Abstract
Study Objectives:
The purpose of this study was to explore the associations between workplace bullying, the characteristics of workplace bullying, and sleep disturbances in a large sample of employees of the French working population.
Design:
Workplace bullying, evaluated using the validated instrument developed by Leymann, and sleep disturbances, as well as covariates, were measured using a self-administered questionnaire. Covariates included age, marital status, presence of children, education, occupation, working hours, night work, physical and chemical exposures at work, self-reported health, and depressive symptoms. Statistical analysis was performed using logistic regression analysis and was carried out separately for men and women.
Setting:
General working population.
Participants:
The study population consisted of a random sample of 3132 men and 4562 women of the working population in the southeast of France.
Results:
Workplace bullying was strongly associated with sleep disturbances. Past exposure to bullying also increased the risk for this outcome. The more frequent the exposure to bullying, the higher the risk of experiencing sleep disturbances. Observing someone else being bullied in the workplace was also associated with the outcome. Adjustment for covariates did not modify the results. Additional adjustment for self-reported health and depressive symptoms diminished the magnitude of the associations that remained significant.
Conclusions:
The prevalence of workplace bullying (around 10%) was found to be high in this study as well was the impact of this major job-related stressor on sleep disturbances. Although no conclusion about causality could be drawn from this cross-sectional study, the findings suggest that the contribution of workplace bullying to the burden of sleep disturbances may be substantial.
Citation:
Niedhammer I; David S; Degioanni S; Drummond A; Philip P. Workplace bullying and sleep disturbances: findings from a large scale cross-sectional survey in the French working population. SLEEP 2009;32(9):1211-1219.
Keywords: Sleep disturbances, workplace bullying
SLEEP DISORDERS MAY BE HIGHLY PREVALENT AMONG MIDDLE-AGED POPULATIONS; STUDIES HAVE REPORTED PREVALENCES RANGING FROM 10% TO 40% in working populations,1–13 with insomnia being one of the most common disorders. In addition, a 1995 study estimated the direct costs of insomnia to be more than $2 billion in France.14 Consequently, sleep disorders may be a serious public health issue because of the high prevalence of these disorders and their social and economic consequences. Poor sleep may also be associated with occupational and health-related problems, such as an increased risk of accidents, mortality, and illnesses, including, for example, coronary heart disease, diabetes, and mental disorders. Poor sleep is also associated with workplace absence due to sickness and with reduced productivity.15–18 The causes of poor sleep are complex and certainly multifactorial. Studies have reported the following risk factors for having a sleep disorder: older age, female sex, low socioeconomic status, living alone, and some environmental and occupational factors, as well as poor mental and psychological health.2–4,7–9,11,19,20
Research has been undertaken that targets sleep disorders in the working population, and numerous studies have focused on shift work and its association with sleep.21,22 The association between work and sleep has been considered to be worth studying because sleep disorders are expected to occur in people of working age and because psychosocial aspects of work, such as job stress, may be strongly related to sleep and sleep problems. Some studies have shown that measures of job stress, such as perceived stress, hectic work, high job demands, working under time pressure, low job control, high job strain, low social support at work, bad atmosphere at work, role conflicts, effort-reward imbalance, job dissatisfaction, low levels of interest in job, and job insecurity are associated with sleep disorders.1–7,9–13,19,20,23–27 These studies, however, were done on relatively small or selective samples, examined nonstandard measures for the assessment of job-related factors, or did not take adequate account of potential confounding factors such as sociodemographic factors, physical and psychological health status, or important occupational risk factors such as shift work and working hours. Furthermore, the effects of workplace bullying, considered to be one of the most damaging factors related to job stress, on sleep disorders have been understudied, and the literature in this area appears to be sparse.3,28–30
Workplace bullying is difficult to evaluate, and no consensus exists regarding its definition. Here, the definition by Leymann31 was adopted: workplace bullying or mobbing “involves hostile and unethical communication, which is directed in a systematic way by one or a few individuals mainly towards one individual who, due to mobbing, is pushed into a helpless and defenceless position, being held there by means of continuing mobbing activities.” Two approaches using self-reported questionnaires have been developed in surveys: (1) inventories of various forms of bullying and (2) self-reports of being exposed to bullying on the basis of a given definition. According to some authors, the combination of both approaches would be adequate to define cases of bullying.30,32–34 Duration and frequency of bullying would also be crucial elements. In the present study, we combined the 2 approaches: (1) the questionnaire developed by Leymann—the Leymann Inventory of Psychological Terror35—considered to have the greatest coverage and acceptable reliabilities36 and evaluating 45 forms of bullying and (2) self-report of being exposed to bullying.
Studies exploring the associations between workplace bullying and health outcomes are still lacking. Nevertheless, workplace bullying has been found to be associated with absence due to sickness,37 psychosomatic complaints and somatic symptoms,38–40 and mental health outcomes, such as job-induced stress, psychological health and well-being, anxiety, depression,29,30,39–47 use of psychotropic drugs,28,30 and physician-diagnosed psychiatric morbidity.48
The objectives of this study were to examine the associations between workplace bullying and sleep disturbances. This study attempted to take the limitations described above into account; because it was based on a large and nonselective sample of the French working population, this study included a standard measure of exposure to workplace bullying and detailed information on this exposure and took into account a large number of confounding factors.
