The prevalence of COPD - Using smoking rates to estimate disease frequency in the general population

Study objectives: To develop and validate a model based on smoking rates that will provide reliable estimates of the true prevalence of COPD that include both clinically detected and undetected patients. Design: Model based on literature review. Age- and gender-specific rates of lung impairment by smoking status were applied to US smoking data. Resultant estimates were compared to the actual prevalence of obstructive airway disease as estimated by US national surveys. The model then was applied to estimate the prevalence of COPD in several European countries, where national data on undiagnosed lung disease do not exist. Setting: The model was adapted from both a literature review and health-care data, and the analysis was applied to the United States and Europe. Results: Using smoking rates, we estimate from our model that 15.3 million people who are > 40 years of age in the United States have COPD. The prevalence estimate, based on spirometric definitions for COPD in the same age group using the Third National Health and Nutrition Examination Survey (NHANES III), is 17.1 million people. NHANES III and other US national health-care surveys further suggest that only between 2.4 and 7 million people actually have COPD diagnosed; thus, the proportion of COPD that is currently being diagnosed in the United States is between 14% and 46% of all cases. Using smoking rates and our model, which was developed and validated for the United States, we calculated the prevalence of COPD for Germany (2.7 million people), the United Kingdom (3.0 million people), Spain (1.5 million people), Italy (2.6 million people), and France (2.6 million people) in those people > 45 years of age. Conclusions: Smoking rates appear to provide a useful method of estimating current COPD prevalence in those countries where more objective data are unavailable. These results are important because recognition of the true burden of disease and corresponding efforts to increase early identification of COPD can help to reduce the morbidity and mortality associated with COPD in populations at risk.