Nobody likes having to work long hours, but a new study provides alarming evidence for why you should just be strong and tell your boss you're heading home for the night. According to researchers in the UK, those who work longer hours during the week significantly increase their chances of having a stroke.

In the largest research project of its kind, researchers from University College London reviewed 25 studies involving more than 600,000 men and women from across Europe, the US, and Australia. Looking at the data, they found that those working 55 hours or more per week had a 33 percent greater risk of stroke than those working a more balanced 35–40 hour work week. Working the longer set of hours also brings with it a 13 percent increased risk of developing coronary heart disease.

"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," said Mika Kivimäki, professor of epidemiology, in an announcement of the results. "Health professionals should be aware that working long hours is associated with a significantly increased risk of stroke, and perhaps also coronary heart disease."

The researchers found a clear pattern that the longer you work, the higher your risk for stroke and heart disease is - even when taking into account other known risk factors such as age, sex, and socioeconomic status, plus behaviour modifiers such as smoking, alcohol consumption, and physical activity. Working between 41 to 48 hours gives you a 10 percent higher risk of stroke, which jumps to a 27 percent increased risk if you work 49 to 54 hours.

The findings, published in The Lancet, could have major implications for the way we approach the concept of work and the working week. Leaving aside all the obvious humane, social concerns, even from an economic standpoint 'burning the midnight oil' just doesn't make sense. Given the staggering amounts of money we have to spend to treat and manage cardiovascular disease, it will be hard for policy makers to ignore what the research is saying.

"Long working hours are not a negligible occurrence… For all OECD countries, a mean of 12 percent of employed men and 5 percent of employed women work more than 50 hours per week," said Urban Janlert, a researcher from Umeå University in Sweden, who was not involved with the research.

"Although some countries have legislation for working hours – eg. the EU Working Time Directive gives people the right to limit their average working time to 48 hours per week – it is not always implemented. Therefore, that the length of a working day is an important determinant mainly for stroke, but perhaps also for coronary heart disease, is an important finding."

In addition to cutting down our hours, workplaces should also consider implementing a policy of work-time power naps, which have been shown to be beneficial to our health in a number of ways. Hey, their most important resource is us, right? Right.