Job strain as a risk factor for clinical depression: systematic review and meta-analysis with additional individual participant data.

BACKGROUND: Adverse psychosocial working environments characterized by job strain (the combination of high demands and low control at work) are associated with an increased risk of depressive symptoms among employees, but evidence on clinically diagnosed depression is scarce. We examined job strain as a risk factor for clinical depression. METHOD: We identified published cohort studies from a systematic literature search in PubMed and PsycNET and obtained 14 cohort studies with unpublished individual-level data from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium. Summary estimates of the association were obtained using random-effects models. Individual-level data analyses were based on a pre-published study protocol. RESULTS: We included six published studies with a total of 27 461 individuals and 914 incident cases of clinical depression. From unpublished datasets we included 120 221 individuals and 982 first episodes of hospital-treated clinical depression. Job strain was associated with an increased risk of clinical depression in both published [relative risk (RR) = 1.77, 95% confidence interval (CI) 1.47-2.13] and unpublished datasets (RR = 1.27, 95% CI 1.04-1.55). Further individual participant analyses showed a similar association across sociodemographic subgroups and after excluding individuals with baseline somatic disease. The association was unchanged when excluding individuals with baseline depressive symptoms (RR = 1.25, 95% CI 0.94-1.65), but attenuated on adjustment for a continuous depressive symptoms score (RR = 1.03, 95% CI 0.81-1.32). CONCLUSIONS: Job strain may precipitate clinical depression among employees. Future intervention studies should test whether job strain is a modifiable risk factor for depression.

Job strain and the risk of severe asthma exacerbations: a meta-analysis of individual-participant data from 100 000 European men and women.

BACKGROUND: Many patients and healthcare professionals believe that work-related psychosocial stress, such as job strain, can make asthma worse, but this is not corroborated by empirical evidence. We investigated the associations between job strain and the incidence of severe asthma exacerbations in working-age European men and women. METHODS: We analysed individual-level data, collected between 1985 and 2010, from 102 175 working-age men and women in 11 prospective European studies. Job strain (a combination of high demands and low control at work) was self-reported at baseline. Incident severe asthma exacerbations were ascertained from national hospitalization and death registries. Associations between job strain and asthma exacerbations were modelled using Cox regression and the study-specific findings combined using random-effects meta-analyses. RESULTS: During a median follow-up of 10 years, 1 109 individuals experienced a severe asthma exacerbation (430 with asthma as the primary diagnostic code). In the age- and sex-adjusted analyses, job strain was associated with an increased risk of severe asthma exacerbations defined using the primary diagnostic code (hazard ratio, HR: 1.27, 95% confidence interval, CI: 1.00, 1.61). This association attenuated towards the null after adjustment for potential confounders (HR: 1.22, 95% CI: 0.96, 1.55). No association was observed in the analyses with asthma defined using any diagnostic code (HR: 1.01, 95% CI: 0.86, 1.19). CONCLUSIONS: Our findings suggest that job strain is probably not an important risk factor for severe asthma exacerbations leading to hospitalization or death.

Job strain in relation to body mass index: pooled analysis of 160 000 adults from 13 cohort studies.

