Sleep duration and quality in permanent night work: an observational field study.

PURPOSE: Permanent night workers conceivably show better adaptation of circadian rhythms to night work than shift workers and therefore better possibilities of obtaining sufficient sleep of good quality after night shifts. We investigated the effect of night shifts including number of consecutive shifts on sleep among self-selected permanent night workers, and studied if the effect of night shifts differed between morning and evening types and compared with 3-shift workers. METHODS: The study population included 90 permanent night workers followed for 14 days (warehouse workers, 1228 observation days, 80% males). For comparison, we included 70 3-shift workers followed for 26 days (police officers, 1774 observation days, 100% men). Total sleep time (TST), primary sleep duration (PSD), and sleep efficiency were assessed by actigraphy. Measures of sleep quality and diurnal type were self-reported. RESULTS: Among permanent night workers, TST, PSD, difficulties falling asleep, disturbed sleep, and the number of awakenings decreased after night shifts compared with days without night work. Sleep efficiency, difficulties awakening, and non-refreshing sleep increased. More consecutive night shifts were associated with shorter TST and PSD. Sleep outcomes did not differ by diurnal type. Permanent night workers had fewer awakenings after night shifts than 3-shift workers, but no other differences were observed. CONCLUSION: This study does not provide evidence that supports recommendation of permanent night work to reduce adverse effects of night shifts on sleep. A limited number of consecutive night shifts is recommended to reduce accumulation of sleep debt.

Does it matter for health if steps are taken during work or leisure? A prospective accelerometer study using register-based long-term sickness absence.

BACKGROUND: Walking is known to be good for health. However, it is unknown whether it matters if steps are taken during work or leisure. Therefore, we aimed to examine the prospective association between accelerometer-measured steps taken during work or leisure and register-based long-term sickness absence (LTSA). METHODS: We included 937 blue- and white-collar workers from the PODESA cohort who wore a thigh-based accelerometer over four days to measure number of steps during work and leisure. Steps were divided into domain based on diary data. First event of LTSA was retrieved from a national register with four years' follow-up. We used Cox proportional hazard models to analyze the association between domain-specific and total daily steps and LTSA, adjusted for age, sex, job type, smoking, and steps in the other domain (e.g., work/leisure). RESULTS: We found more steps at work to be associated with a higher LTSA risk [Hazard Ratio (HR):1.04; 95% CI: 1.00-1.08 per 1000 steps]. No significant association was found between steps during leisure and LTSA (HR: 0.97; 95% CI: 0.91-1.02), nor between total daily steps and LTSA (HR: 1.01; CI 95% 0.99-1.04). CONCLUSIONS: More steps at work were associated with higher risk of LTSA, while steps during leisure was not clearly associated with LTSA risk. These findings partly support 'the physical activity paradox' stating that the association between physical activity and health depends on the domain.

History of working conditions and the risk of old-age dependency: a nationwide Swedish register-based study.

AIMS: There is substantial evidence that previous working conditions influence post-retirement health, yet little is known about previous working conditions' association with old-age dependency. We examined job strain, hazardous and physical demands across working life, in relation to the risk of entering old-age dependency of care. METHODS: Individually linked nationwide Swedish registers were used to identify people aged 70+ who were not receiving long-term care (residential care or homecare) at baseline (January 2014). Register information on job titles between the years 1970 and 2010 was linked with a job exposure matrix of working conditions. Random effects growth curve models were used to calculate intra-individual trajectories of working conditions. Cox regression models with age as the timescale (adjusted for living situation, educational attainment, country of birth, and sex) were conducted to estimate hazard ratios for entering old-age dependency during the 24 months of follow-up (n = 931,819). RESULTS: Having initial adverse working conditions followed by an accumulation throughout working life encompassed the highest risk of entering old-age dependency across the categories (job strain: HR 1.23, 95% CI 1.19-1.27; physical demands: HR 1.36, 95% CI 1.31-1.40, and hazardous work: HR 1.35, 95% CI 1.30-1.40). Initially high physical demands or hazardous work followed by a stable trajectory, or initially low-level physical demand or hazardous work followed by an accumulation throughout working life also encompassed a higher risk of dependency. CONCLUSIONS: A history of adverse working conditions increased the risk of old-age dependency. Reducing the accumulation of adverse working conditions across the working life may contribute to postponing old-age dependency.

