Prospective investigations in asthma. What have we learned from longitudinal studies about lung growth and senescence in asthma?

The natural history of lung growth and senescence in individuals with variable air flow obstruction or clinical asthma has been given less attention than the natural history of chronic airflow obstruction. This article reviews the information available on lung growth during childhood in persons with asthma and on the rate of decline of lung function during adult life in individuals with asthma or bronchial hyperresponsiveness. Lung growth appears to be relatively normal in most children with asthma but is reduced throughout childhood and adolescence in those with severe and persistent symptoms. It is not known if this reflects a failure to reach full growth or reversible bronchoconstriction. During adult life, clinical asthma is associated with a slight increase in the rate of decline in FEV₁. In the middle-aged and elderly smoker it is virtually impossible to separate chronic bronchitis and asthma. Bronchial hyperresponsiveness appears to be associated with an increase in the rate of decline of lung function but it is not clear if this is a result of airway disease due to smoking or a true risk factor. Further research needs are identified.