Putting in long shifts may put extra strain on the heart, experts believe
People who regularly put in overtime and work 10 or 11-hour days increase their heart disease risk by nearly two-thirds, research suggests.
The findings come from a study of 6,000 British civil servants, published online in the European Heart Journal.
After accounting for known heart risk factors such as smoking, doctors found those who worked three to four hours of overtime a day ran a 60% higher risk.
Experts said the findings highlighted the importance of work-life balance.
Overall, there were 369 cases where people suffered heart disease that caused death, had a heart attack or developed angina.
And the number of hours spent working overtime appeared to be strongly linked in many cases.
The researchers said there could be a number of explanations for this.
People who spend more time at work have less time to exercise, relax and unwind.
They may also be more stressed, anxious, or have depression.
A career-minded person will also tend to be a "Type A" personality who is highly driven, aggressive or irritable, they say.
"Employees who work overtime may also be likely to work while ill - that is, be reluctant to be absent from work despite illness," they add.
Lead researcher Mianna Virtanen, an epidemiologist at the Finnish Institute of Occupational Health in Helsinki and University College London, said: "More research is needed before we can be confident that overtime work would cause coronary heart disease."
Cathy Ross, senior cardiac nurse at the British Heart Foundation, which part-funded the research, said: "This study raises further questions about how our working lives can influence our risk of heart disease.
"Although the researchers showed a link between working more than three hours overtime every day and heart problems, the reasons for the increased risk weren't clear.
"Until researchers understand how our working lives can affect the risk to our heart health, there are simple ways to look after your heart health at work, like taking a brisk walk at lunch, taking the stairs instead of the lift, or by swapping that biscuit for a piece of fruit."
Dr John Challenor, from the Society of Occupational Medicine, said: "In many ways it confirms what we as occupational health doctors already know - that work/life balance plays a vital role in well-being.
"Employers and patients need to be aware of all of the risk factors for coronary heart disease and should consider overtime as one factor that may lead to a number of medical conditions."