We searched the full available range of articles on PubMed using the search terms “COPD” and “definition, evaluation, natural history” (search last updated on Feb 21, 2015). We selected articles published in English that addressed early chronic obstructive pulmonary disease (COPD). We further reviewed references cited in reviewed articles. We selected articles that informed the strategy for prevention of early COPD. The development of a research agenda to prevent COPD was the subject of a
SeriesEarly chronic obstructive pulmonary disease: definition, assessment, and prevention
Introduction
Chronic obstructive pulmonary disease (COPD) is, at present, the third leading cause of mortality worldwide.1 Prevention of COPD should be a major public health goal.2 Although this goal can be achieved to some extent by smoking cessation, smoking is not the only cause of COPD and additional preventive strategies are needed. Despite the public health importance of COPD prevention, relatively little is known about it. The diverse causes and pathogenic processes that lead to COPD mean that COPD is a heterogeneous collection of many different diseases that are grouped because of similar features. This is an issue for preventive efforts, which will probably need to be disease specific.
Section snippets
Issues and challenges with the definition of COPD confound the definition of early COPD
The definition of early COPD is complicated by the issues relating to the definition of COPD itself and, more importantly, to the heterogeneity of its natural history. The key defining feature of COPD is post bronchodilator limitation of expiratory airflow by comparison with lung volumes.3, 4 Expiratory airflow is usually measured as the forced expiratory volume in 1 s (FEV1) and lung volume as the forced vital capacity (FVC), both of which are readily assessed with spirometry, a simple
Distinguishing early from mild disease
Whereas the definition of COPD has engendered much discussion, the definition of early COPD has not. Early implies a time in the natural history of COPD, either before the disease is present or a time when the disease has not progressed to full clinical effect. As such, early contrasts with mild COPD. Most of the studies of COPD have many participants aged greater than 60 years. Many of these participants have so-called mild disease, which might have been present for decades, and represents
Natural history beyond FEV1
Airflow limitation is used to define COPD, but it only partly captures the clinical features of COPD. Cough and sputum probably result from airways metaplasia, inflammation, and glandular hyperplasia.3, 4 Dyspnoea in COPD is mostly due to dynamic hyperinflation.52, 53 The extrapulmonary features that are characteristic of COPD are relatively independent of FEV1, and are often the major clinical problems patients face.54, 55, 56 Moreover, extrapulmonary problems might be present when FEV1
Summary of challenges for the definition of early COPD
Early COPD means an interval in time at the beginning of the disease course. This early phase could occur in late life—for example, in an individual who has had a natural history of healthy lung function but who has entered a period of very rapid loss of lung function. Alternatively, early COPD could happen in mid or very early life. Since several pathogenic processes could be active in the same individual, these processes can be early at different times in the individual. Finally, COPD is
Lung function
Several diagnostic tests could define early COPD (panel 3). Spirometry is the most widely used method to assess lung function. The test is well understood, is readily available, is used to assess the prevalence and severity of COPD, and can be practised in various settings and in children aged 3–5 years and older.64, 65, 66, 67 Spirometry could be used to diagnose early COPD, but the diagnosis is likely to need sequential measures. One test, for example, can define so-called mild COPD, but
Types of prevention
Prevention can be classified as primary, secondary, or tertiary. Prevention of disease development in people who are still well is primary prevention. Prevention of clinically apparent disease in people with detectable abnormalities is secondary prevention. Prevention of disease progression in people with clinically apparent disease is tertiary prevention. However, in the context of early COPD, these distinctions are often difficult because of the complex and heterogeneous natural history of
Conclusion
COPD is a major worldwide public health issue. Efforts to control cigarette smoking will have a major effect on COPD prevention. However, smoking is not the only risk factor for COPD and additional preventive efforts are needed. The ability to assess disease progression combined with an understanding of the complex and heterogeneous natural histories of COPD throughout the entire life cycle is creating novel opportunities for preventive interventions, which might need to be selective for
Search strategy and selection criteria
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