An Epidemiologic Study of Chronic Obstructive Pulmonary Disease in the United States

Chronic Obstructive Pulmonary Disease (COPD) is a leading cause of morbidity and mortality in the United States (US), and its risk increases with age resulting in higher prevalence in aging populations like Florida. Understanding geographic disparities and predictors of COPD in such populations is useful for guiding intervention strategies. Occupational exposures increase COPD risk implying that Department of Energy (DOE) workers may have different risk profiles and comorbidity clusters than the general population. However, little is known about the disparities and these differences and yet this information may be important for guiding screening, prevention, and control programs. Therefore, the objectives of this study were to identify: (i) county-level geographic disparities and predictors of COPD in Florida, (ii) predictors of COPD occurrence and severity among DOE former workers, and (iii) comorbidity clusters and predictors of lung function changes and decline among DOE former workers.

Retrospective data were obtained from the Florida Department of Health, US Census Bureau, County Health Rankings and Roadmaps, and the National Supplemental Screening Program. High-prevalence geographic clusters were identified using Tango’s flexible scan statistics. Predictors of COPD prevalence, occurrence, and severity were identified using ordinary least squares, ordinary logistic, and multinomial logistic regression, respectively. Comorbidity clusters were identified using hierarchical clustering, and predictors of lung function change and decline were identified using random forest models.

High-prevalence clusters of COPD were identified in the panhandle, north-central, and south-central counties. Counties with high percentages of smokers and asthma patients tended to have high COPD prevalence. At the individual level, smoking, asthma, age, and body mass index were significant predictors of both COPD occurrence and severity. However, silica and diesel exhaust exposures were significant predictors of occurrence and severity, respectively. Significant predictors of lung function were age, forced expiratory volume per second, age at hire, welding fume exposure, and silica exposure. Characteristics of the comorbidity clusters were: low prevalence of comorbidities (cluster 1), high cardiovascular disease prevalence (cluster 2), high lung cancer prevalence (cluster 3), and high prevalence of multiple comorbidities (cluster 4). Study findings are important for informing disease management programs and ultimately decreasing COPD burden.