Chronic obstructive pulmonary disease in the United States: Recent estimates of disease prevalence, diagnosis, and treatment patterns

Objectives: To update estimates of the prevalence of chronic obstructive pulmonary disease (COPD) and respiratory medication use among US adults. Methods: Data were from the 2007-2008 National Health and Nutrition Examination Survey (NHANES), a nationally representative survey of the non-institutionalized US population. Participants aged 20-79 years with valid spirometry data and height measurement (required for COPD severity staging) (n=4,065) were categorized into severity stages based on pre-bronchodilator spirometric assessment: mild (forced expired volume in 1 second [FEV1]/forced vital capacity [FVC]<0.7 and FEV1>=80% predicted), moderate (FEV1/FVC<0.7 and 50%<=EV1<80% predicted), and severe/very severe (FEV1/FVC<0.7 and FEV1<50% predicted). Restrictive lung disease was defined based on FEV1/FVC>=0.7 and FEV1<80% predicted. Self-report of physician diagnosed emphysema and/or current chronic bronchitis was also determined. Treatment was based on self-reported use in the past month of long- and short-acting bronchodilators and other respiratory medications. Adjusted examination sample weights were used to generate nationally representative estimates. Results: In 2007-2008, 14% (95%CI: 12%-16%) of US adults aged 20-79 years had COPD based on lung function (FEV1/FVC<0.7). An additional 10% had restrictive lung disease and 19% had respiratory symptoms alone. Among COPD participants, most had mild (53%) or moderate (40%) disease; 7% had severe/very severe disease. About 9% of adults with COPD reported a physician diagnosis (95%CI: 5%-13%); among these, 51% (95%CI: 34%-68%) used a respiratory medication in the past month. Conclusions: The prevalence of COPD among US adults remains significant. Over half of adults with COPD who reported being diagnosed were currently treated. However, a significant proportion of adults remain undiagnosed and untreated.