The effect of COVID-19 on schoolteachers' emotional reactions and mental health: longitudinal results from the CLASS study.

PURPOSE: We investigated schoolteachers' emotional reactions to COVID-19 and mental health during three phases of the COVID-19 pandemic. We further analyzed if teachers, who belonged to a COVID-19 risk group, had more emotional reactions and poorer mental health than "non-risk" groups. METHODS: We collected questionnaire data in May, June, and November-December 2020 and used data from 2665 teachers at public schools (871 individuals participated in all three surveys). Participants reported their fear of infection, fear of transmission of infection to their home or pupils, perceived burnout and stress, and worries about their ability to manage the working conditions. We included information about COVID-19 risk group status, gender, age, organization of teaching (physical presence or remote teaching), and the pupils' grade. We estimated prevalence ratios and took repeated measures into account. RESULTS: Emotional reactions and poor mental health increased significantly with 27-84% from May to November-December 2020. Teachers, who were particularly vulnerable to the adverse consequences of COVID-19, had the highest prevalence of fear of infection and poor mental health. CONCLUSION: Teachers play a crucial role in a society's response to a pandemic. Yet, the dual role of teaching and virus control along with concerns regarding the health consequences of an infection may contribute to the observed increase in emotional reactions to COVID-19 and poor mental health.

Heart rate variability during sleep after two, four and seven consecutive night shifts and recovery days: a cross-over intervention study.

OBJECTIVE: Recovery after shift work is an important part reducing the health problems related to shift work. Heart rate variability (HRV) is an indicator of the balance between sympathetic and parasympathetic activity in the autonomic nervous system and can be used as a measure of recovery after night shifts. The aim of the study is to investigate autonomic recovery during sleep in response to night work in a crossover intervention study. METHODS: Seventeen male police officers working in call centres in five different police district participated in the HRV measurements. The participants were exposed to three interventions: 2 + 2: two consecutive night shifts followed by two consecutive day recovery days; 4 + 4: four consecutive night shifts followed by four consecutive recovery days; 7 + 7: seven consecutive night shifts followed by seven consecutive recovery days. On the last day with night shift and the last recovery day in each intervention the participants underwent 24 h HRV recordings. We analysed HRV during sleep. The five 5-min intervals with the lowest heart rate during each sleep period were chosen for spectral analysis of the heart interbeat interval time series. The five 5-min intervals could occur at any time during sleep. RESULTS: There were overall differences in HRV during sleep between days with night shifts and recovery days, primarily in parasympathetic activity. There was no difference in the lowest heart rate obtained, but the timing was different for the three interventions. The lowest heart rate after night shifts occurred 112 (SD 79) min, 174 (SD 115) min and 135 (SD 94) min after sleep onset for the 2 + 2 night shift, the 4 + 4 night shift and the 7 + 7 night shift, respectively. CONCLUSION: Overall sleep-related autonomic recovery had higher parasympathetic modulation of cardiac rhythm on the 2 + 2 shift system compared to the 4 + 4 and 7 + 7 shift system.

COVID-19 risk management at the workplace, fear of infection and fear of transmission of infection among frontline employees.

OBJECTIVES: We compared COVID-19 risk management, fear of infection and fear of transmission of infection among frontline employees working within eldercare, hospital/rehabilitation, psychiatry, childcare and ambulance service and explored if group differences in fear of infection and transmission could be explained by differences in risk management. We also investigated the association of risk management with fear of infection and fear of transmission of infection among eldercare personnel. METHODS: We used cross-sectional questionnaire data collected by the Danish labour union, FOA . Data were collected 5½ weeks after the first case of COVID-19 was registered in Denmark. Data for the first aim included 2623 participants. Data for the second aim included 1680 participants. All independent variables were mutually adjusted and also adjusted for sex, age, job title and region. RESULTS: Fear of infection (49%) and fear of transmitting infection from work to the private sphere (68%) was most frequent in ambulance service. Fear of transmitting infection during work was most frequent in the eldercare (55%). Not all differences in fear of infection and transmission between the five areas of work were explained by differences in risk management. Among eldercare personnel, self-reported exposure to infection and lack of access to test was most consistently associated with fear of infection and fear of transmission, whereas lack of access to personal protective equipment was solely associated with fear of transmission. CONCLUSION: We have illustrated differences and similarities in COVID-19 risk management within five areas of work and provide new insights into factors associated with eldercare workers' fear of infection and fear of transmission of infection.