METHODS
Study Sample
This cross-sectional survey was performed by the National Institute for Health and Medical Research (INSERM) in 2004 among the general working population in the southeast of France in collaboration with a network of 143 voluntary occupational physicians, who, if working full-time, each selected 150 employees randomly and invited them to participate in the survey. Occupational medicine is mandatory for all employees in France; consequently, every employee has a medical examination with an occupational physician periodically; at the time of the survey, the examination was performed annually. To be included in the survey, employees had to have worked for at least 3 months in their company. The survey was based on a self-administered questionnaire, which was anonymous, and was returned using a prepaid envelope to the INSERM. Because employees included in the survey were all working at the time of the survey, it could be assumed that those who had a major mental health disorder or severe sleep disorders might be underrepresented in the sample because these people would be more likely to be on sick leave. Several papers have already been published on the topic of workplace bullying using this study sample.49–51
Measurement of Workplace Bullying
Our questionnaire included the French version of the Leymann Inventory of Psychological Terror, measuring the experience of 45 forms of bullying within the previous 12 months, as well as the frequency and duration of the bullying. The 45 forms of bullying, derived from interviews and heuristic analyses by Leymann,31 are presented in 5 thematic sections, with assignment to section dependent on the effects these situations may have on the victim: social relationships (no possibility to communicate, verbal aggression, criticism, etc.), exclusion (isolation, rejection, etc.), job situations and tasks (no tasks, too many tasks, uninteresting tasks, humiliating tasks, tasks inferior or superior to skills, etc.), personal attacks (attacks on opinions or origins, rumors, gossiping, etc.), and physical violence and threats of physical violence (including sexual harassment). Afterward, the employees were given the following definition developed by the authors: “Bullying may be defined by a situation in which someone is exposed to hostile behavior on the part of one or more persons in the work environment that aim continually and repeatedly to offend, oppress, maltreat, or to exclude or isolate over a long period of time.” The employees were asked if they perceived themselves as being exposed to bullying within the previous 12 months. Cases of bullying were defined using both the definition of Leymann, i.e., exposure to at least 1 form of bullying within the previous 12 months, weekly or more, and for at least 6 months,31 and the self-report of being exposed to bullying, as has been previously recommended.30,32–34 The psychometric properties of the French version of the Leymann Inventory of Psychological Terror questionnaire were studied in a previous paper,49 and we found that the combined evaluation of bullying increased the convergent and predictive validity compared with Leymann's definition alone.
Several variables were used to characterize the exposure to workplace bullying within the previous 12 months: period of exposure (current or past), frequency and duration of exposure, and the fact that the employees may have been observers of bullying directed toward someone else at their workplace within the past 12 months. We also constructed a variable combining the 2 variables of exposure to bullying and observation of bullying by creating 4 categories: no exposure at all, observer of bullying, exposure to bullying, and both exposure to bullying and observer of bullying.
Measurement of Sleep Disturbances
Sleep disturbances were measured using 2 items evaluating difficulty initiating sleep and difficulty returning to sleep after experiencing a premature awakening. These 2 items were based on 4 response categories, which were “no trouble at all,” “a little trouble, “some trouble,” and “a great deal of trouble.” These items were dichotomized to distinguish people with no or little trouble and those with some or a great deal of trouble. Thereafter, sleep disturbances were defined by either trouble initiating sleep or trouble returning to sleep after experiencing a premature awakening, or both.
Covariates
Several variables were used as covariates: age, marital status, presence of children in the home, education level, occupation groups, working hours per week, night work (time schedules involving night work, such as permanent night work or alternating shifts including night shift), and the number of physical or chemical exposures at work, exposure to temperature extremes (outdoor work, cold or hot temperatures), noise, radiation, chemical exposures, or other exposures. Two health-related variables were also studied: poor self-reported health, based on a 4-level scale ranging from “very good” (coded 1) to “very poor” (coded 4) and defined by levels 3 and 4, and depressive symptoms measured using the Center for Epidemiologic Studies Depression scale50 and defined using the available thresholds established for the French population ( ≥ 17 for men and ≥ 23 for women) to dichotomize the score.52
Statistical Analysis
First, the crude associations between 6 variables characterizing bullying (i.e., exposure, period, frequency, duration of bullying, and the 2 variables of observing bullying) and sleep disturbances were studied using the Pearson χ2 test. The associations between covariates and sleep disturbances were also studied using the same test. Next, we used logistic regression analysis to adjust for the same covariates (except self-reported health and depressive symptoms). Consequently, we constructed 6 different models with sleep disturbances as the dependent variable. In each model, we included as independent variables 1 of the 6 variables describing bullying, as well as the covariates. Additional models were also performed with additional adjustment for poor self-reported health and depressive symptoms.
Statistical analysis was performed using SAS (SAS, Inc., Cary, NC).53 Because differences in the prevalence of occupational exposures (bullying) and of health outcomes (sleep disturbances) may be observed in men and women and because the associations between exposures and outcomes may also differ between sexes, analysis was carried out separately for men and women.54
RESULTS
Description of the Study Sample
In 2004, 19,655 employees were asked to participate in the survey. Among them, 7770 responded to the self-administered questionnaire, leading to a response rate of 40%. Seventy-six employees were excluded from the analysis, 57 because they had worked for less than 3 months in their company and 19 because response to the question on male or female sex was missing in the questionnaire. Thus, the study was based on 7694 employees—3132 men and 4562 women—with a mean age of 40 (SD: 10.3). A description of the study sample is shown in Table 1.
Table 1.
Description of the Sample Studied
| Men n = 3132 | Women n = 4562 | |
|---|---|---|
| No. (%) | No. (%) | |
| Age, y | ||
| < 30 | 523 (16.75) | 853 (18.76) |
| 30-39 | 1017 (32.56) | 1349 (29.67) |
| 40-49 | 862 (27.60) | 1344 (29.57) |
| 50+ | 721 (23.09) | 1000 (22.00) |
| Marital status | ||
| Married, cohabiting | 2131 (68.06) | 2876 (63.13) |
| Single, separated, divorced, widowed | 1000 (31.94) | 1680 (36.87) |
| Children present in the home | ||
| Yes | 1681 (53.76) | 2497 (54.98) |
| No | 1446 (46.24) | 2045 (45.02) |
| Education | ||
| Primary, lower vocational, lower secondary | 1367 (43.79) | 1589 (34.91) |
| Upper secondary | 462 (14.80) | 1044 (22.93) |
| University | 1293 (41.41) | 1919 (42.16) |
| Occupation | ||
| Blue-collar worker | 784 (25.14) | 180 (3.97) |
| Clerk, service worker | 582 (18.67) | 2432 (53.64) |
| Associate professional | 1104 (35.41) | 1573 (34.69) |
| Manager, engineer | 648 (20.78) | 349 (7.70) |
| Work/wk, h | ||
| <40 | 1738 (58.26) | 3680 (82.96) |
| ≥ 40 | 1245 (41.74) | 756 (17.04) |
| Night work | ||
| No | 2792 (89.92) | 4258 (94.14) |
| Yes | 313 (10.08) | 265 (5.86) |
| Number of physico-chemical exposures | ||
| 0 | 1667 (53.23) | 3079 (67.49) |
| 1 | 443 (14.14) | 883 (19.36) |
| 2 | 322 (10.28) | 348 (7.63) |
| ≥ 3 | 700 (22.35) | 252 (5.52) |
| Self-reported health | ||
| Good | 2766 (88.97) | 3899 (86.28) |
| Poor | 343 (11.03) | 620 (13.72) |
| Depressive symptoms | ||
| No | 2270 (74.57) | 3499 (78.82) |
| Yesa | 774 (25.43) | 940 (21.18) |
| Sleep disturbances | ||
| No | 2597 (82.92) | 3548 (77.77) |
| Yes | 535 (17.08) | 1014 (22.23) |
Center for Epidemiologic Studies Depression score ≥ 17 for men and ≥ 23 for women
Table 2 describes the characteristics of bullying in the study sample. Leymann's definition alone (exposure to at least 1 form of bullying within the past 12 months, for more than 6 months, and weekly or more) led to a 12-month prevalence of 11% for men and 13% for women. Using the definition of exposure to bullying combining Leymann's definition and the self-reporting of bullying by the employees within the same period, the 12-month prevalence of exposure to bullying were 9% and 11% for men and women, respectively. These results show that most of those defined as exposed to bullying using Leymann's definition also reported being exposed.