BACKGROUND: Evidence of an association between job strain and obesity is inconsistent, mostly limited to small-scale studies, and does not distinguish between categories of underweight or obesity subclasses. OBJECTIVES: To examine the association between job strain and body mass index (BMI) in a large adult population. METHODS: We performed a pooled cross-sectional analysis based on individual-level data from 13 European studies resulting in a total of 161 746 participants (49% men, mean age, 43.7 years). Longitudinal analysis with a median follow-up of 4 years was possible for four cohort studies (n = 42 222). RESULTS: A total of 86 429 participants were of normal weight (BMI 18.5-24.9 kg m(-2) ), 2149 were underweight (BMI < 18.5 kg m(-2) ), 56 572 overweight (BMI 25.0-29.9 kg m(-2) ) and 13 523 class I (BMI 30-34.9 kg m(-2) ) and 3073 classes II/III (BMI ≥ 35 kg m(-2) ) obese. In addition, 27 010 (17%) participants reported job strain. In cross-sectional analyses, we found increased odds of job strain amongst underweight [odds ratio 1.12, 95% confidence interval (CI) 1.00-1.25], obese class I (odds ratio 1.07, 95% CI 1.02-1.12) and obese classes II/III participants (odds ratio 1.14, 95% CI 1.01-1.28) as compared with participants of normal weight. In longitudinal analysis, both weight gain and weight loss were related to the onset of job strain during follow-up. CONCLUSIONS: In an analysis of European data, we found both weight gain and weight loss to be associated with the onset of job strain, consistent with a 'U'-shaped cross-sectional association between job strain and BMI. These associations were relatively modest; therefore, it is unlikely that intervention to reduce job strain would be effective in combating obesity at a population level.

Covert coping with unfair treatment at work and risk of incident myocardial infarction and cardiac death among men: prospective cohort study.

BACKGROUND: Covert coping with unfair treatment at work--occurring when an employee does not show the "aggressor" that he/she feels unfairly treated--has been found to be associated with cardiovascular risk factors. This study examined whether covert coping also predicts incident coronary heart disease. METHODS: A prospective cohort study (the WOLF Stockholm study) of workplaces in the Stockholm area, Sweden. The participants were 2755 men with no history of myocardial infarction at baseline screening in 1992-1995. The main outcome measure was hospitalisation due to myocardial infarction or death from ischaemic heart disease until 2003 obtained from national registers (mean follow-up 9.8 ± 0.9 years). RESULTS: Forty-seven participants had myocardial infarction or died from ischaemic heart disease during follow-up. After adjustment for age, socioeconomic factors, risk behaviours, job strain and biological risk factors at baseline, there was a dose-response relationship between covert coping and risk of incident myocardial infarction or cardiac death (p for trend=0.10). Men who frequently used covert coping had a 2.29 (95% CI 1.00 to 5.29) times higher risk than those who did not use coping. Restricting the analysis to direct coping behaviours only strengthened this association (p for trend=0.02). CONCLUSIONS: In this study, covert coping is strongly related to increased risk of hard-endpoint cardiovascular disease.

The ethical challenges of the occupational physician in our time.

An increasing interest in professional ethics is observed among occupational health professionals. To this may contribute the ongoing financial crisis of world economy. The moral development, induced i.a. by the Nuremberg trials in 1947 has probably contributed to a changing moral landscape. Within health professions, including many categories of occupational health professionals there is an increasing awareness of the needs to revisit points of departure in building up ethical competence to and prepare their members for tasks in the Labour market. Selected topics will be commented on in respect to their challenges to occupational professional health ethics. Widening of perspectives of Ethics in traditional Hippocratic medical ethics issues related to requirements of confidentiality and informed consent.

Mental fatigue, work and sleep.

OBJECTIVE: The study examined the multivariate relationship between mental fatigue and different work-related (work load, work hours) and background/life style factors, as well as disturbed sleep. METHODS: A total of 5720 healthy employed men and women living in the greater Stockholm area participated in a questionnaire study on cardiovascular risk factors. The data were analysed using a multiple logistic regression analysis with self-rated fatigue as the dependent variable. RESULTS: Fatigue was predicted by disturbed sleep (4.31; 3.50-5.45, high immersion in work (4.17; 2.93-5.94), high work demands (2.39; 1.54-3.69), social support, being a female, being a supervisor and high age. Shift work, work hours (including overtime) and influence at work did not become significant predictors. With control for work demands a high number of work hours was associated with lower fatigue. CONCLUSION: Disturbed sleep is an important predictor of fatigue, apparently stronger than previously well-established predictors such as work load, female gender, lack of exercise, etc.

Sleep disturbances, work stress and work hours: a cross-sectional study.

