Contribution of income and job strain to the association between education and cardiovascular disease in 1.6 million Danish employees.

AIMS: We examined the extent to which associations between education and cardiovascular disease (CVD) morbidity and mortality are attributable to income and work stress. METHODS AND RESULTS: We included all employed Danish residents aged 30-59 years in 2000. Cardiovascular disease morbidity analyses included 1 638 270 individuals, free of cardiometabolic disease (CVD or diabetes). Mortality analyses included 41 944 individuals with cardiometabolic disease. We assessed education and income annually from population registers and work stress, defined as job strain, with a job-exposure matrix. Outcomes were ascertained until 2014 from health registers and risk was estimated using Cox regression. During 10 957 399 (men) and 10 776 516 person-years (women), we identified 51 585 and 24 075 incident CVD cases, respectively. For men with low education, risk of CVD was 1.62 [95% confidence interval (CI) 1.58-1.66] before and 1.46 (95% CI 1.42-1.50) after adjustment for income and job strain (25% reduction). In women, estimates were 1.66 (95% CI 1.61-1.72) and 1.53 (95% CI 1.47-1.58) (21% reduction). Of individuals with cardiometabolic disease, 1736 men (362 234 person-years) and 341 women (179 402 person-years) died from CVD. Education predicted CVD mortality in both sexes. Estimates were reduced with 54% (men) and 33% (women) after adjustment for income and job strain. CONCLUSION: Low education predicted incident CVD in initially healthy individuals and CVD mortality in individuals with prevalent cardiometabolic disease. In men with cardiometabolic disease, income and job strain explained half of the higher CVD mortality in the low education group. In healthy men and in women regardless of cardiometabolic disease, these factors explained 21-33% of the higher CVD morbidity and mortality.

Cumulated and most recent job control and risk of disability pension in the Danish Work Life Course Cohort (DaWCo).

BACKGROUND: Previous studies have found low job control to be associated with a higher risk of disability pension (DP). Most studies have measured job control only at one time-point, and there is a lack of knowledge regarding the role of exposure duration. This study examines the prospective association between job control and DP measuring exposure both cumulated throughout work life and most recent. METHODS: We included 712 519 individuals (about 4.5 million person-years) from The Danish Work Life Course Cohort which follows young employees in Denmark from their entry into the labour market. Job control was assessed with a job exposure matrix and DP with register data on public transfer payments. We adjusted for several potential life course confounders, including physical demands at work and parental socioeconomic position and psychiatric and somatic diagnoses. RESULTS: Employees in occupations with low job control had a higher risk of DP. There were effects of both cumulated and most recent job control when mutually adjusted. Fully adjusted hazard ratios (HRs) were 1.14 [95% confidence intervals (CIs) 1.11-1.17] and 1.15 (95% CI 1.02-1.29) for cumulated and most recent job control, respectively. Without mutual adjustment, estimates were 1.15 (95% CI 1.13-1.18) and 1.55 (95% CI 1.39-1.72) for cumulated and most recent low job control, respectively. CONCLUSIONS: Low job control predicts a higher risk of DP, even after adjustment for physical demands at work. The results indicate both gradual and short-term effects of low job control on DP risk.

Psychosocial working conditions and depressive disorder: disentangling effects of job control from socioeconomic status using a life-course approach.

PURPOSE: Job control, the combination of skill discretion and decision authority, is considered a central component of the psychosocial working environment. This longitudinal study examines the relation between job control and risk of incident depressive disorder using a life-course approach. METHODS: We analyze data from The Danish Work Life Course Cohort study, including all Danish individuals aged 15-30 who entered the Danish labor market during 1995-2009 and were free from depressive disorder at entry (955,573 individuals). We measured job control using a job exposure matrix. Depressive disorders were measured using information from nationwide registers of psychiatric in- and outpatient admissions. Using Cox regression models we estimated the prospective association between job control and risk of incident depressive disorders. Analyses accounted for a range of potential confounders prior to workforce entry including socioeconomic status in adolescence and parental psychiatric and somatic diagnoses prior to labor market entry, together with potential confounders in adulthood including income, education, and demographics. RESULTS: Lower levels of past year job control were associated with a higher risk of depressive disorder after adjustment for all covariates (HR = 1.27, 95% CI 1.16-1.38). Results stratified by gender showed associations for both men (HR = 1.38, 95% CI 1.19-1.61) and women (HR = 1.19, 95% CI 1.08-1.32). CONCLUSIONS: Our findings suggest that the level of job control at work affects the risk of clinically diagnosed depressive disorder, and that this association is not due to confounding by socioeconomic status.

