The Association Between Short-term Air Pollution Exposure And Economic Burden Of Ischemic Stroke In Chongqing: A Hospital-based Study

BackgroundIschemic stroke（IS）is a significant public health issue characterized by a high incidence,rapid onset,long duration,and high rates of mortality and disability.In China,the number of individuals affected by ischemic stroke is 24.18 million,resulting in a substantial consumption of social resources,imposed a heavy burden on the affected families.Air pollution is a significant risk factor for ischemic stroke.While numerous studies have examined the association between air pollution and the morbidity or mortality of ischemic stroke in recent years,the relationship between air pollution and the economic burden of ischemic stroke remains poorly understood.Investigating the link between air pollution exposure and the economic impact of the disease can provide valuable health economics evidence,which can inform evidence-based decision-making for environmental and health policies.Objectives1.This study examines the association between short-term exposure to air pollution and hospital visits,length of stay,and hospitalization costs for ischemic stroke in the central metropolitan area of Chongqing.The aim of this study is identifying the susceptible populations and related influencing factors,as well as to improve research methodology while scientifically evaluating the harmful effects of air pollutants.2.We aim to identify the excess economic burden associated with exposure to ambient air pollutants,and make recommendations for prevention and control accordingly.Methods1.We described the characteristics of outpatient and hospitalization data of patients with ischemic stroke admitted to a large tertiary hospital in Chongqing from 2014 to 2019.Mann-Whitney U test was used to compare the differences in length of stay and hospitalization costs in different groups,and Spearman correlation analysis was used to evaluate the correlation between length of stay and hospitalization costs.2.Descriptive analysis and time series decomposition of environmental air pollutants and meteorological data characteristics in the central metropolitan area of Chongqing.The daily reported values of the environment data within the study area are utilized as estimates of patients’exposure.3.Generalized Additive Model（GAM）was used to analyze the correlation between ambient air pollution exposure and the outpatient visits for ischemic stroke.A stratified analysis was performed to identify susceptible populations and influencing factors.Attributable risk of air pollutant exposure was calculated for each population,and the excess economic burden associated with air pollutants exposure was calculated by a modified human capital approach.4.Generalized Linear Model（GLM）was utilized for analyzing the association between air pollution and hospital length of stay.The influences of hospital length of stay on pollution exposure in different populations were evaluated by stratified analysis and attributable risk analysis.The effect of air pollutant exposure on the indirect economic burden of inpatient was assessed by a modified human capital approach.5.The association between exposure of ambient air pollutants and hospitalization costs was assessed using the GAM.We then conducted a stratification and sensitivity analyses.And the efficacy of air pollutant exposure on the direct economic burden of disease for hospitalized patients was estimated using cost-of-illness approach.Results1.This study included a total of 84,422 cases of ischemic stroke outpatients,with an average age of 65.9 years.Among them,males accounted for 55.6%,and patients aged 65 and above accounted for 54.5%.A total of 51.0%of patients sought medical attention during the warm season.The number of visits showed periodic fluctuations,greatly influenced by calendar dates and holidays.Among the patients,13,321 cases were admitted to the hospital,with males accounting for 59%and patients aged 65 and below accounting for 50.4%.Warm season admissions accounted for 52.8%.There were significant gender differences in hospitalization duration and expenses,while age differences were relatively small.The median length of hospital stay for patients was 8 days,and the median hospitalization cost was 21,320.35 yuan.2.During the study period,the average concentrations of inhalable particulate matter(PM₁₀),fine particulate matter(PM_2.5),and nitrogen dioxide（NO₂）exceeded the World Health Organization’s pollutant concentration limits,making them the main pollutants.Among them,PM_2.5 was the primary factor affecting air quality.With the exception of ozone（O₃）and NO₂,pollutant concentrations showed a decreasing trend over time.The variations in pollutant concentrations exhibited significant seasonal characteristics,with pollutant concentrations being lower in summer and higher in winter,except for O₃.3.Environmental air pollutant exposure showed a significant positive association with the daily number of outpatients of ischemic stroke.Male,aged≤65,visiting in cool season,and non-neurology departments visits are sensitive to air pollution exposure.The two-pollutant model results indicated that PM₁₀,PM_2.5,NO₂,and CO exposure were independent risk factors for increased patient visits for ischemic stroke.Among outpatients,the exposure concentrations of the main pollutants(PM₁₀,PM_2.5,NO₂)exceeded the World Health Organization’s air quality guidelines limits,the corresponding excess risk of visits increased8.19%(PM₁₀:1.66%;PM_2.5:2.71%;NO₂:3.82%),resulting in an indirect economic burden of over 1.2 million yuan.4.The ambient PM₁₀,coarse particulate matter（PM_C）,PM_2.5,SO₂,and CO were positively associated with the length of stay and had a significant cumulative effect.Subgroup analysis showed that air pollutants were more strongly associated with the length of stay in women,aged>65,and warm season visits.The indirect economic burden associated with PM₁₀ and PM_2.5 exceeding the concentration limits was 2.1 and 2.7 million Yuan,and the direct economic burden was 49.8 and 66.8 million Yuan,respectively.5.An increase in PM_C,SO₂,and O₃ exposure was positively associated with hospitalization costs.Subgroup analysis showed that air pollutants were more strongly associated with hospitalization costs for ischemic stroke patients in male,aged>65,and warm season admissions.Conclusions1.Exposure to PM₁₀,PM_C,PM_2.5,SO₂,NO₂,CO,and O₃ was positively associated with daily number of ischemic stroke outpatient visits,and this association had a lag effect.Susceptibility was higher in males,younger patients and cold season visits.2.PM₁₀,PM_C,PM_2.5,SO₂,and CO exposure were positively associated with the length of stay,with lagged and cumulative effects.After controlling for the effect of length of stay on hospitalization costs,PM_C,SO₂,and O₃ were positively associated with hospitalization costs.Length of stay and hospitalization costs of males,aged>65,and warm season visits were closer associated with air pollutants.3.Air pollution concentration exceedances caused an estimated excess economic burden of more than 100 million Yuan for patients included in this study,dominated by the direct economic burden of inpatient,and the overall reduction in the air pollution level had a greater benefit in controlling the economic burden associated with hospitalization.Also,reducing single-day fluctuations in pollutant concentrations is beneficial in reducing the risk of visits.