Rationale Some clinical outcomes are worse in current smokers and ex-smokers with mild to moderate asthma compared to never smokers, but little is known about the influence of smoking status in severe asthma.
Objectives The objectives of the analysis were to examine the association of current or previous cigarette smoking with clinical and inflammatory variables in severe asthma.
Methods We compared patient demographics, disease characteristics and biomarkers of inflammation in never smokers (n=461, 62.3%), ex-smokers (n=210, 28.4%) and current smokers (n=69, 9.3%) with refractory asthma (n=760) recruited to the British Thoracic Society Severe Asthma Registry.
Results Current smokers had poorer asthma control, more unscheduled health care visits, more rescue courses of oral steroids and higher anxiety and depression scale scores than ex-smokers or never smokers. Compared to never smokers, current smokers had a reduced proportion of sputum eosinophils (3.75% and 1.25% respectively) and lower fraction of exhaled nitric oxide (FeNO50) values (35 ppb versus 14 ppb), whereas ex-smokers had an increased proportion of sputum neutrophils (43.8% versus 56.9%), but similar proportion of sputum eosinophils (2.8%) and FeNO50 values (35 ppb). Both current and ex-smokers had reduced serum specific IgE levels to some common environmental allergens.
Conclusion Current smokers with severe asthma exhibit worse outcomes for a range of clinical and health care variables compared to ex-smokers and never smokers with severe asthma. Inflammatory profiles in sputum and blood differ between current smokers, ex-smokers and never smokers, possibly constituting separate phenotypes of severe asthma, which may influence responses to targeted therapies.