Traffic may trigger heart attacks

  • Joanne McCarthy

Exposure to road traffic may trigger heart attacks, according to a new study.

People who have had a heart attack are three times more likely to report having been in traffic within an hour of the onset of their heart attack, the researchers said.

The German researchers also observed small increases in the chance that a heart attack happened up to six hours after exposure to traffic.

Driving a car was the most common source of traffic exposure, but taking public transport or riding a bicycle were also included. Females, elderly males, people who were unemployed and those with a history of angina were affected the most by traffic.

“Driving or riding in heavy traffic poses an additional risk of eliciting a heart attack in persons already at elevated risk,” said Dr Annette Peters of the Institute of Epidemiology, Helmholtz Munchen, Germany, who led the study. “In this study, underlying vulnerable coronary artery disease increased the risk of having a heart attack after driving in traffic,” she continued.

According to Dr Peters, one factor which could contribute to the increased risk of heart attacks are the exhaust and air pollution coming from other cars.

“We can’t exclude the synergy between stress and air pollution that could tip the balance,” she said.

Previous studies by the researchers showed that those participating in strenuous activity such as playing soccer or squash or performing heavy work such as painting overhead or snow shovelling had five to six times the risk of heart attack in the subsequent hours after the activity.

This study showed that about 8% of the heart attacks in the group were attributable to traffic, Dr Peters said. “It’s just one of the factors, but it’s not a negligible number,” she said.

“We were initially surprised to observe such a strong connection between traffic and heart attacks, which we first published in 2004 based on a case series of 691 patients. It is reassuring that we were able to reconfirm this association in an extended case series. Now it’s important to find out what is behind this, whether it is air pollution or stress or both,” she continued.

The researchers also said they were surprised that women appeared to be in the higher-risk group. “Their risk is more than five times higher. We’re not sure what the physiological mechanism is behind this,” said Dr Peters.

The researchers are doing further studies to explain the reasons that the exposure to traffic was associated with a higher risk of heart attack.

The research was reported at the American Heart Association’s 49th Annual Conference on Cardiovascular Disease Epidemiology and Prevention.

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