Since the late 1980's, numerous studies have found particulate air pollutant concentrations to be responsible for excess mortality. More recent studies have clarified that most of these deaths are sudden deaths. We have recently shown that particles from traffic are more specifically associated with acute cardiovascular effects. We have also shown the pre-existing diabetes was an important modifier of the particle effect. All of these studies have looked at immediate effects. Two prospective cohort studies have indicated that long-term exposure to particles is also associated with noticeable reductions in life expectancies. To replicate the association between chronic exposure and deaths, and examine the specific role of traffic particles we will conduct a case-control study of myocardial infarctions, using data from the Worcester Heart Attack Study. We will use a GIS system to code the latitude and longitude of home and work locations of cases and controls, and fit models relating concentrations of elemental carbon (a tracer for traffic particles) to population density, distance from roadways, and traffic counts in the Worcester MSA. From this, we will assign exposures to each subject. Controls will be sampled from town census books, which are conducted annually in Massachusetts. Controls will be matched by age, sex, and 10 year age group. Socio-economic data will be merged from the block group of the subjects, and questionnaire data will assess smoking history, alcohol consumption, aspirin and other medication use, educational level, height, weight, age, race, exercise, and air conditioner use. We will also ask about the presence of medical conditions, such as diabetes, that may be modifiers of the effect of pollution. Nonlinearities in covariates will be assessed and controlled for using penalized splines, in conditional logistic regressions. A preliminary analysis will use retrospective data, and not obtain questionnaire data. Effect modification by diabetes, prior MI, COPD, smoking, and angina will be tested using interaction terms.
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