OBJECTIVE: The study examined the multivariate relationship between disturbed sleep and different work-related and background/life style factors. METHODS: 5720 healthy employed men and women living in the greater Stockholm area participated. A factor analysis of eight items provided one main factor: "disturbed sleep." The data were analyzed using a multiple logistic regression analysis against the index disturbed sleep as well as the separate items "not well rested" and "difficulties awakening." RESULTS: The results showed that high work demands [odds ratio (OR) = 2.15] and physical effort at work (OR = 1.94) are risk indicators for disturbed sleep, while high social support is associated with reduced risk (OR = 0.44). In addition, higher age (45+), female gender, a high body mass index (BMI) and lack of exercise are background/life style risk indicators. Introducing into the model an item representing inability to stop thinking about work during free time yielded the highest OR (3.20) and forced work demands out of the regression. With regard to not feeling well rested, the same significant predictors, except physical effort, were obtained, as well as for having night work and being married. In addition, the age effect was reversed--high age predicted reduced risk of not feeling well rested. Difficulties awakening was predicted by high work demands, low social support, being male, low age and smoking. It is notable that, whereas subjective sleep quality decreased with age, the difficulties awakening and feelings of not being well rested after sleep increased with age. CONCLUSION: It was concluded that stress and the social situation at work are strongly linked to disturbed sleep and impaired awakening, that gender and, even more so, age may modify this and that the inability to stop worrying about work during free time may be an important link in the relation between stress and sleep.

Work organisation and unintentional sleep: results from the WOLF study.

BACKGROUND: Falling asleep at work is receiving increasing attention as a cause of work accidents. AIMS: To investigate which variables (related to work, lifestyle, or background) are related to the tendency to fall asleep unintentionally, either during work hours, or during leisure time. METHODS: 5589 individuals (76% response rate) responded to a questionnaire. A multiple logistic regression analysis of the cross sectional data was used to estimate the risk of falling asleep. RESULTS: The prevalence for falling asleep unintentionally at least once a month was 7.0% during work hours and 23.1% during leisure time. The risk of unintentional sleep at work was related to disturbed sleep, having shift work, and higher socioeconomic group. Being older, being a woman, and being a smoker were associated with a reduced risk of unintentionally falling asleep at work. Work demands, decision latitude at work, physical load, sedentary work, solitary work, extra work, and overtime work were not related to falling asleep at work. Removing "disturbed sleep" as a predictor did not change the odds ratios of the other predictors in any significant way. With respect to falling asleep during leisure time, disturbed sleep, snoring, high work demands, being a smoker, not exercising, and higher age (>45 years) became risk indicators. CONCLUSION: The risk of involuntary sleep at work is increased in connection with disturbed sleep but also with night work, socioeconomic group, low age, being a male, and being a non-smoker.

Coping with unfair treatment at work--what is the relationship between coping and hypertension in middle-aged men and Women? An epidemiological study of working men and women in Stockholm (the WOLF study).

BACKGROUND: An important hypothesis in psychosomatic medicine is that exposure to psychosocial factors that arouse anger may accelerate the onset of hypertension, particularly if the subject is not allowed to show anger or to deal constructively with the factor that evoked it. For working men and women, being treated in an unfair way at work may be crucial. The present study was designed to answer the question whether the pattern of coping - primarily directed towards the aggressor (open) or directed inwards or towards others (covert) - is associated with hypertension among working men and women. STUDY GROUP: Five thousand seven hundred and twenty working men and women aged 15-64 participated in the study. The participation rate was 76%. METHODS: The coping pattern was studied by means of a Swedish version of a self-administered questionnaire that was originally introduced by Harburg et al. RESULTS: Significant results were confined to the age group 45-54. All analyses were adjusted for age and body mass index. Smoking habits and social class had no effect on the relationships. Low scores (lowest quartile) for open coping tended to be associated with an elevated prevalence ratio (PR) of hypertension both among men (PR 1.3, 95% confidence interval, CI, 0.9-1.7) and women (PR 1.4, 95% CI 1.0-2.0). High scores for covert coping (highest quartile) were associated with an elevated PR of hypertension among men (PR 1.6, 95% CI 1.2-2.2) but not in women. If the analysis was confined to cases without medication, the relationship between a high level of covert coping and high blood pressure was still significant for men. For women, however, no significant findings were made after this operation. Accordingly, the relationship between a low level of open coping and hypertension in women was confined to women with medication. Coping patterns were correlated with psychosocial work environment factors, in particular decision latitude. CONCLUSION: In men, covert coping was associated with prevalence of hypertension. In women, there tended to be a relationship between low scores for open coping and hypertension.

