Evolution of lung function and radiographic abnormalities in silicosis

To investigate the long-term evolution of radiographic and functional abnormalities in relation to environmental and individual factors in silicosis, 90 silicotic patients were enrolled in a 10-year follow-up survey. At each of the 4 serial examinations a chest radiograph, spirometry, respiratory symptoms and a British Medical Research Council questionnaire were obtained from each patient. The slopes of annual decline of functional and radiographic variables were used as dependent variables in a general linear model analysis, correcting for autoregressive and lung dimension effects. The rate of lung function decline was increased by cumulative silica exposure, respiratory symptoms, current exposure to silica and cigarette smoking and chronic obstructive pulmonary disease (COPD), and by the interaction of COPD and either cumulative silica esposure or current cigarette smoking. The greater declines were observed in patients with higher lung volumes at the start of the study. The progression of radiographic profusion was increased by current silica exposure especially in patients with COPD.