Table 2.
Description of Exposure to Bullying within the Previous 12 Months
| Men n = 3132 | Women n = 4562 | |
|---|---|---|
| No. (%) | No. (%) | |
| Exposed to bullying | ||
| No | 2857 (91.22) | 4074 (89.30) |
| Yes | 275 (8.78) | 488 (10.70) |
| Timeframe of exposure to bullying | ||
| None | 2857 (91.34) | 4074 (89.46) |
| Past | 38 (1.21) | 130 (2.85) |
| Current | 233 (7.45) | 350 (7.69) |
| Frequency of exposure to bullying | ||
| None | 2857 (91.22) | 4074 (89.30) |
| Weekly | 149 (4.76) | 225 (4.93) |
| Daily or almost daily | 126 (4.02) | 263 (5.77) |
| Duration of exposure to bullying, y | ||
| 0 | 2857 (91.22) | 4074 (89.31) |
| <2 | 94 (3.00) | 209 (4.58) |
| ≥ 2 <5 | 114 (3.64) | 179 (3.92) |
| 5+ | 67 (2.14) | 100 (2.19) |
| Observer of bullying | ||
| No | 2165 (69.13) | 3115 (68.28) |
| Yes | 967 (30.87) | 1447 (31.72) |
| Was bullied or observed bullying | ||
| Neither | 2111 (67.40) | 2998 (65.72) |
| Observed bullying | 746 (23.82) | 1076 (23.59) |
| Was bullied | 54 (1.72) | 117 (2.56) |
| Both | 221 (7.06) | 371 (8.13) |
Crude Associations Between Bullying and Sleep Disturbances
Table 3 provides the results of the associations between the variables of bullying and sleep disturbances. All of these associations were strongly significant at P < 0.001. The prevalence of sleep disturbances increased among people exposed to workplace bullying, especially among those who were currently exposed. People who were exposed to bullying in the past were also at a higher risk of having sleep disturbances than were those who had never been exposed. The more frequent the exposure to workplace bullying, the higher the prevalence of sleep disturbances. No dose-response association was observed between the duration of exposure to bullying and sleep disturbances; the prevalence of sleep disturbances was high whatever the duration of bullying. Observing bullying was also associated with an increase in the prevalence of sleep disturbances. The study of the combination of exposure to bullying and observing bullying led to different results for men and women. For men, the highest prevalence of sleep disturbances was observed for those exposed to bullying (with or without observing it), and, for women, the highest prevalence found among those who were simultaneously exposed to bullying and observers of bullying.
Table 3.
Associations between Exposure to Bullying and Prevalence of Sleep Disturbances (No, %)
| Men No. (%) | Women No. (%) | |
|---|---|---|
| Exposed to bullying | ||
| No | 416 (14.56) | 777 (19.07) |
| Yes | 119 (43.27) | 237 (48.57) |
| Timeframe of exposure to bullying | ||
| None | 416 (14.56) | 777 (19.07) |
| Past | 5 (13.16) | 49 (37.69) |
| Current | 113 (48.50) | 183 (52.29) |
| Frequency of exposure to bullying | ||
| None | 416 (14.56) | 777 (19.07) |
| Weekly | 55 (36.91) | 103 (45.78) |
| Daily or almost daily | 64 (50.79) | 134 (50.95) |
| Duration of exposure to bullying, y | ||
| 0 | 416 (14.56) | 777 (19.07) |
| <2 | 40 (42.55) | 89 (42.58) |
| ≥ 2 <5 | 47 (41.23) | 96 (53.63) |
| 5+ | 32 (47.76) | 52 (52.00) |
| Observer of bullying | ||
| No | 272 (12.56) | 553 (17.75) |
| Yes | 263 (27.20) | 461 (31.86) |
| Was bullied or observed bullying | ||
| Neither | 249 (11.80) | 508 (16.94) |
| Observed bullying | 167 (22.39) | 269 (25.00) |
| Was bullied | 23 (42.59) | 45 (38.46) |
| Both | 96 (43.44) | 192 (51.75) |
Data were analyzed using the χ2 test. All associations are significant at P <0.001.
Crude Associations Between Covariates and Sleep Disturbances
Except for the covariates of marital status and occupation, the associations between the covariates studied and sleep disturbances were found to be significant at least for 1 sex (Table 4). The prevalence of sleep disturbances increased with age, among men who had children, among women who had a lower education level, among those working 40 hours or more a week, among women who worked at night, and among those exposed to physical-chemical exposures at work. The prevalence of sleep disturbances also increased strongly with poor self-reported health and depressive symptoms.
Table 4.
