"Chronic noise exposure carries an increased risk of heart attack," said Dr Stefan Willich, a cardiologist and director of the Institute for Social Medicine at the centre.

"It is not as high as the risk from smoking or high blood pressure but it is significant," he told Reuters.

Cardiovascular disease is a leading cause of death in developed countries. Smoking, high blood pressure, raised cholesterol levels, being overweight or obese and lack of exercise increase the odds of developing the illness.

Willich and his team found that environmental noise from traffic and airplanes raised the chances of having a heart attack by nearly 50 percent for men and even more for women.

Although women were not affected by noise in the workplace, it increased the risk of a heart attack by a third in men.

Based on the findings which are reported in the European Heart Journal, the scientists believe workplace ear protection levels should be reduced from the current 85 decibels widely used in western European countries to between 65-75 decibels.

"Companies and industries should consider lowering the threshold for ear protection," said Willich.

Sixty decibels is a typical noise level in a busy large office while 85 decibels is equivalent to road construction equipment, according to the scientists.

They found that the risk of having a heart attack did not rise with increasing noise levels.

"This means we seem to be looking at a threshold at which risk occurs and remains constant above this, and this appears to be around 60 decibels," according to Willich.

The researchers compared more than 2,000 heart attack patients in 32 hospitals in Berlin between 1998 and 2001 and 2,000 other people admitted for trauma or general surgery, to determine the effect of noise on heart attack risk.