Elsevier

The Lancet

Volume 380, Issue 9852, 27 October–2 November 2012, Pages 1491-1497
The Lancet

Articles
Job strain as a risk factor for coronary heart disease: a collaborative meta-analysis of individual participant data

https://doi.org/10.1016/S0140-6736(12)60994-5Get rights and content

Summary

Background

Published work assessing psychosocial stress (job strain) as a risk factor for coronary heart disease is inconsistent and subject to publication bias and reverse causation bias. We analysed the relation between job strain and coronary heart disease with a meta-analysis of published and unpublished studies.

Methods

We used individual records from 13 European cohort studies (1985–2006) of men and women without coronary heart disease who were employed at time of baseline assessment. We measured job strain with questions from validated job-content and demand-control questionnaires. We extracted data in two stages such that acquisition and harmonisation of job strain measure and covariables occurred before linkage to records for coronary heart disease. We defined incident coronary heart disease as the first non-fatal myocardial infarction or coronary death.

Findings

30 214 (15%) of 197 473 participants reported job strain. In 1·49 million person-years at risk (mean follow-up 7·5 years [SD 1·7]), we recorded 2358 events of incident coronary heart disease. After adjustment for sex and age, the hazard ratio for job strain versus no job strain was 1·23 (95% CI 1·10–1·37). This effect estimate was higher in published (1·43, 1·15–1·77) than unpublished (1·16, 1·02–1·32) studies. Hazard ratios were likewise raised in analyses addressing reverse causality by exclusion of events of coronary heart disease that occurred in the first 3 years (1·31, 1·15–1·48) and 5 years (1·30, 1·13–1·50) of follow-up. We noted an association between job strain and coronary heart disease for sex, age groups, socioeconomic strata, and region, and after adjustments for socioeconomic status, and lifestyle and conventional risk factors. The population attributable risk for job strain was 3·4%.

Interpretation

Our findings suggest that prevention of workplace stress might decrease disease incidence; however, this strategy would have a much smaller effect than would tackling of standard risk factors, such as smoking.

Funding

Finnish Work Environment Fund, the Academy of Finland, the Swedish Research Council for Working Life and Social Research, the German Social Accident Insurance, the Danish National Research Centre for the Working Environment, the BUPA Foundation, the Ministry of Social Affairs and Employment, the Medical Research Council, the Wellcome Trust, and the US National Institutes of Health.

Introduction

Investigators have examined the role of psychological factors, such as personality type, cognition, and psychological stress, in the cause of coronary heart disease. Of these factors, psychosocial stress is the most commonly investigated.1, 2, 3 Job strain—the combination of high job demands and low control at work—is one of the most widely studied definitions of psychosocial stress.2 Although some studies4, 5, 6 have shown that job strain is associated with a more than doubling in risk of coronary heart disease, findings from a meta-analysis7 of cohort studies suggest that this excess risk is probably modest, at about 40%. Moreover, the importance of job strain as a risk factor for coronary heart disease continues to be debated because of several methodological shortcomings.

The first limitation is publication bias—ie, studies with significant results in the expected direction are more likely to be published and cited in scientific literature than are those with non-significant findings.8 Second, in studies9, 10 of working hours (job demand), evidence shows that people spontaneously reduce their hours in the years before cardiac events, probably as a response to symptoms of advanced underlying disease. This action could result in perceptions of reduced job demands, which might contribute to reverse causation bias—ie, coronary heart disease affects levels of stress, rather than vice-versa. Exclusion from analysis of coronary heart disease events that occur in the first years of follow-up can reduce such bias, but few studies have been sufficiently powered to do this analysis.

We did a collaborative meta-analysis of individual participant data from published and unpublished studies of job strain and coronary heart disease to address the limitations of previous studies and the discordant evidence base.

Section snippets

Study population

We used data from 13 independent cohort studies started between 1985 and 2006, in Finland, Sweden, Denmark, the Netherlands, Belgium, France, and the UK.11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 All studies were part of the individual-participant-data meta-analysis in working populations (IPD-Work) consortium, which was established at the Four Centres meeting in London, in 2008.24 Details of the study design and participants have been previously published (appendix).

Our analyses were

Results

We excluded from analyses 5124 (3%) of 203 816 participants who had missing data for age, sex, job strain, or incident coronary heart disease events, and 1219 (1%) with a diagnosis of coronary heart disease before the study baseline. Thus, 197 473 participants were included in the analysis (table). Mean age at study entry was 42·3 years (SD 9·8) and half of participants were women. Dependent on the study, between 13% and 22% of participants had job strain (table).

During 1 488 728 person-years

Discussion

The pooling of published and unpublished studies allowed us to investigate the association between coronary heart disease and exposure to job strain with greater precision than has previously been possible. Our findings suggest that job strain is associated with a small, but consistent, increased risk of an incident event of cardiovascular heart disease. Adjustment for lifestyle and conventional risk factors, and for age, sex, and socioeconomic status, did not substantially change the magnitude

References (50)

  • M Kivimäki et al.

    Work stress and risk of cardiovascular mortality: prospective cohort study of industrial employees

    BMJ

    (2002)
  • B Netterstrom et al.

    Psychological job demands increase the risk of ischaemic heart disease: a 14-year cohort study of employed Danish men

    Eur J Cardiovasc Prev Rehabil

    (2006)
  • M Kivimaki et al.

    Work stress in the etiology of coronary heart disease— a meta-analysis

    Scand J Work Environ Health

    (2006)
  • EH Turner et al.

    Selective publication of antidepressant trials and its influence on apparent efficacy

    N Engl J Med

    (2008)
  • S Sokejima et al.

    Working hours as a risk factor for acute myocardial infarction in Japan: case-control study

    BMJ

    (1998)
  • M Virtanen et al.

    Overtime work and incident coronary heart disease: the Whitehall II prospective cohort study

    Eur Heart J

    (2010)
  • D De Bacquer et al.

    Perceived job stress and incidence of coronary events: 3-year follow-up of the Belgian Job Stress Project cohort

    Am J Epidemiol

    (2005)
  • TS Kristensen et al.

    The Copenhagen Psychosocial Questionnaire—a tool for the assessment and improvement of the psychosocial work environment

    Scand J Work Environ Health

    (2005)
  • H Feveile et al.

    Danish Work Environment Cohort Study 2005: from idea to sampling design

    Stat Transit

    (2007)
  • M Kivimäki et al.

    Socioeconomic position, co-occurrence of behavior-related risk factors, and coronary heart disease: the Finnish Public Sector Study

    Am J Public Health

    (2007)
  • M Goldberg et al.

    Cohort profile: the GAZEL Cohort Study

    Int J Epidemiol

    (2007)
  • K Korkeila et al.

    Non-response and related factors in a nation-wide health survey

    Eur J Epidemiol

    (2001)
  • M Nielsen et al.

    The Intervention Project on Absence and Well-being (IPAW): design and results from the baseline of a 5-year study

    Work and Stress

    (2002)
  • M Hooff van et al.

    The Netherlands working conditions survey. Highlights 2003–2006

  • W de Groot et al.

    The Dutch system of official social surveys

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