title: Short-term Exposure to Ambient Fine Particulate Matter Increases Hospitalizations and Mortality in COPD: A Systematic Review and Meta-analysis.
abstract: BACKGROUND
  Many epidemiologic studies have documented variable relationships between ambient particulate matter (PM) and COPD hospitalizations and mortality in cities worldwide.
  
  
  METHODS
  Comprehensive and systematic searches were performed in the electronic reference databases (PubMed, EMBASE, Google Scholar, Ovid, and Web of Science) with specific search terms and selection criteria for relevant studies. Summary ORs and 95% CIs were calculated to evaluate the relationship between short-term exposure to PM with aerodynamic diameters ≤ 2.5 μm (PM2.5) and COPD hospitalizations and mortality. The sources of heterogeneity and the effect of potential confounders were explored using subgroup analyses. Study findings were analyzed using a random effects model and a fixed effects model in COPD hospitalizations and mortality, respectively.
  
  
  RESULTS
  The search yielded 12 studies suitable for meta-analysis of hospitalizations and six studies suitable for the mortality meta-analysis until April 15, 2015. A 10-μg/m(3) increase in daily PM2.5 (lag days 0-7) was associated with a 3.1% (95% CI, 1.6%-4.6%) increase in COPD hospitalizations and a 2.5% (95% CI, 1.5%-3.5%) increase in COPD mortality. Significant publication bias was not found in studies focusing on the relationship between short-term PM2.5 exposure and COPD hospitalizations and mortality.
  
  
  CONCLUSIONS
  Our combined analysis indicated that short-term exposure to a 10-μg/m(3) increment of ambient PM2.5 is associated with increased COPD hospitalizations and mortality. Further study is needed to elucidate to what extent this relationship is causal, together with other factors, and to elucidate the mechanism by which PM2.5 induces activation of cellular processes promoting COPD exacerbations.
authors.affiliation: Department of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China; Soochow University, Suzhou, China.
authors.forename: Man-Hui
authors.initials: MH
authors.lastname: Li
authors.affiliation: Department of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China.
authors.forename: Li-Chao
authors.initials: LC
authors.lastname: Fan
authors.affiliation: Department of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China; Soochow University, Suzhou, China.
authors.forename: Bei
authors.initials: B
authors.lastname: Mao
authors.affiliation: Department of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China; Soochow University, Suzhou, China.
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Yang
authors.affiliation: Joan and Sanford I. Weill Department of Medicine, Weill Cornell Medical College and New York-Presbyterian Hospital, New York, NY.
authors.forename: Augustine M K
authors.initials: AMK
authors.lastname: Choi
authors.affiliation: Department of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China; Soochow University, Suzhou, China.
authors.forename: Wei-Jun
authors.initials: WJ
authors.lastname: Cao
authors.affiliation: Department of Respiratory Medicine, Shanghai Pulmonary Hospital, Tongji University School of Medicine, Shanghai, China; Soochow University, Suzhou, China. Electronic address: jfxucn@gmail.com.
authors.forename: Jin-Fu
authors.initials: JF
authors.lastname: Xu
mesh_terms: D002947:Cities; D004781:Environmental Exposure / Q000009:adverse effects*; D014943:Global Health; D006760:Hospitalization / Q000639:trends*; D006801:Humans; D008962:Models, Theoretical; D052638:Particulate Matter / Q000009:adverse effects*; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality* / Q000628:therapy*; D015996:Survival Rate / Q000639:trends; D013997:Time Factors
chemical_list: D052638:Particulate Matter
keywords: COPD; air pollution; environmental health; environmental pollution