CMHC Pulse Blog

As the leading cause of death and disability across the globe, ischemic heart disease is a chief driver of disease burden worldwide. Continuous research efforts have been working to identify risk factors, confounding variables, and other disease characteristics that can impact both patient risk and health outcomes.

Increasing evidence points to the significance of the workplace environment as a potential setting for cardiometabolic health improvement and prevention techniques. More specifically, research has linked long working hours (LWH) to increased risk of ischemic heart diseases (IHD) however, study findings have been mixed and have not examined the impact of exposure duration.

A recent study published in the Journal of the American Heart Association aimed to investigate the associations between cumulative exposure to long working hours and the incidence of ischemic heart disease.

Cumulative Exposure to Long Working Hours

As part of the retrospective study, the team of investigators analyzed participants of the French population-based cohort study CONSTANCES. Data from part-time employees and subjects who reported cardiac events in the 5 years before exposure were not included. Researchers administered self-assessments and clinical examinations to obtain subjects’ age, sex, body mass index, occupational status, smoking habits, blood pressure, diabetes status, familial history of cardiovascular disease, dyslipidemia, exposure to long working hours, and duration of exposure. Long working hours were defined as values above 10 hours per day for a minimum of 50 days per year; the main outcome was a reported history of ischemic heart disease, myocardial infarction, or angina pectoris during clinical examinations.

Out of 137,854 participants, nearly 70,000 were males. In total, there were 1,875 (1.36%) reported cases of IHD; exposure to LWH occurred at a rate of 30.8%. Among this group, 14,474 or 10.5% reported exposure for a duration of at least 10 years.

LWH Associated with Increased IHD Risk in Men

The researchers reported that exposure to LWH greater than 10 years was significantly associated with an increased risk of ischemic heart disease; the results were even stronger after the exclusion of patients with angina pectoris. However, in stratified analyses, the results did not persist in the women, regardless of angina pectoris. Interestingly, study findings reveal that increased IHD risk was similar without adjusting for diabetes and blood pressure levels.

Explaining the observed differences, researchers suggest a lack of statistical power given low incidence of IHD among women and the exclusion of part-time employees (primarily women) from the sample. “The observed sex differences in our study and others are worth future exploration to examine other potential explanations including differently gendered work and sex-specific worker survivor effects, changes in work trajectory attributable to child-rearing, diagnostic biases and other cultural and biological differences,” Marc Fadel, MD, of the French National Institute of Health and Medical Research, and colleagues noted .

The latest evidence from the population-based study indicates that cumulative exposure to long working hours has a detrimental effect on cardiometabolic health, especially in the case of increased IHD risk in men. As such, future research efforts should not only explore the underlying causes of differences in IHD incidence between sexes, but also investigate potential preventative strategies aimed at reducing both the exposure and duration of long working hours to improve cardiovascular health outcomes.

“Intervention and implementation research should address the reduction of cumulative exposure to long working hours as a step toward attenuating the global burden of work-related ischemic heart disease,” the authors wrote.


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