Respiratory symptoms in British coal miners.

This report is concerned with the prevalence of certain respiratory symptoms, including persistent cough, persistent phlegm, breathlessness, wheeze, weather affecting the chest, and previous chest illness in a population of approximately 30,000 working coal miners in Great Britain. For each symptom, the prevalence tended to increase with increasing age. By the use of suitable statistical techniques, comparisons were made between the prevalences of different symptoms in the same population and of the same symptom in different populations, account being taken of age. Increased prevalence of each of the symptoms was associated with smoking and with radiographic evidence of pneumoconiosis, and for certain symptoms these factors appeared to act independently. Further analyses were made of the association between the susceptibilities of the same subject to the development of the various symptoms. On this basis, two main groups of symptoms were discerned: a group consisting of persistent cough and persistent phlegm, and a group consisting of breathlessness, wheeze, and weather affecting the chest.