Contribution to the natural history of chronic bronchitis in coal-miners.

Two epidemiological surveys were made by the same research team on the prevalence and the aetiological factors of chronic bronchitis symptoms in coalminers. The first study was made in a coalminers' community of Belgian Limburg, the other one in a representative sample of coalminers regularly at work. In both surveys an excess of dyspnea complaints was observed in comparison to the prevalence of this symptom in controls. These dyspnea complaints often presented themselves as isolated symptoms, without chronic cough or phlegm production. Dyspnea in excess could not be explained by massive fibrosis. The prevalence of the symptom was not linked, neither to the spirometric values, nor to the results of respiratory challenge tests with acetylcholine, tobacco use, or the length of exposure at the coalface. When dyspnea was associated with cough and phlegm production there was on the contrary a statistically significant relation with the spirometric values and the effect of acetylcholine. It seems therefore reasonable to explain at least partially the isolated dyspnea complaints in coalminers by specific mechanisms not related to bronchitis but resulting from the pathological lesions characteristic of simple pneumoconiosis. Complaints of cough and phlegm production appear as a rule later in the coalminer's life. In the groups taken into consideration in the study they were linked with cigarette smoking which appeared as the predominant aetiological factor for these complaints; in a subgroup a synergic action of coaldust, tobacco use and air pollution could be discussed in this respect. Notwithstanding the pathogenic independence of some dyspnea complaints versus cough and expectoration, it is quite clear that when productive bronchitis develops and causes broncho-obstruction, it may aggravate pre-existing dyspneic patterns.