Associations between Covariates and Prevalence of Sleep Disturbances (No, %)
| Men |
Women |
|||
|---|---|---|---|---|
| No. | % | No. | % | |
| Age, y | a | b | ||
| <30 | 70 | 13.38 | 140 | 16.41 |
| 30-39 | 169 | 16.62 | 266 | 19.72 |
| 40-49 | 161 | 18.68 | 297 | 22.10 |
| 50+ | 134 | 18.59 | 304 | 30.40 |
| Marital status | NS | NS | ||
| Married, cohabiting | 373 | 17.50 | 620 | 21.56 |
| Single, separated, divorced, widowed | 162 | 16.20 | 392 | 23.33 |
| Children present in the household | c | NS | ||
| Yes | 320 | 19.04 | 563 | 22.55 |
| No | 215 | 14.87 | 443 | 21.91 |
| Education | NS | c | ||
| Primary, lower vocational, lower secondary | 240 | 17.56 | 397 | 24.93 |
| Upper secondary | 76 | 16.45 | 229 | 21.93 |
| University | 217 | 16.78 | 386 | 20.11 |
| Occupation | NS | NS | ||
| Blue collar worker | 121 | 15.43 | 46 | 25.56 |
| Clerk, service worker | 109 | 18.73 | 551 | 22.66 |
| Associate professional | 198 | 17.93 | 348 | 22.12 |
| Manager, engineer | 107 | 16.51 | 67 | 19.20 |
| Work/wk, h | c | b | ||
| <40 | 267 | 15.36 | 779 | 21.17 |
| ≥ 40 | 247 | 19.84 | 204 | 26.98 |
| Work at night | NS | a | ||
| No | 472 | 16.91 | 933 | 21.91 |
| Yes | 62 | 19.81 | 73 | 27.55 |
| Physical-chemical exposures, no. | c | b | ||
| 0 | 249 | 14.94 | 608 | 19.75 |
| 1 | 87 | 19.64 | 231 | 26.16 |
| 2 | 55 | 17.08 | 90 | 25.86 |
| ≥ 3 | 144 | 20.57 | 85 | 33.73 |
| Self-reported health | b | b | ||
| Good | 360 | 13.02 | 614 | 15.75 |
| Poor | 173 | 50.44 | 395 | 63.71 |
| Depressive symptoms | b | b | ||
| No | 206 | 9.09 | 466 | 13.32 |
| Yesd | 320 | 41.34 | 524 | 55.74 |
Results of χ2 test
P <0.05
P <0.001
P <0.01
CES-D score ≥ 17 for men and ≥ 23 for women
Associations Between Bullying and Sleep Disturbances After Controlling for Covariates
Table 5 provides the results of logistic regression analysis. Each model shows the association between each variable of bullying and sleep disturbances after adjustment for covariates. All of these associations were strongly significant at P < 0.001, suggesting that covariates did not modify the strong associations observed in Table 3. Exposure to workplace bullying within the last 12 months was found to be a strong risk factor for sleep disturbances. Past exposure to bullying also increased this risk among women. The more frequent the exposure to bullying, the higher the prevalence of sleep disturbances. Observing bullying of someone else increased the risk of having sleep disturbances. The combination of exposure to bullying and observing bullying at the workplace led to the highest increase in risk for women.
Table 5.
Exposure to Bullying and Sleep Disturbances According to Logistic Regression Analysis
| Men | Women | |
|---|---|---|
| OR (95% CI) | OR (95% CI) | |
| Exposed to bullying | ||
| No | 1 | 1 |
| Yes | 4.40 (3.35-5.78) | 3.83 (3.12-4.70) |
| Timeframe of exposure to bullying | ||
| None | 1 | 1 |
| Past | 0.91 (0.35-2.38) | 2.63 (1.80-3.86) |
| Current | 5.47 (4.09-7.32) | 4.35 (3.44-5.51) |
| Frequency of exposure to bullying | ||
| None | 1 | 1 |
| Weekly | 3.25 (2.27-4.66) | 3.38 (2.54-4.49) |
| Daily or almost daily | 6.34 (4.31-9.33) | 4.28 (3.27-5.60) |
| Duration of exposure to bullying, y | ||
| 0 | 1 | 1 |
| <2 | 4.52 (2.91-7.03) | 3.22 (2.38-4.34) |
| <2 <5 | 4.20 (2.81-6.28) | 4.63 (3.37-6.36) |
| 5+ | 4.58 (2.74-7.66) | 3.91 (2.57-5.95) |
| Observer of bullying | ||
| No | 1 | 1 |
| Yes | 2.53 (2.07-3.09) | 2.20 (1.89-2.57) |
| Was bullied or observed bullying | ||
| Neither | 1 | 1 |
| Observed bullying | 2.08 (1.66-2.62) | 1.70 (1.42-2.03) |
| Was bullied | 5.33 (2.96-9.60) | 3.04 (2.03-4.55) |
| Both | 5.71 (4.18-7.79) | 5.12 (4.03-6.50) |
Odds ratio (OR) adjusted for age, marital status, presence of children in the home, education level, occupation, number of hours working per week, working at night, and physical-chemical exposures with 95% confidence intervals (CI).
All bullying variables were significant at P <0.001.
Additional adjustment for poor self-reported health and depressive symptoms led to a reduction in the magnitude of the odds ratios, but the associations remained significant at P < 0.01 (Table 6). These additional results confirmed those provided in Table 5. Note that dose-response associations were observed for duration of bullying for both sexes.
Table 6.
Exposure to Bullying and Sleep Disturbances According to Logistic Regression Analysis Including Additional Adjustment for Poor Self-Reported Health and Depressive Symptoms
| Men |
Women |
|||
|---|---|---|---|---|
| OR | 95% CI | OR | 95% CI | |
| Exposed to bullying | a | a | ||
| No | 1 | 1 | ||
| Yes | 1.84 | 1.34-2.53 | 1.60 | 1.26-2.05 |
| Timeframe of exposure to bullying | a | a | ||
| Never | 1 | 1 | ||
| Past | 0.34 | 0.11-1.06 | 1.58 | 1.02-2.47 |
| Current | 2.29 | 1.64-3.22 | 1.61 | 1.21-2.13 |
| Frequency of exposure to bullying | a | a | ||
| None | 1 | 1 | ||
| Weekly | 1.48 | 0.98-2.24 | 1.47 | 1.05-2.06 |
| Daily or almost daily | 2.39 | 1.54-3.71 | 1.73 | 1.26-2.38 |
| Duration of exposure to bullying, y | b | a | ||
| 0 | 1 | 1 | ||
| <2 | 1.73 | 1.05-2.85 | 1.33 | 0.94-1.90 |
| ≥ 2 <5 | 1.74 | 1.09-2.77 | 1.82 | 1.25-2.65 |
| 5+ | 2.21 | 1.23-3.96 | 1.87 | 1.14-3.06 |
| Observed bullying | a | b | ||
| No | 1 | 1 | ||
| Yes | 1.71 | 1.37-2.14 | 1.30 | 1.09-1.56 |
| Was bullied or observed bullying | a | a | ||
| Neither | 1 | 1 | ||
| Observed bullying | 1.60 | 1.25-2.05 | 1.20 | 0.98-1.47 |
| Was bullied | 1.71 | 0.89-3.30 | 1.46 | 0.91-2.34 |
| Both | 2.38 | 1.66-3.40 | 1.81 | 1.36-2.40 |
Odds ratio (OR) adjusted for age, marital status, presence of children in the home, education level, occupation, number of hours working per week, working at night, physical-chemical exposures, self-reported health, and depressive symptoms with 95% confidence intervals (CI).
