Relationship between biomass smoke exposure and chronic obstructive pulmonary disease among residents in China: a meta-analysis

Objective To explore the relationship between biomass smoke exposure and chronic obstructive pulmonary disease (COPD) and to provide references for COPD prevention. Methods Observational studies published from January 1990 through December 2015 in China and abroad on the association of biomass smoke and COPD among Chinese populations were searched in Chinese literature databases including Chinese National Knowledge Infrastructure (CNKI), Wanfang and Weipu database and English literature database including PubMed and Science Direct, supplemented by literature tracing.All studies enrolled were analyzed synthetically and quantitatively with meta-analysis by Stata 11.0 software. Results Totally 25 studies (22 in Chinese and 3 in English) were enrolled and the quality scores for all the studies were not less than 6.There were 16 cross-sectional studies which included 56 801 people and 9 case-control studies which included 2 149 cases and 2 757 controls.For the cross-sectional studies, the pooled odds ratio(OR)of COPD was 1.94 (95%confidence interval95%CI:1.49-2.53) for the people with biomass smoke exposure compared to those without the exposure;for the case-control studies, the pooled OR of COPD was 2.66 (95%CI:1.75-4.04) for the cases with biomass smoke exposure compared to the controls without the exposure.Subgroup analyses showed that for the cross-sectional studies, the biomass smoke-exposed subgroups of being male, living rural areas, using biofuel for both cooking and heating were at higher risk of COPD and the studies adjusting for confounding factors and involving a study population larger than 3 000 reported a higher biomass smoke exposure-related COPD risk (P < 0.01);for the case-control studies, the studies with hospital-based cases, with non-community-based controls, categorizing exposure levels by coal-burning and wood-burning index, adjusting for confounding factors, and adopting 1:1 matched design reported higher OR of COPD for the cases (all P < 0.01).Sensitivity and publication bias analysis revealed that the results of the meta-analysis were stable and there were no publication bias for the included cross-sectional and case-control studies (Z=1.40 and 0.52, both P > 0.05). Conclusion Biomass smoke exposure is a risk factor of chronic obstructive pulmonary disease among residents in China.