Abstract

Seven mutually exclusive groups of non-bronchitics and chronic bronchitics are derived from 10,816 steel workers questioned and examined at Port Talbot. These groups are based on various combinations of responses to the Medical Research Council questionnaire on cough, phlegm, dyspnoea, increased cough and phlegm, and chest illness. The groups are formed on defined criteria of (1) a reasonable number of men in each group; (2) impairment of lung function (FEV₁) related to the severity of chronic bronchitis symptoms; and (3) impairment of lung function from certain other diseases.

The ideal group of non-bronchitics (NB 0) answered `no' to every symptomatology question (46·4%). Non-bronchitics grade 1 (NB 1) were either symptom-free or had only occasional cough and phlegm with either or both increased cough and phlegm and chest illness (24·2%). Non-bronchitics grade 2 (NB 2) complained of dyspnoea in the absence of persistent cough and phlegm (4·3%). Chronic bronchitics grade 1 (CB 1) had persistent cough and phlegm in the absence of any other complaint (11·3%). Chronic bronchitics grade 2 (CB 2) had the additional impairment of increased cough and phlegm and/or chest illness (8·1%). Grade 3 (CB 3) complained of dyspnoea with or without increased cough and phlegm (2·5%). Grade 4 (CB 4) had both dyspnoea and chest illness (3·2%).

Lung function (FEV₁) in three of the groups of chronic bronchitics (CB 1, CB 2, CB 3: 21·9%) was no worse than in the two groups of non-bronchitics with complaints of other respiratory disorders (NB 1, NB 2: 28·6%). An overall comparison on a binary division between non-bronchitics and bronchitics hides the severity of some of the bronchitic groups. For this reason it is recommended that epidemiological studies of chronic bronchitis should separate the suggested grades of bronchitics (CB 1, 2, 3, and 4) and compare them with the ideal group of non-bronchitics (NB 0: 46·4%) which has the lowest prevalence of heart trouble and asthma and those who have had pneumonia.