Occupational exposures and chronic obstructive pulmonary disease : a hospital-based case-control study.

Abstract

Aim The aim of this study was to determine the contribution of occupational exposures to the burden of Chronic Obstructive Pulmonary Disease (COPD) among a sample of hospital based patients. Methods Cases (n=110) with specialist physician diagnosed COPD from the three public sector specialist respiratory clinics in KZN and controls (n=102) from other nonrespiratory chronic ailment specialist clinics at the same institutions were selected. An interviewer administered questionnaire and exposure history was obtained for each participant. In addition, a valid lung function test was obtained for each case. Data was analysed using STATA version 10. Multivariate regression models were developed to examine the relationship between COPD and occupational exposures while adjusting for age, sex, smoking and previous history of tuberculosis. The relationship of FEV1 and occupational exposures, adjusted for age, height, previous history of tuberculosis and smoking history, was investigated among cases. Results Cases and controls were similar with respect to age and sex distribution. Cigarette smoking differed significantly between cases and controls with a larger proportion of cases having ceased to smoke compared to controls (72% vs 46%, p<0.01). A higher proportion of controls reported employment in administrative, managerial and quality control positions (21.3% vs 12.0%, 7.7% vs 2.6% and 5.4% vs 0.3% respectively). Employment in the construction and shoe manufacturing industries was reported more frequently by cases (10.3% vs 3.2% and 10.0% vs 4.9% respectively). Cases were more likely than controls to have been exposed to dust (72% vs 28%, p<0.001) or to chemicals, gas or fumes (74% vs 25.5%, p<0.001) and reported exposure durations 3-4 fold higher than that of controls (p<0.001). Dust and chemical, gas or fume exposure was associated with an increased odds of developing COPD. Exposure to dusts (OR 7.9, 95% CI 3.9-15.7, p<0.001), chemicals, gas or fumes (OR 6.4, 95% CI 3.2-12.8, p<0.001) were significantly associated with odds of developing COPD. In addition, previous history of tuberculosis, as well as smoking were associated with an increased odds of COPD (OR 5.7, 95% CI 1.2-27.4 p<0.001 and OR 6.4, 95% CI 2.3-17.7, p<0.001). Discussion and Conclusion This is one of the first hospital based case-control studies looking at occupational contribution to COPD undertaken in South Africa. In this sample of participants, strong associations were observed between self-reported occupational exposures to dust, and chemicals, gas or fumes, and physician’s diagnosis of COPD. The study also demonstrated a strong association between smoking and previous history of tuberculosis, and risk of COPD. The findings suggest that persons with known occupational exposures to respiratory irritants should be monitored to detect the onset of respiratory ill-health and that preventive strategies should reduce exposure to these agents in the workplace.