Short Term Exposure to Ambient Fine Particulate Matter (PM2.5) Increases Hospitalizations and Mortality of Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis.
Many epidemiologic studies have documented variable relationships between ambient particulate matter (PM) and chronic obstructive pulmonary disease (COPD) hospitalizations and mortality in cities worldwide.
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 odds ratios (ORs) and 95% confidence intervals (CIs) were performed to evaluate the relationship between short-term PM2.5 exposure 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 random-effect model and fixed effect model in COPD hospitalizations and mortality, respectively.
The search yielded 12 studies suitable for meta-analysis of hospitalizations and six studies for the mortality meta-analysis during the period. A 10 ug/m3 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.
Our combined analysis indicated that short-term exposure to 10 μg/m3 increment of ambient PM2.5 is associated with increased COPD hospitalizations and mortality. Further study is needed to elucidate to which 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.