General environmental noise, such as traffic, made women three times more likely to have a heart attack, but increased the risk for men by less than 50%. In contrast, workplace noise increased the risk for men by nearly a third, but did not seem to have an impact on women.

Heart attack risk rose with increasing noise levels until a threshold point above which it remained constant. This appeared to be around 60 decibels - the level of noise typically experienced in a large, busy office.

Study leader Dr Stefan Willich, director of the Institute for Social Medicine, Epidemiology and Health Economics at the Charite University Medical Centre in Berlin, said: "Our results demonstrate that chronic noise exposure is associated with a mildly to moderately increased risk of heart attack. The increase appears more closely associated with actual sound levels rather than with subjective annoyance. However, there were differences between men and women and these need further investigation."

Dr Willich's team recruited 4,115 patients admitted to the trauma and general surgery departments of 32 hospitals in Berlin between 1998 and 2001. The patients had an average age of 56 for men and 58 for women. Roughly half had been admitted to hospital after suffering a heart attack.

Interviews and independent environmental and work noise assessments were carried out and the results for both groups compared. The analysis revealed a statistical link between noise exposure and heart attacks.

Men appeared to be generally more affected by work noise and women by environmental noise. Dr Willich said some of the gender differences may be explained by the fact that women tend to spend more time at home and are less exposed to loud workplace noise. But the possibility that men and women were programmed to respond to noise differently could not be ruled out.

The study did not look at short-term noise exposure, such as driving to work, or include rural populations or people aged over 70.

But the findings convinced the team that the current European safety level for workplace noise was set too high. Throughout western Europe ear protection is required for employees when noise levels reach 85 decibels, the typical volume of noise produced by construction equipment. "We should definitely be looking at something lower," said Dr Willich. "The exact value is unclear, but somewhere between 65 and 75 decibels."

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