Global Associations between Air Pollutants and Chronic Obstructive Pulmonary Disease Hospitalizations. A Systematic Review.
Exacerbations are key events in chronic obstructive pulmonary disease (COPD), affecting lung function decline and quality of life. The effect of exposure to different air pollutants on COPD exacerbations is not clear.



To carry out a systematic review, examining associations between air pollutants and hospital admissions for COPD exacerbations.



MEDLINE, Embase, BIOSIS, Science Citation Index, and the Air Pollution Epidemiology Database were searched for publications published between 1980 and September 2015. Inclusion criteria were focused on studies presenting solely a COPD outcome defined by hospital admissions and a measure of gaseous air pollutants and particle fractions. The association between each pollutant and COPD admissions was investigated in metaanalyses using random effects models. Analyses were stratified by geographical clusters for investigation of the consistency of the evidence worldwide.



Forty-six studies were included, and results for all the pollutants under investigation showed marginal positive associations; however, the number of included studies was small, the studies had high heterogeneity, and there was evidence of small-study bias. Geographical clustering of the effects of pollution on COPD hospital admissions was evident and reduced heterogeneity significantly.



The most consistent association was between a 1-mg/m3increase in carbon monoxide level and COPD-related admissions (odds ratio, 1.02; 95% confidence interval, 1.01-1.03). The heterogeneity was moderate, and there was a consistent positive association in both Europe and North America, although levels were clearly below World Health Organization guideline values. There is mixed evidence on the effects of environmental pollution on COPD exacerbations. Limitations of previous studies included the low spatiotemporal resolution of pollutants, inadequate control for confounding factors, and the use of aggregated health data that ignored personal characteristics. The need for more targeted exposure estimates in a large number of geographical locations is evident.
1 National Heart and Lung Institute, Imperial College London, London, United Kingdom.
Elizabeth
0000-0003-1660-7598
E
Moore
2 Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
Lia
L
Chatzidiakou
3 Division of Medicine, University College London, London, United Kingdom.
Moyosore-Oluwa
MO
Kuku
2 Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom.
Roderic L
RL
Jones
4 London School of Hygiene and Tropical Medicine, London, United Kingdom; and.
Liam
L
Smeeth
5 Analytical & Environmental Sciences Division, King's College London, London, United Kingdom.
Sean
S
Beevers
5 Analytical & Environmental Sciences Division, King's College London, London, United Kingdom.
Frank J
FJ
Kelly
5 Analytical & Environmental Sciences Division, King's College London, London, United Kingdom.
Benjamin
B
Barratt
1 National Heart and Lung Institute, Imperial College London, London, United Kingdom.
Jennifer K
JK
Quint
D000393:Air Pollutants / Q000009:adverse effects*; D018450:Disease Progression; D004784:Environmental Monitoring; D005740:Gases / Q000009:adverse effects; D006801:Humans; D052638:Particulate Matter / Q000009:adverse effects; D010343:Patient Admission / Q000706:statistics & numerical data*; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology*; D011788:Quality of Life
D000393:Air Pollutants; D005740:Gases; D052638:Particulate Matter
environmental monitoring; gases; particulate matter; patient admission