Car fumes and traffic stress trigger heart attacks

Travelling in traffic, either in a car or on public transport, almost trebles the risk of a heart attack for at least an hour afterwards, a study has found.

Travelling in traffic, either in a car or on public transport, almost trebles the risk of a heart attack for at least an hour afterwards, a study has found.

Fumes from car exhausts, noise and stress brought on by traffic congestion are likely to be the main causes of the increase in risk, researchers say. Air pollution is known to be a factor in heart disease, which develops slowly over decades, and research has shown that people living close to a main road have twice the risk of dying from the condition.

The findings are based on 691 heart attack survivors in the city of Augsburg in southern Germany who were interviewed by the national research centre for environment and health at Neuherberg about their activities in the four days before the attack. The researchers found that one hour before the attack happened, exposure to traffic was twice as frequent as at any other time.

Most patients had been travelling by car but some had been on bicycles and others on buses and trolley cars. Women and those aged over 60 or with other conditions such as diabetes had the greatest increase in risk.

Publishing their findings in the New England Journal of Medicine, the authors estimate that 8 per cent of the heart attacks they studied were attributable to traffic. The triggers for a heart attack, which is a sudden event, are little understood, but, if the findings are confirmed, traffic will have to be added to the known list of triggers, which include outbursts of anger, strenuous exercise and use of cocaine.

They say it is "unlikely that the effect is entirely attributable to the stress linked with driving a car" because people who travelled by public transport, including buses or trolley cars were equally affected.

Pollution is likely to be the key factor. Particulates in the air expelled by vehicle exhausts have been shown to increase the stickiness of the blood when breathed in, which can lead to blood clots forming, as well as altering the function of the heart and blood vessels.

"These changes have been observed in healthy officers of the highway patrol in association with the concentration of particulate matter in their vehicles and might be consistent with an increased risk of myocardial infarction [heart attack] after a transient elevation in the concentration of ambient particles in vulnerable subjects," the authors write.

Studies have shown that passengers in cars and buses are exposed to a higher level of particulates from exhaust fumes than is measured 100 metres or more from traffic on the road. People in cars or buses have twice the level of exposure of cyclists even though cyclists breathe more heavily and thus draw the particulates more deeply into their lungs.