Long-Term Exposure to Ambient Air Pollution and Myocardial Infarction: A Systematic Review and Meta-Analysis

Background and Objective: An increasing number of epidemiological original studies suggested that long-term exposure to particulate matter (PM_2.5 and PM₁₀) could be associated with the risk of myocardial infarction (MI), but the results were inconsistent. We aimed to synthesized available cohort studies to identify the association between ambient air pollution (PM_2.5 and PM₁₀) and MI risk by a meta-analysis. Methods: PubMed and Embase were searched through September 2019 to identify studies that met predetermined inclusion criteria. Reference lists from retrieved articles were also reviewed. A random-effects model was used to calculate the pooled relative risk (RR) and 95% confidence intervals (CI). Results: Twenty-seven cohort studies involving 6,764,987 participants and 94,540 patients with MI were included in this systematic review. The pooled results showed that higher levels of ambient air pollution (PM_2.5 and PM₁₀) exposure were significantly associated with the risk of MI. The pooled relative risk (RR) for each 10-μg/m³ increment in PM_2.5 and PM₁₀ were 1.18 (95% CI: 1.11-1.26), and 1.03 (95% CI: 1.00-1.05), respectively. Exclusion of any single study did not materially alter the combined risk estimate. Conclusions: Integrated evidence from cohort studies supports the hypothesis that long-term exposure to PM_2.5 and PM₁₀ is a risk factor for MI.