P <0.001
P <0.01
DISCUSSION
Main Findings
The results of this study show that workplace bullying was strongly associated with sleep disturbances. Past exposure to bullying increased the risk of sleep disturbances among women, and, the more frequent the exposure to bullying, the higher this risk. Observing bullying of someone else at the workplace was a risk factor for having sleep disturbances. Women exposed to both bullying and observing the bullying were at particular increased risk of having sleep disturbances. All of these associations were independent of potential confounding factors.
Strengths and Limitations of the Study
The response rate may be considered low (40%), but it is similar to that of previous studies on this sensitive topic.42,55–57 Selection bias may not be ruled out, but the differences between respondents and nonrespondents were small for the questions regarding sex, age, economic activities, and occupation. In addition, a comparison between the census population and the sample studied suggested that the study sample was roughly representative for age, economic activities, and occupations.49 In addition, this potential selection bias may have an impact on prevalence estimates of workplace bullying for example, but it seems unlikely that it has greatly altered the association between workplace bullying and sleep disturbances.
A healthy-worker effect may have been a factor if people in poor health shifted to less exposed jobs or left their jobs, leading to a potential underestimation of the association between workplace bullying and sleep disturbances. This is reinforced by the fact that this survey included employees who were working at the time of the survey and did not include employees who were absent due to illness within the survey period, including those who were on sick leave because of the health consequences of workplace bullying. This suggests that our findings on the associations between workplace bullying and sleep disturbances are more likely to be underestimated than overestimated.
The cross-sectional design of our study did not allow us to make conclusions on the causal nature of the association between workplace bullying and sleep disturbances, and a reverse causation may not be excluded (workers with sleep disturbances may be more likely to be exposed to bullying). A reporting bias may also be suspected because both workplace bullying and sleep disturbances were measured using self-report. This reporting bias, which is connected to “common method variance”—for example through negative affectivity and social desirability—may lead to inflated associations between bullying and outcome.
Another limitation is related to the use of a rather crude measure for sleep disturbances (already used by others)58 that did not allow us to study severity and duration of these disturbances. We also studied sleep disturbances by a score higher than 4 on the basis of the sum of the 2 initial items (score ranging from 2 to 8) and found very similar results to those provided in our Tables, confirming the robustness of our results. We were also able to study the 2 subtypes of sleep disturbances (trouble falling asleep and trouble staying asleep) separately and found significant associations between all bullying variables and both subtypes of sleep disturbances, even after adjustment for all covariates. Stronger associations (odds ratios of larger magnitude) were observed for trouble staying asleep. In addition, because strong and consistent associations were found between classic risk factors (age, education, working hours, night work, physical-chemical exposures at work, self-reported health, and depressive symptoms) and sleep disturbances, these results reinforce the validity of our study. Finally, our study did not include some previously reported risk factors for having sleep disturbances, such as use of alcohol and stimulants (e.g., caffeine or tobacco), poor sleeping environment, specific family stressors, and medical and psychiatric history. However, it seems unlikely that these factors would completely explain the strong associations observed here between workplace bullying and sleep disturbances.
The strengths of this study were (1) our sample included a very large number of employees of the general working population, allowing us to study a nonselective population, as well as men and women separately, which has been shown to be crucial54; (2) a validated instrument was used to measure workplace bullying (Leymann Inventory of Psychological Terror), and various variables were constructed to describe the exposure to workplace bullying, which has never been done in the study of sleep disturbances, and provided detailed information on exposure to bullying and its associations with sleep disturbances; and (3) the statistical analysis took into account important covariates—sociodemographic and occupational factors—and these covariates did not modify the strong associations between bullying and sleep disturbances. Additional adjustment for health-related variables diminished the associations that remained significant. It is likely that the additional adjustment for poor self-reported health and depressive symptoms constitutes an overadjustment because self-reported health and depressive symptoms may be intermediate variables between workplace bullying and sleep disturbances,37,47,50 or even consequences of sleep disturbances.15,16,18 Consequently, the actual associations between bullying and sleep disturbances may be closer to those observed in Table 5.
We also observed that the associations between bullying and sleep disturbances were significant after adjustment for the psychosocial work factors by Karasek (i.e., psychological demands, decision latitude, and social support), although the magnitude of the associations was somewhat reduced. Note, however, that adjusting for psychosocial work factors may lead to underestimation of the effects of workplace bullying on sleep disturbances because these factors may be considered as risk factors for being bullied. We also performed an additional analysis stratified on social support at work and observed results that were different according to sex: the association between bullying and sleep disturbances was no longer significant among men with high levels of social support at work, whereas this association remained significant among women with high levels of support. These findings suggest, at least partly, that social support at work may act as a buffer on the association between bullying and sleep disturbances or that workplaces with high levels of social support may promote better working conditions with lower levels of bullying. Indeed, we observed that high social support was significantly associated with a lower prevalence of bullying and a lower frequency and duration of bullying, as well as a lower prevalence of observing someone else being bullied.
Comparison with the Literature
Few studies have examined the association between workplace bullying and sleep disturbances. The study by Eriksen et al.3 showed that exposure to threats and violence at work predicted poor sleep quality in a population of nurses' aides in Norway, after adjustment for age, sex, marital status, presence of preschool-aged children in the household, and other occupational factors. Vartia et al.30 reported that bullied employees used sleep-inducing drugs and sedatives more often than did subjects who were not bullied; observers were also more likely to use sleep-inducing drugs and sedatives, as compared with the subjects who were not bullied, but the use of these drugs did not correlate with the duration or the frequency of bullying. In this study, based on a sample of Finnish municipal employees, no information was provided on confounding factors. In these 2 studies, the measurement of bullying or sleep-related outcomes was based on a single item. Other studies have underlined the association between low levels of social support at work and sleep disorders.3,6,9,19,20,59 Authors have studied other markers, such as bad perceived atmosphere at work, that can also be considered as proxies of the quality of interpersonal relationships at work.4
Our results are in agreement with the results of these studies. Our finding of dose-reponse associations between frequency (and partly duration) of exposure to bullying and sleep disturbances have not been previously reported. Past exposure to bullying still had an impact on sleep disturbances among women, highlighting the long-term effects of bullying, even when the exposure had stopped. Finally, being an observer of bullying was a risk factor for having sleep disturbances, and the combination of exposure to bullying and observing bullying was still a stronger risk factor, especially for women. Our results are in agreement with the study by Vartia et al.,30 who found an association between observing bullying and the use of sleep-inducing drugs and sedatives, although these authors did not distinguish, among people observing bullying, between those who were directly exposed to bullying and those who were not.
