Asthma and COPD may overlap (ACO) but information about incidence and risk factors are lacking. This study aimed to estimate prevalence, incidence and risk factors of chronic airway obstruction (CAO) in a population-based adult asthma cohort.
During 1986-2001 a large population-based asthma cohort was identified (n?=?2055, 19-72y). Subsamples have participated in clinical follow-ups during the subsequent years. The entire cohort was invited to a clinical follow-up including interview, spirometry, and blood sampling in 2012-2014 when n?=?983 subjects performed adequate spirometry. CAO was defined as post-bronchodilator FEV1/FVC