Working 55 hours or more per week might be associated with greater risk of stroke and developing coronary heart disease compared with working a standard 35 to 40 hour week, according to a study published Thursday in the journal The Lancet.
The study was led by researchers from University College London. They did a systematic review and meta-analysis of published studies and unpublished individual-level data examining the effects of longer working hours on cardiovascular disease.
Analysis of data from 25 studies involving 603,838 men and women from Europe, theUnited States, and Australia who were followed for an average of eight and a half years, found a 13 percent increased risk of incident coronary heart disease in people working 55 hours or more per week compared with those putting in a normal 35 to 40 hour week.
Meanwhile, analysis of data from 17 studies involving 528,908 men and women who were followed up for an average of 7.2 years, found a 1.3 times higher risk of stroke in individuals working 55 hours or more a week compared with those working standard hours.
Importantly, the researchers found that the longer people worked, the higher their chances of a stroke. For example, compared with people who worked standard hours, those working between 41 and 48 hours had a 10 percent higher risk of stroke, and those working 49 to 54 hours had a 27 percent increased risk of stroke.
"The pooling of all available studies on this topic allowed us to investigate the association between working hours and cardiovascular disease risk with greater precision than has previously been possible," said Prof. Mika Kivimaki, who led the study.
The researchers said increasing health-risk behaviors, such as physical inactivity and high alcohol consumption, as well as repetitive triggering of the stress response, might increase the risk of stroke, although the causal mechanisms of these relationships need to be better understood.