Unravelling the many faces of chronic obstructive pulmonary disease: A hitchhiker's guide to <scp>COPD</scp>

Chronic obstructive pulmonary disease (COPD) is a global epidemic afflicting 200–300 million people worldwide and causing deaths and suffering for millions of people each year.1 The greatest burden of COPD is found in Asia, which has the highest age-adjusted mortality rate anywhere in the world. Shockingly, in 2010, 76% of all COPD deaths occurred in Asia, killing 2.1 million individuals.2 The causes and mechanisms for the disproportionate burden of COPD in this region are largely unknown. In East Asia, the COPD epidemic is being fuelled in large measure by the massive increase in smoking rates over the past decade. In 2013, Asia consumed 64% of the global cigarette market (up from 54% in 2005),3 and in China alone there are currently more than 280 million active smokers (including nine million child smokers), with an annual consumption of more than two trillion cigarettes.4 However, in countries such as India, where cigarette smoking rates are relatively low, the large burden of COPD is harder to explain. Interestingly, in the largest study of its kind, Duong et al. found that healthy non-smokers from South Asia (India, Bangladesh, and Pakistan) had forced expiratory volume in 1 s (FEV1) values that were on average 31% lower than that of individuals living in North America or Europe, following adjustments for age, sex and height, while those living in Southeast Asia (e.g. Malaysia) and East Asia (e.g. China) had FEV1 values that were 24% and 13% lower, respectively.5 The FEV1/forced vital capacity ratios, however, were higher in Asia compared with North America, which suggests smaller lung size rather than smaller airway calibre relative to lung size.The underlying basis of smaller lungs in Asian populations is unknown, but there is a suggestion that it may be environmental, given that Asian immigrants born in Western countries are taller and have lung sizes that approximate that of the local population.6 It raises the interesting possibility of complex interactions between environmental exposures (including tobacco but also biomass fuel and other pollutants), nutrition and lung size/development in Asians that may predispose them to COPD. Irrespective of the mechanism, a more pressing clinical question is what can be done to address the growing burden of COPD in Asia and throughout the world? In this series, we have invited a panel of internationally recognized experts in COPD to unravel the many mysteries of COPD and to impart ‘new’ knowledge, which can advance the field and most importantly improve the care and outcomes of patients with COPD. Our experts will provide an overview on the current global burden of COPD and a glimpse of the future of COPD in Asia. They will also teach us about the ‘natural history’ of COPD, which may surprise and shock many readers like us who have grown up with the timeless ‘Fletcher and Peto’ curves.7 They will move us from the current treatment paradigm based on ‘population-based averages’, which is costly and inefficient, to personalized medicine where each patient will be treated based on his/her own needs and responsiveness to treatments. Our experts will examine the ‘ACOS’ (asthma–COPD syndrome), a new-old problem in COPD for which we have no answers but many (unresolved) questions. They will also teach us that we are not alone and that there is a rich microbiome in the airways, which becomes perturbed in COPD, contributing to disease and destruction. They will take us on a journey in HIV/AIDS where the burden of COPD is two to four times higher than in the general population.8 They will once again prove the old adage ‘a picture is worth a thousand words’ by demonstrating the value of computed tomography, magnetic resonance imaging and emerging technologies in optical coherence tomography and others in bringing to focus the multiple phenotypes of COPD. Our global experts will educate us on the importance of air pollution on small airway function and will provide new insights in the physiological impairments of COPD and across GOLD (Global initiative for chronic Lung Disease) severities in both men and women with the disease. They will show us how and why the pulmonary vasculatures matter in COPD and how disease in these vessels impacts on patient-related outcomes. Our experts' review on exacerbations will be of great interest to practising clinicians who struggle to effectively manage and prevent exacerbations in COPD. They will also clarify how and when we should use one, two or three different bronchodilators to optimally control disease activity and symptoms of COPD. Our experts will persuade us that there is more to COPD management than just drugs, and provide us the latest update on non-pharmacological treatments for COPD. They will also impart new knowledge to enable patients to implement effective exercise regimens in their daily lives for better symptom control and improved outcomes. Finally, they will educate us on the role of animal models in unravelling the molecular underpinnings of COPD with the hope that this knowledge will lead to new drugs and therapies in the future. COPD is a complex heterogeneous disease with a reactive past but with a preventive future. It is our deepest hope that this review series will be interesting, informative and most importantly helpful for the practising clinicians in improving the care and health outcomes of their patients with COPD. We also hope that these papers will encourage a dialogue in Asia and throughout the world to bring about greater awareness of the increasing contribution of COPD to the global burden of disease, and provide greater impetus to finding new biomarkers and therapeutic solutions that will bring new breath for millions of people who suffer from this menacing disease.

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