Triggering of acute myocardial infarction by different means of transportation

Background: Prior studies have reported an association between
traffic-related air pollution in urban areas and exacerbation of
cardiovascular disease. We assess here whether time spent in
different modes of transportation can trigger the onset of acute
myocardial infarction (AMI). Design: We performed a case-crossover
study. We interviewed consecutive cases of AMI in the KORA
Myocardial Infarction Registry in Augsburg, Southern Germany
between February 1999 and December 2003 eliciting data on potential
triggers in the four days preceding myocardial infarction onset.
Results: A total of 1459 cases with known date and time of AMI
symptom onset, who had survived 24 hours after the onset, completed
the registry's standard interview on potential triggers of AMI. An
association between exposure to traffic and AMI onset 1 hour later
was observed (odds ratio: 3.2; 95% confidence interval CI]:
2.7-3.9, p < 0.001). Using a car was the most common source of
traffic exposure; nevertheless, times spent in public transport or
on a bicycle were similarly associated with AMI onset 1 hour later.
While the highest risk for AMI onset was within 1 hour of exposure
to traffic, the elevated risk persisted for up to 6 hours. Women,
patients aged 65 years or older, patients not part of the
workforce, and those with a history of angina or diabetes exhibited
the largest associations between times spent in traffic and AMI
onset 1 hour later. Conclusion: The data suggest that transient
exposure to traffic regardless of the means of transportation may
increase the risk of AMI transiently.