Effects Of Ambient Air Pollution On Hospital Admission And In-Hospital Mortality For Different Subtypes Of Acute Myocardial Infarction

BackgroundCardiovascular diseases(CVDs)are the leading causes of death and disability in China and worldwide.Air pollution is the most important environmental risk factor for CVDs incidence and mortality,and it still has harmful effects even at low concentrations.Therefore,it is important to focus on the impacts of air pollution on CVDs such as acute myocardial infarction(AMI).Previous studies suggested that air pollution effected on STsegment elevated myocardial infarction(STEMI)and non-ST-segment elevated myocardial infarction(NSTEMI)differently.Furthermore,lager effects of air pollution on AMI were found among particular populations with specific comorbidities and previous history of CVDs.However,very few studies from China focused on particulate matter and gaseous pollutants’ effects on different AMI subtypes,and there is a lack of evidences for the vulnerability of population with specific comorbidities or history of CVDs.ObjectivesThis study aims to investigate the short-term effects of exposure to ambient air pollution on hospital admission and in-hospital mortality for different AMI subtypes,and search for susceptible populations with some specific demographic characteristics,comorbidities or history of CVDs in Beijing,China.MethodsWe collected hospitalization data of AMI patients aged ≥20 years who were admitted from 1st January 2013 to 31st December 2019 in Beijing,China.Time-stratified casecrossover(CCO)design and conditional Poisson general linear model were applied to explore the association between the risk of hospital admission and 30-day in-hospital mortality for total AMI and different AMI subtypes and the daily concentration of six air pollutants[particulate matter ≤2.5 μm in diameter(PM2.5),particulate matter ≤10 μm in diameter(PM10),sulfur dioxide(SO2),nitrogen dioxide(NO2),carbon monoxide(CO),and ozone(O3)],adjusting for meteorological factors,public holiday,heat.Stratified analyses were performed by age,gender,comorbidities,and history of CVDs to investigate susceptible population.In sensitivity analysis,we built two-pollutants models and adjusted the lag effects of meteorological factors.Additionally,time-series Poisson general additive model and multivariate Logistic regression models were used to validate the main findings in CCO design.ResultsA total of 149,632 AMI admissions were identified between 2013 and 2019 in Beijing,China,including 70,730 STEMI,69,594 NSTEMI,and 9,308 patients with an unknown type.We identified 10,983 30-day in-hospital death for AMI,among which 4,361 were admitted for STEMI,4,299 for NSTEMI,and 2,323 for an unknown type.The 24-hour average concentrations of PM2.5,PM10 and NO2 exceeded the World Health Organization air quality standards in 87.6%,78.4%,and 85%of the study period.AMI hospital admissions:In single-pollutant models,higher levels of PM2.5,PM10,SO2,NO2,and CO were significantly associated with increased risks of hospital admissions for total AMI,STEMI and NSTEMI.The strongest effects of these five pollutants were shown on the current day(lag0)for total AMI admissions and STEMI admissions while on the previous day(lagl)for NSTEMI admissions.A higher level of O3 at lag4 was significantly associated with a decreased risk of STEMI admissions.No significant association between the level of O3 and admissions for total AMI or NSTEMI was found.In subgroup analysis,significantly stronger effects of PM2.5,SO2,and NO2 on total AMI admissions and that of SO2 on NSTEMI admissions were observed in people with asthma.People with chronic obstructive pulmonary disease(COPD)had a significantly higher risk of STEMI admission associated with a higher level of O3 than those without COPD.Comparing with people without previous stroke,the association between a higher level of PM10 and an increased risk of STEMI admissions was much stronger in people with previous stroke.In two-pollutant models,the harmful effects of PM2.5,PM10,SO2,and CO on total AMI admissions showed robustness.While the protective effect of O3 on AMI admissions was affected by lag effects of daily mean temperature and air pressure a lot and lacked of robustness.The main findings in CCO analysis and time-series analysis were consistent.AMI in-hospital mortality:In single-pollutant models,higher levels of PM2.5,PM10,SO2,NO2 and CO were significantly associated with increased risk of 30-day in-hospital mortality for total AMI and NSTEMI and the strongest effects of these five pollutants were observed on the previous day(lag1).Significantly positive associations between pollutants O3 and 30-day in-hospital mortality were found for total AMI while only in specific subgroups for STEMI and NSTEMI.Subgroup analyses indicated that people without diabetes had significantly higher risks of 30-day in-hospital mortality for STEMI associated with higher levels of NO2 and CO than people with diabetes.The association between a higher level of NO2 and an increased risk of 30-day in-hospital mortality for NSTEMI was much stronger in people without previous stroke.People with a history of old myocardial infarction(OMI)and PCI/CABG(percutaneous coronary intervention and coronary artery bypass grafting)had a significantly higher risk of 30-day in-hospital mortality for NSTEMI associated with a higher level of CO than people without those.The effects of NO2 were robust in two-pollutant models.While the effect of O3 was affected by lag effects of daily mean temperature a lot and was not robust.In multivariate Logistic regression models adjusting for age,sex comorbidities,complications,therapies,and other risk factors of death,higher levels of PM2.5,PM10,SO2,NO2,and CO were still significantly associated with an increased risk of 30-day in-hospital mortality for NSTEMI.ConclusionsThis study suggested that short-term exposure to particular matter(PM2.5,PM10)and gaseous pollutants(SO2,NO2,and CO)had an adverse effect on admissions for total AMI,STEMI and NSTEMI as well as in-hospital mortality for NSTEMI.People with specific comorbidities or CVDs history such as asthma,COPD and so on were more susceptible to pollutants’ adverse effects on AMI admission or in-hospital mortality.AMI subtypes,lag times,and individual characteristics should be taken into account while analyzing the effects of ambient air pollution on AMI.The impact of air pollution on the morbidity and mortality of AMI should be taken seriously,and reduced by reducing pollution and protecting susceptible populations.