Chronic bronchitis: should it worry us?

Chronic Respiratory Disease 2004; 1: 173-176 www.CRDjournal.com REVIEW SERIES: the ageing lung Chronic bronchitis: should it worry us? J Vestbo North West Lung Centre, South Manchester University Hospital Trust, Manchester, UK Background: Chronic bronchitis (CB) has been studied using standardized questionnaires for decades. From being the key element in the 'British hypothesis' chronic bronchitis was reduced to being an innocent disorder in the 1980s. However, there is now good evidence that chronic bronchitis is associated with an increased risk from both overall and chronic obstructive pulmonary disease (COPD) specific mortality. Presumably through increasing the frequency of lower respiratory tract infections chronic bronchitis is associated with excess decline in lung function, hospital admission and other disease specific outcomes. The prevalence of chronic bronchitis increases with increasing age and the burden associated with chronic bronchitis in this growing proportion of the population is large. Vital prognosis in the elderly is affected by CB and this condition presumably deserves more attention from the medical profession. Chronic Respiratory Disease 2004; 1: 173-176 Key words: COPD; epidemiology; hospitalization; infection; mortality; mucus Introduction Chronic bronchitis (CB) is defined as cough and phlegm for at least three months every year for at least two years. This clinical and easily applicable definition was decided on at the CIBA Guest Symposium in 19591 and the usual tool for assessing CB, the British Medical Research Council (BMRC) questionnaire,2'3 was extensively validated in pioneering work by British epidemiologists decades ago.4 6 Because of the possibility of applying the BMRC questionnaire in an epidemiological setting most studies in respiratory epidemiology have included assessment of CB. Chronic bronchitis is generally believed to be due to chronic mucus hypersecretion and the prevalence of the condition varies roughly from 1% to 2% in female never smokers to 30% in unselected male heavy smokers and generally CB is three times more frequent than airflow obstruction in the general population.7 In general, increased prevalence of CB is associated with increasing age, male gender, tobacco smoking, occupational exposures and socioeconomic status. CB is far more frequent in the middle-aged and elderly but the reason is not clear. It is possible that CB becomes more frequent with ageing but probably more likely that the effect of ageing is to a large extent a cohort effect. The purpose of this review is to describe the changing attitudes to the role of CB and to outline its role in the ageing population. Early studies The rationale for looking at CB in respiratory epidemiology is closely linked to infections and 'The British Hypothesis'. This hypothesis linked recurrent lower respiratory tract infections with the development of fixed airflow limitation.8 The British Hypothesis was tested - and rejected - by Fletcher et al. in their seminal study of male postal workers in London.9'10 Fletcher et al. recognized that lower respiratory tract infections (LRTI) undoubtedly became more frequent with advancing chronic obstructive pulmonary disease (COPD); however, their purpose was to examine the role of CB in early disease and they did not find any relationship suggesting CB and/or LRTI to be the cause of COPD. The fact that they studied a working population is often overlooked but the authors stated clearly 'In the preclinical stages of these disorders, which we have studied, we find ...'. Their statements, however, significantly influenced the view on CB: 'The hypersecretory disorder is also caused, in susceptible subjects, by smoking and consists of chronic excessive 10. I191/1479972304cdO22rs Correspondence: J0rgen Vestbo, North West Lung Centre, South Manchester University Hospital Trust, Southmoor Road, Manchester, M23 9LT, UK. E-mail: jvestbo(man.ac.uk ,tC Arnold 2004

Chronic bronchitis: should it worry us?

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