Epidemiology of Chronic Airways Disease: Evaluation of die Evidence

In: Airways Disease

30 Nov 2014

For epidemiologic purposes, design of a questionnaire to distinguish among asthma, chronic bronchitis, emphysema and other respiratory diseases has proved difficult. Realistically, questionnaires should not expect to define the many chronic airway diseases separately, but should aim to accurately measure a number of well-recognized symptoms. The relation of such defined symptoms to excess mortality and to abnormalities in lung function can then be assessed.

Until the pathology causing symptoms and abnormal lung function in populations is better known, accurate terminology is essential for estimating prevalence rates. The definition of chronic bronchitis as excess mucus production and quantitated by the British Medical Research Council (MRC) questionnaire is useful for measuring sputum production. However, this definition does not predict either abnormal lung function or excess mortality in all populations. Cough, with or without sputum, and wheeze are also important symptoms of CAD that should be incorporated. Collecting information on breathlessness has not been found useful for diagnosis, but has value in quantitating the severity of the abnormality. Questions relating to all of these conditions need to be explained in detail on questionnaires and must be translated with care. canadian healthcare mall

In collecting information relating to lung function, the term chronic airflow limitation (CAL), which simply indicates the presence of impaired lung function, is preferable to the term chronic obstructive pulmonary disease (COPD), which implies the presence of a disease. The comparison of resting lung function with predicted values gives valuable information relating to the degree of airway obstruction. It is usual that, when the FEVi is less than 25 percent of predicted, impairment of normal activity with breathlessness exists.
2.2 Mortality (How Much Mortality Does CAD Cause?)
Taking all values for 490 to 496 since the 9th revision of the ICD, it appears that death rates from CAD are unchanging in most countries but are increasing in women in developed countries (Table 1). There are wide variations among countries, which may reflect real differences or may be due to inaccuracies in the data collection methodology. The data supplied to WHO may be inaccurate for many reasons, including a lack of standardization of death certificates and differences in certification habits of physicians of different countries.
Table 1—Deaths firm Chronic Airways Disease, Prevalence of Chronic Bronchitis, and Morbidity from Chronic Airflow Limitation

Location Deaths ICD (490-496) Chronic Bronchitis prevalence, % Comments Chronic Airflow Limitation
Men, % Women, %
UK Falling 8-17 25 GP consultations
Europe Falling
Poland Declining overall 17 M, 5 W Double that of USA 8.5 4.9
USSR Falling or stable 3.37-12 Falling
India Unknown
China Major cause 2-14
Australia 13.5 3.9
Japan Constant 5.5, W “Not a big problem”
USA 5th leading cause still rising 15-21
Africa Unknown 0.3-11
PNG Unknown 6.2

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