Ambient Air Pollution Is Associated With the Severity of Coronary Atherosclerosis and Incident Myocardial Infarction in Patients Undergoing Elective Cardiac Evaluation

BACKGROUND: The effect of air pollution exposure on atherosclerosis severity or incident clinical events in patients with coronary artery disease is not known. METHODS AND RESULTS: We conducted a prospective longitudinal cohort study of 6575 Ohio residents undergoing elective diagnostic coronary angiography. Multinomial regression and Cox proportional hazards models were used to assess the relationship between exposure to fine particulate matter <2.5 μm in diameter (PM (2.5)) and nitrogen dioxide on coronary artery disease severity at baseline and risk of myocardial infarction, stroke, or all‐cause mortality over 3 years of follow‐up. Among participants with coronary artery disease, exposure to PM (2.5) levels was associated with increased likelihood of having coronary atherosclerosis that was mild (odds ratio 1.43, 95% CI 1.11–1.83, P=0.005) and severe (odds ratio 1.63, 95% CI 1.26–2.11, P<0.0001), with the effect on severe coronary artery disease being significantly increased compared with mild disease (P (trend)=0.03). Exposure to higher PM (2.5) levels was also significantly associated with increased risk of incident myocardial infarction (hazard ratio 1.33, 95% CI 1.02–1.73, P=0.03) but not stroke or all‐cause mortality. The association of PM (2.5) with incident myocardial infarction was not affected after adjustment for Framingham Adult Treatment Panel III (ATP III) risk score or statin therapy. In comparison, there were no significant associations between nitrogen dioxide levels and all‐cause mortality or risk of stroke after adjustment for Framingham ATP III risk score. CONCLUSIONS: Exposure to PM (2.5) increased the likelihood of having severe coronary artery disease and the risk of incident myocardial infarction among patients undergoing elective cardiac evaluation. These results suggest that ambient air pollution exposure may be a modifiable risk factor for risk of myocardial infarction in a highly susceptible patient population.