Workplace stress can be fatal, particularly to middle-aged workers who have already suffered a heart attack, new Canadian research shows.

The study, published this week in the Journal of the American Medical Association, found that workers who go back to a chronically stressful job after an initial heart attack have twice the risk of a second "coronary heart event" — heart attack, unstable angina, death — as those who return to work in a more laid-back environment.

The study is the first to link job anxieties with recurrent heart attacks and other major events, the report's authors said.

"Generally speaking, we don't take workplace stress and its impact on the heart seriously enough," said Corine Aboa-Éboulé, a cardiologist and co-author of the study, conducted by researchers from Laval University in Quebec.

Dr. Aboa-Éboulé said the findings should not be interpreted as suggesting people with heart disease cannot return to work, but rather that the workplace should change and rehabilitation programs should teach coping skills.

"Work is beneficial to health — that is well-established," she said. "But chronic stress is not beneficial."

The new study focused on middle-aged workers who returned to paid employment after suffering a heart attack. A total of 972 women and men, aged 35 to 59, participated between February 1996 and June 2005.

They returned to work, on average, within six weeks of having a heart attack.

The researchers monitored the patients for about six years, and during that period 206 participants suffered a second cardiovascular event — including 13 fatal heart attacks, 111 non-fatal heart attacks and 82 cases of unstable angina.

After adjusting for risk factors for heart disease, as well as lifestyle, sociodemographic and work-environment characteristics, workplace stress doubled the odds of such heart troubles, the team found.