Objectives To assess the association between job strain (JS) and the incidence of coronary heart disease (CHD) in North Italian employed men, adopting a stratified analysis by occupational class (OC).
Methods The study was conducted on 4103 working men, CHD-free at baseline, enrolled in population-based and factory-based cohorts. Risk factor measurements and follow-up procedures were carried out adopting the WHO MONICA standardised procedures. OCs were derived from the Erikson-Goldthorpe-Portocarero classification. JS categories were defined based on overall sample medians of psychological job demand (PJD) and decision latitude (DL) derived from items of the Job Content Questionnaire, satisfying construct validity criteria. Age-adjusted and risk factors-adjusted CHD HRs were estimated from Cox models, contrasting high-strain (high PJD and low DL) versus non-high-strain categories.
Results In a median follow-up of 14.6 years, 172 CHD events occurred, corresponding to a CHD incidence rate of 2.78/1000 person-years. In the overall sample, high-strain compared with non-high-strain workers evidenced a 39% excess CHD risk, not statistically significant. No association was found among managers and proprietors. Conversely, the HR of high strain versus non-high strain was 1.78 (95% CI 1.20 to 2.66) among non-manual and manual workers, with no substantial differences between them. The exclusion of the events occurring in the first 3 years of follow-up did not change the results. Adopting the quadrant-term JS groupings, among manual and non-manual workers, high-strain and active (high PJD and high DL) categories in comparison to the low strain one (low PJD and high DL) showed HRs of 2.92 and 2.47, respectively.
Conclusions Our findings support the association of JS and CHD incidence among manual and non-manual workers. The non-high strain may not be the best reference category, when assessing the contribution of JS in determining CHD incidence.
- coronary heart disease
- job strain
- occupational class
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Contributors MMF conceived the research question, drafted the manuscript and is the principal investigator (PI) of the MONICA-Brianza and the SEMM study cohorts. GV and LB were responsible of the statistical analyses, contributed to interpretation of the data and revised the manuscript. GG and GC are the PIs of the PAMELA study and of the MONICA-Brianza cohorts, respectively; they both helped with data interpretation and contributed critically to the Introduction and Discussion sections. All authors read and approved the final version of the paper, and agree 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.
Funding This work and the latest activities of the MONICA Brianza Study were mainly supported by the Health Administration of Regione Lombardia (grant numbers 17155/2004 and 10800/2009). The follow-up was partially supported with grants from the Italian Ministry of Health (grant 2012/597) and it was carried out in collaboration with the Centro di Epidemiologia, Sorveglianza e Promozione della Salute of the Istituto Superiore di Sanità in Roma.
Competing interests None declared.
Ethics approval San Gerardo Hospital, Monza, Italy.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Statistical details are available on request to the corresponding author.
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