GM volume in clusters within both thalamus and insula in older individuals, and total sleep time seems to play a role in this association. Possibly, this suggests that larger GM volume in these clusters may be protective against sleepiness in older individuals. This notion needs confirmation in further studies.

The mediating effect of work-life interference on the relationship between work-time control and depressive and musculoskeletal symptoms.

Objectives Evidence shows that work-time control (WTC) affects health but underlying mechanisms are still unclear. Work-life interference (WLI) might be a step on the causal pathway. The present study examined whether WLI mediates effects on mental and physical health and contrasted these to other causal pathways. Methods Four biennial waves from the Swedish Longitudinal Occupational Survey of Health (SLOSH, N=26 804) were used. Cross-lagged analyses were conducted to estimate if WLI mediated effects from WTC (differentiating between control over daily hours and time off) to subsequent depressive and musculoskeletal symptoms. Other causal directions (reversed mediation, direct and reversed direct effects) and robustness of mediation (by including covariates) were examined. Results WLI partially mediated the relationship of WTC (control over daily hours/time off) with both health outcomes. Indirect effect estimates were small for depressive symptoms (-0.053 for control over time off and -0.018 for control over daily hours) and very small for musculoskeletal symptoms (-0.007 and -0.003, respectively). While other causal directions were generally weaker than causal mediational pathways, they played a larger role for musculoskeletal compared to depressive symptoms. Estimates relating to control over time off were in general larger than for control over daily hours. Conclusions Our results suggest that WLI mediates part of the effect from WTC to mental/musculoskeletal symptoms, but small estimates suggest that (i) WTC plays a small but consistent role in effects on health and (ii) particularly regarding musculoskeletal disorders, other causal directions and mediators need to be further examined.