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published cohort studies from a systematic literature search in PubMed and PsycNET and obtained 14 cohort studies with unpublished individual-level data from the Individual-Participant-Data Meta-analysis in Working Populations (IPD-Work) Consortium.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 From unpublished datasets we included 120 221 individuals and 982 first episodes of hospital-treated clinical depression.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risk of clinical depression in both published [relative risk (RR) = 1.77, 95% confidence interval (CI) 1.47-2.13] and unpublished datasets (RR = 1.27, 95% CI 1.04-1.55).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.

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.

Coping with long-term musculoskeletal pain and its consequences: is gender a factor?

We did a descriptive study of 121 patients (71 women and 50 men) to explore the role of gender in coping with long-term intractable pain of the neck, shoulder and back and to determine the consequences of pain. Questionnaires used to assess the dependent variables were the Coping Strategy Questionnaire (CSQ) and the Multidimensional Pain Inventory (MPI). Distinctions were found between men and women. In particular, the coping strategies used by women were those which in previous research had been found to be associated with dysfunction and poor outcome in terms of rehabilitation. Moreover, considering the consequences of pain on daily living, a more complex pattern of related factors was found in women rather than men. Given the high proportion of working women in Sweden with long-term musculoskeletal pain and considering recent observations in controlled studies showing that the benefits of cognitive behaviourally based treatments are confined to women, our findings suggest the need to tailor rehabilitative strategies differently for men and women and point to a research agenda which pays more attention to the distinctive challenges of women in the workplace when they are affected by chronic ailments.

Mortality and cancer morbidity in a group of Swedish VCM and PCV production workers.

The cohort of workers employed in a Swedish vinyl chloride/poly(vinyl chloride) plant since its start in the early 1940's has been followed for mortality and cancer morbidity patterns. Only 21 of the 771 persons could not be traced. Difficulties in establishing exposure levels at different work areas in the past makes an evaluation of dose-effect relationships impossible. A four- to fivefold excess of pancreas/liver tumors was found, including two cases later classified as angiosarcomas of the liver. The number of brain tumors and suicide do not deviate significantly from expected. Cardiovascular and cerebrovascular diseases, on the other hand, differ significantly from the expected. The discrepancies between previous reports on VCM/PVC workers and this report are discussed. The possible etiology of the cardiovascular deaths is also discussed.

Mortality and cancer rates among workers in the Swedish PVC processing industry.

Personnel lists from four PVC-processing industries were collected on production of employees with at least three months of employment at the beginning of 1945 and the last day of employment December 31, 1974. Of 2073 persons, 103 could not be followed up, because they had moved abroad. The remaining persons comprise the cohort of 1970 individuals who were analyzed and compared with the national population with respect to mortality from various diseases and cancer morbidity. The death risk from myocardial infarction is elevated in the cohort. This elevation is most clearly apparent in the subcohort which had at least two years of exposure time and where the analysis was directed at circumstances chronologically close to the time of exposure. The myocardial infarction risk related to vinyl chloride exposure is discussed in relation to earlier studies on the vascular effects of vinyl chloride. An indication of an elevated risk of morbidity and mortality from tumors in the digestive organs is also present. However, this is not statistically confirmed. A few future follow-ups of the present study are necessary in order to clarify any possible elevated risk of tumors in the PVC-processing industry.

Comparison of information on occupation and lifestyle habits obtained from European man-made vitreous fibre production workers and their relatives.

BACKGROUND: Studies of the aetiology of fatal diseases often rely on data obtained from relatives, which can cause loss of precision and introduce bias. We assessed the quality of such information on demographics, occupation, smoking and alcohol habits. METHODS: We compared contemporary interviews, based on a structured questionnaire, with male workers from the man-made vitreous fibre production industry in four European countries and their relatives. The participation rate was 63% (74 pairs of workers and relatives). RESULTS: Only minor differences in the ability to answer the questions appeared among workers and relatives, except for specific occupational questions. There was moderate to excellent agreement for demographics, residential and work history (kappa or intraclass correlation range: 0.44-0.98). For smoking habits, beer and wine consumption the agreement was good to excellent (range: 0.59-0.99). In particular, number of different residential areas, jobs, industries, and duration of wine drinking were significantly underreported by the relatives. No general determinant for reduced agreement appeared. CONCLUSIONS: In general, the quality of information obtained from relatives appeared good. However, information on specific occupational exposures may be improved by supplementing the information from relatives with details obtained from colleagues, occupational hygiene experts or occupation-exposure matrices.

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).

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.

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.

Mortality and cancer incidence in the man-made mineral fiber industry in Sweden.

This report gives an account of the Swedish contribution to the joint European epidemiologic study on production workers in the man-made mineral fiber (MMMF) industry. The information sources utilized and the follow-up procedure, making extensive use of record-linkage operations extracting data from computerized data banks, are described in some detail. The follow-up with regard to vital status, deaths and causes of death, diagnosed cancers, and emigration could essentially be based on such techniques. The problems of tracing immigrant and emigrant subpopulations are given particular attention. The exposed Swedish cohort consisted of 3,600 persons giving 61,690 person-years of observation. A total of 524 deaths was observed in the cohort, 230 cohort members had emigrated during the period of observation (147 of whom could be traced to other Nordic countries), and 62 other persons were lost to follow-up. It was observed that most of the persons contracting lung cancer in the Swedish cohort had been exposed during relatively short periods of time, ie, during one to four years of employment. This finding applied to both the rock-wool and glass-wool industry. The authors point out that the observed excess risk in lung cancer deaths may also have other explanations than occupational exposure to MMMF.

Delivery outcome for women working in the pulp and paper industry.

