Objective To quantitatively analyze the associations between ambient fine particulate matter (PM_2.5) exposure and the risks of myocardial infarction and heart failure, and to examine the geographic heterogeneity of these health risks.

Methods This article summarized environmental epidemiological studies on the associations of ambient PM_2.5 concentrations with myocardial infarction and heart failure since 2005 from databases including Wanfang, VIP, CNKI, Web of Science, PubMed, and Cochrane Library. Meta-analysis was performed to estimate pooled effect sizes, evaluate whether ambient PM_2.5 exposure is a risk factor for the two diseases, and obtain quantitative risk estimates. Subgroup analysis, sensitivity analysis, and publication bias test were conducted to assess the robustness of results and the major sources of heterogeneity.

Results For every 10 μg/m³ increase in ambient PM_2.5 mass concentration, the overall risks of myocardial infarction and heart failure increased by an average of 1.7% (95% confidence interval CI: 1.1%-2.4%) and 3.1% (95%CI: 2.0%-4.2%), respectively. The level of national economic development and geographical factors were identified as major sources of heterogeneity for the PM_2.5-induced risk of myocardial infarction. Specifically, for every 10 μg/m³ increase in ambient PM_2.5 mass concentration, the risk of myocardial infarction increased by 3.1% (95%CI: 1.8%-4.5%) in South China, 1.8% (95%CI: 0.4%-3.3%) in North China, 2.1% (95%CI: 1.1%-3.0%) in China, 1.5% (95%CI: 0.9%-2.1%) in developed countries, and 1.8% (95%CI: 0.9%-2.6%) in developing countries. Geographical factors were major sources of heterogeneity for the PM_2.5-induced risk of heart failure. For every 10 μg/m³ increase in ambient PM_2.5 mass concentration, the risk of heart failure increased by 6.6% (95%CI: 2.8%-10.4%) in South China, 1.2% (95%CI: 0.4%-2.0%) in North China, 3.2% (95%CI: 1.3%-5.2%) in China, 3.1% (95%CI: 2.0%-3.8%) in developed countries, and 2.8% (95%CI: 1.1%-4.5%) in developing countries. The meta-analysis of myocardial infarction showed stable and reliable results, and publication bias had no significant impact on the pooled effect size. In contrast, publication bias significantly affected the studies on the risk of heart failure induced by ambient PM_2.5.

Conclusion Exposure to ambient PM_2.5 is a risk factor for both myocardial infarction and heart failure, and the associated risks present remarkable geographic heterogeneity.