Ambient Air Pollution and the Risk of Acute Myocardial Infarction and Stroke: A National Cohort Study

We used a large national cohort in Canada to assess the incidence of acute myocardial infarction (AMI) and stroke hospitalizations in association with long-term exposure to fine particulate matter (PM), nitrogen dioxide (NO), and ozone (O). The study population comprised 2.7 million respondents from the 2006 Canadian Census Health and Environment Cohort (CanCHEC), followed for incident hospitalizations of AMI or stroke between 2006 and 2016. We estimated 10-year moving average estimates of PM, NO, and O, annually. We used Cox proportional hazards models to examine the associations adjusting for various covariates. For AMI, each interquartile range (IQR) increase in exposure was found to be associated with a hazard ratio of 1.026 (95% CI: 1.007-1.046) for PM, 1.025 (95% CI: 1.001-1.050) for NO, and 1.062 (95% CI: 1.041-1.084) for O, respectively. Similarly, for stroke, an IQR increase in exposure was associated with a hazard ratio of 1.078 (95% CI: 1.052-1.105) for PM, 0.995 (95% CI: 0.965-1.030) for NO, and 1.055 (95% CI: 1.028-1.082) for O, respectively. We found consistent evidence of positive associations between long-term exposures to PM, and O, and to a lesser degree NO, with incident AMI and stroke hospitalizations.