An increased risk of stroke and coronary heart disease was associated with employees working 55 hours or more per week, according to a study published in the journal The Lancet.

Mika Kivimӓki, professor of Epidemiology at University College London in the United Kingdom, and fellow researchers performed a systematic review and meta-analysis of published studies and unpublished data up to August 20, 2014, to determine if there was a link between long working hours and the incidence of stroke and cardiovascular disease.

An analysis of 25 studies including 603,838 men and women from Europe, United States, and Australia showed a 13% increase in risk of coronary heart disease in people working ≥55 hours per week compared to those working standard hours (35–40 hours per week). The analysis was adjusted for other risk factors including age, sex, and socioeconomic status.

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An analysis of 17 studies including 528,908 men and women showed that people working ≥55 hours per week had 1.3 times greater risk of stroke compared to those working standard hours. Further, people who worked 41–48 hours had a 10% higher risk of stroke, and those working 49–54 hours had a 27% higher risk of stroke.

Overall, working ≥55 hours per week was linked to a significantly increased risk of stroke and possibly coronary artery disease. Researchers believe that the increased risk may be due to physical inactivity, high alcohol consumption, and repetitive triggering of the stress response.

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