Study On The Impact Of Air Pollution On Hospitalization For Upper Respiratory Infection In Four Cities In Gansu Province

Research BackgroundWith the rapid development of economy and the change of people’s lifestyles,air pollution in China is becoming serious increasingly.Pollutants seriously affect people’s physical health.Previous studies have shown that PM_2.5,PM₁₀,SO₂,NO₂,O₃8h and CO in the air are related to the incidence of respiratory diseases closely.Yet,most studies on the impact of air pollution on respiratory diseases are limited to individual cities or regions,in domestic and foreign.There are relatively few investigations that focus on multiple cities as research objects.Moreover,each country and city has its own climate characteristics,air pollutant concentrations,and social population conditions,and previous research results may not be applicable to other cities.Gansu is located at the intersection of three major plateaus:the Loess Plateau,the Qinghai-Tibet Plateau and the Inner Mongolia Plateau,with rich mineral resources,developed industrial levels and high concentrations of air pollution,which have obvious harmful effects on humans.There are few studies of domestic scholars related to the effects of air pollution on the respiratory tract in northwest China.The study on the relationship between air pollution and hospitalization of upper respiratory infection in many cities is still blank.Therefore,we conducted this study to provide a theoretical basis for formulating effective policies for the prevention and treatment of respiratory diseases and improving the health level of residents.Research methodsCollect daily hospitalization data of upper respiratory infection patients,air pollutant data,and meteorological data from hospitals in Zhangye,Dingxi,Tianshui,and Longnan Cities in Gansu Province from January 1,2016 to December 31,2019.First,conduct a descriptive analysis of the three types of data.Second,conduct a Spearman rank correlation analysis of air pollutant data and meteorological data.Finally,after controlling for confounding factors such as long-term time trends,meteorological factors,weekday effects,and holiday effects,a distributed lag non-linear model（DLNM）based on Poisson regression is used to quantitatively analyze the relationship between daily air pollutant concentrations and daily hospitalization numbers for upper respiratory infection.Explore whether there are lag and cumulative effects of air pollutants on respiratory infections,and conduct stratified analysis by gender,age and season.In addition,exposure-response curves were fitted,and the stability of the model was tested using a two-pollutant model and changing degrees of freedom over time.Research results（1）Descriptive data analysis resultsThe total number of hospitalisations due to upper respiratory infection in Zhangye City,Dingxi City,Tianshui City and Longnan City from 1 January 2016 to31 December 2019 were 7884,18054,10138 and 5667,respectively.The average daily number of hospitalizations was 6,14,9 and 7 cases respectively.The number of male hospitalisations for upper respiratory infection was higher than the number of female hospitalisations in all four Cities,and the 0-14 age group had the highest average number of daily hospitalisations compared to other age groups.The number of hospital admissions for upper respiratory infection was higher in the cold season than in the warm season in all four Cities.The average daily concentrations of air pollutants PM_2.5,PM₁₀,SO₂,NO₂,O₃8h and CO in Zhangye City were 33.03μg/m3,82.50μg/m3,14.99μg/m3,19.98μg/m3,103.70μg/m3and 0.56mg/m3respectively,and the average daily temperature and relative humidity were 8.73℃and 35.16%.The daily average concentrations of air pollutants PM_2.5,PM₁₀,SO₂,NO₂,O₃8h and CO in Dingxi City were 34.45μg/m3,77.58μg/m3,18.59μg/m3,27.50μg/m3,93.17μg/m3and0.69mg/m3,and the daily average temperature and relative humidity were 8.11℃and61.28%.The daily average concentrations of air pollutants PM_2.5,PM₁₀,SO₂,NO₂,O₃8h and CO in Tianshui City were 36.86μg/m3,74.81μg/m3,19.64μg/m3,33.28μg/m3,88.83μg/m3and 0.81mg/m3respectively,and the daily average temperature and relative humidity were 11.22℃and 65.75%.The daily average concentrations of air pollutants PM_2.5,PM₁₀,SO₂,NO₂,O₃8h and CO in Longnan City were 28.34μg/m3,53.92μg/m3,18.98μg/m3,24.52μg/m3,82.05μg/m3,0.78mg/m3,and the daily average temperature and relative humidity were 15.75℃and 54.50%.（2）Association of air pollutants with hospitalisation in different CitiesThe relative risk（RR）and 95%confidence interval（95%CI）for upper respiratory admissions generated by each 10μg/m3increase in the concentration of air pollutants PM_2.5（lag7）,PM₁₀（lag7）,NO₂（lag06）and O₃8h（lag07）in Zhangye City were1.009（95%CI:1.000-1.018）,1.003（95%CI:1.001-1.006）,1.089（95%CI:1.007-1.177）,and 0.969（95%CI:0.943-0.996）.No correlation was found between upper respiratory infection admissions and SO₂and COThe relative risk（RR）and 95%confidence interval（95%CI）for upper respiratory admissions arising from each 10μg/m3increase in the concentrations of air pollutants PM_2.5（lag07）,PM₁₀（lag07）,SO₂（lag07）and NO₂（lag07）and each 1mg/m3increase in the concentration of CO（lag07）in Dingxi City were 1.052（95%CI:1.027-1.078）,1.083（95%CI:1.002-1.014）,1.070（95%CI:1.040-1.101）,1.079（95%CI:1.038-1.121）,1.578（95%CI:1.378-1.807）.No correlation was found between upper respiratory infection admissions and O₃8h.The RR and 95%confidence interval（95%CI）for the relative risk of upper respiratory admissions