Fine particulate air pollution and hospital admissions and readmissions for acute myocardial infarction in 26 Chinese cities

Monitoring data on fine particulate matter (PM_2.5) level in China's major cities were available since 2013. We conducted a time-stratified case-crossover study to evaluate the association between short-term exposure to PM_2.5 and hospital admissions for acute myocardial infarction (AMI), as well as subsequent cardiac and AMI readmissions among AMI survivors. Hospital admissions for ST-elevation myocardial infarction (STEMI) and non ST-elevation myocardial infarction (NSTEMI) from 1 January 2014 through 31 December 2015 were identified from electronic Hospitalization Summary Reports. Conditional logistic regression was used to explore the relation between PM_2.5 and hospital admissions for AMI. Individuals discharged alive following STEMI in 2014 were followed up for subsequent readmissions through 31 December 2015. We used the Cox proportional hazards model to evaluate the effect of PM_2.5 pollution on subsequent cardiac and STEMI readmissions. Hospital admissions for STEMI (n = 106,467) and NSTEMI (n = 12,719) were examined separately. Exposure to an interquartile range (IQR) increase in PM_2.5 concentration (47.5 μg/m³) at lags 2, 3, 4 and 0–5 days corresponded with 0.6% (95% CI, 0.1%–1.1%), 0.8 (95% CI, 0.3%–1.3%), 0.6% (95% CI, 0.1%–1.1%) and 0.9% (95% CI, 0–1.8%) increases in STEMI admissions, respectively. For NSTEMI, no significant association was observed with PM_2.5. We also observed significant associations of PM_2.5 concentration with both subsequent cardiac and STEMI readmissions among STEMI survivors. In conclusion, short-term elevations in PM_2.5 concentration may increase the risk of STEMI but not NSTEMI, and the association appeared to be more evident among STEMI survivors.