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Working extended hours increases the risk of recurrent cardiovascular events

Although working long hours is known to increase the risk of cardiovascular events, whether the risk remains elevated in those returning to work after an adverse cardiac event is less clear.

In a 2015 systematic review, it was shown how long working hours increased the risk of stroke and cardiovascular disease. Moreover, this risk is higher in those with existing cardiometabolic disease than in those without. Nevertheless, what is less clear, is if the risk of a recurrent cardiovascular event remains elevated in those who have already suffered a prior cardiac event and then return to work. This led a team from the department of social and preventative medicine, Laval University, Quebec, Canada, to longitudinally examine the risk of a subsequent cardiovascular event among patients who had returned to work after a myocardial infarction (MI). The team recruited patients from 30 hospitals across Quebec and included those younger than 60 years of age who had an MI and planned to return to work for a minimum of 10 hours per week within 18 months of their MI. Data on demographics, hospital readmissions and coronary heart disease (CHD) risk factors was collected an average of 6 weeks after returning to work and then after 2 and 6 subsequent years. In the follow-up interviews, the team collected information on any hospital readmissions and information on recurrent CHD events obtained from hospital databases. For the study, long working hours were defined as greater than 55 hours/week and CHD events were a composite of fatal CHD, nonfatal MI and unstable angina. Job strain was defined in terms of an 18-item questionnaire and which includes components related to psychological impact, intellectual demands and decision-making. For the subsequent analysis, the authors included several covariates including sociodemographic factors, attendant CHD risk factors and lifestyle factors such as exercise, alcohol consumption, smoking etc.

In total, 967 individuals aged 35 to 59 years were followed-up for a mean of 5.9 years and a higher proportion of men reported working > 55 hours/week (10.7% vs 1.9%, male vs female). Recurrent CHD events occurred among 205 participants and long working hours (i.e., > 55 hrs/week) was associated with a 2-fold increased risk of a recurrent CHD event (hazard ratio, HR = 2, 95% CI 1.36 – 2.95) and this risk remained elevated and significant after adjustment for covariates, (HR = 1.67, 95% CI 1.10 – 2.53). In addition, those exposed to the highest job strain and working > 55 hrs/week, also had a higher risk of recurrent CHD events (HR = 2.55).

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In discussing their results, the authors note how the data strongly suggests that working long hours and exposed to high job strain were significant factors in the recurrence of a CHD event. However, they also recognised that it was not possible to prove that working longer hours adversely affected CHD health because this may have been due to a change in other factors such as higher levels of smoking, greater inactivity or alcohol consumption etc.

The authors concluded that long working hours should be assessed as part of the early routine clinical follow-up of patients to improve the prognosis for post-MI patients.

Trudel X et al. Long working hours and risk of recurrent coronary events. J Am Coll Cardiol 2021;77:1616-25.