Risk of COPD from Exposure to Biomass Smoke: A Metaanalysis

Guoping Hu, MD, PhD; Yumin Zhou, MD, PhD; Jia Tian, MD; Weimin Yao, MD, PhD; Jianguo Li, MD, PhD; Bing Li, MD; Pixin Ran, MD, PhD, FCCP

Disclosures

CHEST. 2010;138(1):20-31. 

In This Article

Abstract and Introduction

Abstract

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.

Introduction

Wood and other forms of biomass (animal dung, crop residues, and so forth) are commonly used as sources of energy in developing countries[1,2] and are estimated to be used for 50% of household cooking and heating fuels worldwide. Combustion of biomass produces a large amount of smoke that spreads into the environment as air pollutants. Exposure to such biomass smoke has been documented as playing an important role in mortality and morbidity globally.[1,3]

Over the past decade, COPD has become a major public health problem, with increasing prevalence throughout the world,[4] and this prevalence results from an interaction between host and environmental factors. As widely recognized, tobacco smoke is the most important risk factor for COPD; however, exposure to biomass smoke can be as hazardous where indoor ventilation is inefficient.[2,5] Recently, considerable attention has been devoted to the relationship between smoke from biomass combustion and declined pulmonary function in COPD.[6–32] Although most studies did show an association, controversies over this issue remain. Moreover, the extent of such an association remains largely unknown. We searched the literature on the association between biomass smoke and COPD to determine whether ethnicity, sex, smoking status, study design, phenotype of COPD, and duration of exposure to biomass smoke have different effects on the development of COPD.

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