Long working hours may increase the risk of a stroke

In a recent survey published in The Lancet, reports suggested that people with the habit of working extra hours are more likely to incur a stroke.

The survey conducted by Mika Kivimäki, Professor of Epidemiology at University College London, UK, and her colleagues on over 600000 individuals revealed that people with 55 or more hours of work over a course of a week runs to a 33 percent greater risk of stroke and a modest 13 percent increased risk of developing coronary heart disease compared with working a standard 35 to 40 hour week.

As many as 603838 people from Europe, The USA and Australia were followed for an average 8.5 years and 25 studies later, the data accumulated found a 13 percent increased risk of incident coronary heart disease. This result was oblivious to sex, caste and socio-economic backgrounds.

Analysis of data from 17 studies involving 528908 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. This association remained even after taking into account health behaviours such as smoking, alcohol consumption, and physical activity, and standard cardiovascular risk factors including high blood pressure and high cholesterol.

Kivimäki said, “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. Health professionals should be aware that working long hours is associated with a significantly increased risk of stroke, and perhaps also coronary heart disease.”

Although the causal mechanisms of these relationships need to be better understood, the authors 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.

Dr Urban Janlert from Umeå University in Sweden points out, “Long working hours are not a negligible occurrence. Among member countries of the Organisation for Economic Cooperation and Development (OECD), Turkey has the highest proportion of individuals working more than 50 h per week (43%), and the Netherlands the lowest (<1%). For all OECD countries, a mean of 12% of employed men and 5% of employed women work more than 50 h per week. Although some countries have legislation for working hours—eg, the EU Working Time Directive (2003/88/EC) gives people the right to limit their average working time to 48 h per week—it is not always implemented. Therefore, that the length of a working day is an important determinant mainly for stroke, but perhaps also for coronary heart disease, is an important finding.”