Working late again? You could be putting yourself at higher risk of having a stroke.
New research in the UK has found working 55 hours a week instead of 40 makes it 33 percent more likely you'll suffer a stroke and 13 percent more likely you'll develop coronary heart disease.
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.
After adjusting for other factors, they found a strong link between long hours and stroke, and a weaker correlation with heart disease.
Writing in journal The Lancet, the researchers outlined some possible causes of the links.
"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," they suggest.
"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."
In an accompanying editorial, Urban Janlert of the Department of Public Health and Clinical Medicine at Umea University in Sweden called the research "pioneering".
Because stroke is rarer in people of working age than heart disease, he says it's possible this large study has picked up something smaller studies have missed.
"Working conditions are important determinants of people's health. Some of these conditions might be difficult to change because of the nature of the work (underground work, climate conditions, or toxic exposures), but the length of a working day is a human decision.
"Essentially, if long working hours present a danger to health, it should be possible to change them, which is not always the case with other work environmental factors."
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.