Working Long Hours May Increase Odds of Second MI

Among patients who return to work after a first myocardial infarction (MI), those who work more than 55 hours per week, compared to those working an average full-time job of 35-40 hours a week, may increase their odds of having a second MI by about twofold, according to a prospective cohort study published March 29 in the Journal of the American College of Cardiology.

Xavier Trudel, PhD, et al., recruited 967 patients from 30 hospitals across Quebec, Canada, between 1995 and 1997. Patients had a history of MI, were younger than 60 years of age, held a paying job within the year prior to their MI and planned to return to work. Follow-up interviews and questionnaires were conducted over the next six years. Based on their total weekly working hours, individual participants were placed into four categories: 1) part-time (21-34 hours/week), 2) full-time (35-40 hours/week), 3) low overtime (41-54 hours/week) and 4) medium/high overtime (>55 hours/week).

Using an assessment questionnaire, the researchers measured levels of stressful work through job strain. If a participant had high psychological demands at work (quantity of work, time constraints and level of intellectual effort required) and low decision control (opportunities for learning, autonomy and participation in the decision-making process), they were classified as having job strain. In addition, social support in and out of work were measured.

Results showed that during the study period, 21.5% of participants had a second MI. In addition, working long hours was associated with about a twofold increase in the risk of a second MI. Men were more likely to be working medium/high overtime hours (10.7% of men vs. 1.9% of women), as well as younger workers. Further, those with worse lifestyle risk factors (smoking, alcohol intake, physical inactivity) and those who worked a more stressful job were also more likely to be in the medium/high overtime category.

"To reduce the risk of coronary heart disease recurrence, secondary prevention interventions aimed at reducing the number of working hours should be evaluated in future studies," Trudel said. "Long working hours should be assessed as part of early and subsequent routine clinical follow-up to improve the prognosis of post-heart attack patients."

In an accompanying editorial comment, Jian Li, MD, PhD, and Johannes Siegrist, PhD, said the study results have important implications for clinical practice, such as more comprehensive measures for secondary prevention for MI patients. "The study provides a new piece of research evidence that work-related factors play an important role in coronary heart disease prognosis," they explain. "Occupational health services are urgently needed to be incorporated into secondary prevention of cardiovascular disease."

Clinical Topics: Prevention, Smoking

Keywords: Middle Aged, Occupational Health Services, Cardiovascular Diseases, Secondary Prevention, Return to Work, Employment, Risk Factors, Social Support, Smoking, Myocardial Infarction, Coronary Disease, Prognosis, Cardiology, Alcohol Drinking, Hospitals, Decision Making

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