THE INFLUENCE OF SILICOSIS ON DETERIORATING LUNG-FUNCTION IN GOLD MINERS

Study objective: To reexamine the symptoms, lung function, and chest r adiographs of older gold miners who continued to work in or around gol d mines 5 years after their enrollment in the cohort. Design: A follow -up study of a stratified sample of a cohort of gold miners. Setting: A health-care center for 24 gold mines in Welkom, South Africa. Popula tion: A stratified, random sample of 242 miners who were part of a coh ort of 1,197 gold miners who had been employed underground in gold min es for a mean period of 29 years. No silicosis was apparent on entry i n 59 men, 78 had silicosis with category I nodule profusion, 73 had ca tegory 2, and 32 had category 3. Measurements: The men were assessed w ith questionnaires, lung function tests, and chest radiographs approxi mately 4.5 years after their initial assessment. Results: Radiologic f eatures of silicosis had progressed an average of one subcategory (eg, 2/1 to 2/2) in the follow-up period. Lung function deteriorated more rapidly in the men with silicosis and the deterioration increased in p roportion to the degree of silicosis at the start of the study. Thus, the annual loss of FEV1 was 37 mL in those without silicosis, 57 mL in those with category 1, 100 mL with category 2, and 128 mL in the men with category 3 nodule profusion (p=0.000001). A similar pattern of lo ss was noted for the FVC (p=0.00003) and the single-breath lung diffus ion (p=0.004). These changes remained significant after controlling fo r age, original lung function, and for smoking. Conclusion: The men wi th silicosis suffered a substantial loss of lung function during the p eriod of follow-up that was directly in proportion with the nodule pro fusion on their initial chest radiographs.