Conclusion
Our findings highlight the strong association between workplace bullying and sleep disturbances and suggest that workplaces that are prone to bullying may have a detrimental effect on employees' sleep, even if employees are not directly concerned by the phenomenon. Given the high prevalence of workplace bullying observed in France, and its impact on sleep, it may be assumed that such a job-stress factor may substantially contribute to the burden of sleep-related disorders. Because this study did not provide information about causality, more prospective studies are needed to better understand bullying, its determinants, and its consequences. Efforts toward prevention should also be increased.
ACKNOWLEDGMENTS
The authors thank Drs. JL Battu, C Beyssier, N Blanchet, C Breton, M Buono-Michel, JF Canonne, G Dalivoust, A Faivre, F Fournier, G Gazazian, G Gibelin-Dol, E Griffaton, T Ibagnes, B Jaubert, J Leroy, M Lozé, G Magallon, P Presseq, G Roux, and C Vitrac, as well as Drs. J Chiaroni, C Kaltwasser, and M Signouret, for their help in constructing the network of voluntary occupational physicians, and, last but not least, S Mocaer and P Sotty for their support and interest in this research program. A pretest of this survey was performed in 2003 thanks to the contribution of Drs. AM Boustiére, C Breton, C Cervoni, A Faivre, C Gravier, E Halimi, M Isnard, MC Jacquin, M Lafon-Borelli, J Laudicina, D Londi, M Lozé, G Magallon, V Marcelot, M Méric, C Milliet, F Occhipinti, P Occhipinti, H Raulot-Lapointe, and MO Vincensini. The authors' thanks also go to T Theorell for his help in providing the German version of the Leymann Inventory of Psychological Terror questionnaire and to I Revue and R Revue for their help in translating and back-translating this questionnaire. Finally, the authors thank all of the employees who participated to the survey and made this study possible. This study was supported by the DRTEFP PACA of the French Minister of Labor.
DISCLOSURE STATEMENT
This was not an industry supported study. The authors have indicated no financial conflicts of interest.
Occupational Physicians
Acquarone D, Aicardi F, André-Mazeaud P, Arsento M, Astier R, Baille H, Bajon-Thery F, Barre E, Basire C, Battu JL, Baudry S, Beatini C, Beaud'huin N, Becker C, Bellezza D, Beque C, Bernstein O, Beyssier C, Blanc-Cascio F, Blanchet N, Blondel C, Boisselot R, Bordes-Dupuy G, Borrelly N, Bouhnik D, Boulanger MF, Boulard J, Bourreau P, Bourret D, Boustiére AM, Breton C, Bugeon G, Buono-Michel M, Canonne JF, Capella D, Cavin-Rey M, Cervoni C, Charreton D, Charrier D, Chauvin MA, Chazal B, Cougnot C, Cuvelier G, Dalivoust G, Daumas R, Debaille A, De Bretteville L, Delaforge G, Delchambre A, Domeny L, Donati Y, Ducord-Chapelet J, Duran C, Durand-Bruguerolle D, Fabre D, Faivre A, Falleri R, Ferrando G, Ferrari-Galano J, Flutet M, Fouché JP, Fournier F, Freyder E, Galy M, Garcia A, Gazazian G, Gérard C, Girard F, Giuge M, Goyer C, Gravier C, Guyomard A, Hacquin MC, Halimi E, Ibagnes T, Icart P, Jacquin MC, Jaubert B, Joret JP, Julien JP, Kacel M, Kesmedjian E, Lacroix P, Lafon-Borelli M, Lallai S, Laudicina J, Leclercq X, Ledieu S, Leroy J, Leroyer L, Loesche F, Londi D, Longueville JM, Lotte MC, Louvain S, Lozé M, Maculet-Simon M, Magallon G, Marcelot V, Mareel MC, Martin P, Masse AM, Méric M, Milliet C, Mokhtari R, Monville AM, Muller B, Obadia G, Pelser M, Peres L, Perez E, Peyron M, Peyronnin F, Postel S, Presseq P, Pyronnet E, Quinsat C, Raulot-Lapointe H, Rigaud P, Robert F, Robert O, Roger K, Roussel A, Roux JP, Rubini-Remigy D, Sabate N, Saccomano-Pertus C, Salengro B, Salengro-Trouillez P, Samsom E, Sendra-Gille L, Seyrig C, Stoll G, Tarpinian N, Tavernier M, Tempesta S, Terracol H, Torresani F, Triglia MF, Vandomme V, Vieillard F, Vilmot K, Vital N
REFERENCES
- 1.Akerstedt T, Fredlund P, Gillberg M, Jansson B. Work load and work hours in relation to disturbed sleep and fatigue in a large representative sample. J Psychosom Res. 2002;53:585–8. doi: 10.1016/s0022-3999(02)00447-6. [DOI] [PubMed] [Google Scholar]
- 2.Doi Y, Minowa M, Tango T. Impact and correlates of poor sleep quality in Japanese white-collar employees. Sleep. 2003;26(4):467–471. doi: 10.1093/sleep/26.4.467. [DOI] [PubMed] [Google Scholar]
- 3.Eriksen W, Bjorvatn B, Bruusgaard D, Knardahl S. Work factors as predictors of poor sleep in nurses' aides. Int Arch Occup Environ Health. 2008;81(3):301–310. doi: 10.1007/s00420-007-0214-z. [DOI] [PubMed] [Google Scholar]
- 4.Jacquinet-Salord MC, Lang T, Fouriaud C, Nicoulet I, Bingham A. Sleeping tablet consumption, self reported quality of sleep, and working conditions. Group of Occupational Physicians of APSAT. J Epidemiol Community Health. 1993;47(1):64–68. doi: 10.1136/jech.47.1.64. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Kalimo R, Tenkanen L, Harrma M, Poppius E, Heinsalmi P. Job stress and sleep disorders: findings from the Helsinki Heart Study. Stress Med. 2000;16:65–75. [Google Scholar]
- 6.Linton SJ. Does work stress predict insomnia? A prospective study. Br J Health Psychol. 2004;9(Pt 2):127–136. doi: 10.1348/135910704773891005. [DOI] [PubMed] [Google Scholar]
- 7.Linton SJ, Bryngelsson IL. Insomnia and its relationship to work and health in a working-age population. J Occup Rehabil. 2000;10(2):169–183. [Google Scholar]
- 8.Nakata A, Haratani T, Kawakami N, et al. Sleep problems in white-collar male workers in an electric equipment manufacturing company in Japan. Ind Health. 2000;38(1):62–68. doi: 10.2486/indhealth.38.62. [DOI] [PubMed] [Google Scholar]
