Occupational exposures and chronic obstructive pulmonary disease: a hospital based caseecontrol study

Background Occupational exposures are associated with chronic obstructive pulmonary disease (COPD). This study investigated this association among a population with a high prevalence of tuberculosis and smoking. Methods Cases (n1⁄4110) diagnosed by pulmonologists were selected from specialist respiratory clinics. Frequency sexand age-matched controls (n1⁄4102) were selected from other clinics at the same institutions. Lifetime occupational exposure histories were obtained through interviews. Exposure variables derived from the ALOHA Job Exposure Matrix (JEM) were used to complement the self-reporting variables. ORs were calculated from logistic regression models, adjusting for smoking and past history of tuberculosis. Percentage population attributable risk (PAR%) was also calculated. Results The adjusted ORs for COPD from the JEMderived high cumulative biological dust exposure, high cumulative mineral dust exposure and high cumulative gas and fumes exposure were 2.1 (95% CI 1.1 to 4.2), 1.1 (95% CI 0.6 to 2.4) and 1.8 (95% CI 0.8 to 3.9), respectively. Self-reported occupational exposures were associated with higher risks, with adjusted ORs for high dust exposure-years and high chemical, gas and fumes exposure-years of 5.9 (95% CI 2.6 to 13.2) and 3.6 (95% CI 1.6 to 7.9), respectively. Among ever smokers, there was an increased risk for COPD, with ORs ranging from 5.0 to 5.5. Tuberculosis was a strong risk factor, with an OR ranging from 7.7 to 8.1. The PAR% was 25% for selfreported high exposures, but lower when the JEM variables were used. Conclusions Lifetime occupational exposures contribute to the risk of COPD, adjusted for smoking. These risks are present in populations with a high burden of tuberculosis, which is considered an important causative factor. INTRODUCTION Chronic obstructive pulmonary disease (COPD) is increasing worldwide, in both developed and developing countries. According to the 2001 World Bank/WHO Global Burden of Disease report, COPD is the sixth leading cause of death in developing countries, responsible for 4.9% of deaths. Despite smoking being the most important risk factor for this disease, accounting for >75% of cases of disease, occupational exposures, alone or in combination with smoking, are responsible for a substantial proportion of disease. Work may have an interactive effect with tobacco smoke, resulting in greater severity of disease with greater disability or by accelerating the rate of loss of lung function among those with the disease. Since the seminal paper on chronic airflow limitation and occupational exposures by Margaret Becklake in 1989, the evidence for work-related COPD has grown substantially. Occupational exposures such as to vapours, gases, dusts and fumes present an important risk factor for the development of the disease, by itself and through interaction with other risk factors. A US study of >10 000 adults concluded that COPD attributable to work was w19% in the total population, and 31.1% among never smokers. The American Thoracic Society ’s consensus statement suggests that between 10% and 20% of COPD is attributable to workplace exposures. The epidemiological evidence supporting the role of occupational exposures (organic and inorganic dusts, metal fumes, chemical vapours) as risk factors has been published in population-based studies, and also studies regarding working environments with specific exposures. In developing countries, in addition to smoking, COPD is associated with the high burden of infectious respiratory diseases, particularly tuberculosis (TB). The role of occupational exposures against this background of infectious diseases has not been investigated previously. This study Key Messages What is the key question? < Are occupational exposures associated with chronic obstructive airways disease in a population with ahigh prevalence of tuberculosis? What is the bottom line? < Occupational exposures contribute to the risk of chronic obstructive pulmonary disease, adjusted for smoking. These risks are present in populations with a high burden of tuberculosis, which is considered an important causative factor. Why read on? < Although occupational exposures have been consistently documented to be associated with chronic obstructive pulmonary disease over the last several years, there is a limited understanding of these associations in countries with other important risk factors such as chronic pulmonary infections. This study investigates associations among a high tuberculosis prevalence population. Department of Occupational and Environmental Health, University of KwaZulu-Natal, Durban, South Africa Department of Pulmonology and Critical Care Medicine, University of KwaZulu-Natal, Durban, South Africa Correspondence to Professor Rajen Naidoo, Department of Occupational and Environmental Health, George Campbell Building, University of KwaZulu-Natal, Durban 4041, South Africa; [email protected] Received 20 August 2010 Accepted 17 March 2011 Govender N, Lalloo UG, Naidoo RN. Thorax (2011). doi:10.1136/thx.2010.149468 1 of 5 Chronic obstructive pulmonary disease Thorax Online First, published on April 17, 2011 as 10.1136/thx.2010.149468 Copyright Article author (or their employer) 2011. Produced by BMJ Publishing Group Ltd (& BTS) under licence. group.bmj.com on April 18, 2011 Published by thorax.bmj.com Downloaded from