Active asthma and the prevalence of physician-diagnosed COPD.

INTRODUCTION: Despite the considerable overlap of asthma and chronic obstructive pulmonary disease (COPD), the extent to which the two diagnoses are the manifestations of the same disease remains unresolved. We conducted these analyses to evaluate the role of active asthma in the prevalence of physician-diagnosed COPD. METHODS: From 2006 through 2010, 74,209 adults aged 18-99 years and with a history of asthma participated in the Behavioral Risk Factor Surveillance System (BRFSS) Asthma Call-back Survey and responded to interview-administered questionnaires via telephone. We used publicly available data from 71,639 (97%) participants to identify respondents with and without active manifestations of asthma and self-reported, physician-diagnosed COPD. We generated population-weighted estimates of physician-diagnosed COPD prevalence and conducted linear regression to estimate associations between active asthma status and the prevalence of COPD among current smokers, former smokers, and lifetime nonsmokers separately. RESULTS: Physician-diagnosed COPD was reported in an estimated 29% of the population with any history of asthma, including both active and inactive asthma. Age-specific prevalences of physician-diagnosed COPD were consistently higher among adults with active asthma than adults without active asthma. Compared to inactive asthma, active asthma was associated with an 8.3% [95% confidence interval (CI) 6.1, 10.5] higher prevalence of physician-diagnosed COPD among lifetime nonsmokers, a 20.6% (95% CI 18.0, 23.3) higher prevalence among former smokers, and a 26.7% (95% CI 22.5, 30.9) higher prevalence among current smokers. CONCLUSIONS: Among adults with a history of asthma, active manifestations of asthma may play an important role in the epidemiology of COPD.