Long working hours are dangerous for your heart

Long working hours can lead to irregular heart rhythm, a large scale study shows. 

People that work long hours are at higher risk of developing atrial fibrillation, according to a new large scale study published in the European Heart Journal.

Compared with people that have a normal working schedule, between 35-40 hours a week, those that toil for 55 hours or more are at 40% more likely to develop atrial fibrillation, over the next decade.

 “These findings show that long working hours are associated with an increased risk of atrial fibrillation, the most common cardiac arrhythmia,” Professor Mika Kivimaki, director of the Whitehall II Study, from the Department of Epidemiology at University College London , who led the research, said. “This could be one of the mechanisms that explain the previously observed increased risk of stroke among those working long hours. Atrial fibrillation is known to contribute to the development of stroke, but also other adverse health outcomes, such as heart failure and stroke-related dementia.”

Professor Kivimaki and colleagues from the Individual-Participant-Data Meta-analysis in Working Populations Consortium analysed data from 85,494 men and women from the UK, Denmark, Sweden and Finland who took part in one of eight studies in these countries. They assessed the participants’ working hours and classified them as less than 35 hours a week, 35-40 hours, which was considered as the standard working hours of full-time workers, 41 to 48 hours, 49 to 54 hours, and 55 hours or more a week. None of the participants had atrial fibrillation at the start of the studies.

In the ten-year follow-up period, there were 1061 new cases of atrial fibrillation. This means an incidence rate of 12.4 per 1000 people in the study, but among the 4,484 people working 55 hours or more, the incidence was 17.6 per 1000.

“Those who worked long hours had a 1.4 times higher risk of developing atrial fibrillation, even after we had adjusted for factors that could affect the risk, such as age, sex, socioeconomic status, obesity, leisure time physical activity, smoking and risky alcohol use,” said Prof Kivimaki.

Scientists say further research is needed on the subject but the study shows that working hours, much more than any previous cardio-vascular condition, contributes to developing abnormal heart rhythm.

“A 40% increased extra risk is an important hazard for people who already have a high overall risk of cardiovascular disease due to other risk factors such as older age, male sex, diabetes, high blood pressure, high cholesterol, overweight, smoking and physical inactivity, or living with an established cardiovascular disease. For a healthy, young person, with few if any of these risk factors, the absolute increased risk of atrial fibrillation associated with long working hours is small,” the study shows.

The study does have some limitations, including the fact that working hours were only assessed once at the beginning of the study and that the type of job and whether it involved working night shifts was not recorded.