From Childhood Asthma to Chronic Obstructive Pulmonary Disease: Evidence Supporting a Disease Continuum

In this review, we analyze the available evidence showing a link between asthma and chronic obstructive pulmonary disease (COPD). Many features (epidemiologic, physiologic, and histologic) overlap between these two conditions. Both environmental cigarette smoke exposure and early lung development are risk factors for the development of asthma and COPD. However, recent studies suggest that up to 25% of COPD cases were nonsmokers. Asthma during early childhood, independent of smoking history, may be an independent risk factor for the later development of COPD. One explanation for this phenomenon suggests that early small airway dysfunction (including chronic airway inflammation and airway remodeling) can lead to permanent impairment in lung physiology. Several reasons why control of airway inflammation is difficult in some patients are explored. Finally, we examine the available evidence suggesting overlapping histologic features in both asthma and COPD.