Workers working overnight shift
A worker stands next to a light stand as another worker sleeps after an overnight shift at a road construction site in Colombo, early morning January 4, 2014. Reuters

Working longer hours during the week could significantly increase chances of having a stroke, a new study suggests. The study provides evidence that those who work 55 hours or more per week are linked to a 33 percent greater risk of stroke.

The study, published in The Lancet, shows the analysis of data from 25 studies involving 603,838 men and women across Europe, the US, and Australia who were followed for an average of 8.5 years. Researchers found the higher possibility of stroke may still occur even when taking into account other known risk factors such as age, sex, and socioeconomic status of the person.

Researchers from University College London also discovered working less than 55 hours may also increase the risk, compared with people who worked the standard 35 to 40 hours a week. Working 41 to 48 hours gives a 10 percent higher risk of stroke, and those who work 49 to 54 hours had a 27 percent higher risk of stroke.

The association of the increasing risk of stroke to longer hours of working remained even after the researchers have taken into account health behaviours such as smoking, alcohol consumption and physical activity. Working overtime was also found linked to a 13 percent increased risk of developing coronary heart 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 Mika Kivimäki, professor of epidemiology, in a report of the results. “Health professionals should be aware that working long hours is associated with a significantly increased risk of stroke, and perhaps also coronary heart disease.”

The findings could change the way that business approaches the concept of work and the working week, researchers said, although the causal mechanisms of the relationship of working longer hours and the health risks need more understanding. The researchers suggest that physical inactivity and high alcohol consumption, as well as repetitive triggering of the stress response, are also the health-risk behaviours that may increase the risk of stroke.

Contact the writer at or tell us what you think below