Stress can cause a surge of adrenaline that boosts blood pressure and makes blood stickier and more likely to form atherosclerotic plaques. But more research is needed to determine whether stress is involved in the heightened heart disease risk among overtime workers, Williams said.
Whether cutting back work hours would lessen the risk also remains to be seen. And given the current economy, clocking out early is not an option for everyone. But Williams said there are other options -- particularly if stress is in fact the culprit.
"We could stop adrenaline from going up or block its effects," Williams said.
Behavioral interventions, such as stress management training, can minimize the rise in adrenaline during stressful situations. And certain drugs, like beta blockers, can minimize its effects.
But until scientists tease out the link between overtime work and heart attack, workaholics would do well to limit their other controllable risk factors.
"The take home message could be that if a person has to work long hours, it's very important for them to eat healthy food, exercise enough and keep their blood pressure, glucose and cholesterol levels within the healthy limits," Kivimaki said.