Following a systematic review and meta-analysis of various published and unpublished studies, the research team of Mika Kivimäki, Professor of Epidemiology at University College London, UK discovered that working for 55 or more hours a week increases the risk of stroke by 33 percent, and the risk of coronary heart disease by 13 percent. These results were in comparison to standard working hours of 35 to 40 hours a week.

Data Accumulation And Analysis

In the largest study of this field, researchers compared individual-level data of more than 600,000 participants to examine the effects of longer working hours on cardiovascular ailments. They analyzed 25 studies, including both men and women, from Europe, Australia and the US. The individuals were followed for about 8.5 years, and the results obtained were controlled for age, gender and socioeconomic status.

In another analysis of 17 studies, consisting of 528,908 men and women who were followed for about 7.2 years, the stroke risk associated with longer working hours was 1.3 times higher as compared to standard hours. The association withstood even after controlling for factors such as smoking, drinking, physical activity, blood pressure and cholesterol.  

More importantly, the researchers observed that the longer the working hours, the greater the stroke risk. It was seen that working between 41 and 48 hours increased the risk of having a stroke by 10 percent; those working between 49 to 54 hours had a 27 percent increased risk.

Inferences And Precautions

Published in The Lancet, the authors state that health-risk behaviors, such as lack of physical activity and alcohol consumption, combined with repetitive work-related stress, could significantly increase the risk of stroke.

“Pooling together all available studies on this topic permitted us to explore the association between working hours and the risk of developing cardiovascular disease with greater precision than has previously been possible”, explained Professor Kivimäki. “Health professionals should be aware that working long hours is linked with a significantly increased risk of stroke, and perhaps also coronary heart disease”.