| Background:Coronary heart disease(CHD)refers to a type of heart disease caused by narrowing or obstruction of the blood vessel cavity due to coronary artery atherosclerosis,which leads to myocardial ischemia,hypoxia,or necrosis.With the growth of population,the increase of aging proportion and the extension of average life expectancy,the prevalence of CHD is on the rise,which indirectly leads to an increase in hospital admissions for CHD,bringing serious disease burden to the families and society.A series of epidemiological studies have shown that air pollutants are risk factors for hospital admissions for CHD.In order to reduce the harm of air pollutants to human health,the Chinese government has promulgated a number of regulations on air pollution prevention to reduce the concentration of air pollutants in the environment since 2010.These measures controlled the concentration of pollutants in the environment effectively.In the current context of air quality improvement,a growing number of studies have begun to evaluate the health benefits,with a view to providing reference for air pollution control plans in the future.Current studies used the average number of hospital admissions for diseases around reference concentrations instead of reference numbers(the number of hospital admissions for diseases caused by air pollutants at reference concentrations)to quantify the health benefits of reducing the concentration of air pollutants.Because the number of hospital admissions was influenced not only by the effects of air pollutants but also by behavioral,lifestyle,genetic and other factors.The above method may overestimate the health benefits of pollutants.Moreover,although many previous studies assumed a linear relationship between air pollutants and diseases,the relationship may be complex nonlinear,so a linear approach to calculating health benefits may not be appropriate.Health benefits reflect the effects of single air pollutant.However,people are usually exposed to a mixture of multiple air pollutants in real life,so the effect of a single pollutant cannot fully reflect the effect of the mixture.It is an effective method to apply air quality health index(AQHI),a comprehensive indicator of reflecting air pollutants,to evaluate the total effects of air pollutants.Based on the above background,this study explored the association between air pollutants and hospital admissions for CHD based on the data of Zibo City,Shandong Province.The calculation methods of health benefits were determined based on the exposedresponse relationships between air pollutants and hospital admissions for CHD,and the attributable fractions of air pollutants and hospital admissions reduced by improving air quality were further quantified under different reference number Settings.Meanwhile,air quality health index(AQHI)constructed by principal component analysis was used to quantify the combined effects of air pollutants.The purpose of this study is to provide reference for relevant departments to implement intervention measures,as well as for the formulation of air pollution control plans in the future.Materials and Methods:The hospital admission data of CHD in Zibo City from 2015 to 2019 was collected to describe the temporal,spatial and population distribution characteristics.At the same time,meteorological data and air pollutant data were collected during the same period.We used a generalized additive model to explore the association between air pollutants and hospital admissions for CHD,and assessed the impact of reference numbers on health benefits.We also applied principal component analysis to extract variables from multiple air pollutants to construct AQHI,and then explored the association between AQHI and hospital admissions for CHD.At the same time,subgroups were divided according to gender and age.Then the effects of different AQHI subgroups were compared.Results:1.A total of 21105 hospitalized cases for CHD were reported in Zibo from 2015 to 2019,and the number of hospitalized patients showed an overall rising trend.The hospital admissions for CHD were more likely to occur in winter.The number of hospital admissions of male was higher than female,sex ratio of male to female was 1.30:1,and age group with high admission risk for CHD was aged 75 years and older.The central region of Zibo city was the high admission area for CHD.2.At Lag04,there was a log-linear exposure response relationship between O3 and hospital admissions for CHD,with RR(relative risk)of 1.0143(95%CI:1.0047～1.0239).There was a log-nonlinear exposure response relationship between PM10,PM2.5 and SO2 and the number of hospital admissions.With the increase of concentration of pollutant,the risk for hospital admission showed a trend of increasing first and then decreasing.3.Using World Health Organization air quality guidelines as reference,when the reference number was set as the average of the admissions around the reference concentration and the concentrations of O3,PM10,and PM2.5 were reduced to 100μg/m3,45μg/m3,and 15μg/m3,the avoidable number of hospital admissions for CHD was 416(95%CI:133～717),2495(95%CI:1815～3216)and 2496(95%CI:1856～3175),respectively.The attributive fractions were 1.97%(95%CI:0.63%～3.40%),11.82%(95%CI:8.60%～15.24%)and 11.82%(95%CI:8.79%～15.04%),respectively.When the reference number was set as the number of hospital admissions predicted by generalized additive model.the avoidable number of hospital admissions for CHD were 45(95%CI:14～77),208(95%CI:152～269),and 239(95%CI:178,304),respectively.The attribution fractions were 0.21%(95%CI:0.07%～0.37%),0.99%(95%CI:0.72%～1.27%)and 1.13%(95%CI:0.84%～1.44%).Similar results were obtained using Chinese ambient air quality standards,but attributed numbers and attributed fractions of PM10 and PM2.5 decreased slightly.4.According to the cumulative contribution rate and the eigenvalue of principal component,the first two principal component variables were extracted to construct AQHI.The effect of AQHI on hospital admissions for CHD was log-linear.For each one standard deviation increase in AQHI,the relative risk of hospital admission at lag04 were 1.0215(95%CI:1.0018～1.0415).The effect of AQHI on female was greater than male,but the difference between the two groups was not statistically significant.Although the effect of AQHI was higher at age 65 and older than at age 18-64,the difference of effect value between age subgroups was not statistically significant.Conclusions:1.In Zibo city,the number of hospital admissions for CHD tended to occur in winter.The central region of Zibo City was the area with high admission for CHD.The main hospitalized population for CHD were male and 75 years old and above.2.O3,PM10,PM2.5 and SO2 were important risk factors for admission for CHD.The higher the O3 concentration,the greater the admission risk of CHD.With the increase of PM10,PM2.5 and SO2 concentrations,the risk of admission showed a trend of first increasing and then decreasing.3.When quantifying the health benefits brought by the improvement of air quality,first,we should determine the exposure response relationship between air pollutants and outcomes.Second,set the number of admissions predicted by the generalized additive model as the reference number,which can accurately quantify the health benefits brought by the improvement of air quality.4.Hospital admissions for CHD can be significantly reduced by improving air quality.Stringent air quality standards can bring greater health benefits and should be taken into account when revising ambient air quality standards in the future.5.As an effective comprehensive indicator of air quality,AQHI can provide the public with more accurate information about the health risks related to pollutants,and also help guide the population to take protective measures to reduce the harm of pollutants. |
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