Gender differences in the healthy worker effect among synthetic vitreous fiber workers.

The aim of this study was to determine whether the healthy worker effect and its component parts operate similarly for women and men. A cohort of workers from 14 synthetic vitreous fiber factories in seven countries, employed for at least 1 year between 1933 and 1977 and followed up to the early 1990s, included 375 deaths and 53,608 person-years among females and 2,568 deaths and 210,073 person-years among males. Standardized mortality ratios for all-cause and circulatory diseases were adjusted for country, age, calendar time, and gender. In addition, internal comparisons were adjusted for time since hire and employment status. The analyses addressed the following: 1) the healthy hire effect, 2) the time since hire effect, and 3) the healthy worker survivor effect. In this cohort, an overall healthy worker effect was not present in either gender. The healthy hire effect, based on standardized mortality ratios for years 1-4 since hire, was observed in males (standardized mortality ratio (SMR) = 0.8; 95% confidence interval (CI): 0.7, 1.0) but was less in females (SMR = 0.9; 95% CI: 0.5, 1.6). The relative risks increased slightly with time since hire in males but not in females. Higher mortality ratios were seen among those leaving employment than among those who remained actively employed; however, this effect was substantially greater for women (relative risk (RR) = 3.4; 95% CI: 1.8, 6.3) than men (RR = 1.8; 95% CI: 1.5, 2.1). The gender difference for active versus inactive status was stronger up to age 60 (men: RR = 1.7; 95% CI: 1.4, 2.0; women: RR = 3.6; 95% CI: 1.8, 7.1) than above that age. In conclusion, it appears that there is a stronger selection of healthy men than women into the workforce, while health-related selection out of the workforce is stronger for women than men.

Does a stressful psychosocial work environment mediate the effects of shift work on cardiovascular risk factors?

OBJECTIVES: Associations between shift work, chronic psychosocial work stress, and 2 important cardiovascular risk factors, hypertension and atherogenic lipids were studied. The hypothesis was tested that psychosocial work stress, as defined by the model of effort-reward imbalance, mediates the effects of shift work on cardiovascular risk. METHODS: Altogether 2288 male participants aged 30-55 years in the baseline screening of the Swedish WOLF (work organization, lipids, and fibrinogen) study underwent a clinical examination and answered a standardized questionnaire measuring shiftwork schedules, effort-reward imbalance at work, and health-adverse behavior. RESULTS: In addition to the direct effects of shift work on cardiovascular risk, mediating effects of effort-reward imbalance at work were found. The respective odds ratios (OR) ranged from 2.18 to 2.27 for hypertension and from 1.34 to 1.45 for atherogenic lipids. While the effects remained significant after extensive confounder control concerning hypertension, part of the observed effect on atherogenic lipids was due to behavioral influences. CONCLUSIONS: Despite obvious limitations, the results indicated that a stressful psychosocial work environment acts as a mediator of health-adverse effects of shift work on hypertension and, partly, atherogenic lipids. In terms of occupational health the findings call for a more comprehensive assessment of the health risks associated with shift work.

Cancer incidence among European man-made vitreous fiber production workers.