- 9.Nakata A, Haratani T, Takahashi M, et al. Job stress, social support, and prevalence of insomnia in a population of Japanese daytime workers. Soc Sci Med. 2004;59(8):1719–1730. doi: 10.1016/j.socscimed.2004.02.002. [DOI] [PubMed] [Google Scholar]
- 10.Ota A, Masue T, Yasuda N, et al. Association between psychosocial job characteristics and insomnia: an investigation using two relevant job stress models—the demand-control-support (DCS) model and the effort-reward imbalance (ERI) model. Sleep Med. 2005;6(4):353–358. doi: 10.1016/j.sleep.2004.12.008. [DOI] [PubMed] [Google Scholar]
- 11.Ribet C, Derriennic F. Age, working conditions, and sleep disorders: a longitudinal analysis in the French cohort E.S.T.E.V. Sleep. 1999;22(4):491–504. [PubMed] [Google Scholar]
- 12.Tachibana H, Izumi T, Honda S, Takemoto TI. The prevalence and pattern of insomnia in Japanese industrial workers: relationship between psychosocial stress and type of insomnia. Psychiatry Clin Neurosci. 1998;52(4):397–402. doi: 10.1046/j.1440-1819.1998.00407.x. [DOI] [PubMed] [Google Scholar]
- 13.Utsugi M, Saijo Y, Yoshioka E, et al. Relationships of occupational stress to insomnia and short sleep in Japanese workers. Sleep. 2005;28(6):728–735. doi: 10.1093/sleep/28.6.728. [DOI] [PubMed] [Google Scholar]
- 14.Leger D, Levy E, Paillard M. The direct costs of insomnia in France. Sleep. 1999;22(Suppl 2):S394–S401. [PubMed] [Google Scholar]
- 15.Breslau N, Roth T, Rosenthal L, Andreski P. Sleep disturbance and psychiatric disorders: a longitudinal epidemiological study of young adults. Biol Psychiatry. 1996;39(6):411–418. doi: 10.1016/0006-3223(95)00188-3. [DOI] [PubMed] [Google Scholar]
- 16.Gangwisch JE, Heymsfield SB, Boden-Albala B, et al. Sleep duration as a risk factor for diabetes incidence in a large U.S. sample. Sleep. 2007;30(12):1667–1673. doi: 10.1093/sleep/30.12.1667. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Hublin C, Partinen M, Koskenvuo M, Kaprio J. Sleep and mortality: a population-based 22-year follow-up study. Sleep. 2007;30(10):1245–1253. doi: 10.1093/sleep/30.10.1245. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Liu Y, Tanaka H. Overtime work, insufficient sleep, and risk of non-fatal acute myocardial infarction in Japanese men. Occup Environ Med. 2002;59(7):447–451. doi: 10.1136/oem.59.7.447. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Akerstedt T, Knutsson A, Westerholm P, et al. Sleep disturbances, work stress and work hours: a cross-sectional study. J Psychosom Res. 2002;53(3):741–748. doi: 10.1016/s0022-3999(02)00333-1. [DOI] [PubMed] [Google Scholar]
- 20.Cahill J, Landsbergis PA. Job strain among post office mailhandlers. Int J Health Serv. 1996;26(4):731–750. doi: 10.2190/PUHN-DLH6-C33X-EFLF. [DOI] [PubMed] [Google Scholar]
- 21.Akerstedt T. Shift work and disturbed sleep/wakefulness. Occup Med (Lond) 2003;53(2):89–94. doi: 10.1093/occmed/kqg046. [DOI] [PubMed] [Google Scholar]
- 22.Harma M, Tenkanen L, Sjoblom T, Alikoski T, Heinsalmi P. Combined effects of shift work and life-style on the prevalence of insomnia, sleep deprivation and daytime sleepiness. Scand J Work Environ Health. 1998;24(4):300–307. doi: 10.5271/sjweh.324. [DOI] [PubMed] [Google Scholar]
- 23.Akerstedt T. Psychosocial stress and impaired sleep. Scand J Work Environ Health. 2006;32(6):493–501. [PubMed] [Google Scholar]
- 24.Estryn-Behar M, Kaminski M, Peigne E, et al. Stress at work and mental health status among female hospital workers. Br J Ind Med. 1990;47(1):20–28. doi: 10.1136/oem.47.1.20. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Goldenhar LM, Swanson NG, Hurrell JJ, Jr, Ruder A, Deddens J. Stressors and adverse outcomes for female construction workers. J Occup Health Psychol. 1998;3(1):19–32. doi: 10.1037/1076-8998.3.1.19. [DOI] [PubMed] [Google Scholar]
- 26.Rosmond R, Lapidus L, Bjorntorp P. A cross-sectional study of self-reported work conditions and psychiatric health in native Swedes and immigrants. Occup Med (Lond) 1998;48(5):309–314. doi: 10.1093/occmed/48.5.309. [DOI] [PubMed] [Google Scholar]
- 27.Theorell T, Perski A, Akerstedt T, et al. Changes in job strain in relation to changes in physiological state. A longitudinal study. Scand J Work Environ Health. 1988;14(3):189–196. doi: 10.5271/sjweh.1932. [DOI] [PubMed] [Google Scholar]
- 28.Appelberg K, Romanov K, Honkasalo ML, Koskenvuo M. The use of tranquilizers, hypnotics and analgesics among 18,592 Finnish adults: associations with recent interpersonal conflicts at work or with a spouse. J Clin Epidemiol. 1993;46(11):1315–1322. doi: 10.1016/0895-4356(93)90100-f. [DOI] [PubMed] [Google Scholar]
- 29.Richman JA, Rospenda KM, Nawyn SJ, et al. Sexual harassment and generalized workplace abuse among university employees: prevalence and mental health correlates. Am J Public Health. 1999;89(3):358–363. doi: 10.2105/ajph.89.3.358. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 30.Vartia ML. Consequences of workplace bullying with respect to the well-being of its targets and the observers of bullying. Scand J Work Environ Health. 2001;27(1):63–69. doi: 10.5271/sjweh.588. [DOI] [PubMed] [Google Scholar]
- 31.Leymann H. The content and development of mobbing at work. Eur J Work Org Psychol. 1996;2:165–184. [Google Scholar]
- 32.Vartia M. The sources of bullying: psychological work environment and organizational climate. Eur J Work Org Psychol. 1996;5:203–214. [Google Scholar]
