Objectives Several recent large-scale studies have indicated a prospective association between job strain and coronary heart disease, stroke and diabetes. Job strain is also associated with poorer mental health, a risk factor for cardiometabolic disease. This study investigates the prospective relationships between change in job strain, poor mental health and cardiometabolic disease, and whether poor mental health is a potential mediator of the relationship between job strain and cardiometabolic disease.
Methods We used data from five cohort studies from Australia, Finland, Sweden and UK, including 47 757 men and women. Data on job strain across two measurements 1–5 years apart (time 1 (T1)–time 2 (T2)) were used to define increase or decrease in job strain. Poor mental health (symptoms in the top 25% of the distribution of the scales) at T2 was considered a potential mediator in relation to incident cardiometabolic disease, including cardiovascular disease and diabetes, following T2 for a mean of 5–18 years.
Results An increase in job strain was associated with poor mental health (HR 1.56, 95% CI 1.38 to 1.76), and a decrease in job strain was associated with lower risk in women (HR 0.70, 95% CI 0.60–0.84). However, no clear association was observed between poor mental health and incident cardiometabolic disease (HR 1.08, 95% CI 0.96–1.23), nor between increase (HR 1.01, 95% CI 0.90–1.14) and decrease (HR 1.08, 95% CI 0.96–1.22) in job strain and cardiometabolic disease.
Conclusions The results did not support that change in job strain is a risk factor for cardiometabolic disease and yielded no support for poor mental health as a mediator.
- mental health
- diabetes mellitus
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Contributors All authors contributed to the conception and design of the study, interpretation of data and critical revision of the manuscript for important intellectual content; gave approval of the version to be published; and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. LMH, JV, SS, MK and HW contributed to data acquisition, and LMH and JP contributed to the analysis of data for the work. LMH drafted the paper. JP had full access to data from FPS and HeSSup. LMH had full access to individual participant data from HILDA, SLOSH and WHII and takes responsibility for the integrity of the unpublished data and the accuracy of the data analysis.
Funding The study was financially supported by the NordForsk, the Nordic Programme on Health and Welfare (grant number 75021). MK was also supported by the Medical Research Council (K013351). The funders had no role in the design or in the collection, analysis, interpretation of data, writing of the report or decision to submit the article for publication. This paper uses unit record data from the Household, Income and Labour Dynamics in Australia (HILDA) Survey. The HILDA Project is initiated and funded by the Australian Government Department of Social Services (DSS) and is managed by the Melbourne Institute of Applied Economic and Social Research (Melbourne Institute). The findings and views reported in this paper, however, are those of the authors and should not be attributed to either DSS or the Melbourne Institute.
Competing interests None.
Patient consent for publication Not required.
Ethics approval Ethical approval was given for each cohort in each country from relevant ethical committees/boards. The Finnish Public Sector study was approved by the ethics committee of the Finnish Institute of Occupational Health (60/13/03/00/2011), and Health and Social Support study was approved by the concurrent joint ethics committee of the University of Turku and the Turku University Central Hospital. The Household, Income and Labour Dynamics in Australia study was approved by both the human research ethics committee of University of Melbourne and the ethics committee of the Australian Institute of Health and Welfare. The Swedish Longitudinal Occupational Survey of Health was approved by the Regional Research Ethics Board in Stockholm (2006/158-31, 2008/240-32, 2008/1808-32, 2010/0145-32, 2012/373-31/5, 2013/2173-32 and 2015/2187-32). The Whitehall II study was approved by the University College London Medical School committee on the ethics of human research. Informed consent was obtained for all participants.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement No data are available.
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