But lighting up a cigarette or remaining chained to your desk rather than getting out to do some exercise is far more damaging for your heart health, researchers said.

A study of nearly 200,000 people from seven European countries found around 3.4 percent of heart attacks can be attributed to job strain - a significant proportion, but far less than the 36 percent attributable to smoking and 12 percent put down to lack of exercise.

For the study, which was published online in The Lancet medical journal, researchers analyzed job strain in employees who had no previous coronary heart disease (CHD).

Participants completed questionnaires about their job demands, workload, the level of time-pressure demands, and their freedom to make decisions.

"Our findings indicate that job strain is associated with a small, but consistent, increased risk of experiencing a first CHD event such as a heart attack," said Mika Kivimaki from University College London, who led the research.

Peter Weissberg, medical director at the British Heart Foundation, said the findings confirmed that being under stress at work and being unable to change the situation could increase the risk of developing heart disease.

But he noted they also showed the negative effects of workplace strain are much smaller than the damage caused by smoking or lack of exercise.

"Though stresses at work may be unavoidable, how you deal with these pressures is important, and lighting up a cigarette is bad news for your heart," he said in an emailed comment.

"Eating a balanced diet, taking regular exercise and quitting smoking will more than offset any risk associated with your job."

(Reporting by Kate Kelland, editing by Paul Casciato)

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