A report on unusually many wasted pregnancies among women working at a laboratory in a paper industry gave rise to a cohort study on pregnancy outcome among all women working in the pulp and paper industry in Sweden during 1973--1977. A total of 890 deliveries were identified (899 infants born). The total number of malformed infants or perinatally dead infants was according to expectations. When the material was broken up according to occupation, it was found that, in the group of infants whose mothers worked in laboratories during pregnancy, the rate of malformed infants appeared high. These data, added to previously published data, seem to support the notion that work in laboratories represents a pregnancy hazard.

Fiber exposure assessment in the Swedish rock wool and slag wool production industry in 1938-1990.

OBJECTIVE: A multiplicative model was developed to assess past exposure to respirable fibers among rock wool and slag wool production workers in Sweden in 1938-1990. METHODS: Information on the job titles, work tasks and employment times of 1487 workers exposed to man-made vitreous fibers was obtained from company records and interviews with older employees. A mathematical model developed earlier for assessing historical fiber exposure, based on factory averages, was further developed. Matrices of multipliers for each plant that were specific for job title were modified to assess fiber exposure with respect to job title and calendar period. The model was based on measurements made in 1977. Two methods of exposure assessment were compared, cumulative exposure based on factory average (model I) and cumulative exposure based on job title (model II). RESULTS: The exposure changed considerably in the two factories during the period 1938-1990, and it varied also between job titles. The estimated average fiber (f) exposure level at the two plants in the middle of the 1940s was 1.32 and 0.78 f.ml-1. These values are 26 and 16 times higher, respectively, than the exposure in 1980. Process changes, as well as the addition of binders and oil, reduced the exposure drastically around 1950. The mean cumulative respirable fiber exposure for the 1487 subjects was 1.44 (range 0.05-18.40) f.ml-1.year. The cleaners had 14 times higher annual fiber exposure than the preproduction workers. CONCLUSIONS: Model II was judged to be more valid than model I in assessing exposure to man-made vitreous fibers.

Long-term exposure to jet fuel: an investigation on occupationally exposed workers with special reference to the nervous system.

In the present study the results of a neurological and neurophysiological health examination of 29 aircraft factory workers chronically exposed to jet fuel vapors are presented. The exposed subjects were classified into a heavily exposed and a less heavily exposed group. The examination included a standardized clinical neurological examination, measurements of the conduction velocities in the peripheral nerves, and threshold determinations of vibratory sensations in the extremities. All 13 persons examined in the heavily exposed group and 7 of the 16 in the less heavily exposed group stated that they had repeatedly experienced acute effects (dizziness, respiratory tract symptoms, heart palpitations, a feeling of pressure on the chest, nausea, headache) of the jet fuel vapors in the inhaled air. A high rate of symptoms indicative of neurasthenia and psychasthenia and symptoms and signs indicative of polyneuropathy was observed both in the heavily exposed group and in the two groups combined in comparison with reference groups. Considering the presented facts concerning (a) the acute effects on repeated occasions, (b) the high rates of symptoms indicative of neurasthenia and psychasthenia and symptoms and signs indicative of polyneuropathy, and (c) the differences in the observations made between the two groups with varying degrees of exposure to jet fuel, the authors interpreted the results as indicative of a possible effect of long-term exposure to jet fuel on the nervous system.

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, mortality and exposure-response among Swedish man-made vitreous fiber production workers.

OBJECTIVE: The objective of this study was to provide an extended follow-up of workers in three Swedish plants producing man-made vitreous fibers (MMVF). METHOD: Mortality and cancer incidence was investigated among 3539 male and female workers, employed for at least one year before 1978. Mortality was followed from 1952 to 1990 and cancer incidence from 1958 to 1989. National and regional mortality and cancer incidence rates were used to calculate the expected numbers. RESULTS: Twenty-seven lung cancer deaths were observed compared with 23 expected (standardized mortality ratio 117, 95% confidence interval 81-176), based on regional mortality. With a latency time of 30 years, the lung cancer risk was significantly elevated, but not trend was found for the standardized mortality ratio with increasing duration of exposure to MMVF. The lung cancer and stomach cancer mortality was higher in the rock wool industry than in the fiber glass industry. Fiber exposure from 1938 to 1990 was estimated in the two rock wool plants by applying a model for historical fiber exposure estimation, specific for different job titles in the rock wool production industry. No relationship was found between individually cumulated rock wool fiber exposure and lung cancer or stomach cancer risk. CONCLUSIONS: The numbers of lung cancers and stomach cancer cases were low and did not therefore allow more general conclusions regarding the cancer hazard for exposed workers. A large European study in progress will probably allow more precise conclusions.

Retrospective cohort study of two plants in the Swedish rubber industry.

A cohort of 13,114 workers employed during 1930-1975 in two Swedish plants producing tires and industrial rubber goods was investigated with regard to cancer mortality and cancer incidence. Separate analyses were performed on the following subgroups of the cohort: mixers/weighers, other production workers, and white-collar employees. For all causes of death no increase of risk was observed in the population as a whole. Mixers/weighers showed however an increased overall standardized mortality ratio. The pattern of causes of death was not changed in the total cohort. An increased risk to die from liver cancer (risk ratio 4.12) and pancreatic cancer (risk ratio 2.70) was, however, observed for the category other production workers. An increased risk of death from tumors of the respiratory organs was also observed for the categories other production workers (risk ratio 1.89) and white-collar employees (risk ratio 2.63). For tumors in the urinary bladder (risk ratio 2.50) and for ischemic heart diseases (risk ratio 1.27) the death risk was elevated for the category other production workers. The cancer morbidity pattern showed an increase in malignant melanomas (risk ratio 2.50) for the category other production workers and for lung cancer (risk ratio 2.09), as well as for tumors in the nervous system (risk ratio 3.18) for white-collar employees.

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.