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Sustained exposure to the roar of traffic, the non-stop cacophony of office machinery or the thunder of industrial machinery is not only a threat to hearing, it may also spark a heart attack in people predisposed to cardiovascular disease, a study suggests.

In the study of about 2,000 people in hospital for a heart attack and an equal number hospitalized for other reasons, researchers at the Charite University Medical Centre in Berlin found that heart attack victims had experienced a far greater “noise burden” at work or home than those in the comparison group.

“We feel that if you have a higher and longer exposure to noise, either environmental or workplace noise, you are at a higher risk for a heart attack,” lead investigator Dr. Stefan Willich said Wednesday from Berlin.

The study, which involved interviews with patients at 32 Berlin hospitals and measurements of ambient sound in neighbourhoods throughout the city, found that men and women did not react in the same way to noise.

“There was a marked difference,” said Dr. Willich, director of the centre's Institute for Social Medicine, Epidemiology and Health Economics.

With environmental noise — such as heavy traffic, machinery like lawn mowers, yelling kids and barking dogs — the study showed that men with sustained exposure had a 50 per cent higher risk of heart attack, while women had a risk three times higher than their counterparts not regularly blasted by loud sound.

But when it came to workplace noise, men's risk for heart attack went up by nearly one-third, while women didn't seem affected at all, the study showed.

Dr. Willich said researchers aren't sure why men and women react differently to noise, but he theorizes that it may be based on long-ingrained evolutionary roles, making men more sensitive to workplace sounds and women to those involving the home environment, such as a child's cry.

“However, I believe there may also be additional biologic differences,” he said. Studies have shown that risk factor profiles for heart disease differ somewhat for men and women, as do the sexes' responses to treatments.

What is the same, however, is the mechanism that sets off a heart attack in both men and women — stress. But it is not the stress that arises from annoyance at unwanted sound, Dr. Willich hypothesized.

“We looked at annoyance, which is a subjective thing, and objective sound,” he said. “We looked at both issues. And objective sound level was more important than subjective annoyance.”

In other words, a neighbour playing the piano loudly may severely irritate one person while another “may love it,” he said.

But both will be affected because loud sound causes stress hormones like adrenaline and norepinephrine to rise, which in turn push up blood pressure and alter cholesterol and other fat levels in the blood.

And in some people, that may lead to a heart attack, concluded the study, published in Thursday's issue of the European Heart Journal.

“It means it's not necessarily how you perceive it in that moment,” said Willich. “Long-term loudness, long-term sound exposure may also put you at risk, even though you may feel that you adjust to it.”

Dr. Willich's institute is calling for the threshold of sound at which ear protection is mandatory in Germany be lowered from 85 decibels to 70 or 80 decibels, although even those lower levels boosted the risk of heart attack among some study subjects.

In Canada, it is recommended that ear protection be used during exposure to sound above 85 decibels (the level of a diesel truck going 50 km/h, 20 metres away, for instance).

Two recent Health Canada surveys found eight per cent of Canadians were highly annoyed by noise outside their homes, with sound from traffic and other people and animals ranked as the most irritating. Aircraft, trains, construction equipment and power landscaping tools were also identified as irritants by respondents.

A leaf blower, rock concert and chainsaw all hit the 115-decibel level, while an ambulance siren and jackhammer can bash the ear drums at 125 decibels and send stress levels soaring, says the organization Dangerous Decibels.

“If you know you have an increased risk of heart attacks, if you already have heart disease or you have risk factors — a family history, you're a smoker and you have high blood pressure and so on — then it's good to also have a look at your noise burden,” said Dr. Willich.

“And if you have a chance to reduce that, you'd better do it.”