The effect of occupational physical activity on dementia: Results from the Copenhagen Male Study.

Leisure-time physical activity (LTPA) reduces the risk of dementia, while the effect of occupational physical activity (OPA) on dementia is uncertain. Therefore, the aim of this study was to investigate the effect of OPA on dementia. For comparison, also the association between LTPA and dementia was analyzed. In this longitudinal study, we used self-reported questionnaire data on OPA and LTPA collected in 1970-71 from 4721 male employees, who were 40-59 years old at baseline. Dementia was identified through national registers and participants were followed from they turned 60 years and until 2016. We estimated incidence rate ratios (IRR) and adjusted for age, socioeconomic status, marital status, and psychological stress. In additional analyses, we included health behaviors and blood pressure and mutually adjusted OPA and LTPA. We identified 697 dementia cases during 86 557 person-years. We found an IRR of 1.48 (95% CI: 1.05-2.10) among participants with high OPA compared with participants in sedentary jobs. Participants with high LTPA had a non-significantly lower IRR of dementia compared with participants with a sedentary leisure time. In conclusion, LTPA and OPA are differentially associated with dementia. Therefore, current recommendations regarding the beneficial effect of physical activity on dementia only concern LTPA, and more research on OPA and dementia is needed.

Day-to-day pattern of work and leisure time physical behaviours: are low socioeconomic status adults couch potatoes or work warriors?

BACKGROUND: Most studies on day-to-day patterns of physical behaviours (i.e. physical activities and sedentary behaviour) are based on adults with high socioeconomic status (SES) and without differentiating between work and leisure time. Thus, we aimed to characterise the day-to-day leisure time physical behaviours patterns among low SES adults and investigate the influence of work physical behaviours. METHODS: This cross-sectional study included 963 adults from low SES occupations (e.g. manufacturing, cleaning and transportation). The participants wore accelerometers for 1-7 days to measure physical behaviours during work and leisure time, expressed as time-use compositions consisting of time spent sedentary, standing or being active (walking, running, stair climbing, or cycling). Compositional multivariate multilevel models were used to regress daily leisure time-use composition against work time-use compositions. Interaction between weekday and (1) type of day, (i.e., work/non-work) and (2) the work time-use composition were tested. Compositional isotemporal substitution was used to interpret the estimates from the models. RESULTS: Each weekday, workers consistently spent most leisure time being sedentary and most work time standing. Leisure time physical behaviours were associated with type of day (p < 0.005, more sedentary on workdays vs. non-workdays), weekday (p < 0.005, more sedentary on Friday, Saturday and Sunday), standing work (p < 0.005, more sedentary and less standing and active leisure time on Sunday), and active work (p < 0.005, less sedentary and more standing and active leisure time on Sunday). Sedentary leisure time increased by 18 min, while standing and active leisure time decreased by 11 and 7 min, respectively, when 30 min were reallocated to standing at work on Sunday. Conversely, sedentary leisure time decreased by 25 min, and standing and active leisure time increased by 15 and 10 min, respectively, when 30 min were reallocated to active time at work on Sunday. CONCLUSIONS: While low SES adults' leisure time was mostly sedentary, their work time was predominantly standing. Work physical behaviours differently influenced day-to-day leisure time behaviours. Thus, public health initiatives aiming to change leisure time behaviours among low SES adults should consider the influence of work physical behaviours.

Physical and psychosocial work factors as explanations for social inequalities in self-rated health.

