Asthma and lower airway diseaseClinical outcomes and inflammatory biomarkers in current smokers and exsmokers with severe asthma

BackgroundClinical outcomes are worse in current smokers and exsmokers with mild-to-moderate asthma compared with never smokers, but little is known about the influence of smoking status in patients with severe asthma.ObjectivesWe sought to examine the association of current or previous cigarette smoking with clinical and inflammatory variables in patients with severe asthma.MethodsWe compared patients' demographics, disease characteristics, and biomarkers of inflammation in current smokers (n = 69 [9%]), exsmokers (n = 210 [28%]), and never smokers (n = 461 [62%]) with severe asthma (n = 760) recruited to the British Thoracic Society Severe Asthma Registry.ResultsCurrent smokers had poorer asthma control, more unscheduled health care visits, more rescue courses of oral steroids, and higher anxiety and depression scale scores than exsmokers or never smokers. Current smokers had a reduced proportion of sputum eosinophils compared with never smokers (1% and 4%, respectively) and lower fraction of expired nitric oxide (50 mL/s; 14 ppb and 35 ppb, respectively). Exsmokers compared with never smokers had an increased proportion of sputum neutrophils (59% and 43%, respectively) but a similar proportion of sputum eosinophils (3%) and fraction of expired nitric oxide (50 mL/s; 35 ppb). Both current smokers and exsmokers had reduced serum specific IgE levels to several common environmental allergens.ConclusionCurrent smokers with severe asthma exhibit worse clinical and health care outcomes compared with exsmokers and never smokers with severe asthma. Their inflammatory profiles in sputum and blood differ.