People who work long hours are at a greater risk of stroke and coronary heart disease than people who work a standard week, according to the largest study of the issue to date, published in The Lancet.
The research showed that working for 55 hours or more a week increased the risk of stroke by 33% and the risk of coronary heart disease by 13% compared with working a standard 35 to 40 hour week. The findings suggest that individuals who work long hours need to pay more attention to managing any vascular risk factors.
Furthermore, the risk of stroke increased the more hours people worked; compared with working standard hours, those who worked between 41 and 48 hours had a 10% greater risk of stroke, while those who worked 49 to 54 hours had a 27% greater risk.
The study authors write:
Sudden death from overwork is often caused by stroke and is believed to result from a repetitive triggering of the stress response,”
“Behavioural mechanisms, such as physical inactivity, might also link long working hours and stroke; a hypothesis supported by evidence of an increased risk of incident stroke in individuals who sit for long periods at work.
“Physical inactivity can increase the risk of stroke through various biological mechanisms and heavy alcohol consumption – a risk factor for all types of stroke – might be a contributing factor because employees working long hours seem to be slightly more prone to risky drinking than are those who work standard hours.”
Mika Kivimäki, Professor of Epidemiology (University College London, UK) and colleagues performed a systematic review and meta-analysis of published and unpublished studies involving more than 600,000 individuals from the USA, Europe and Australia and examined the effects of a longer working week on cardiovascular disease.
For stroke, the team pooled and analysed data from 17 studies involving almost 530,000 men and women who were followed for an average of 7.2 years. For coronary heart disease, data was analyzed from 25 studies involving 603,838 men and women who were followed for a median of 8.5 years.
"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,” says Kivimäki.
Dr Tim Chico, reader in cardiovascular medicine at the University of Sheffield says that for many people, it would be very difficult or even impossible to cut down their working hours. However, he also suggests:
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,” concludes Chico.