OBJECTIVE: We investigated the contribution of physical and psychosocial work factors to social inequalities in self-rated health (SRH) in a sample of Danish 40 and 50 years old occupationally active women and men. METHODS: In this longitudinal study, the study population consisted of 3338 Danish women and men. Data were collected by postal questionnaires in 2000 (baseline) and 2006 (follow-up). The independent variable, socioeconomic position (SEP), was assessed by the highest achieved educational level at baseline. We conducted gender-stratified parallel multiple mediation analyses. In the mediation analyses, SEP was categorised as SEP I, II, III, VI and V among men. Among women, SEP was dichotomised into SEP I-IV and V. The outcome, SRH, was assessed at baseline and follow-up. A wide range of physical and psychosocial work factors were included as potential mediators. RESULTS: We found a social gradient in SRH across all levels of SEP among men. Among women, we only found a poorer SRH among those with the lowest SEP. Mediation analyses showed that work factors together accounted for 56% of the social inequalities in SRH among men and 44% among women. In both genders, ergonomic exposures and job insecurity seemed to play the major role for social inequalities in SRH. For women only, we also found noise to contribute to the social inequalities in SRH. CONCLUSION: Physical and psychosocial work factors partially explained social inequalities in SRH among both genders. Improvement of the working environment can potentially contribute to the reduction of social inequalities in health.

Stress diagnoses in midlife and risk of dementia: a register-based follow-up study.

OBJECTIVES: Previous studies indicated that stress diagnoses increase the risk of dementia. However, previous results may be biased by confounding, reverse causation and misclassification. Therefore, the main aim of this study was to investigate the association between clinically diagnosed stress in midlife and later dementia risk, while addressing limitations of previous studies. METHODS: The study population was selected from all individuals in Denmark born 1935-1956. Individuals diagnosed with stress in midlife (aged 37-58 years) were matched (1:5) with individuals without stress diagnoses based on sex and birthdate (N = 103,484). Data were retrieved from national registers. Cox regression models were adjusted for socio-demographic factors and different morbidities. RESULTS: We found a 2.20 (95% CI: 1.93-2.50) times higher rate of dementia among individuals with any stress diagnosis registered in midlife compared with no stress diagnosis. Hazard rate ratios of dementia were 1.73 (95% CI: 1.13-2.65) among individuals with acute stress reactions, 2.37 (95% CI: 2.05-2.74) among individuals with adjustment disorders, and 2.20 (95% CI: 1.73-2.80) among individuals with unspecified stress reactions. Individuals with PTSD and other stress reactions had non-significantly elevated rates of dementia. Adjustment for confounding only slightly attenuated the association, and reverse causation did not appear to bias the results substantially. CONCLUSION: Our results support the hypothesis that severe stress in midlife is an important risk factor for dementia. This finding emphasizes the importance of identifying and treating severe stress in midlife to reduce potential detrimental consequences for brain health in later life.

The longitudinal association between shift work and headache: results from the Danish PRISME cohort.

PURPOSE: We investigated the effect of shift work on headache. Furthermore, we investigated whether the association between shift work and headache was explained by potential mediators in terms of perceived stress, poor sleep and health behaviors. METHODS: In this longitudinal study, we used questionnaire data (collected in 2007 and 2009) from civil servants and hospital employees from the PRISME study. 2952 individuals were available for the analyses of shift work and headache and 2272 individuals were available for the analyses of shift work and migraine. Headache was operationalized as the participants' experience of "being bothered by headache during the past 4 weeks". Migraine was operationalized as "ever being diagnosed with migraine by a medical doctor". We used binary logistic regression to compare shift workers with permanent day workers and adjusted for socio-demographic factors. In a subsequent step, we adjusted for potential mediators. RESULTS: We found higher odds of unspecific headache (OR = 1.25; 95% CI 1.02-1.54) and migraine (OR = 1.72; 95% CI 1.04-2.86) among shift workers compared with day workers. Our results suggest that the effect of shift work on headache and migraine differ between men and women. Inclusion of potential mediators in the analyses did not attenuate the associations. CONCLUSION: Shift workers have higher risk of reporting being bothered by headache as well as reporting being diagnosed with migraine. Future research is needed to disentangle the underlying mechanisms with the aim of reducing headache related to occupational exposures.

Perceived stress and dementia: Results from the Copenhagen city heart study.

