Elsevier

The Lancet

Volume 370, Issue 9589, 1–7 September 2007, Pages 765-773
The Lancet

Review
Global burden of COPD: risk factors, prevalence, and future trends

https://doi.org/10.1016/S0140-6736(07)61380-4Get rights and content

Summary

Chronic obstructive pulmonary disease (COPD) continues to be an important cause of morbidity, mortality, and health-care costs worldwide. It is a global health issue, with cigarette smoking being an important risk factor universally; other factors, such as exposure to indoor and outdoor air pollution, occupational hazards, and infections, are also important. As the global population ages, the burden of COPD will increase in years to come. Prevalence estimates of the disorder show considerable variability across populations, suggesting that risk factors can affect populations differently. Other advances in our understanding of COPD are increased recognition of the importance of comorbid disease, identification of different COPD phenotypes, and understanding how factors other than lung function affect outcome in our patients. The challenge we will all face in the next few years will be implementation of cost-effective prevention and management strategies to stem the tide of this disease and its cost.

Section snippets

Definition

The working definition of COPD, as noted in the 2006 update of the Global Initiative for Obstructive Lung Disease (GOLD) guidelines, is that COPD is “a preventable and treatable disease with some significant extrapulmonary effects that may contribute to the severity in individual patients. Its pulmonary component is characterised by airflow limitation that is not fully reversible. The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lungs to

Disease classification

COPD can be classified with respect to both phenotype and disease severity. It is a heterogeneous disease process that varies greatly from person to person with respect to lung pathology, natural history of disease, and comorbidity. A result of this heterogeneity is that different researchers have championed alternative hypotheses about COPD development over the past four decades: the British hypothesis stated that the presence of cough and sputum was the key factor in COPD,22 and the Dutch

Risk factors

Risk for COPD is related to an interaction between genetic factors and many different environmental exposures, which could also be affected by comorbid disease. Risk factors for the disease are described below.

Prevalence estimates

Two reviews have been published58, 59 in which the prevalence of COPD was noted to be highly variable, probably because of differences in methods for establishment of disease prevalence. Figure 4 shows the findings from the 12 sites of the BOLD study26 and the five sites in the Latin American Project for the Investigation of Obstructive Lung Disease (PLATINO) study.60 These estimates, even with identical methodologies, show a large amount of variability. For example, in the BOLD study,26 GOLD

Morbidity and mortality

Additional measures of the burden of COPD, such as morbidity, mortality, and costs, present challenges similar to those seen in attempting to measure disease prevalence. Table 3 shows WHO estimates of deaths and disability-adjusted life years attributable to COPD for the world's 25 most populous nations.1 This table highlights some of the difficulties with these other measures of COPD. For example, the estimated COPD death rate in Japan of 4·4/100 000 is nearly 30 times lower than that in China

Future trends

When Calverley and Walker reviewed COPD in 2003 they made some predictions about progress in disease.2 With respect to pathogenesis, they forecast that there would be greater phenotypic characterisation of COPD, identification of candidate susceptibility genes, clarification of the basis of steroid resistance, and enhanced animal models of the disease. With respect to clinical characteristics, they predicted that there would be better methods of detecting flow limitation and staging systems

Conclusion

Our knowledge of COPD has grown over the past few years. Additional questions are raised by this new knowledge, which are discussed here. One of the biggest advances in COPD is greater understanding of disease burden in different countries and cultures. Publication of data from the PLATINO60 and BOLD26 studies is vital to establish how important COPD is, particularly in view of the disease's consistent underdiagnosis at sites where it has been investigated.76, 77, 78 Other relevant components

Search strategy and selection criteria

The material covered in this Review is based on an extensive literature search and participation in expert meetings during the writing and updating of guidelines for the treatment of chronic obstructive pulmonary disease, along with many years of research in the area. We did a systematic Medline search for articles in English or with English abstracts with the keywords: “COPD” or “emphysema” or “chronic bronchitis” AND “prevalence” or “burden” or “risk factors” or “cost” or “morbidity” or

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