OBJECTIVES: This study analyzed cancer incidence among man-made vitreous fiber workers. METHODS: A cancer incidence follow-up was conducted among 3685 rock-slag wool (RSW) and 2611 glass wool (GW) production workers employed for > or =1 year in Denmark, Finland, Norway, or Sweden, and the standardized incidence ratios (SIR) were calculated on the basis of national incidence rates. RESULTS: Overall cancer incidence was close to expectation. Lung cancer incidence was increased among the RSW [SIR 1.08, 95% confidence interval (95% CI) 0.85-1.36] and GW (SIR 1.28, 95% CI 0.91-1.74) workers. For both subcohorts, a trend was suggested for time since first employment (P-value for linear trend 0.1 and 0.2, respectively). Neither subcohort showed an association with employment during the early technological phase, when fiber exposure was high. The incidence of oral, pharyngeal, and laryngeal cancer was increased among the RSW (SIR 1.46, 95% CI 0.99-2.07) and the GW (SIR 1.41, 95% CI 0.80-2.28) subcohorts. Despite a trend in risk for these neoplasms among the GW workers with time since first employment, the lack of a positive relation with other indirect indicators of fiber exposure points against a causal interpretation. No association between RSW or GW exposure and the risk of other neoplasms was suggested. CONCLUSIONS: These lung cancer results are similar to those of a mortality study that included a larger number of factories. For other cancers there was no suggestion of an association with RSW or GW exposure.

Increase in interleukin-6 and fibrinogen in peripheral blood after swine dust inhalation.

OBJECTIVES: The inhalation of dust from swine confinement buildings causes inflammatory responses in the airways with a rise of interleukin-6 (IL-6). The purpose of this study was to confirm the increase in serum IL-6 after inhalation of swine dust and investigate a possible increase in plasma fibrinogen. METHODS: Eight healthy nonsmoking volunteers inhaled dust for 4 hours inside a swine confinement building. Inhalable dust and endotoxin were sampled. The concentrations of IL-6 and fibrinogen were determined in serum and plasma. RESULTS: The study showed a clear increase in the concentrations of IL-6 and fibrinogen after exposure. CONCLUSIONS: As fibrinogen is an important risk factor for ischemic heart disease, the increased concentration of fibrinogen among persons exposed to swine dust may increase the risk for this disease.

Challenges facing occupational health services in the 21st century.

The mission and tasks of occupational health services are reviewed in the context of the global megatrends of productivity increase, population overgrowth, and the implications of changes in the technology of information and communication. Current trends in attempts to achieve harmonization with respect to the concept and tasks of occupational health services in the European Union are described, along with the basic features of occupational health services as a human service organization with implications for the setting of objectives and criteria for assessing quality and performance and ethics. The need to adopt a quality-focused approach to occupational health service programs is emphasized, and some of the inhibitions and obstacles to quality work are mentioned. The need for professional commitment to develop and implement quality concepts is outlined. Evidence-based health care in the setting of occupational health services and some salient aspects of professional ethics in the 21st century are commented on.

Non-neoplastic mortality of European workers who produce man made vitreous fibres.

OBJECTIVE: To study mortality from non-neoplastic diseases among European workers who produce man made vitreous fibres (MMVF). METHODS: 11,373 male workers were studied, who were employed for at least 1 year in the production of rock or slag wool (RSW), glass wool (GW), and continuous filament (CF) in 13 factories from seven European countries. Workers were followed up from the beginning of production, between 1933 and 1950 to 1990-2 and contributed 256,352 person-years of observation. Standardised mortality ratios (SMRs) were calculated with national mortalities for reference; an internal exposure-response analyses based on multivariate Poisson regression models was also conducted. RESULTS: Mortality from bronchitis, emphysema, and asthma was not increased (SMR 1.03, 95% confidence interval (95% CI) 0.82 to 1.28). In RSW workers, there was no overall increase in mortality from non-malignant renal diseases (SMR 0.97, 95% CI 0.36 to 2.11), although there was the suggestion of an increase in risk with duration of employment. Mortality from ischaemic heart disease was not increased overall (SMR 1.03, 95% CI 0.96 to 1.11), but RSW and CF workers with > or = 30 years since first employment had a higher risk. RSW and CF workers showed an increased mortality from external causes, mainly motor vehicle accidents and suicide, which was higher among workers with a short duration of employment. CONCLUSIONS: Mortality from most non-neoplastic diseases does not seem to be related to employment in the MMVF industry. The results on mortality from ischaemic heart disease and non-malignant renal diseases, however, warrant further investigations.

