Differences between asthma-COPD overlap syndrome and adult-onset asthma

Differences between asthma-COPD overlap syndrome (ACOS) and adult-onset asthma are poorly understood. This study aimed to evaluate these differences in a clinical cohort of patients with adult-onset asthma, as a part of the Seinajoki Adult Asthma Study (SAAS). 188 patients were diagnosed with adult-onset asthma and re-evaluated 12 years after diagnosis. They were divided into three groups based on smoking history and post bronchodilator spirometry values: 1) never-and ex-smokers with < 10 smoked pack-years; 2) non-obstructive (forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) >= 0.7) patients with >= 10 pack-years; and 3) ACOS patients with >= 10 pack-years and FEV1/FVC < 0.7. ACOS patients had lower diffusing capacity (D-LCO/V-A 86% predicted versus 98 or 96% predicted; p< 0.001), higher blood neutrophil levels (4.50 versus 3.60 or 3.85x10(9) L-1; p=0.008), and higher IL-6 levels (2.88 versus 1.52 or 2.10 pg . mL(-1), p< 0.001) as compared to never-and ex-smokers with < 10 pack-years, or non-obstructive patients with >= 10 pack-years smoking history, respectively. ACOS patients also showed reduced lung function, higher remaining bronchial reversibility and a higher number of comorbidities. This study shows distinct differences in diffusing capacity, blood neutrophil and IL-6 levels, bronchial reversibility, lung function and comorbidities between ACOS and adult-onset asthma. The present findings should be considered in the comprehensive assessment of adult asthma patients.