A Case-Control Analysis of Exposure to Traffic and Acute Myocardial Infarction
Tonne, Cathryn, Melly, Steve, Mittleman, Murray, Coull, Brent, Goldberg, Robert, Schwartz, Joel, Environmental Health Perspectives
BACKGROUND: Long-term exposure to particulate air pollution has been associated with an increased risk of dying from cardiopulmonary and ischemic heart disease, yet few studies have evaluated cardiovascular end points other than mortality. We investigated the relationship between long-term exposure to traffic and occurrence of acute myocardial infarction (AMI) in a case-control study.
METHODS: A total of 5,049 confirmed cases of AMI were identified between 1995 and 2003 as part of the Worcester Heart Attack Study, a community-wide study examining changes over time in the incidence of AMI among greater Worcester, Massachusetts, residents. Population controls were selected from Massachusetts resident lists. We used cumulative traffic within 100 m of subjects' residence and distance from major roadway as proxies for exposure to traffic-related air pollution. We estimated the relationship between exposure to traffic and occurrence of AMI using logistic regression, and we adjusted for the following potential confounders: age, sex, section of the study area, point sources emissions of particulate matter with aerodynamic diameter < 2.5 [micro]m, area socioeconomic characteristics, and percentage of open space.
RESULTS: An increase in cumulative traffic near the home was associated with a 4% increase in the odds of AMI per interquartile range [95% confidence interval (CI), 2-7%], whereas living near a major roadway was associated with a 5% increase in the odds of AMI per kilometer (95% CI, 3-6%).
CONCLUSIONS: These results provide support for an association between long-term exposure to traffic and the risk of AMI.
KEY WORDS: air pollution, case-control studies, myocardial infarction, vehicle emissions. Environ Health Perspect 115:53-57 (2007). doi: 10.1289/ehp.9587 available via http://dx.doi.org/ [Online 11 October 2006]
Cohort studies in the United States and Europe have shown associations between long-term exposure to particulate air pollution and increased mortality, particularly for cardiopulmonary and ischemic heart disease-related deaths (Dockery et al. 1993; Hoek et al. 2002; Pope et al. 2002, 2004). Several of these cohort studies were limited, however, by the number of deaths from a particular cause, limiting their ability to identify particular diseases at higher risk from exposure to air pollution. Case-control studies, in contrast, allow the accumulation of a large number of cases of a specific disease. Moreover, the coding of specific causes of death on death certificates has been shown to have relatively low specificity, (Coady et al. 2001; Pope et al. 2004), further limiting the interpretation of cohort studies that have examined the association between air pollution and specific causes of death. Furthermore, relatively few studies have evaluated the effects of long-term exposure on cardiovascular end points other than mortality, such as acute myocardial infarction (AMI). The evidence from the few case-control studies evaluating long-term exposure to traffic-related air pollution and myocardial infarction has been inconclusive (Grazuleviciene et al. 2004; Rosenlund et al. 2006).
Most cohort studies to date that assessed the association between air pollution and risk of disease or mortality have also had limited ability to account for geographic variation in exposure within cities (e.g., Dockery et al. 1993; Pope et al. 2002). Recent studies have suggested that this variation is quite important in assessing the effects of long-term exposure to air pollution. Epidemiologic studies that have accounted for intraurban variability in exposure due to local sources, such as traffic, have generally found larger effect estimates than studies that relied on between-city comparisons (Hoek et al. 2002; Jerrett et al. 2005). Although there is relatively little spatial variation in particulate matter < 2.5 [micro]m aerodynamic diameter ([PM.sub. …