Does working more than 8 hours a day raise stroke risk?

The results don’t prove that bigger workloads were responsible for the increased risk of heart disease or stroke, but there are several reasons to think the extra hours were responsible, the researchers wrote.

The British Heart Foundation’s Dr Mike Knapton said: “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”.

Limitations of the study include a lack of data on variables such as the workload, sleeping hours, “the degree to which an employee is engaged in and enthusiastic about doing his or her work”, and the fact not everyone works a set number of hours over their career.

Dr Mika Kivimäki of University College London and colleagues combined a range of previous studies covering more than 600,000 individuals, looking at their self-reported working hours and incidences of heart disease and stroke. Compared to people who worked a standard 35 to 40 hour work week, those who worked between 41 to 48 hours had a 10 percent higher risk of stroke. Worst off were those who worked at least 55 hours per week and saw their stroke risk jump by 33 percent. But the study authors suggest it could be down to increased stress, along with associated unhealthy behaviour like drinking too much alcohol and failing to exercise.

People who work long hours are also more likely to ignore the warning signs, they say – leading to delays in getting treatment.

The researchers identified 528,908 people who were stroke-free when they joined a study. Among developed countries, Janlert noted, Turkey has the highest proportion of individuals working more than 50 hours a week (43 per cent), and the Netherlands the lowest (less than 1 per cent). “Therefore, that the length of a working day is an important determinant mainly for strokes, but perhaps also for coronary heart disease, is an important finding”.

” 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”. Worryingly it is heart surgeons who work some of the longest hours in Britain, with the average consultant spending 61.5 hours at their post each week, the longest of any medical professional.

Dr Tim Chico, Reader in Cardiovascular Medicine / consultant cardiologist, University of Sheffield, added: “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”.

‘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’.