The Impacts Of Ambient Air Pollution And Diurnal Temperature Range On Hospitalizations For Acute Exacerbations Of Chronic Obstructive Pulmonary Disease

BackgroundThe adverse effects of air pollution on human health have arisen more and more attention.With the acceleration of industrialization and urbanization,the problem of air pollution has become prominent in China.The association between air pollution and chronic respiratory diseases is widely concerned,because air pollutants can affect the human body directly through the respiratory tract.Chronic obstructive pulmonary disease（COPD）is a kind of chronic respiratory disease with high prevalence.Studies on Health burden in multiple countries suggest that the medical burden of acute exacerbations of COPD accounts for the most important part of the overall burden of COPD.Epidemiological studies abroad suggest that environmental factors such as air pollution can also induce acute exacerbation of COPD.There are the temporal and spatial differences in air pollution.In addition,the effect of meteorological conditions（e.g.,diurnal temperature range）on acute exacerbations of COPD is not well understood.In southern China,there is limited evidence on the associations of air pollution or diurnal temperature range with acute exacerbation of COPD.Therefore,it is necessary to carry out a time series analysis in Guangdong Province to fill this research gap.ObjectiveTo verify the associations of short-term air pollution or diurnal temperature range with hospitalizations for acute exacerbations of COPD.MethodsA time series analysis was conducted across 21 cities in Guangdong Province from January 1,2013 to December 31,2017.A generalized additive model with Poisson distribution was used for time series analysis to assess the association between short-term exposure to air pollution and admission to hospital with severe acute exacerbation of COPD.The method of moving average was adapted to represent the lag effect.Data of holidays,weekends,long-term trends,temperature,humidity,and atmosphere pressure were set as covariables in the model.Meta-analysis was used to pool the estimates from21 cities to determine the exposure-response relationship between short-term exposure to air pollution and admission to hospital with severe acute exacerbations of COPD in Guangdong Province.In order to confirm the robustness of the model,several sensitivity analyses were also performed.To accurately assess the potential health benefits of changes in air quality in Guangdong Province from 2013 to 2017,we calculated the attributable risk of air pollution.Principal component analysis was used to solve the collinearity problem among air pollutants and generalized additive model mentioned above was adapted to analyze the association between air pollution principal components and admission to hospital with acute exacerbation of COPD.On this basis,the attributable risks of air pollution in Guangdong Province were calculated,including the number of COPD hospitalizations and hospitalization costs attributable to air pollution,so as to achieve a comprehensive assessment of air pollution health risks.To further explore the association between daily temperature range and admission to hospital of patients with acute exacerbations of COPD,we carry out a time series analysis in Guangdong Province from January 1,2013 to December 31,2017.The generalized additive model with Poisson distribution was used.With the control of daily mean temperature,relative humidity,particulate matter and other factors,a two-stage method was used to evaluate the relationship between daily temperature range and hospitalizations for acute exacerbations of COPD.Subgroup analysis was also performed to identify potential confounding factors,including seasonal and population characteristics.ResultsTime series analysis of Guangdong Province showed that the relative risk（RR）at lag0-3 of acute exacerbation of COPD was increased to different degrees with the interquartile interval increase of pollutant concentration:RR=1.091（95%CI 1.05,1.14）for PM₁₀;RR=1.093（95%CI 1.06,1.13）for PM_2.5;RR=1.063（95%CI 1.03,1.10）for PM_coarse;RR=1.092（95%CI 1.08,1.11）for O₃;RR=1.092（95%CI 1.05,1.14）for SO₂;RR=1.099（95%CI 1.02,1.18）for NO₂;RR=0.999（95%CI 0.98,1.02）for CO.The dose-response patterns of diverse pollutants are different.From 2013 to 2017,the average daily concentrations of SO₂,PM₁₀ and PM_2.5 in Guangdong decreased by nearly 40%,30%and 26%,respectively.The number of days in which the maximum 8 hour O₃ concentration exceeded the WHO target increased from103 in 2015 to 152 in 2017.The number of hospital admissions for acute exacerbations of COPD caused by air pollution decreased from 9.5%in 2013 to 4.9%in 2016 and rose to6.0%in 2017.A similar downward trend was observed in direct hospitalization costs for acute exacerbations of COPD.An interquartile range increase in diurnal temperature range was associated with an increased risk of hospitalizations for acute exacerbations of COPD,RR=1.13（95%CI 1.12,1.15）.Low-level diurnal temperature range in warm season and high-level diurnal temperature range in cold season have higher risks of hospitalizations for AECOPD.The vulnerability of COPD patients to diurnal temperature range was not affected by age or sex.ConclusionShort-term exposure to air pollution(i.e.,PM₁₀,PM_2.5,PM_coarse,SO₂,NO₂,O₃,and CO)is correlated with admission to hospital for acute exacerbation of COPD.Improvements in air pollution in Guangdong Province may have reduced the number of hospital admissions and hospitalization costs for acute exacerbations of COPD.Our study provides evidence on the association between diurnal temperature range and hospital admissions for AECOPD.Preventive measures should be taken to reduce the adverse effects of air pollution and diurnal temperature range on COPD patients.