If you ever needed an excuse or three to leave work on time then this could be it.
New research shows that people working 55 hours a week or more are over a third more likely to suffer a stroke than those working a 35 to 40 hour week. They are also 13% more likely to suffer a heart attack.
The largest study conducted on the issue, carried out in three continents and led by scientists at University College London, makes a clear statement on the dangers of burning the midnight oil.
The researchers, who published their findings in the Lancet medical journal, cannot state categorically that long hours cause people to have strokes – but their study shows that there is a link between the two.
And this correlation increases the longer the hours that people put in at the office.
But strokes and heart disease aren’t the only risks involved in working longer hours - there’s also research to suggest that it can make you unproductive, depressed and give you diabetes.
In need of an excuse to leave at 5.30pm on the dot tonight? Look no further - we've rounded up three reasons why it can do more harm than good:
It gives you a foggy brain
There is one thing essential for productivity: the movement of muscles to pump fresh blood and oxygen through to the brain and trigger the release of mood-enhancing chemicals. When we are sedentary for a long time everything slows in the body, including our brain function.
Research that attempts to quantify the relationship between hours worked and productivity found that employee output falls sharply after a 50-hour work-week, and falls off a cliff after 55 hours - so much so that someone who puts in 70 hours produces nothing more with those extra 15 hours, according to a study published last year by John Pencavel of Stanford University.
It can trigger depression
According to researchers at University College London, stressful work conditions - including long work hours - can double your risk of depression. British experts said working alone at a computer for hours on end could lead to a sense of isolation, even in a busy office.
Psychology Professor Cary Cooper from the University of Manchester Institute of Science and Technology says concern is growing over mental health problems caused by working long hours at computers.
“We are finding that people are working with machines as opposed to other people,” he said. “The problem is not just sitting in front of a computer but the fact that people don't take a break and cannot prioritise what they are doing. They are overloaded then they worry about the work they are not doing.
“People are not interacting with each other and the longer you do that, the less work meets your social needs.”
Professor Brian Shackel, from Loughborough University, agrees: “Even in a full office, the likelihood is staff would have targets to meet, so the opportunities for social chit-chat would be considerably diminished.”
It can cause diabetes
A study of more than 4,000 civil servants found that those who spend less than 12 hours sitting down a week can decrease their risk of diabetes by 75%, and that those who sit more than 25 hours per week increase the chance developing metabolic risk factors like “bad” cholesterol and insulin resistance. The study was published by the British Journal of Sports Medicine.
Taking into consideration smoking, waist circumference, dietary quality, exercise habits and other variables, the scientists were able to isolate the specific effect that the hours of sitting seemed to be having on people’s life spans: Every single hour of television watched after the age of 25 reduces the viewer’s life expectancy by 21.8 minutes.
By comparison, smoking a single cigarette reduces life expectancy by about 11 minutes, the authors said.
Dr John Buckley from the University of Chester, found that if you stand for three hours a day for five days you burn around 750 calories more than you would sitting. Over the course of a year it would add up to about 30,000 extra calories, or around 8lb of fat.
“If you want to put that into activity levels," Dr Buckley says, “then that would be the equivalent of running about 10 marathons a year. Just by standing up three or four hours in your day at work.”