Objectives: We investigated if perceived stress in midlife increased the risk of dementia. Furthermore, we explored differences between subgroups related to sex, age and employment status when reporting stress.Methods: In this longitudinal study, we used information on perceived stress from 10,814 participants (mean age 56.7 years). Participants were followed through Danish national registers for development of dementia. Participants were considered at risk of dementia from the date they turned 60 years. Perceived stress was assessed as a combination of self-reported intensity and frequency of stress, and categorized into low (score 0-1), medium (score 2-4), and high stress (score 5-6). We used Poisson regression to estimate incidence rate ratios (IRR) and their 95% confidence intervals (CI) and adjusted for sociodemographic factors and psychiatric morbidity at baseline (main model) as well as cardio/cerebrovascular diseases and health behaviors at baseline (additional model).Results: The mean follow-up time was 13.8 years, and 1,519 participants were registered with dementia. Dementia risk was higher in participants reporting medium stress (IRR = 1.11, 95% CI: 0.99-1.24) and high stress (IRR = 1.36, 95% CI: 1.13-1.65). Adjustment for cardio/cerebrovascular diseases and health behaviors did not alter the results. We did not find strong support for differences between subgroups, although the association between stress and dementia was stronger for those who were employed at the time of reporting high stress.Conclusion: Our results provide empirical support for an effect of perceived stress on the risk of dementia in old age.

Shift work and incidence of dementia: A Danish Nurse Cohort study.

INTRODUCTION: A few studies suggest that working night and rotating shifts increase the risk of dementia. We examined the association between shift work and the incidence of dementia in a cohort of female Danish nurses. METHODS: We linked Danish Nurse Cohort participants, who reported work schedules (day, evening, night, rotating shifts) in 1993 and/or 1999 and their duration in 2009, to Danish registers to obtain information on dementia hospitalizations and prescription medication until November 2018. RESULTS: Among 6048 nurses who reported work schedules in 1993 and 1999, nurses working night shifts ≥6 years had higher dementia incidence (hazard ratio: 2.43, 95% confidence interval: 1.39 to 4.23) than those working day shifts ≥6 years. Among 8059 nurses who reported shift work duration, nurses working night shifts ≥6 years had higher dementia incidence than those working night shifts <1 year (1.47, 1.06 to 2.06). DISCUSSION: Persistent night shift work may increase the risk of dementia.

Mid- to late-life migraine diagnoses and risk of dementia: a national register-based follow-up study.

BACKGROUND: Previous studies found an association between migraine and dementia, which are two leading causes of disability. However, these studies did not differentiate between migraine types and did not investigate all prevalent dementia subtypes. The main objective of this national register-based study was to investigate whether migraine was a risk factor for dementia. Additionally, we explored potential differences in dementia risk for migraine with and without aura. METHODS: We obtained data on birth cohorts born between 1935 and 1956 (n = 1,657,890) from Danish national registers. Individuals registered with migraine before age 59 (n = 18,135) were matched (1:5) on sex and birthdate with individuals without migraine (n = 1,378,346). Migraine was defined by International Classification of Diseases (ICD) diagnoses and dementia was defined by ICD diagnoses and anti-dementia medication. After matching, 62,578 individuals were eligible for analysis. For the statistical analyses, we used Cox regression models and adjusted for socio-demographic factors and several psychiatric and somatic morbidities. RESULTS: During a median follow-up time of 6.9 (IQR: 3.6-11.2) years, 207 individuals with migraine developed dementia. Compared with individuals without migraine, we found a 50% higher rate of dementia among individuals with migraine (HR = 1.50; 95% CI: 1.28-1.76). Individuals without aura had a 19% higher rate of dementia (HR = 1.19; 95% CI: 0.84-1.70), and individuals with aura had a two times higher rate of dementia (HR = 2.11; 95% CI: 1.48-3.00). CONCLUSIONS: Our findings support the hypothesis that migraine is a midlife risk factor for dementia in later life. The higher rate of dementia in individuals with a hospital-based diagnosis of migraine with aura emphasizes the need for studies on pathological mechanisms and potential preventative measures. Furthermore, given that only hospital-based migraine diagnoses were included in this study, future research should also investigate migraine cases derived from the primary healthcare system to include less severe migraine cases.

Midlife Forgetfulness and Risk of Dementia in Old Age: Results from the Danish Working Environment Cohort Study.

