Job stress raises the risk of heart disease by disrupting the body’s internal systems.

The findings from a long–running study involving more than 10,000 British civil servants also suggest stress–induced biological changes may play a more direct role than previously thought.

The researchers measured stress among the civil servants by asking questions about their job demands such as how much control they had at work, how often they took breaks, and how pressed for time they were during the day.

The team conducted seven surveys over a 12–year period and found chronically stressed workers – people determined to be under severe pressure in the first two of the surveys – had a 68 percent higher risk of developing heart disease. The link was strongest among people under 50.

Stressed workers also eat unhealthy food, smoke, drink and skip exercise – all behaviors linked to heart disease.

In the study, stressed workers also had lowered heart rate variability – a sign of a poorly–functioning weak heart – and higher–than–normal levels of cortisol, a “stress” hormone that provides a burst of energy for a fight–or–flight response.

Too much cortisol circulating in the blood stream can damage blood vessels and the heart.