Traffic-Generated Air Pollution and Myocardial Infarction

Background: Although long-term air pollution exposure has been linked to cardiovascular mortality, data on incidence and nonfatal coronary disease are limited and inconclusive. The aim of this study was to investigate the association between long-term residential exposure to air pollution from traffic and the risk of nonfatal and fatal myocardial infarction. Methods: The records of all individuals aged 15 to 79 with a first event of myocardial infarction in Stockholm County during 1985 to 1996 were retrieved from a registry. Population controls were randomly selected from the study base stratified by age, sex, and calendar year. Individual socioeconomic data and home addresses were obtained from population censuses 1970 to 1995. Annual air pollution exposure was assessed by dispersion modeling at the home addresses of 24,347 cases and 276,926 controls. Results: Five-year average traffic-generated air pollution exposure corresponding to a difference in nitrogen dioxide from the fifth to the 95th percentile (31 mu g/m(3)) was associated with an odds ratio for fatal myocardial infarction adjusted for age, sex, calendar year, and socioeconomic status of 1.23 (95% confidence interval [CI] = 1.15-1.32). The corresponding odds ratio was 2.54 (1.96-3.29) among those with least expected misclassification of true individual exposure (those who did not move between censuses). Different time-windows and analyses of other pollutants including carbon monoxide and particles less than 10 mu m in diameter (PM10) produced weaker associations. There was no increased risk for nonfatal myocardial infarction (ORs 0.94-0.98). Conclusions: Long-term exposure to traffic-generated air pollution is associated with fatal myocardial infarction but not with nonfatal infarction.