BACKGROUND: Despite the current evidence of a high prevalence of forgetfulness in middle-aged individuals, and the evidence of a link between midlife memory complaints and biological changes in the brain, no previous study has yet investigated midlife forgetfulness in relation to risk of dementia in old age. AIMS: We investigated whether midlife forgetfulness was an indicator of an increased risk of dementia in old age. METHODS: We used data from 3,136 employed men and women who participated in the Danish Work Environment Cohort Study in 1990. These data were linked to Danish national registers. Participants were asked whether their closest relative had ever told them that they were forgetful. Incidence rate ratios (IRR) were estimated using Poisson regression analysis. RESULTS: At baseline, 749 (24%) study participants were categorized as forgetful, and 86 (2.7%) participants were diagnosed with dementia during a total of 31,724 person-years at risk. After adjusting for sociodemographic factors, comorbidities, and work-related factors, midlife forgetfulness was associated with a higher risk of dementia (IRR = 1.82; 95% CI: 1.12-2.97). CONCLUSIONS: This study is the first to investigate midlife forgetfulness and dementia, and the results suggest that midlife forgetfulness is an early indicator of an increased risk of dementia in old age.

The association between occupational standing and sedentary leisure time over consecutive workdays among blue-collar workers in manual jobs.

PURPOSE: Blue-collar workers spend much leisure time sedentary, which is associated with numerous health impairments. The extensive sedentary leisure time among blue-collar workers could be caused by fatigue from physically demanding work, like stationary standing. Occupational stationary standing is prevalent in many blue-collar jobs and has been shown to induce fatigue. The objective of this study was to investigate the association between occupational standing and sedentary leisure time over several workdays among blue-collar workers. METHODS: This study used data from 925 workers from Danish workplaces within cleaning, transportation, manufacturing, construction, road maintenance, garbage disposal, and health service. Eligible workers wore accelerometers for 2-5 consecutive workdays. A linear regression was used to investigate the association between percent of work time spent standing and leisure time spent sedentary. A multilevel growth model was used to assess the association between standing during work and sedentary leisure time over consecutive workdays. RESULTS: We found no association between percent of work hours spent standing and percent of leisure time spent sedentary (coef. = 0.01, p = 0.84). The results showed an increase in the workers' sedentary leisure time over a week (coef. = 0.70, p < 0.01). However, this increase was not associated with consecutive workdays exposed to occupational standing (coef. = 0.02, p = 0.42). CONCLUSION: In this study, we found no support of a positive association between occupational standing and sedentary leisure time. This lack of association could be attributable to a low variation in sedentary leisure time or the chosen definition and measurement of occupational standing.

Prolonged or serious conflicts at work and incident dementia: a 23-year follow-up of the Copenhagen City Heart Study.

PURPOSE: Only a few studies have investigated the impact of negative aspects of social relations on cognitive function, and they have shown mixed results. Conflicts at work are part of the negative aspects of social relations, but the impact of experiencing conflicts at work has not yet been investigated as a risk factor for dementia. Therefore, we investigated whether experiencing prolonged or serious conflicts with a supervisor or colleagues at work was associated with incident dementia in old age. METHODS: We analyzed data of 6,436 men and women from the third survey of the Copenhagen City Heart Study. At baseline in 1991-1994, the participants reported whether they had ever had a prolonged or serious conflict at work. The participants were followed until 2014. We used Poisson regression to estimate incidence rate ratios (IRR) and their 95% confidence intervals (CI). RESULTS: After adjusting for potential confounders, the IRR for dementia was 1.53 (95% CI 0.77-3.03) among participants who had reported having prolonged or serious conflicts both with a supervisor and colleagues compared with participants who had never had such conflicts. In separate analyses stratified by sex, the IRRs were 2.14 (95% Cl 0.97-4.71) for men and 0.98 (95% Cl 0.29-3.32) for women. CONCLUSIONS: Our findings did not support an overall association between experiencing prolonged or serious conflicts at work and incident dementia. However, because of the large differences in the point estimates for men and women, future research could aim at investigating potential sex differences regarding the association between conflicts at work and dementia.

