Think a job in construction or waiting tables is just as good as exercise? A new study reveals just the opposite: physically demanding work increases risk of cardiovascular disease.

People with physically demanding jobs should be the main concern for prevention of heart disease because they are at higher risk, said Demosthenes Panagiotakos, associate professor of biostatistics-epidemiology at Harokopio University in Athens, at the EuroPRevent 2013.

The study involved 250 participants who experienced first strokes, 250 who had a first acute coronary event and 500 matching controls. Participants were graded on their work load on a scale of one to nine, where one was the most physically demanding and nine was the least. The study adjusted for weight, eating and smoking habits, prior health conditions, family history of heart disease and adherence to the Mediterranean diet.

Researchers found that those who were working in a less physically demanding job (i.e. a job with a work load one point higher) had a 20% lower risk of strokes or adverse coronary events such as heart attacks. The risk reduction from the least physically demanding jobs to the most is even greater.

Stress could also be a compounding issue with these occupations, unlike exercise which is considered a stress-reliever and promotes well-being. Researchers also say more physically demanding jobs don't pay as well, which reduces their ability to access better health care.

In their second-part study, they followed more than 14,000 middle-aged men free of coronary disease for more than three years with examinations and questionnaires. Men with physically demanding jobs experienced adverse health effects, while men with more leisure time gained health benefits.

"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," said Els Clays, co-author from the department of public health at the University of Ghent in Belgium, in a press release. "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."

Clays added that many studies failed to demonstrate the relationship between different demanding jobs and heart disease, until now.

According to the Centers for Disease Control and Prevention, coronary artery disease is the most common type of heart disease and could lead to fatal heart attacks. It kills more than 385,000 people every year.