Lung cancer mortality among European rock/slag wool workers: exposure-response analysis.

OBJECTIVES: The purpose was to analyze the relationship between semi-quantitative indices of exposure to manmade vitreous fibers and lung cancer mortality among European rock/slag wool (RSW) workers. METHODS: The study population comprised 9,603 male workers employed in RSW production in seven factories in Denmark, Norway, Sweden, and Germany, followed up for mortality as of 1990-91. Estimates of past exposure to respirable fibers were used to calculate cumulative exposure with a 15-year lag and maximum annual exposure based on employment history up to 1977. Rate ratios were estimated via multivariate Poisson regression, adjusting for country, age, calendar year, time since first employment, and employment status. RESULTS: A total of 159 lung cancer deaths were included in the analysis of which 97 among workers with more than one year of employment. We found nonstatistically significant trends in lung cancer risk according to cumulative exposure. Relative risks (RR) in the four quartiles were 1.0 (reference), 1.3 (95 percent confidence interval [CI] = 0.8-2.4), 1.2 (CI = 0.7-2.1), and 1.5 (CI = 0.7-3.0, P test for trend = 0.4). When workers with less than one year of employment were excluded, there was no increased risk; the RRs in the four quartiles were 1.0, 0.9 (CI = 0.4-2.0), 0.8 (CI = 0.3-1.9), and 1.0 (CI = 0.4-2.7). No trend was present according to maximum annual exposure. The results were not consistent among countries. CONCLUSIONS: We found a positive association between exposure to respirable fibers and lung cancer mortality. However, the lack of statistical significance, the dependence of the results on inclusion of short-term workers, the lack of consistency among countries, and the possible correlation between exposure to respirable fibers and to other agents reduce the weight of such evidence.

High effort, low reward, and cardiovascular risk factors in employed Swedish men and women: baseline results from the WOLF Study.

STUDY OBJECTIVE: To examine associations between measures of work stress (that is, the combination of high effort and low reward) and cardiovascular risk factors. DESIGN: Cross sectional first screening of a prospective cohort study. SETTING AND PARTICIPANTS: The study was conducted among 5720 healthy employed men and women living in the greater Stockholm area aged 19-70 years. All analyses were restricted to subjects with complete data (n = 4958). The investigation of associations between indicators of effort-reward imbalance and cardiovascular risk factors was restricted to the age group 30-55 years (n = 3427). MAIN RESULTS: Subjects reporting high effort and low reward at work had a higher prevalence of well known risk factors for coronary heart disease. After adjustment for relevant confounders, associations between a measure of extrinsic effort and reward (the effort-reward ratio) and hypertension (multivariate prevalence odds ratio (POR) 1.62-1.68), increased total cholesterol (upper tertile 220 mg/dl)(POR = 1.24) and the total cholesterol/high density lipoprotein(HDL)-cholesterol ratio (upper tertile 4.61)(POR 1.26-1.30) were found among men. Among women a measure of high intrinsic effort (immersion) was related to increased low density lipoprotein (LDL)-cholesterol (upper tertile 130 mg/dl)(POR 1.37-1.39). Analyses of variance showed increasing mean values of LDL cholesterol with an increasing degree of the effort-reward ratio among men and increased LDL-cholesterol among women with high levels of intrinsic effort (upper tertile of immersion). CONCLUSIONS: Findings lend support to the hypothesis that effort-reward imbalance represents a specific constellation of stressful experience at work related to cardiovascular risk. The relation was not explained by relevant confounders (for example, lack of physical exercise, body weight, cigarette smoking).