Prevalence and characteristics of asthma with fixed airflow obstruction:a CADSET European multi-cohort collaboration

Asthma with fixed airflow obstruction (AFO) is an important understudied sub-phenotype encompassing features of both asthma and COPD. We aimed to determine the prevalence and comorbidities of AFO patients in a large multi-cohort sample. Patients at least 50 years of age with lung function data were from nine European cohorts (69,866 participants), including population-based studies, COPD-based studies and asthma-based studies. AFO was defined as a documented doctor diagnosis of asthma and FEV1/FVC ratio The prevalence of AFO (n=2,378) differed between population-based cohorts (2.0%, n=1,299/63,504), COPD-based cohorts (15.9%, n= 857/5,402) and asthma-based cohorts (23.1%, n= 222/960). The LLN-based definition showed lower AFO prevalence in the general and asthmatic populations (1.4% and 15.7%) but higher prevalence (20.6%) in a smoking COPD population. While hypertension was the most prevalent comorbidity in all 3 conditions, AFO patients were significantly more likely to be diagnosed with depression, osteoporosis, coronary artery disease and gastroesophageal reflux compared to asthma-alone or COPD-alone. AFO has a prevalence ranging from 2.0% in the general population to 23.1% in an asthma population. The LLN-based definition seems to detect more patients suffering from AFO in populations with substantial smoking history. AFO patients have frequent comorbidities which may underlie their worse health outcomes.