Comprehensive evaluation of the impact of workplace exposures on physician-certified sick leave in the general working population

BACKGROUND

Our objective was to quantify the prospective associations between work factors across chemical, physical, mechanical, and psychosocial domains and the onset of medically certified sick leave.

METHODS

Eligible respondents were interviewed in 2009, 2013, or 2016 and were registered in the national sick leave register with an employee relationship lasting more than 50 working days during the year of the survey interviews and the following year (n = 15,294 observations). To focus on the onset of high-level sick leave (HLSL; >16 days a year), we excluded individuals with HLSL during the survey year (baseline). We then used mixed-effect logistic regression models to assess prospective associations between self-reported work conditions and the occurrence of doctor-certified HLSL in the following year.

RESULTS

The average occurrence of HLSL was 13.1%. After adjusting for sex, age, level of education, chronic health problems, and smoking, we observed an exposure-response relationship between cumulative exposure to work factors within all domains and the occurrence of HLSL. When evaluating the impact of combined exposures, predicted odds ratios (OR) for employees exposed to 1, 2, and 3 or more work factors within all domains were 1.60 (95%CI 1.32 - 1.94), 2.56 (95%CI 1.73 - 3.74) and 4.09 (95%CI 2.28 - 7.25), compared to those not exposed.

CONCLUSIONS

The results support the notion that exposure to multiple work factors in various domains, including psychosocial, mechanical, chemical, and physical work conditions, is associated with an increased risk of high-level sick leave. Employers and occupational health professionals should consider the joint impact of these domains when designing interventions.

Adverse social behaviour at work and health-related employment exit: a prospective population-based four-wave survey

BACKGROUND

The level of evidence for various aspects of adverse social behaviour (ASB) at work as risk factors for exit from employment due to health problems or diseases is inconclusive.

METHODS

We obtained data from four consecutive surveys (2006/09/13/16) of the general population of Norway. Respondents who were interviewed in two consecutive surveys and employed at the first survey time point constituted the sample (n = 17 110 observations). We investigated associations of self-reported exposure to ASB (i.e. experiencing sexual harassment, bullying or violence/threats in the first survey) and health-related employment exit (i.e. individuals reporting exit from employment due to health problems or disease between two consecutive surveys) by means of mixed-effect logistic regression.

RESULTS

The prevalence of ASB and health-related employment exit was 10.8% (n = 1853) and 2.6% (n = 440), respectively. Adjusted for age, sex, level of education, occupation and weekly work hours, sexual harassment, bullying and violence/threats were associated with an increased risk of exit from employment. The odds ratios (ORs) for the association between exposure to any of the three aspects of ASB and employment exit was 1.78 [95% confidence interval (CI) 1.33-2.38]; the estimated corresponding population attributable risk was PAR% = 7.32 [95% CI 2.67-12.27]. Further adjustment of mental distress attenuated the observed association between exposure to any ASB and exit from employment (OR = 1.45 [95% CI 1.07-1.95], i.e. a reduction of 42% in the OR).

CONCLUSIONS

ASB at work increases the risk of health-related exit from employment in the Norwegian workforce.

Work-life interference and physician-certified sick leave: a prospective study of a general working population

BACKGROUND

Work-life interference has been associated with adverse health outcomes. Here, we quantify the association between work-life interference and subsequent sick leave.

METHODS

Respondents from a randomly drawn cohort of the general working Norwegian population were interviewed in 2009, 2013 and/or 2016. Mixed-effects logistic regression models were used to assess prospective associations of self-reported work-life interference and risk of subsequent physician-certified sick leave of 1-16 days (low-level) and >16 days (high-level) in strata of men and women. To quantify the importance of work-life interference as risk factors for sick leave, we estimated the population attributable risk (PAR).

RESULTS

Both low- and high-level sick leave were most prevalent among women while the prevalence of work-life interference was similar between sexes. Risk of sick leave was higher among women reporting work-life interference sometimes or often in comparison with seldom or never {low- and high-level sick leave odds ratio (OR) = 1.21 [95% confidence interval (CI) = 1.07-1.37] and 1.30 (95% CI = 1.14-1.49), respectively}. The associations for high-level sick leave progressively increased with the level of work-life interference [highest OR = 1.44 (95% CI = 1.19-1.75)]. In men, there was no consistent higher risk of sick leave according to more frequent work-life interference [low- and high-level sick leave OR = 1.00 (95% CI = 0.87-1.14) and 0.98 (95% CI = 0.84-1.16), respectively], but the risk of high-level sick leave tended to be higher among men reporting work-life interference often (OR = 1.21, 95% CI = 0.98-1.50). Estimating PAR, 6.69% (95% CI = 1.52-11.74) of low-level and 9.94% (95% CI = 4.22-15.45) of high-level sick leave could be attributed to work-life interference among women.

CONCLUSIONS

Self-reported work-life interference was associated with a higher risk of sick leave, with the most consistent results among women.