- 33.Einarsen S. Harassment and bullying at work: a review of the Scandinavian approach. Aggression Violent Behav. 2000;5(4):379–401. [Google Scholar]
- 34.Einarsen S, Skogstad A. Bullying at work: epidemiological findings in public and private organizations. Eur J Work Org Psychol. 1996;5(2):185–201. [Google Scholar]
- 35.Leymann H. Materialie Nr 33. Tübingen, Germany: Deutsche Gesellschaft füur Verhaltenstherapie; 1996. Handanleitung für den LIPT-Fragebogen (Leymann Inventory of Psychological Terror) [Google Scholar]
- 36.Cowie H, Naylor P, Rivers I, Smith P-K, Pereira B. Measuring workplace bullying. Aggression Violent Behav. 2002;7:33–51. [Google Scholar]
- 37.Kivimüaki M, Elovainio M, Vahtera J. Workplace bullying and sickness absence in hospital staff. Occup Environ Med. 2000;57(10):656–660. doi: 10.1136/oem.57.10.656. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 38.Zapf D, Knorz C, Kulla M. On the relationship between mobbing factors, and job content, social work environment, and health outcomes. Eur J Work Org Psychol. 1996;2:215–237. [Google Scholar]
- 39.Frone MR. Interpersonal conflict at work and psychological outcomes: testing a model among young workers. J Occup Health Psychol. 2000;5(2):246–255. doi: 10.1037//1076-8998.5.2.246. [DOI] [PubMed] [Google Scholar]
- 40.Niedl K. Mobbing and well-being: economic and personnel development implications. Eur J Work Org Psychol. 1996;5:239–249. [Google Scholar]
- 41.Quine L. Workplace bullying in NHS community trust: staff questionnaire survey. BMJ. 1999;318(7178):228–232. doi: 10.1136/bmj.318.7178.228. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 42.Bjorkqvist K, Osterman K, Hjelt-Back M. Aggression among university employees. Aggressive Behav. 1994;20:173–184. [Google Scholar]
- 43.Einarsen S, Raknes BI. Harassment in the workplace and the victimization of men. Violence Vict. 1997;12(3):247–263. [PubMed] [Google Scholar]
- 44.Vartia M, Hyyti J. Gender differences in workplace bullying among prison officers. Eur J Work Org Psychol. 2002;11:113–126. [Google Scholar]
- 45.Zapf D. Organizational, work group related and personal causes of mobbing/bullying at work. J Manpower. 1999;20:70–85. [Google Scholar]
- 46.Mikkelsen EG, Einarsen S. Bullying in Danish work-life: prevalence and health correlates. Eur J Work Org Psychol. 2001;10(4):393–413. [Google Scholar]
- 47.Kivimüaki M, Virtanen M, Vartia M, et al. Workplace bullying and the risk of cardiovascular disease and depression. Occup Environ Med. 2003;60(10):779–783. doi: 10.1136/oem.60.10.779. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 48.Romanov K, Appelberg K, Honkasalo ML, Koskenvuo M. Recent interpersonal conflict at work and psychiatric morbidity: a prospective study of 15,530 employees aged 24-64. J Psychosom Res. 1996;40(2):169–176. doi: 10.1016/0022-3999(95)00577-3. [DOI] [PubMed] [Google Scholar]
- 49.Niedhammer I, David S, Degioanni S et 143 médecins du travail. [The French version of the Leymann's questionnaire on workplace bullying: the Leymann Inventory of Psychological Terror (LIPT)] Rev Epidemiol Sante Publique. 2006;54(3):245–262. doi: 10.1016/s0398-7620(06)76720-7. [DOI] [PubMed] [Google Scholar]
- 50.Niedhammer I, David S, Degioanni S 143 occupational physicians. Association between workplace bullying and depressive symptoms in the French working population. J Psychosom Res. 2006;61(2):251–259. doi: 10.1016/j.jpsychores.2006.03.051. [DOI] [PubMed] [Google Scholar]
- 51.Niedhammer I, David S, Degioanni S 143 occupational physicians. Economic activities and occupations at high risk for workplace bullying: results from a large-scale cross-sectional survey in the general working population in France. Int Arch Occup Environ Health. 2007;80(4):346–353. doi: 10.1007/s00420-006-0139-y. [DOI] [PubMed] [Google Scholar]
- 52.Fuhrer R, Rouillon F. La version française de l'échelle CES-D (Center for Epidemiologic Studies - Depression scale) Description et traduction de l'échelle d'autoévaluation. Psychiatr Psychobiol. 1989;4:163–166. [Google Scholar]
- 53.SAS Institute. Cary, NC: SAS Institute Inc; 1988. SAS/STAT user's guide, release 6.03 edition; p. 1028. [Google Scholar]
- 54.Niedhammer I, Saurel-Cubizolles MJ, Piciotti M, Bonenfant S. How is sex considered in recent epidemiological publications on occupational risks? Occup Environ Med. 2000;57(8):521–527. doi: 10.1136/oem.57.8.521. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 55.Hoel H, Cooper CL, Faragher B. The experience of bullying in Great Britain: the impact of organizational status. Eur J Work Org Psychol. 2001;10(4):443–465. [Google Scholar]
- 56.Einarsen S, Raknes BI, Matthiesen SB. Bullying and harassment at work and their relationships to work environment quality: an exploratory study. European Work and Organizational Psychologist. 1994;4(4):381–401. [Google Scholar]
- 57.Salin D. Prevalence and forms of bullying among business professionals: a comparison of two different strategies for measuring bullying. Eur J Work Org Psychol. 2001;10(4):425–441. [Google Scholar]
- 58.Rugulies R, Norborg M, Sorensen TS, Knudsen LE, Burr H. Effort-reward imbalance at work and risk of sleep disturbances. Cross-sectional and prospective results from the Danish Work Environment Cohort Study. J Psychosom Res. 2009;66(1):75–83. doi: 10.1016/j.jpsychores.2008.05.005. [DOI] [PubMed] [Google Scholar]
- 59.Landsbergis P. Occupational stress among health care workers: a test of the job demands control model. J Org Behav. 1988;9:217–39. [Google Scholar]