Workplace Bullying, Stress Response and Long-term Sickness Absence-Exploring Mechanisms: Results from Six Cohort Studies

Publikation: Bog/antologi/afhandling/rapportDoktordisputats

This thesis consists of a summarizing synopsis on workplace bullying, stress responses and LTSA and 11 papers. The thesis focuses on 1) methodological issues with respect to design, compliance with sampling and analytical measurement validity when using salivary cortisol as a stress response in epidemiological studies, 2) investigate the associations between workplace bullying and the stress response, measured by perceived stress, salivary cortisol, and poor sleep, 3) explore if LTPA moderated in the association between workplace bullying and sleep, 4) finally, to explore possible pathways between workplace bullying and LTSA.
The thesis is based on data from 6 cohort studies 1) the atherosclerosis and work – study that included 130 employees in 1998, 2) The Swedish study, a study in five companies, where 437 participates 3) the Workplace bullying and harassment study, a Danish workplace study, where 3363 participated in 2006 and followed up in 2008 4) the PRISME study, where 4489 participated in 2007 and were followed up in 2009, 5) The health promotion study, where 549 public employed participated, and 6) the Workplace bullying, depression and negative behaviour study (MODENA), a combination of the WBH and PRISME studies, where all respondents from WBH and PRISME cohorts were invited and 5000 responded.
There are several main findings. The thesis address the methodological and design problems related to including physiological measures, such as salivary cortisol as stress response. That is the importance of having knowledge on normal biological variation (e.g., diurnal variation, within-subject variation, and between-subject variation) as well as methodological variation (laboratory techniques, material specifications etc.). The two first Papers (I and II) provide empirical knowledge of biological variation in salivary cortisol and identifying sources of variability, such as time of sampling and time of awakening that may lead to changes erroneously interpreted as effects or as absence of effects.
Paper I provides a method evaluation for the method used to measure salivary cortisol in Papers III, IV, V, VI, and VII. Paper I also estimated reference intervals for morning and evening samples in 130 people at work. Paper II further provides an overview of knowledge and recommendations on different topics that may influence collecting saliva samples in field studies by addressing the impact of biological variation that is theoretically independent of individual choices (i.e. diurnal salivary cortisol profiles, within and between subject variation, seasonal variation, and effects on age and gender), biological variation in relation to behaviour (i.e. life style choices, diet, medication, smoking, alcohol, and physical activity), methodological variation relating to sampling and storage procedures (i.e. cotton versus polyester tampons and freezing of samples in different temperatures) and methodological variation relating to applied laboratory techniques (i.e. analytical method, analytical precision of the measurement, and long-term stability of measurements).
Papers III, IV and V showed that workplace bullying was, across cohorts, consistently associated with physiological responses in terms of lower salivary cortisol. They supplemented each other by using three different ways of measuring workplace bullying in different cohorts. Paper III is the first full study combining workplace bullying (yes/ no), health outcomes and physiological stress response in terms of salivary cortisol. Paper IV adds knowledge by using frequency of workplace bullying (now and then to daily) and salivary cortisol. Paper V is the first study using the
operational methods to assess workplace bullying, i.e. measuring negative acts at the workplace and salivary cortisol as the outcome.
Paper VI found, that low morning cortisol was associated with increased sleep problems during a four-week period prior to sampling and that the respondents. At follow-up three months later, those with sleep problems had a flattened cortisol profile. Paper VI studied the association between physical activity during leisure time and perceived energy stress. If respondents were physically active in leisure time and perceived high energy they also had higher evening saliva cortisol.
We showed in Paper VIII that workplace bullying was associated with sleep problems at baseline and two-years later. Paper IX studied whether leisure time physical activity moderated the association between workplace bullying and sleep problems. We found no indication that LTPA at baseline moderated these associations. Thus, our hypothesis that high LTPA would reduce the hazardous effect of workplace bullying on sleep was not supported.
Papers X and XI studied psychological stress and sleep as mediators between workplace bullying and LTSA. Paper X showed that workplace bullying was associated with high levels of perceived stress and with an increased risk of LTSA during a two-year follow-up period. We also found that perceived stress partially mediated the association between workplace bullying and LTSA. Paper XI showed that the association between workplace bullying and LTSA was partly mediated by poor sleep.
Workplace bullying is detrimental for the individual, but also the workplaces are affected by workplace bullying as bullied employees are at risk of LTSA. This thesis underlines, that workplace bullying was related to stress reactions in terms of sleep problems and low salivary cortisol as well as LTSA. The thesis also provides knowledge on mechanisms (sleep and psychological stress) for how exposure to workplace bullying workplace can lead to LTSA. Moreover, the thesis provided on LPTA not being a protective factor in the relationship between workplace bullying and poor sleep.
ForlagUniversity of Copenhagen
Antal sider60
ISBN (Elektronisk)978-87-997494-8-5
StatusUdgivet - 2017

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