August 20, 2015

expert reaction to study on long working hours, stroke and coronary heart disease

A possible link between working hours and risk of cardiovascular disease is explored in a paper published in The Lancet journal, with the authors reporting a higher risk for stroke and coronary heart disease in those who worked longer than standard working hours.

Dr Mike Knapton, Associate Medical Director, British Heart Foundation, said:

“This research shows an association between long working hours and an increased risk of having a stroke and heart disease.  It is plausible that there could be a causal relationship behind the link as sudden death following long working hours is often caused by stroke, due to long and repeated periods of stress, although that was not demonstrated in this study. More research is needed if we are to understand and treat the biological mechanisms that can lead to increased risk of stroke and heart disease for people who work long hours.

“This study highlights to doctors that they need to pay particular attention to cardiovascular risk factors when they advise people who work long hours.”

Dr Tim Chico, Reader in Cardiovascular Medicine / consultant cardiologist, University of Sheffield, said:

“This study shows longer working times are associated with a higher (1.3 times greater) risk of suffering a stroke. It does not prove strokes are directly caused by longer working hours, only that there is an “association” between these things. The difference is important as many such associations are not directly causal. However, it is almost certainly impossible to prove whether there is a direct link as this would require thousands of people to be randomly allocated to work more or less hours and followed up for years to see if this changes the risk of stroke, while keeping all other behaviours the same between groups.

“For many people, reducing their working hours would be difficult or impossible, and this study does not show that it would reduce the risk of stroke.

“Most of us could reduce the amount of time we spend sitting down, increase our physical activity and improve our diet while working and this might be more important the more time we spend at work. We should all consider how the working environment could be altered to promote healthy behaviour that will reduce strokes, irrespective of how long we work.”

‘Long working hours and risk of coronary heart disease and stroke: a systematic review and meta-analysis of published and unpublished data for 603 838 individuals’ by Kivimäki et al. published in The Lancet on Thursday 20th August. 

Declared interests

Dr Mike Knapton works at the British Heart Foundation, which part funded this study.

Dr Tim Chico: No interests to declare