BioEd Online

Chronic exposure to noise raises the risk of suffering a heart attack, according to a survey of more than 4,000 German heart patients. The health experts who carried out the study argue that the current legal noise-exposure threshold may not be sufficient to protect against this effect.

Living or working in a noisy environment raises the odds of suffering a heart attack by around 50%, reports a team led by Stefan Willich of the Charité Medical Centre in Berlin. They made the discovery after quizzing heart-attack patients in Berlin hospitals. They then looked at 'noise maps' and data from workplaces to quantify how noisy the patients' lives were.

The effect does not seem simply to be down to annoyance at constant or frequent loud noise, the researchers add. When patients were asked to rate how annoyed they are by noise in their surroundings, the heart patients were not generally more likely than other patients to report being aggravated.

Another possible explanation might be that poorer people may live and work in noisier environments, and may also have a less healthy lifestyle or worse access to health care. But Willich says his team controlled for this effect by looking at the patients' education. He doesn't think it is simply a matter of the less wealthy being hit by heart problems.

Instead, Willich suggests, constant exposure to noise might raise levels of stress hormones in those working in loud factories or living next to busy roads, which can ultimately affect heart health.

With a bang

Lifestyle factors such as smoking or obesity are generally thought to roughly double heart-attack risk, Willich points out. "So noise is halfway up to the level of those 'normal' risk factors," he says.

The risk to industrial workers occurs at around 70 decibels, below the 85-decibel threshold recommended by the US Occupational Safety and Health Administration to protect workers' hearing, the researchers point out in the European Heart Journal¹. More research should be done to see whether this limit should be reduced to safeguard hearts as well as ears, says Willich.

Most surprisingly of all, the results show that women living in noisy homes are more than three times more likely than other women to suffer a heart attack. "We were absolutely astonished," says Willich. "This may be because women generally tend to spend more time in the home. But there may be biological differences."