The likely toll of long working hours is revealed in a major new study. In the study it shows that employees still at their desks into the evening run an increased risk of developing a stroke – and the longer the hours they put in, the higher the risk. The largest study conducted on the issue, carried out in three continents and led by scientists at University College London, found that those who work more than 55 hours a week have a 33% increased risk of stroke compared with those who work a 35- to 40-hour week. They also have a 13% increased risk of coronary heart disease.
The findings will confirm the assumptions of many that work a long-hours culture working well into the evening, with work also intruding into weekends, is harmful to health. The researchers, publishing their findings in the Lancet medical journal, say they cannot state categorically that long hours cause people to have strokes – but their study shows that there is a link, and it gets stronger as the hours people put in get longer.
“Sudden death from overwork is often caused by stroke and is believed to result from a repetitive triggering of the stress response,” they write. “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.”
People who work long hours are also more likely to ignore the warning signs, they say – leading to possible delays in getting treatment. Mika Kivimäki, professor of epidemiology at UCL, and colleagues looked separately at heart disease and at stroke. For coronary heart disease, they pulled together 25 studies involving more than 600,000 men and women from Europe, the USA and Australia who were followed for an average of 8.5 years.
They then pooled and analysed the data that had been collected. This produced the finding of a 13% increase in the chances of a new diagnosis of heart disease or hospitalisation or death. For stroke, they analysed data from 17 studies involving nearly 530,000 men and women who were followed up for an average of 7.2 years. They found a 1.3 times higher risk of stroke in individuals working 55 hours or more, compared with those working a standard 35- to 40-hour week.