Demanding physical work may boost a person's risk of heart disease, two new studies suggest.
"Physicians know that high stress can be associated with increased risk of heart disease," said one expert not connected to the study, Lawrence Phillips, M.D., a cardiologist at NYU Langone Medical Center in New York City. "These two studies suggest that, in addition to normal life stressors, the physical demands a person experiences in the workplace can independently increase their risk as well."
"The reason for this [labor-linked risk] is unclear, but might be related to higher stress levels," Dr. Phillips said.
In one study, researchers looked at 250 patients who had suffered a first stroke and 250 who had suffered a first heart attack or other type of heart event. They were compared to a control group of 500 healthy people.
Stroke and heart patients were more likely to have physically demanding jobs than those in the control group, researchers found. After adjusting for age, sex and a number of lifestyle and health factors, they concluded that having a less physically demanding job was associated with a 20 percent lower risk of a heart event or stroke.
The findings suggest that people with physically demanding jobs should be considered an important target group for prevention of cardiovascular disease, said study author Demosthenes Panagiotakos, M.D., an associate professor of biostatistics and epidemiology at Harokopio University in Athens, Greece.
The results seem to conflict with recommendations that people should exercise to reduce their risk of heart trouble. But Dr. Panagiotakos said the increased risk of stroke and heart events among people with physically demanding jobs may be due to mental stress, while exercise helps reduce stress. He also said people with physically demanding jobs tend to have lower incomes, which might limit their access to health care.
The study suggests that leisure-time exercise might be important to "balance out" the physical stress encountered in laborious jobs, said Tara Narula, M.D., associate director of the cardiac care unit at Lenox Hill Hospital in New York City. She was not connected to the study.
"This delicate interaction between work and leisure-time activity warrants further research in order to appropriately guide public health," she said.
The study was presented at a meeting of the European Society of Cardiology, taking place this week in Rome.
In a second study presented at the same meeting, researchers looked at more than 14,000 middle-aged men who did not have heart disease and were followed for about three years on average. The investigators found that physically demanding work was a risk factor for developing coronary heart disease.
They also found that men with physically demanding jobs who also did moderate to high levels of exercise during their leisure time had an even greater risk (more than four-fold higher) of developing coronary heart disease.
Dr. Phillips, who also is an assistant professor in the department of medicine at NYU Langone, said the finding was a bit surprising. "This is a new finding that was not previously seen," he said. "Further studies to support this finding will be needed. As with many areas of medicine, a one-size-fits-all approach to leisure exercise might not work."
Study author Els Clays, M.D., of the department of public health at the University of Ghent, in Belgium, weighed in on the study in a society news release.
"From a public health perspective, it is very important to know whether people with physically demanding jobs should be advised to engage in leisure-time activity," Dr. Clays said.
"The results of this study suggest that additional physical activity during leisure time in those who are already physically exhausted from their daily occupation does not induce a 'training' effect but rather an overloading effect on the cardiovascular system," Dr. Clays said.
On the other hand, the study did find that men with less physically demanding jobs were 60 percent less likely to develop heart disease if they exercised during their leisure time.
"Further studies will be needed to find out the cause of increased heart disease in those people who have high physical job demands," Dr. Phillips said.
Both studies could point only to an association between hard physical labor and increased heart risk, not a cause-and-effect. Studies presented at a medical meetings typically are viewed as preliminary until published in a peer-reviewed journal.