A person who works 55 hours or more per week has a 33 percent greater risk of having a stroke and a 13 percent increased risk of developing coronary heart disease, compared to colleagues with a standard 35- to 40-hour work week, according to a large analysis published in The Lancet
Researchers at University College London conducted a systematic review and meta-analysis of published studies and unpublished individual-level data examining the effects of longer working hours on cardiovascular disease.
“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 lead researcher Mika Kivimäki, Ph.D., professor of epidemiology.
“Health professionals should be aware that working long hours is associated with a significantly increased risk of stroke, and perhaps also coronary heart disease.”
In the first analysis, researchers looked at data from 25 studies involving 603,838 men and women from Europe, the U.S., and Australia who were followed for an average of 8.5 years. They found a 13 percent increased risk of incident coronary heart disease (a new diagnosis, hospitalization, or death) in people working 55 hours or more per week compared with those putting in a normal 35 to 40 hour week.
The findings were consistent even after taking into account risk factors such as age, sex, and socioeconomic status.
Another analysis of 17 studies involving 528,908 people who were followed 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.
The link remained consistent even after taking into account health behaviors such as smoking, alcohol consumption, and physical activity, and standard cardiovascular risk factors including high blood pressure and high cholesterol.
In fact, 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.
Although the causal mechanisms of these relationships need to be better understood, the researchers suggest that 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.
Source: The Lancet