Workplace stress can be fatal, particularly to middle-aged workers who have already suffered a heart attack, new Canadian research shows.
The study, published in today's edition of 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.
"It's a pretty big risk and substantial population who are at risk," said Corine Aboa-Éboulé, a Montreal cardiologist and co-author of the study.
"Generally speaking, we don't take workplace stress and its impact on the heart seriously enough."
About 70,000 Canadians a year suffer heart attacks and more than 18,000 of them die, according to the Heart and Stroke Foundation of Canada.
Tony Di Nardo, a bus driver in Mississauga, Ont., said his job was extremely stressful with the challenges of commuter traffic, pressure to be on time and constant worries about passenger safety.
"There's all sorts of things coming up," he said. "Your mind is always going, and you're always worried."
Mr. Di Nardo, 55, suffered a first heart attack in June, 2006, and a second in October, 2006.
When he returned to work last February, it was with lighter duties and a lot less stress.
Dr. Aboa-Éboulé conducted the research as part of her PhD thesis at Laval University in Quebec City.
She 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."
Earlier studies looked at the impact of stress on healthy workers and found it can damage the heart.
Biologically, stress triggers the body's endocrine system, releasing hormones that influence inflammation and damage the immune system.
In particular, stress can drive up blood pressure, a leading cause of heart attacks. People under stress also tend to neglect their health, sleeping and eating poorly, smoking and drinking to excess, and eschewing exercise.
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.
The patients were interviewed at regular intervals during the research, particularly about their work conditions.
Brian Baker, a cardiology psychiatrist and spokesman for the Heart and Stroke Foundation, said job stress can have a profound effect on workers, particularly those with heart disease.
"It is true that work can kill you if you are a person who has a vulnerability to heart disease," he said.
Dr. Baker said the studies "highlight the importance of changing what you can: Decrease the demands of work, increase the control at work. This can make you more healthy."
A second study, also published in today's edition of JAMA, shows that in addition to cardiovascular disease, stress is a major contributor to depression.
Sheldon Cohen, a psychologist at Carnegie Mellon University in Pittsburgh, said that "social stressors" such as divorce and the death of a loved one are the biggest culprits in depression.
Depression is also common among people who have been diagnosed with a serious illness, suggesting that physical disease itself is a stressful event that can lead to depression, Dr. Cohen said.