Prevalence and etiology of chronic cough without sputum production in coal miners.

Chronic cough in the sense of the international definition was found in 50.5% of a group of 970 coal-miners at work without pneumoconiosis. In 14.7% of these subjects the cough was without phlegm production. Non productive cough is therefore not a rare event and this symptom may not be neglected in the natural history of chronic bronchitis in coal-miners. The changes in lung function are similar whether the cough is productive or not. In both cases endoscopic and histological features are suggestive of an established chronic inflammatory process. Allergy is not more frequent in subjects with dry cough than in those with productive cough.