Physical work demands and psychosocial working conditions as predictors of musculoskeletal pain: a cohort study comparing self-reported and job exposure matrix measurements.

OBJECTIVES: Determining exposure to occupational factors by workers' job titles is extensively used in epidemiological research. However, the correspondence of findings regarding associations to health between job exposure matrices (JEMs) and individual-level exposure data is largely unknown. We set out to examine the prospective associations of physical work demands and psychosocial working conditions with musculoskeletal pain, comparing JEMs with individual-level self-reported exposures. METHODS: We analysed data of 8132 participants from the Work Environment and Health in Denmark cohort study. Using random intercept multilevel modelling, we constructed age-specific and sex-specific JEMs estimating predicted exposures in job groups. We analysed associations between working conditions (individual and JEM level) at baseline and musculoskeletal pain at follow-up using multilevel modelling stratified by sex, adjusting for age, education and baseline pain. RESULTS: Any consistent associations present in the individual-level analysis were also found in the JEM-level analysis. Higher pain levels at follow-up was seen for employees with higher baseline physical work demands, women exposed to violence and men with lower decision authority, whether measured at the individual or JEM level. Higher JEM-level quantitative demands were associated with less pain, but no association was seen at the individual level. CONCLUSIONS: We found predominately comparable prospective associations between working conditions and pain, whether using JEMs or individual level exposures, with the exception of quantitative demands. The results suggest that, with few notable exceptions, findings obtained using JEMs may be comparable with those obtained when using self-reported exposures.

Work-related violence and depressive disorder among 955,573 employees followed for 6.99 million person-years. The Danish Work Life Course Cohort study: Work-related violence and depression.

BACKGROUND: We examined the association between probability of work-related violence and first diagnosis of depressive disorder whilst accounting for the potential selection of individuals vulnerable to depression into occupations with high probability of work-related violence. METHODS: Based on a pre-published study protocol, we analysed nationwide register data from the Danish Work Life Course Cohort study, encompassing 955,573 individuals followed from their entry into the workforce, and free from depressive disorder before work-force entry. Depressive disorder was measured from psychiatric in- and outpatient admissions. We measured work-related violence throughout the worklife by the annual average occupational risk of violence exposure. Using Cox proportional hazards regression, we examined the longitudinal association between work-related violence (both past year and cumulative life-long exposure) and first depressive disorder diagnosis, whilst adjusting for numerous confounders including parental psychiatric and somatic diagnoses, childhood socioeconomic position, and health services use before workforce entry. RESULTS: The risk of depressive disorder was higher in individuals with high probability of past year work-related violence (hazard ratio: 1.11, 95% CI: 1.06-1.16) compared to employees with low probability of exposure, after adjustment for confounders. Among women, associations were robust across industries, whereas among men, associations were limited to certain industries. LIMITATIONS: Violence was measured on the job group and not the individual level, likely resulting in some misclassification of the exposure. CONCLUSIONS: Work-related violence may increase the risk of depressive disorder, independent of pre-existing risk factors for depressive disorder. These findings underline the importance of preventing work-related violence.

Persistent and changing job strain and risk of coronary heart disease. A population-based cohort study of 1.6 million employees in Denmark.

