Estimating the U.S. prevalence of chronic obstructive pulmonary disease using pre- and post-bronchodilator spirometry: the National Health and Nutrition Examination Survey (NHANES) 2007–2010

BACKGROUND: During 2007–2010, the National Health and Nutrition Examination Survey (NHANES) conducted a spirometry component which obtained pre-bronchodilator pulmonary lung function data on a nationally representative sample of US adults aged 6–79 years and post-bronchodilator pulmonary lung function data for the subset of adults with airflow limitation. The goals of this study were to 1) compute prevalence estimates of chronic obstructive pulmonary disease (COPD) using pre-bronchodilator and post-bronchodilator spirometry measurements and fixed ratio and lower limit of normal (LLN) diagnostic criteria and 2) examine the potential impact of nonresponse on the estimates. METHODS: This analysis was limited to those aged 40–79 years who were eligible for NHANES pre-bronchodilator spirometry (n=7,104). Examinees with likely airflow limitation were further eligible for post-bronchodilator testing (n=1,110). Persons were classified as having COPD based on FEV(1)/FVC < 70% (fixed ratio) or FEV(1)/FVC < lower limit of normal (LLN) based on person’s age, sex, height, and race/ethnicity. Those without spirometry but self-reporting both daytime supplemental oxygen therapy plus emphysema and/or current chronic bronchitis were also classified as having COPD. The final analytic samples for pre-bronchodilator and post-bronchodilator analyses were 77.1% (n=5,477) and 50.8% (n=564) of those eligible, respectively. To account for non-response, NHANES examination weights were adjusted to the eligible pre-bronchodilator and post-bronchodilator subpopulations. RESULTS: In 2007–2010, using the fixed ratio criterion and pre-bronchodilator test results, COPD prevalence was 20.9% (SE 1.1) among US adults aged 40–79 years. Applying the same criterion to post-bronchodilator test results, prevalence was 14.0% (SE 1.0). Using the LLN criterion and pre-bronchodilator test results, the COPD prevalence was 15.4% (SE 0.8), while applying the same criterion to post-bronchodilator test results, prevalence was 10.2% (SE 0.8). CONCLUSIONS: The overall COPD prevalence among US adults aged 40–79 years varied from 10.2% to 20.9% based on whether pre- or post-bronchodilator values were used and which diagnostic criterion (fixed ratio or LLN) was applied. The overall prevalence decreased by approximately 33% when airflow limitation was based on post-bronchodilator as compared to pre-bronchodilator spirometry, regardless of which diagnostic criterion was used

Prevalence and factors associated with self-reported chronic obstructive pulmonary disease among adults aged 40-79: the National Health and Nutrition Examination Survey (NHANES) 2007-2012.

IntroductionChronic obstructive pulmonary disease (COPD) is a respiratory disease that often goes undiagnosed, particularly in its early stages.ObjectiveTo examine sociodemographic, general health, and COPD specific factors, including severity of lung obstruction, that are associated with healthcare provider-diagnosed COPD among U.S. adults.MethodsNHANES cross-sectional data collected from 2007-2012 on adults aged 40-79 years (n=10,219) were analyzed. The primary outcome was self-reported COPD diagnosis with predictive factors analyzed via chi-square and logistic regression analyses.ResultsDuring 2007-2012, 5.2% of US adults aged 40-79 reported being diagnosed with COPD. Among those diagnosed, 50.8% reported fair or poor health, 47.1% were currently smoking cigarettes, 49.1% were taking prescription respiratory medication, 36.4% had moderate or worse lung obstruction, and nearly 90% had one or more respiratory symptoms. Logistic regression revealed positive associations between receiving a COPD diagnosis and the following: being white (AOR: 3.08, 95% CI: 1.82-5.20); being aged 60-79 years (AOR: 1.65, 95% CI: 1.07-2.53); reporting fair/poor health (AOR: 2.91, CI: 1.55-5.46); having 4-9 (AOR: 3.5, CI: 1.3-9.4) or 10 or more healthcare visits in prior year (AOR: 5.06, CI: 1.62-15.77); being a former (AOR: 1.75, CI: 1.2-2.5) or current smoker (AOR: 1.70, CI: 1.17-2.48); having more severe lung obstruction (AOR: 4.90, CI: 3.28-7.32); having 3 or more respiratory symptoms (AOR: 22.07, CI: 12.03-40.49).ConclusionsMultiple factors are associated with self-reported COPD diagnosis with number of reported respiratory symptoms having the strongest association. After controlling for other factors, having mild lung obstruction was not associated with being diagnosed