arising from each 10μg/m3increase in the concentrations of air pollutants PM_2.5（lag07）,PM₁₀（lag02）and NO₂（lag04）and each 1mg/m3increase in the concentration of CO（lag07）in Tianshui City were 1.034（95%CI:1.009-1.060）,1.008（95%CI:1.001-1.016）,1.060（95%CI:1.025-1.095）,1.155（95%CI:1.006-1.326）.No correlation was found between upper respiratory infection admissions and SO₂and O₃8h.The RR and 95%confidence interval（95%CI）for the relative risk of upper respiratory admissions arising from each 10μg/m3increase in the concentrations of the air pollutants PM_2.5（lag07）,PM₁₀（lag07）,SO₂（lag06）and NO₂（lag06）and each 1mg/m3increase in the concentration of CO（lag06）in Longnan City were1.045（95%CI:1.001-1.091）,1.024（95%CI:1.004-1.043）,1.110（95%CI:1.025-1.202）,1.064（95%CI:1.010-1.120）,1.313（95%CI:1.075-1.603）.No correlation was found between upper respiratory infection admissions and O₃8h.（3）Effects of air pollution on different subgroups of the populationThe effects of the air pollutants PM_2.5,PM₁₀,SO₂,NO₂and CO were more significant in females in Zhangye.PM_2.5,PM₁₀,SO₂,NO₂and O₃8h were more significant in children aged 0-14 years.The effects of the six air pollutants PM_2.5,PM₁₀,SO₂,NO₂,O₃8h and CO were more significant for females in Dingxi City.PM_2.5,PM₁₀,SO₂,NO₂,O₃8h and CO were more significant for the age group 15-64years.The effects of air pollutants PM_2.5,PM₁₀,NO₂and CO were more significant for females in Tianshui.The effects of PM_2.5,PM₁₀,and NO₂were more significant in Tianshui City for older people aged≥65 years.The effects of O₃8h and CO were more significant for children aged 0-14 years.In Longnan City PM_2.5,PM₁₀,SO₂,CO have more significant effects on females.The effects of air pollutants PM_2.5,PM₁₀,SO₂,NO₂and CO were more significant in Longnan City for older people aged 65 years and above,and O₃8h for children aged 0-14 years.（4）Effects of air pollution in different seasonsThere were significant differences in the risk of hospitalisation for upper respiratory infection between seasons.The effect estimates for four important pollutants,PM_2.5,PM₁₀,SO₂,NO₂and CO,were greater in the cold season than in the warm season in Zhangye.The effect estimates of four important pollutants,including PM_2.5,PM₁₀,SO₂,NO₂and CO,were greater in the cold season than in the warm season in Dingxi City except for O₃8h.The effect estimates for the four important pollutants PM_2.5,SO₂,NO₂and CO on the City of Shui were greater in the cold season than in the warm season,except for O₃8h.The effect estimates of four important pollutants such as PM_2.5,PM₁₀and SO₂on Longnan City were greater in the cold season than in the warm season.And the effect values for NO₂and CO were greater in the warm season.（5）Exposure-response curvesThe exposure-response curves for selected air pollutants PM_2.5,PM₁₀,NO₂and O₃8h in Zhangye City were approximately linear,with no thresholds indicating their association with upper respiratory infection admissions;cumulative RR values increased with increasing concentrations of PM_2.5,PM₁₀and NO₂,while cumulative RR values decreased with increasing concentrations of O₃8h.cumulative RR values for SO₂and CO showed a linear change with increasing concentration,but it was not statistically significant.The exposure-response curves for selected air pollutants PM_2.5,PM₁₀,SO₂,NO₂and CO in Dingxi City were approximately linear and there was no threshold indicating their association with upper respiratory infection admissions;the cumulative RR values increased with increasing concentrations of PM_2.5,PM₁₀,SO₂,NO₂and CO,while the cumulative RR values for O₃8h varied linearly with increasing concentrations but were not statistically significance.The exposure-response curves for some air pollutants PM_2.5,PM₁₀,NO₂and CO in Tianshui City were approximately linear and there was no threshold indicating their association with upper respiratory infection admissions;cumulative RR values increased with increasing concentrations of PM_2.5,PM₁₀,NO₂and CO,while those for SO₂and O₃8h varied linearly with increasing concentrations but were not statistically significant.The exposure-response curves for PM_2.5,PM₁₀,SO₂,NO₂and CO were approximately linear and there was no threshold indicating their association with upper respiratory infection admissions;cumulative RR values increased with increasing concentrations of PM_2.5,PM₁₀,SO₂,NO₂and CO,whereas cumulative RR values for O₃8h varied linearly with increasing concentrations but were not statistically significant.Research conclusions（1）The overall trend of air pollutant concentrations in four Cities in Gansu Province from 2016 to 2019 showed a year-on-year decrease.The concentrations of some air pollutants,including PM_2.5,PM₁₀,SO₂,NO₂,and CO,were higher in the cold season than in the warm season.However,the concentration of O₃8h showed the opposite trend with higher concentrations in the warm season than in the cold season.（2）Higher concentrations of some air pollutants in Zhangye,Dingxi,Tianshui and Longnan Cities of Gansu Province will lead to an increase in the number of hospital admissions for upper respiratory infection,and there is a lagging effect of air pollutants on the respiratory tract of residents.（3）The impact patterns of air pollutants on different genders,age groups,and seasons are different in the four Cities in Gansu Province.（4）The exposure-response curves of some air pollutants and hospital admissions for upper respiratory infection in four Cities in Gansu Province were approximately linear,with no threshold effect.