Risk factors for small airway dysfunction in different phenotypes of adult asthma patients 

Background: Small airway dysfunction (SAD) presents in asthma of all severities and is associated with asthma control and exacerbations. However, risk factors for SAD in adult asthma patients with different allergy-related phenotypes remain unclear. Methods The medical records of 222 adult patients with allergic asthma, 200 patients with allergy-related non-allergic asthma, and 118 patients with non-allergy-related non-allergic asthma were retrospectively analyzed. Clinical characteristics were compared among groups, and independent risk factors for SAD in each group were identified by performing backward stepwise multivariate logistic regression analyses. Results Patients with allergic asthma had an obviously higher male proportion, a significantly younger onset age, and a significantly lower value of blood neutrophil percentage than the two other groups. The values of blood eosinophil percentage and total IgE were highest in patients with allergic asthma and lowest in patients with non-allergy-related non-allergic asthma. Backward stepwise multivariate logistic regression analyses revealed smoking as the independent risk factor for SAD in adult patients with allergic asthma, age as the independent risk factor in patients with allergy-related non-allergic asthma, and family history of asthma as the independent risk factor in patients with non-allergy-related non-allergic asthma, respectively. Conclusion Smoking, age, and family history of asthma are independent risk factors for SAD in adult patients with allergic asthma, in adult patients with allergy-related non-allergic asthma, and in adult patients with non-allergy-related non-allergic asthma, respectively.