Outdoor air pollution impacts chronic obstructive pulmonary disease deaths in South Asia and China: a systematic review and meta-analysis

Background: Chronic obstructive lung disease is among leading causes of death globally. Exposure to outdoor pollution is an important cause for increased mortality and morbidity. Objective: To present a systemic synthesis evidence regarding impact of outdoor pollution on COPD mortality in south asia and china. Methods: A systematic search on studies with statistical power has been conducted from 1990 - June 30th 2021, in English electronic databases following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines from MEDLINE and PUBMED databases with terms: Chronic Obstructive Pulmonary disease OR COPD OR Chronic Bronchitis OR Emphysema OR COPD Deaths OR Chronic Obstructive Lung Disease OR Airflow Obstruction OR Chronic Airflow Obstruction OR Airflow Obstruction, Chronic OR Bronchitis, Chronic AND Mortality OR Death OR Deceased AND Outdoor pollution, ambient pollution was conducted. Results: Out of 1899 papers screened only 16 found eligible to be included in the study. Subjects with COPD exposed to higher levels of outdoor air pollution had a 49 % higher risk of death as compared to COPD subjects exposed to lower levels of outdoor air pollution. When taken individual pollutants into consideration, common air pollutants like PM10 had an OR of 1.06 at CI 95%, where as SO2 had OR of 0.66 at 95% CI , and NO2 with 1.01 OR at 95% CI. These values suggest that there is an effect of outdoor pollution on COPD but not to a significant level. Conclusion: Despite heterogeneity across selected studies, exposure to outdoor pollutants  found to have risk of COPD mortality. Though it appears to have risk, COPD mortality was not significantly associated with outdoor pollutants. Controlling air pollution can substantially decrease the risk of COPD in South Asia and China. Further research including more prospective and longitudinal studies are urgently needed in COPD sub-groups.