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Jinhui Li,1,2 Shengzhi Sun,1,2 Robert Tang,1,2 Hong Qiu,2 Qingyuan Huang,3 Tonya G Mason,2 Linwei Tian1,2 1Shenzhen Institute of Research and Innovation, Nanshan, The University of Hong Kong, Shenzhen, People’s Republic of China; 2School of Public Health, The University of Hong Kong, Pok Fu Lam, Hong Kong Special Administrative Region; 3Department of Thoracic Surgery, Shanghai Chest Hospital, Shanghai Jiao Tong University, Minhang, Shanghai, People’s Republic of China Background: Short-term exposure to major air pollutants (O3, CO, NO2, SO2, PM10, and PM2.5) has been associated with respiratory risk. However, evidence on the risk of chronic obstructive pulmonary disease (COPD) exacerbations is still limited. The present study aimed at evaluating the associations between short-term exposure to major air pollutants and the risk of COPD exacerbations.Methods: After a systematic search up until March 30, 2016, in both English and Chinese electronic databases such as PubMed, EMBASE, and CNKI, the pooled relative risks and 95% confidence intervals were estimated by using the random-effects model. In addition, the population-attributable fractions (PAFs) were also calculated, and a subgroup analysis was conducted. Heterogeneity was assessed by I2.Results: In total, 59 studies were included. In the single-pollutant model, the risks of COPD were calculated by each 10 µg/m3 increase in pollutant concentrations, with the exception of CO (100 µg/m3). There was a significant association between short-term exposure and COPD exacerbation risk for all the gaseous and particulate pollutants. The associations were strongest at lag0 and lag3 for gaseous and particulate air pollutants, respectively. The subgroup analysis not only further confirmed the overall adverse effects but also reduced the heterogeneities obviously. When 100% exposure was assumed, PAFs ranged from 0.60% to 4.31%, depending on the pollutants. The adverse health effects of SO2 and NO2 exposure were more significant in low-/middle-income countries than in high-income countries: SO2, relative risk: 1.012 (95% confidence interval: 1.001, 1.023); and NO2, relative risk: 1.019 (95% confidence interval: 1.014, 1.024).Conclusion: Short-term exposure to air pollutants increases the burden of risk of COPD acute exacerbations significantly. Controlling ambient air pollution would provide benefits to COPD patients. Keywords: COPD exacerbations, air pollution, meta-analysis, acute exposure |
