Long-Term PM Exposure and Risks of Ischemic Heart Disease and Stroke Events: Review and Meta-Analysis.

Background Fine particulate matter <2.5 µm in diameter (PM) has known effects on cardiovascular morbidity and mortality. However, no study has quantified and compared the risks of incident myocardial infarction, incident stroke, ischemic heart disease (IHD) mortality, and cerebrovascular mortality in relation to long-term PM exposure. Methods and Results We sought to quantitatively summarize studies of long-term PM exposure and risk of IHD and stroke events by conducting a review and meta-analysis of studies published by December 31, 2019. The main outcomes were myocardial infarction, stroke, IHD mortality, and cerebrovascular mortality. Random effects meta-analyses were used to estimate the combined risk of each outcome among studies. We reviewed 69 studies and included 42 studies in the meta-analyses. In meta-analyses, we found that a 10-µg/m increase in long-term PM exposure was associated with an increased risk of 23% for IHD mortality (95% CI, 15%-31%), 24% for cerebrovascular mortality (95% CI, 13%-36%), 13% for incident stroke (95% CI, 11%-15%), and 8% for incident myocardial infarction (95% CI, -1% to 18%). There were an insufficient number of studies of recurrent stroke and recurrent myocardial infarction to conduct meta-analyses. Conclusions Long-term PM exposure is associated with increased risks of IHD mortality, cerebrovascular mortality, and incident stroke. The relationship with incident myocardial infarction is suggestive of increased risk but not conclusive. More research is needed to understand the relationship with recurrent events.