FORTUNE — Americans work longer hours, take fewer vacations, and retire later than employees in most other industrialized countries, so it figures that many of us are prime candidates for job burnout — the physical and cognitive exhaustion that comes from too much stress at work over a long period of time.
Even so, when researchers at the business and medical schools at Tel Aviv University teamed up to see if they could find a link between job burnout and heart disease, they got a surprise: The most disenchanted employees developed heart problems at a 79% higher rate than their less-stressed peers.
“This is alarming and much more extreme than we expected,” says Sharon Toker, who led the study, which was published in the journal Psychosomatic Medicine. The findings suggest that job burnout is “a stronger predictor of coronary heart disease than many other known risk factors, including blood lipid levels, physical activity, and smoking.
“Some of the factors that contribute to burnout are common experiences in the workplace, including high stress, a heavy workload, a lack of control over job situations, a lack of emotional support, and long work hours,” she adds. “These things lead to wear and tear, which will eventually weaken the body.”
Earlier research had shown that job burnout can lead to a range of health problems, including obesity, insomnia, and anxiety. For this study, to analyze whether staying too long in a job that makes you miserable could be connected to developing coronary heart disease (CHD) — the buildup of plaque in the arteries that causes angina and heart attacks — researchers tracked a population of 8,838 “apparently healthy” employed men and women for three-and-a-half years. Each participant was “measured for burnout levels” and examined for symptoms of heart disease. The study controlled for other risk factors such as sex, age, family history of heart disease, and smoking.
“During the follow-up period, 93 new cases of CHD were identified,” the report says. “Burnout was associated with a 40% increased risk … But the 20% of participants with the highest burnout scores had a 79% increased risk.”
“These results are valuable for preventive medicine,” Toker notes. “Health care providers who know that their patients are experiencing high levels of stress at work can monitor them closely for signs of coronary heart disease as well.”
Let’s say that you — like 92% of employees surveyed in a recent poll from consultant Right Management — have been more stressed out at work over the past five years than you were before the recession. How can you tell whether you’re headed for a serious case of burnout? The Tel Aviv University study posed these five questions, asking participants to answer with “never,” “sometimes,” “often,” or “always”:
1. How often are you tired and lacking energy to go to work in the morning?
2. How often do you feel physically drained, as if your batteries were dead?
3. How often is your thinking process sluggish or your concentration impaired?
4. How often do you struggle to think over complex problems at work?
5. How often do you feel emotionally detached from coworkers or customers, and unable to respond to their needs?
Two or more responses of “often” or “always” are a red flag. Toker notes that time-tested stress reducers like exercise and more sleep could help. Looking for a different job might help even more.