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

Study objectives: To develop and validate a model based on smoking rates th at will provide reliable estimates of the true prevalence of COPD that incl ude 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. Resulta nt estimates were compared to the actual prevalence of obstructive airway d isease as estimated by US national surveys. The model then was applied to e stimate the prevalence of COPD in several European countries, where nationa l data on undiagnosed lung disease do not exist. Setting: The model was adapted from both a literature review and health-car e 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 preval ence estimate, based on spirometric definitions for COPD in the same age gr oup using the Third National Health and Nutrition Examination Survey (NHANE S III), is 17.1 million people. NHANES III and other US national health-car e surveys further suggest that only between 2.4 and 7 million people actual ly have COPD diagnosed; thus, the proportion of COPD that is currently bein g 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 Uni ted States, we calculated the prevalence of COPD for Germany (2.7 million p eople), 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 peop le > 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 un available. These results are important because recognition of the true burd en of disease and corresponding efforts to increase early identification of COPD can help to reduce the morbidity and mortality associated with COPD i n populations at risk.