Epidemiology of Childhood Asthma

Abstract

Over recent years, wheezing illness in children of the Western world has become synonymous with asthma, but as in adults there remains no universally accepted epidemiological definition of the condition. Existing definitions of asthma in adults are more descriptive than definitive, focussing on the clinical characteristics of reversible airways obstruction, chronic airway inflammation, and increased bronchial responsiveness to a variety of stimuli. The definition of asthma in children is even more difficult however, partly because of practical contraints on the objective measures of airflow in young children, and also because of the particular susceptibility of infants and younger children to wheeze in response to viral respiratory tract infection. Although the term wheezy bronchitis was used to describe this condition, the emergence of evidence in the 1970s that children with either a diagnosis of bronchitis or of asthma differed from healthy controls with respect to family and personal history of allergic disease and personal atopy [1], that some children with the diagnosis of wheezy bronchitis responded positively to asthmatic therapy [2], and that children were more likely to be treated appropriately if their condition acquired the label asthma [3], lead to an increased tendency to diagnose asthma in these children. The nature of the condition now labelled childhood asthma may therefore be at least as diverse as diagnosed asthma in adults, and probably reflects contributions from virtually any process resulting in the production of the symptom of wheeze. It is therefore extremely difficult to identify and define unique wheezing conditions in children, and the working definitions adopted in practice inevitably reflect a substantial degree of compromise.