Before you think about tacking on a few more hours of overtime this week, be forewarned. If you work 10 or 11 hours a day, you are more likely to suffer serious heart problems, an 11-year study finds.

Folks who logged three or more hours of OT had a 60 percent higher risk of heart-related problems. Those problems included non-fatal heart attacks, angina and death due to heart disease.

"Our findings suggest a link between working long hours and increased CHD [coronary heart disease] risk, but more research is needed before we can be confident that overtime work would cause CHD," says Dr. Marianna Virtanen, an epidemiologist at the Finnish Institute of Occupational Health in Helsinki.

"In addition, we need more research on other health outcomes, such as depression and type 2 diabetes."

The study followed 10,000 British civil servants, starting in 1985.

Workers who put in an extra hour or two beyond their seven-hour day didn't have a higher risk, but those who clocked three or four extra hours did.

Researchers say there could be a number of explanations for the connection between overtime and heart disease. Contributing factors, they say, could include Type-A personalities, depression, anxiety, not enough sleep and high blood pressure. What they call "sick presenteeism" -- where you work OT while sick -- also may factor in.

The study's authors say it remains unclear whether the findings would translate to blue-collar workers and private sector employees.

The research is published in the "European Heart Journal."

WTOP's Kristi King contributed to this report.