Exposure to urban nitrogen dioxide pollution and the risk of myocardial infarction

Objectives This study attempted to determine whether long-term exposure to nitrogen dioxide (NO2) an indicator of motor vehicle exhaust, increases the risk of myocardial infarction (MI). Methods A population-based case-control study was conducted among men aged 25-64 years and residing in Kaunas, Lithuania. The study included all cases of first-time myocardial infarction in 1997-2000. Interviews with patients treated in hospitals elicited information on smoking and other risk factors, including residential histories. A high response rate (77.4%) resulted in 448 cases and 1777 controls. Nitrogen dioxide (NO2) was selected for analysis as an indicator of traffic-related air pollution. The annual air pollution levels were estimated for the residential districts; thereafter the data were linked to the home addresses of the cases and controls. Results After adjustment for age, education, smoking, blood pressure, body mass index, marital status, and psychological stress, the risk of myocardial infarction was higher for the men exposed to medium [odds ratio (OR) 1.43, 95% confidence interval (95% CI) 1.04-1.96] and high (OR 1.43,95% CI 1.07-1.92) NO2 levels. The data suggested a stronger association among 55- to 64-year-old men. The risk of myocardial infarction increased by 17% among the 25- to 64-year-old men (OR 1.17, 95% CI 1.0 1- 1.35) and by 34% among those aged 55-64 years (OR 1.34, 95% CI 1.08-1.67) from the first to the third tertile of NO, exposure. Conclusions The results indicate that urban NO2 pollution may increase the risk of myocardial infarction and that vehicle emissions may be of particular importance.