COPD: Who Has it, Who Hasn't – and Then What ?

COPD Stage 0 was left out of the GOLD guidelines in 2006 ([1]). Until then, presence of chronic respiratory symptoms in subjects without airflow obstruction, i.e. Stage 0, had been regarded a marker of being “at risk” of developing COPD. Having a “Stage 0” served several purposes. In order for prevention to be effective, awareness is needed and some measure of early disease must be identifiable. Concerning the latter, chronic respiratory symptoms seemed an option although the data supporting that symptoms were useful were sparse. In fact it revived all the discussions around the “British Hypothesis” stating that recurrent lower respiratory tract infections were the cause of airflow limitation seen in COPD. This hypothesis was formulated, elegantly tested, and refuted by Fletcher et al decades ago ([2]). In a more recent analysis of data from the Copenhagen City Heart Study we showed that in this urban setting “Stage 0” did not predict 5 and 15 years incident COPD cases ([3]).

Subsequently, other studies have found some association between “Stage 0” and subsequent development of COPD and especially a recent study by de Marco et al ([4]) was of interest as it studies young adults, the very population in which early identification of risk is of most importance. However, studying this population may not be entirely straight-forward and more data are needed in this age group ([5]).

Several issues around “Stage 0” should be noted. Chronic bronchitis in a smoker is not a normal phenomenon and should not just be discarded as a smoker's cough. The study in this issue of COPD by Maleki-Yazdi et al ([6]) as well as the study by Antonelli-Incalzi et al ([7]) clearly shows that chronic bronchitis is associated with a low health status and in 3 large-scale epidemiological settings presence of “Stage 0” was associated with worse survival than among healthy subjects ([8],[9],[10]). Thus, having chronic bronchitis is definitely worse than not having this condition. There could be several explanations for this but independent of these the presence of chronic respiratory symptoms should be seen as a marker of both current and future poor health. However, the question remains: Does “Stage 0” predict subsequent airflow limitation? If not, the term “Stage 0” has correctly been taken out of the GOLD staging. If it does, we need to see this in more prospective population studies for us to be able to evaluate not just a possible epidemiological relationship but also the value of such a marker – after all, defining an ‘at risk’ population we run the risk that those not considered at risk may falsely feel ‘safe’.

Finally, any “at risk” group should be identified for the purpose of secondary prevention and early treatment of disease. Regarding the latter, it seems quite clear that we are not doing very well. In the present study by Maleki-Yazdi et al ([6]) a disappointingly low proportion of patients with moderate and severe COPD seemed to receive adequate medication. One would fear that the same would be the case for pulmonary rehabilitation and the study leaves us with yet another snap-shot of a category of patients not being managed optimally. We should be able to do better.