Travelling by car or bus is the trigger of more heart attacks than alcohol, caffeine or over-eating, a new study has revealed.
It found time spent in vehicles sparked 7.4 per cent of all cardiac cases - more than physical exertion, at 6.2 per cent, and alcohol and coffee, both on 5 per cent.
Air pollution triggered 4.8 per cent of cases, negative emotions 3.9 per cent, and anger 3.1 per cent. Only 2.7 per cent were from a heavy meal, slightly higher than positive emotions on 2.4 per cent, with sexual activity on 2.2 per cent.
Less than 1 per cent of heart attacks were the result of cocaine abuse, despite it making people 23 times more vulnerable.
Alcohol made people three times more likely to suffer an attack, while coffee increased their vulnerability by 50 per cent.
The researchers based their findings on 36 separate studies worldwide.
Scotland has long been known as the "sick man of Europe" when it comes to heart disease, but experts say the country's record is improving.
Keith Fox, professor of cardiology at Edinburgh University, said: "Clearly, rates of coronary disease have been much higher in Scotland, but death rates are coming down - halved in the last ten years. About half of that is down to improved lifestyle and half is better treatment.
"Smoking is a much bigger factor in Scotland. It's exercise, diet and lifestyle combined with genes - that's the critical issue."
The study, published in the Lancet, found smoking bans in public places had reduced heart attacks by 17 per cent. Prof Fox said: "The reduction in acute coronary syndrome (in Scotland, as a result of the smoking ban] appeared to be greater than that."
Dr Tim Nawrot, of Hasselt University in Diepenbeek, Belgium, who wrote the report, said: "Of the triggers for heart attack studied, cocaine is the most likely to trigger an event in an individual, but traffic has the greatest population effect as more people are exposed to the trigger."
Previous research has shown inhaling tiny particles of pollution could trigger a heart attack within two hours.
Dr Nawrot said: "Our work shows ever-present small risks might have considerable public health relevance. Improvement of the air we breathe is a very relevant target to reduce the incidence of this disease in the general population."
Judy O'Sullivan, senior cardiac nurse at the British Heart Foundation, said: "It's important to remember this study looked at the triggers and not the causes of heart attacks."
She added: "Given the large number of people living in the UK with heart disease and the likelihood of their exposure to air pollution, this study highlights how important it is that UK governments ensure they meet European Commission targets to improve air quality."