Cognitive function and brain plasticity in a rat model of shift work: role of daily rhythms, sleep and glucocorticoids

Many occupations require operations during the night-time when the internal circadian clock promotes sleep, in many cases resulting in impairments in cognitive performance and brain functioning. Here, we use a rat model to attempt to identify the biological mechanisms underlying such impaired performance. Rats were exposed to forced activity, either in their rest-phase (simulating night-shift work; rest work) or in their active-phase (simulating day-shift work; active work). Sleep, wakefulness and body temperature rhythm were monitored throughout. Following three work shifts, spatial memory performance was tested on the Morris Water Maze task. After 4 weeks washout, the work protocol was repeated, and blood and brain tissue collected. Simulated night-shift work impaired spatial memory and altered biochemical markers of cerebral cortical protein synthesis. Measures of daily rhythm strength were blunted, and sleep drive increased. Individual variation in the data suggested differences in shift work tolerance. Hierarchical regression analyses revealed that type of work, changes in daily rhythmicity and changes in sleep drive predict spatial memory performance and expression of brain protein synthesis regulators. Moreover, serum corticosterone levels predicted expression of brain protein synthesis regulators. These findings open new research avenues into the biological mechanisms that underlie individual variation in shift work tolerance.

No Escaping the Rat Race: Simulated Night Shift Work Alters the Time-of-Day Variation in BMAL1 Translational Activity in the Prefrontal Cortex

Millions of people worldwide work during the night, resulting in disturbed circadian rhythms and sleep loss. This may cause deficits in cognitive functions, impaired alertness and increased risk of errors and accidents. Disturbed circadian rhythmicity resulting from night shift work could impair brain function and cognition through disrupted synthesis of proteins involved in synaptic plasticity and neuronal function. Recently, the circadian transcription factor brain-and-muscle arnt-like protein 1 (BMAL1) has been identified as a promoter of mRNA translation initiation, the most highly regulated step in protein synthesis, through binding to the mRNA “cap”. In this study we investigated the effects of simulated shift work on protein synthesis markers. Male rats (n = 40) were exposed to forced activity, either in their rest phase (simulated night shift work) or in their active phase (simulated day shift work) for 3 days. Following the third work shift, experimental animals and time-matched undisturbed controls were euthanized (rest work at ZT12; active work at ZT0). Tissue lysates from two brain regions (prefrontal cortex, PFC and hippocampus) implicated in cognition and sleep loss, were analyzed with m⁷GTP (cap) pull-down to examine time-of-day variation and effects of simulated shift work on cap-bound protein translation. The results show time-of-day variation of protein synthesis markers in PFC, with increased protein synthesis at ZT12. In the hippocampus there was little difference between ZT0 and ZT12. Active phase work did not induce statistically significant changes in protein synthesis markers at ZT0 compared to time-matched undisturbed controls. Rest work, however, resulted in distinct brain-region specific changes of protein synthesis markers compared to time-matched controls at ZT12. While no changes were observed in the hippocampus, phosphorylation of cap-bound BMAL1 and its regulator S6 kinase beta-1 (S6K1) was significantly reduced in the PFC, together with significant reduction in the synaptic plasticity associated protein activity-regulatedcytoskeleton-associated protein (Arc). Our results indicate considerable time-of-day and brain-region specific variation in cap-dependent translation initiation. We concludethat simulated night shift work in rats disrupts the pathways regulating the circadian component of the translation of mRNA in the PFC, and that this may partly explain impaired waking function during night shift work.

A Rodent Model of Night-Shift Work Induces Short-Term and Enduring Sleep and Electroencephalographic Disturbances

Millions of people worldwide are working at times that overlap with the normal time for sleep. Sleep problems related to the work schedule may mediate the well-established relationship between shift work and increased risk for disease, occupational errors and accidents. Yet, our understanding of causality and the underlying mechanisms that explain this relationship is limited. We aimed to assess the consequences of night-shift work for sleep and to examine whether night-shift work-induced sleep disturbances may yield electrophysiological markers of impaired maintenance of the waking brain state. An experimental model developed in rats simulated a 4-day protocol of night-work in humans. Two groups of rats underwent 8-h sessions of enforced ambulation, either at the circadian time when the animal was physiologically primed for wakefulness (active-workers, mimicking day-shift) or for sleep (rest-workers, mimicking night-shift). The 4-day rest-work schedule induced a pronounced redistribution of sleep to the endogenous active phase. Rest-work also led to higher electroencephalogram (EEG) slow-wave (1-4 Hz) energy in quiet wakefulness during work-sessions, suggesting a degraded waking state. After the daily work-sessions, being in their endogenous active phase, rest-workers slept less and had higher gamma (80-90 Hz) activity during wake than active-workers. Finally, rest-work induced an enduring shift in the main sleep period and attenuated the accumulation of slow-wave energy during NREM sleep. A comparison of recovery data from 12:12 LD and constant dark conditions suggests that reduced time in NREM sleep throughout the recorded 7-day recovery phase induced by rest-work may be modulated by circadian factors. Our data in rats show that enforced night-work-like activity during the normal resting phase has pronounced acute and persistent effects on sleep and waking behavior. The study also underscores the potential importance of animal models for future studies on the health consequences of night-shift work and the mechanisms underlying increased risk for diseases.