The associations between workplace bullying, salivary cortisol, and long-term sickness absence: a longitudinal study.

BACKGROUND: Workplace stressors, such as bullying, are strongly related to subsequent long-term sickness absence, but little is known of the possible physiological mechanisms linking workplace stressors and sickness absence. The primary aim of this study was to investigate to what extent cortisol levels were associated with subsequent sickness absence and if cortisol mediated the association between workplace bullying and sickness absence. We additionally investigated possible bidirectional associations between bullying, cortisol, and long-term sickness absence. METHODS: Participants came from two Danish cohort studies, the "Psychosocial RIsk factors for Stress and MEntal disease" (PRISME) cohort and the "Workplace Bullying and Harassment" (WBH) cohort (n = 5418). Information about exposure to workplace bullying and morning and evening salivary cortisol was collected at three time points with approximately two years in between. After each data collection, all participants were followed for two years in registers, and cases with long-term sickness absence lasting 30 or more consecutive days were identified. The association between cortisol levels and subsequent sickness absence was assessed by logistic regression, while the extent to which the association between bullying and sickness absence was mediated by cortisol was quantified through natural direct and indirect effects. RESULTS: High evening cortisol was associated with a decreased risk of sickness absence (OR = 0.82, 95% CI = 0.68-0.99), but we did not find that high morning cortisol levels (OR = 0.98, 95% CI = 0.81-1.18) or high morning-to-evening slope (OR = 0.99, 95% CI = 0.82-1.18) were associated with subsequent sickness absence. We also tested for reverse causation and found that long-term sickness absence, but not salivary cortisol, was a strong risk factor for subsequent workplace bullying. There was no indication that cortisol mediated the association between workplace bullying and sickness absence. CONCLUSION: We found no straightforward and simple association between cortisol and long-term sickness absence. Furthermore, the association between workplace bullying and long-term sickness absence was not mediated by cortisol.

The association between shift work and treatment-seeking migraine in Denmark.

In Europe, the one-year prevalence of migraine is 14.9% and migraine is on the top-10 list of leading causes of years lost to disability. Sleep disturbances and irregular daily routines are considered triggers of migraine and these factors are well-known consequences of shift work. We studied the association between treatment-seeking migraine and shift work, categorised as fixed evening work, fixed night work and variable working hours with and without night work in a Danish working population of 5872 participants. When compared with fixed day workers, only participants with fixed evening work were found to have significantly increased odds of reporting treatment-seeking migraine after adjustment for socio-demographic and behavioural covariates (OR = 1.56; 95% CI 1.05-2.32). Participants with seniority of 10 years or more notably accounted for this association. Due to the cross-sectional design, selection mechanisms may have biased the results. Practitioner Summary: The study showed higher odds of treatment-seeking migraine among evening workers even when taking a range of potential confounders into account. Due to the cross-sectional design, we cannot draw any causal inferences, but potential mechanisms underlying the present study are discussed, with an emphasis on possible selection into evening work.

Do working environment interventions reach shift workers?

PURPOSE: Shift workers are exposed to more physical and psychosocial stressors in the working environment as compared to day workers. Despite the need for targeted prevention, it is likely that workplace interventions less frequently reach shift workers. The aim was therefore to investigate whether the reach of workplace interventions varied between shift workers and day workers and whether such differences could be explained by the quality of leadership exhibited at different times of the day. METHODS: We used questionnaire data from 5361 female care workers in the Danish eldercare sector. The questions concerned usual working hours, quality of leadership, and self-reported implementation of workplace activities aimed at stress reduction, reorganization of the working hours, and participation in improvements of working procedures or qualifications. RESULTS: Compared with day workers, shift workers were less likely to be reached by workplace interventions. For example, night workers less frequently reported that they had got more flexibility (OR 0.5; 95 % CI 0.3-0.7) or that they had participated in improvements of the working procedures (OR 0.6; 95 % CI 0.5-0.8). Quality of leadership to some extent explained the lack of reach of interventions especially among fixed evening workers. CONCLUSIONS: In the light of the evidence of shift workers' stressful working conditions, we suggest that future studies focus on the generalizability of results of the present study and on how to reach this group and meet their needs when designing and implementing workplace interventions.