Objectives This study aimed to examine the association between job strain and incident coronary heart disease (CHD) in Denmark, while accounting for changes of job strain. Methods We included all employees residing in Denmark in 2000, aged 30-59 years with no prevalent CHD (N=1 660 150). We determined exposure to job strain from 1996-2009 using a job exposure matrix (JEM) with annual updates. Follow-up for incident CHD was from 2001-2010 via linkage to health records. We used Cox regression to calculate hazard ratios (HR) and 95% confidence intervals (CI) for the association between job strain and incident CHD. Results During 16.1 million person-years, we identified 24 159 incident CHD cases (15.0 per 10 000 person-years). After adjustment for covariates, job strain in 2000 predicted onset of CHD during a mean follow-up of 9.71 years (HR 1.10, 95% CI 1.07-1.13). When analyzing changes in job strain from one year to the next and CHD in the subsequent year, persistent job strain (HR 1.07, 95% CI 1.03-1.10), onset of job strain (HR 1.20, 95% CI 1.12-1.29) and removal of strain (HR 1.20, 95% CI 1.12-1.28) were associated with higher CHD incidence compared to persistent no job strain. Associations were similar among men and women. Conclusions Job strain is associated with a higher risk of incident CHD in Denmark. As we used a JEM, we can rule out reporting bias. However, under- or overestimation of associations is possible due to non-differential misclassification of job strain and residual confounding by socioeconomic position.

Cohort profile: the Danish Work Life Course Cohort study (DaWCo).

PURPOSE: The Danish Work Life Course Cohort (DaWCo) was initiated to study relations between working conditions, health and labour market affiliation using repeated measures of these factors throughout the working life, while accounting for health-differences pre-existing labour market entry. PARTICIPANTS: The cohort encompasses all 15-30-year-old individuals residing in Denmark who entered the labour market during the years 1995-2009 (960 562 individuals and 7 136 188 observations). Data include information on working conditions measured by job exposure matrices linked with registers on health, labour market affiliation and sociodemographics for both the cohort members and their parents. The median age at cohort entry was 20 years and men and women were equally represented. FINDINGS TO DATE: Currently, one study has been published, which found that low job control was associated with increased risk of depressive disorder, independently from indicators of socioeconomic position measured throughout the life-course. The present cohort profile presents data regarding the transitions of cohort members between states of labour market affiliation and data on health services use. All cohort members were employed in their year of entry, but this proportion decreased across the years to 82.4% in the 10th year since cohort entry. The proportion of students peaked at 5 years since cohort entry with 13.9%. FUTURE PLANS: This large prospective cohort offers the possibility to study associations between psychosocial working conditions and rare outcomes and to examine the potential accumulation of effects while accounting for health-differences pre-existing labour market entry. Currently, we are working on analyses on risk of hospital-diagnosed incident depression and disability pensioning. The study is ongoing, and we are planning to extend the study to include the years 2010-2018 and expand the cohort with individuals entering the Danish workforce during these years.

The impact of self-reported health and register-based prescription medicine purchases on re-employment chances: A prospective study.

In this paper, we investigate the influence of self-reported health and register-based prescription medicine purchases on re-employment chances, and whether these health indicators measure similar aspects of health in this analysis. Data came from a 2006 Danish unemployment survey among a random sample of unemployed individuals enriched with register data (2006-2008, N=1806). The survey participants all received unemployment benefits from the welfare system and had been unemployed for more than 20 weeks at the time of the interview in 2006. We combined these data with longitudinal register data on individual prescription medicine purchases for somatic illnesses and prescription medicine purchases for mental illnesses, information on re-employment and various socio-demographic variables. We conducted binary logistic regression analyses to investigate the impact of self-reported health and prescription medicine purchases measured in 2006 on re-employment chances in 2007 and 2008. Our analyses show that unemployed workers with poor self-reported health and workers who had prescription medicine purchases for mental illnesses were less likely to be re-employed in 2007 and 2008. Furthermore, the impact of both prescription medicine purchases for somatic illnesses and for mental illnesses increased when adding self-reported health to the model although prescription purchases for somatic illnesses became statistically insignificant. The impact of prescription medicine purchases for somatic illnesses was mediated by self-reported health, whilst prescription medicine purchases for mental illnesses was only partly mediated. Finally, SRH seemed a much stronger prediction than prescription medicines. From these results, we propose, when possible, the inclusion of both an indicator of self-reported health and an indicator of mental health in studies on re-employment.