People who have stressful jobs could be twice as likely to die from heart problems, according to research published on Friday.

A study of more than 800 apparently healthy employees of a Finnish metal company were studied over a 25 year period.

Each was questioned to determine the nature of their work, and to gauge how stressful it was.

Results must not ignore the importance of other major risk factors such as obesity, smoking and lack of exercise

Spokesman, British Heart Foundation

Each was classified under the "effort-reward imbalance model" - those with the biggest mismatch between the effort they put in, and their perceived reward as a result got the highest scores.

Rewards included not only salaries, but also social approval, job security and career opportunities.

Other research has already found a link between the number of people falling ill with heart disease and this measure of job stress.

However, this is one of the first to link such stresses to actual heart deaths.

Unbalanced diet

The researchers found that those assessed as having the greatest imbalance between effort and reward were more than twice as likely to die from heart disease compared with those with the least imbalance.

Those with high job strain and a perceived lack of control over their job also had more than a doubled risk.

The reasons behind the extra risk are unclear - other studies have linked stressful jobs with high cholesterol levels.

Employees here with "effort-reward imbalance" were more likely to be fatter than their more-balanced counterparts, and obesity is a risk factor for heart disease.

Change needed

Professor Mika Kivimaki, who led the study at the Finnish Institute for Occupational Health, said that more effort should be made by employers.

He said: "The evidence from industrial employees suggests that attention should be paid to the prevention of work stress."

The British Heart Foundation agrees - its own work has linked lack of job control with increased rates of heart disease.

A spokesman said: "This long term study to analyse the links between workplace stress and heart disease provides us with a significant insight into the implications of work stress on heart health.

"The results echo recent research published by the BHF that people with jobs with low control (manual workers) could be at greater risk of coronary heart disease than those in professional employment.

"While the conclusion of this Finnish study is significant, the results must not ignore the importance of other major risk factors such as obesity, smoking and lack of exercise."

The study was published in the British Medical Journal.