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In fact, people who work three or more hours of overtime a day have a 60% increased risk of heart-related problems such as dying from heart disease, having a heart attack or angina, the researchers noted.
"Be aware of potential risks in excessive overtime work," said study author Marianna Virtanen, an epidemiologist at the Finnish Institute of Occupational Health in Helsinki.
"We do not yet know how long exposure is needed before cardiovascular health is affected," she added. "Short periods of overtime work are not necessarily dangerous to health."
The report is published in the May 12 online edition of the European Heart Journal.
For the study, Virtanen's team collected data on more than 6,000 British civil servants. Over 11 years of follow-up, 369 of these people died from heart disease or had heart attacks or angina.
When the researchers took into account factors such as age, sex, marital status and occupational level, they found those who worked three to four hours of overtime each day, but not one to two hours, increased their risk for heart disease by 60%.
When Virtanen's group looked at 21 other risk factors, there was little difference in the findings.
"Working overtime may be a risk for some individuals in terms of cardiovascular health," Virtanen said.
"Mechanisms that relate to this risk may be unhealthy lifestyle, stress, depression and lack of sleep," she said. "People who work long hours may also be those who ignore their early symptoms and are less likely to go to physical health check-ups."
While it isn't clear why working overtime increases the risk for heart disease, Virtanen's team speculates that the people who choose to work overtime may be those with so-called type A personalities.
This makes them more aggressive, competitive, tense, time-conscious and generally hostile. They may also have signs of depression and anxiety, and may not get enough sleep, or not enough time to relax before going to sleep.
It is also possible that people who have more freedom over work-related decisions may have a lower risk of heart disease even if they work overtime, the researchers added.
Yet another possibility is that the chronic stress, associated with working long hours, has an adverse effect on health.
Dr. Gregg C. Fonarow, director of the Ahmanson-UCLA Cardiomyopathy Center at the University of California, Los Angeles, said that "emerging data suggest that consistently working overtime may be associated with adverse health status including hypertension, sleep deprivation, lack of exercise and depression."
There have also been studies suggesting a higher risk of cardiovascular events such as heart attack or stroke with excess overtime work, he said.
"There are a number of potential mechanisms by which excess overtime work could adversely impact cardiovascular event risk including increased stress, excess sympathetic nervous system activity, increased exposure to secondhand smoke, unhealthy dietary habits, less time to exercise, and individuals with excess overtime work being less included to seek timely and appropriate medical care," Fonarow said.
Further studies should examine whether these findings apply to other populations and whether reductions in overtime work or other interventions reduce cardiovascular risk, he added.
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