A study published in the British Medical Journal found that, compared to people who work an average of seven to nine hours a day, those who work fewer than seven are three times more likely to suffer a heart attack.

However, the risk is two-and-a-half times greater for those who work more than 11 hours a day.

Genuine link

Researchers in Japan set out to investigate if there was a genuine link between the number of hours someone works and their chances of having a heart attack.

They found that people who work very few or very long hours are at greatest risk of suffering a heart attack.

They also found that the risk increased as the hours piled up.

Spurts of overtime are particularly dangerous. People who work a normal week, but then have days when they work three or more hours overtime are two-and-a-half times more likely to suffer a coronary as someone who works just one hour extra.

The study looked at 195 men who had been admitted to hospital with heart attacks, and compared them to 331 healthy men.

Working hours

On discharge, each patient completed a questionaire giving details of the average number of hours they had worked in the two months before the attack.