Chest
Volume 138, Issue 1, July 2010, Pages 20-31
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ORIGINAL RESEARCH
COPD
Risk of COPD From Exposure to Biomass Smoke: A Metaanalysis

https://doi.org/10.1378/chest.08-2114Get rights and content

Background

Although many studies have suggested that biomass smoke is a risk factor for COPD, the relationship between the two has not been firmly established. In particular, the extent of the association between exposure of biomass smoke and COPD in different populations, as well as the relationship between biomass smoke and cigarette smoke, is not clear. To ascertain the relationship between biomass smoke and COPD, we performed a metaanalysis.

Methods

We searched MEDLINE, EMBASE, and the Latin American and Caribbean Literature in Health Sciences Database and analyzed 15 epidemiologic (11 cross-sectional and four case-control) studies that met our criteria. Data were extracted and analyzed independently by two investigators using a standardized protocol.

Results

Overall, people exposed to biomass smoke have an odds ratio (OR) of 2.44 (95% CI, 1.9-3.33) for developing COPD, relative to those not exposed to biomass smoke. Biomass smoke exposure was clearly identified as a risk factor for developing COPD in both women (OR, 2.73; 95% CI, 2.28-3.28) and men (OR, 4.30; 95% CI, 1.85-10.01), and in both the Asian population (OR, 2.31; 95% CI, 1.41-3.78) and the non-Asian population (OR, 2.56; 95% CI, 1.71-3.83). This risk factor has also been revealed in patients with chronic bronchitis (OR, 2.56; 95% CI, 1.77-3.70) and COPD (OR, 2.65; 95% CI, 1.75-4.03), and in cigarette smokers (OR, 4.39; 95% CI, 1.40-4.66) and non-cigarette smokers (OR, 2.55; 95% CI, 2.06-3.15).

Conclusions

Exposure to biomass smoke is a risk factor for COPD.

Section snippets

Search of the Literature

Papers published in the MEDLINE database, the Latin American and Caribbean Literature in Health Sciences Database, and EMBASE were searched (up to January 2009) with key words including “COPD,” “chronic bronchitis,” “emphysema,” “chronic obstructive pulmonary disease,” “biomass fuel,” “biofuel,” “organic fuel,” “wood,” and “indoor air pollution.” Articles about relevant studies in the references were also obtained. Only studies published in the English language were included in the analysis. We

Characteristics of the Included Studies

A detailed flow chart of the review process is presented in Figure 1. The initial search resulted in 984 hits of potential interest. Nine hundred fifty-seven studies were excluded upon review of the titles and abstracts. Among the remaining 27 articles6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32 on biomass smoke and the incidence of COPD, some were further excluded because of duplicated publication,6 lack of adequate data for the

Discussion

Metaanalytic methods are powerful tools for studying cumulative data from individual studies with small sample sizes and low statistical power. Pooling the effects from individual studies by a metaanalysis may increase the statistical power and can help detect modest risk differences among study groups. The large data set of this pooled analysis enabled us to investigate aspects of biomass smoke and subgroup-specific associations that could not be addressed adequately in previous studies.

Conclusions

In conclusion, our metaanalysis suggests that biomass smoke is associated with an increase in the risk of COPD. Given the high prevalence of biomass smoke, especially in rural areas, the public health consequences of biomass smoke with regard to COPD are important and suggest that COPD incidence could be reduced by interventions targeting biomass smoke.

Acknowledgments

Author contributions: Dr Hu: contributed to research conception, the first draft of the study protocol, literature searches and selected studies, additional data extraction, data management, statistical analyses, and the final version of the report.

Dr Zhou: contributed to the first draft of the study protocol, literature searches and selected studies, statistical analyses, and the final version of the report.

Dr Tian: contributed to data management and the final version of the report.

Dr Yao:

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