COPD: Worldwide prevalence

Imprecise and variable definitions have made it hard to quantify the prevalence and burden of chronic obstructive pulmonary disease (COPD) in both developed and developing countries (1). A number of different approaches have been used to estimate the prevalence of COPD. Historically, most of these have been surveys based on symptoms and/or diagnosed conditions. Few have included lung function. A different approach has been used by the Global Burden of Disease (GBD) Study, sponsored by the World Health Organization (WHO) and the World Bank (2,3). This study is described below and essentially involves finding all published and unpublished data and filling in the gaps with best estimates. These different approaches will inevitably provide widely varying estimates of COPD prevalence. All estimates, however, provide useful information that helps to complete the picture of the burden of COPD, so the three approaches will be discussed briefly.